Victron + Wakespeed + Battle Born power system

Rendezvous came with a decent power system which I had hoped to use for a year before upgrading. However, performance and other problems cropped up in the first few months of using it, so I moved this project earlier in the list and jumped in. ?

Original System

Original 840 amp hour house bank using 6x 6v GC2 flooded batteries

The original system was pretty standard, and worked OK, except for overall capacity and charging issues. Here’s an overview of the system itself.



  • House battery bank – 6x 6 volt GC2 style flooded batteries – 280 amp hours each, for a total of 840 amp hours (only 420 usable at 50% DOD)
  • Start batteries – 2x 8D flooded batteries – one for each engine
  • Generator battery – 4D flooded battery
Original Magnum 2800W inverter

Charging / Inverting

  • Magnum 2800W inverter/charger – both at the dock via shore power and underway via the 8Kw Onan generator
  • Magnum battery combiner
  • ProMariner 3 bank AC charger – charges generator and start batteries
  • 70 amp “newer” alternator and 40 amp original alternator (more than 20 years old) charging start banks
  • Battery combiner switch at DC panel


  • Overall capacity – while 420 usable amp hours is quite a bit, the amount of electrical stuff on the boat, even before I added electronics, meant that you needed to charge at least twice a day while at anchor.
  • Charging is slow – normal with flooded batteries – the last 10% always takes forever, and the charge sources with this system are very small or inefficient.
  • No charge control between house + start batteries – only a combiner switch – this meant remembering to combine the batteries when charging, and hopefully remembering to disconnect them when at anchor, or you deplete the starting batteries (which happened several times). There was also more than 40′ of cable between the house and start bank by the time it went from the battery banks, to the combiner switch, and back. Voltage drop anyone?
  • Bad AC charger – ProMariner AC charger – excellent at cooking batteries! – this thing was a nightmare piece of equipment, and after I put voltage monitoring in place, routinely pumped 16-18v into my start and generator batteries. Plus, there was a Magnum battery combiner ALSO in the mix that would routinely connect the banks together. Both of these needed to be simplified.
  • Large start batteries – 8D batteries to start each engine, and a 4D battery for the generator. These were huge, took up a lot of space, and could be optimized with newer technologies. They also routinely had issues due to the bad charger and cross connection while charging the house bank.

New System Design

Like the other systems I’ve installed on previous boats and for other people, including the LiFePO4 system on Grace, I wanted a Lithium-based system with more overall amp hours, higher charging rates, but with a simpler design.


  • Higher overall amp hour capacity
  • Faster charging rates both underway and at the dock
  • Local and remote monitoring of all parts of the system
  • Simplification vs. other LiFePO4 systems I had installed before
  • Redundancy / separation between house, start and generator banks

AC & DC System

For the heart of my system, I chose a Victron MultiPlus 3000W inverter, combined with a BMV-712 battery monitor and Color Control GX display. I’ve used these before in many designs, and love the feature set provided by the combo, and the visibility provided by the Color Control GX.

One big change to the system was to run my shore and generator power connections directly to the inverter, rather than having it hang off of a circuit on the AC panel. This provided the following benefits:

  • Central control for all inbound AC power
  • Victron Power Assist feature (seen below) which would help during high AC use periods while connected to shore power
  • Simplified operation and control
  • Simplified grounds/neutrals
Victron inverter in assist mode, augmenting my 30 amp shore power with battery capacity

Rendezvous only has a single, 30 amp, 120VAC shore power connection. I considered rewiring things to 50 amp, 240VAC, but that is a project for another time. Instead, having the MultiPlus in-line for all incoming shore power allows me to use the Power Assist feature when I am at the dock and exceed the 30 amp shore power limit. Particularly in the winter when we might have an AC oil heater running while also on board using the microwave, stove, or the hot water heater, it will allow for bursts over that limit without any interaction. While out away from the dock, the generator provides up to 50 amps of AC power which we never have exceeded.

I also added a cut out switch that allows me to bypass the entire inverter in the event of a catastrophic failure of the device.

Alternators charging house only

I made an intentional design choice that seems less common on most boats I’ve worked on, but has proven to be very effective & simpler to understand. I chose to have both engine alternators charge the house bank directly, and nothing else.

Using a split system with one alternator charging the house bank, and one charging the start batteries seemed like a waste of an alternator. The one dedicated to the start bank isn’t going to do much work since it shouldn’t take much power to start the engines normally, and it would only work for a short period, while the house alternator would be busy all the time.

Having both of the alternators charge the start batteries, and using an automatic charge relay, combiner technology, or something else was a more traditional option, but I have always disliked having to sacrifice something for that type of setup. In many cases, you have to choose a charging profile that matches both banks, or risk over/under charging one bank or another. There’s also issues with higher amperage charging when configured in either of these ways, as the connections between banks turns into a bottleneck.

There are several challenges with this design. First, you need to ensure that you have a way to protect the alternators in the event that the house bank BMS’es shut things off because of overcharging or other reasons. Not having that safety valve can result in your alternator being damaged when that happens. Second, to get the most out of the system with two alternators charging one battery bank, you need regulators on each alternator that can work together to ensure they are not fighting each other.

Balmar XT-170 dual foot alternator

Given how my Volvo Penta engines were made, there is not a ton of room for a bigger alternator without major metal work. The biggest dual foot alternator I could fit was the Balmar XT-170 series. They are capable of 170 amps, but I have them de-rated to 125 amps and have seen absolutely no heat issues. The XT series have only been out a year or so, and seem very well made. I’m not a fan at all of the plug in connector you see at the top of the photo – I would much rather have terminals or bolts or something similar that cannot be damaged. The length of wire provided with that terminal is comically short. Other than that, the alternators have performed extremely well the last 5 months in very hot conditions with little belt wear and very good performance.

Wakespeed WS-500 regulator plus two Sterling Alternator Protection devices

To protect the alternators, I used Sterling Power’s Alternator Protection Device on each alternator, ensuring that if there is some sort of spike or cutoff to the battery bank, that the alternators are as protected as possible.

To control each alternator, I used Wakespeed’s WS-500 regulators for each alternator, connected together using their CAN bus technology. They also provide a level of surge/spike protection as well, but their real benefit is outlined below.

Wakespeed WS-500 regulators

Wakespeed WS-500 regulator

The WS-500 is one of the main reasons my entire system works as well as it does while underway. There are two major reasons for this.

First, the two regulators are connected together, and are able to coordinate their efforts to charge the battery bank. This means they can adjust the charge rates to be the same, and ensure that one alternator is not doing the majority of the work, or fighting with the other. There are other solutions on the market that allow you to do some parts of this, but they are extremely complex (Balmar Centerfielder comes to mind with tons of connections) and are far more basic at how they deal with conflict resolution. The Wakespeed system actually exchanges data across an ethernet cable that connects the two regulators together via CAN bus, and can be upgraded, modified, and tuned.

The second reason is one of the core parts of why Wakespeed is so awesome – using voltage, temperature and current to make calculations about how to charge your batteries. I have mine using the same shunt my Victron BMV-712 uses to see the actual current coming into the battery bank from all sources. This combined with advanced and completely configurable charging logic finally brings the world of alternator regulators to the same level as an advanced battery charger. This is truly a revolutionary product, and one we have needed for a long time.

It has always surprised me that the primary method most people use to charge while away from the dock (alternator on an engine) has far less technology and control than any other part of your charging system. You end up relying on this system to do the bulk of all charging, yet it is not anywhere near as smart or safe as all of the other systems.

With the Wakespeed WS-500, you have a very intelligent system that looks at the same data as a standard battery charger and can control multiple alternators efficiently and safely.

I have a dedicated article planned on the installation, configuration, and usage of my Wakespeed WS-500 system that will be published very soon, and contain a lot more details.

Start and Generator Batteries

Since the alternators were no longer charging the starting batteries, I needed a solution to ensure the start and generator batteries were still charged both at the dock and underway. I found a very elegant solution in the Sterling Power DC to DC battery chargers.

These devices have been around a long while, and are not as used as I think they should be. They are full-fledged battery chargers with programmable profiles, completely isolating one battery bank from the other, and only allowing current to flow one way.

In my case, I have three of them – one for each starting battery and one for the generator battery. All three get their DC source from the house bank, and connect directly to each of the batteries to be charged. Since those batteries are Lifeline AGM group 31 batteries, I’ve customized the charging profiles to match the manufacturers recommendation to ensure long life and good performance.

The DC to DC chargers are set to charge when the house bank is 13v or greater, and do a fantastic job at it. Whenever the house bank is under charge, whether that be from the engines running the alternators, generator providing AC power to the Victron inverter/charger, or the Victron getting AC power from the dock, the DC to DC chargers are keeping those battery banks topped up.

It is also a one way relationship – the chargers can only ever charge the start/generator batteries, ensuring they are isolated from the house bank and never drawn down accidentally. I do still have a combiner switch at my main DC panel that would allow me to use power from the start batteries to run house DC loads in the event of a full house bank failure, but that would only be in emergency.

Some have questioned not using a higher amperage device like an ACR in the event my start batteries need lots of amps quickly. This issue was brought up as if I were in a dire situation priming an engine and needed to crank the starter for long periods of time. Based on my engine specs, I did the calculations, and I could crank the engine between 40-60 times for 10-15 second intervals before depleting one of the Group 31 AGM batteries. That seems like a lot of time, and I likely have many other issues at that point. Also, I have a second battery connected to the other engine, and can combine the bank if needed.

Charging theory

Taking all of the systems above, I focused on trying to design a very predictable, controllable, and safe charging system, which is usually where compromises are made when retrofitting a boat. Getting good quality DC power is much easier with modular busses, better cabling, etc.  High quality inverted and AC power is also pretty easy to do with various inverter systems from Victron and many other vendors. Charging is getting easier, but is still the hardest problem to solve well.

The key takeaways from this design are:

  • Each charging source is smart and uses voltage and amperage to charge the destination batteries according to manufacturer guidance as closely as possible. The alternators have the Wakespeed regulators with a custom charge profile while underway, the Victron inverter/charger has a custom charge profile, and the start and generator banks have a custom profile as well. At no point are there odd voltages or other badness that you would see with less accurate regulators, automatic charging relays, or voltage drops due to longer runs of wire between house + start + ACR.
Charging at 370 amps with both engines and inverter
  • Amperage is sent to the bank that needs it most, with appropriate protection. At peak charging rates, with both engines at 1000 RPM or more, and the generator on running the Victron inverter/charger, I can generate around 370 amps continuously.
  • Most charging comes from the engines, which already have to run while underway, and see very little impact from having to spin a bigger alternator. It also adds redundancy since there are two alternators charging the same bank.
  • Start and generator battery banks are isolated from the house bank, and have their own very predictable and controllable charge source that works both away from the dock and on shore power without fussing.

Battery Choice

One of the biggest choices in the design was the type and size of LiFePO4 batteries. There are two major types to choose from – dedicated LiFePO4 batteries like the Victron 300 amp hour one I used on Grace which require an external BMS, and “drop-in” LiFePO4 batteries with built in BMS and other tech. Both types have their pros and cons, and have varying costs.

Victron 300 amp hour LiFePO4 battery that I used on my previous boat

Standard LiFePO4 batteries usually have higher charge/discharge rates, are made in more form factors, and generally have more monitoring available via connections to the cells or on-board chips. However, they require an external BMS of some sort which can add a lot of complexity. In addition, they almost always require some sort of cut off device, such as the Victron Battery protect, which adds even more wiring, terminations, and complexity. These types of batteries are also more sensitive to charging rates, and can be slightly to excessively more expensive than drop-ins, depending on the brand.

Drop-in batteries are usually made to standard form factors and are easily added to an existing setup without changing other equipment around it, including your inverter. They do not require a BMS since it is built into the battery, nor a cut off device as that is factored in as well. The major brands have large communities of people who are using their products in multiple industries, and seem to have excellent track records. On the con side, these batteries have much lower charge/discharge rates which you need to plan for in your design, have simpler BMS’es built into the battery that can become a problem in some situations. There are also concerns from the industry that drop-in batteries won’t last their listed 3000-5000 discharge cycles, but I am not sure if that is true, or just non-drop-in battery companies trying to market you their products.

After months of investigation and consultation with a number of vendors, I decided on Battle Born 100Ah 12V GC2 LiFePO4 Deep Cycle Batteries for my design. Battle Born has one of the largest communities of users I could find, excellent reviews from tons of people who use them, and really awesome customer service that put up with my litany of questions via email and on the phone prior to purchase.

Their specs matched my design which include a 100 amp discharge and 50-100 amp charge rate per battery. The other huge plus was their form factor, which matched my existing golf cart battery size and space. This cut down on building a new enclosure and made wiring and install simpler.  I could have literally bought these batteries, and nothing else, dropped them in, and had 200 amp hours more capacity without doing a single other part of this project.  I still would have had slower charging than I would have liked, but this is a huge point in favor of drop-in batteries as a solution for weight/capacity issues.

There were a number of other nice design features, including having the offset terminal connections on the top of the battery at one end, which also had a slight depression so that your cabling could be run in a way that it wouldn’t exceed the overall height of the battery. There were also molded sliding strap holders on the side of the batteries to help with installation and removal.

One other thing to consider with drop-in batteries is shipping. I’ve found that anything less than 100 amp hours can be shipped by normal FedEx or UPS methods, although it still uses the ground versions of those shippers, so it can take 3-5 business days to reach you. The larger Victron, Lithionics batteries I’ve ordered take multiple weeks, if not longer, to ship, and usually can only be delivered at a loading dock via shipping companies that can be challenging to work with. If speed or shipping locations are a challenge for you, drop-in batteries including Battle Born may be a better option.

Final Design

Final system diagram – note that control connections, fuses, switches, and the entire negative bus have been omitted for display simplicity

The whole system is as follows:


The author in his element

Installation happened over a 2 week period and included a few additional detours. I had already removed the two hulking 8D start batteries, and slightly less hulking 4D generator start battery after they failed. The new Lifeline G31 AGM starting batteries were already in place, being charged by a temporary AC-based charger.

Old house bank coming out

The first challenge was getting the old and heavy 6V golf cart house bank out of the engine room and off the boat. Each of these weighed close to 80 pounds, and required multiple lifts to safely get them out.

The new Battle Born 100 amp hour GC2 sized batteries were only 31 pounds, so much easier to move around and get into place.

Test fitting the Battle Born batteries

I ended up re-using the existing battery box, as it was in OK condition. Longer term I want to remove this box, and the one astern of it that houses the two Group 31 Lifeline AGM starting batteries for the main engines. If I redesign this to a much larger sectioned box, I could get 2-3 more 100 amp hour batteries in the space to increase my house bank, or use the extra space for something completely different.

Marinco Pro Series busses, fuses, and switches – early version of the layout

I leveraged the Marinco Pro Installer Series busses and fuses to create proper fusing and distribution for the alternators, house bank, inverter/charger, and DC distribution. Prior to this, it was simply cables without fuses in most places, which was the way boats were built back when Rendezvous was originally set up, but I wanted it to be as current as possible.

Victron MultiPlus 3000W inverter mid-install

I rerouted the main AC input through the Victron inverter/charger. This allowed me to control my entire 30 AMP connection from one place, and use load sharing and other features which will prevent me from tripping the shore side breaker. It also could allow for automatic generator start/stop in the future, if I want to get to that point.

I should buy stock in Ancor….

I also replaced the main DC house wiring from the battery bank to the main panel. It originally ran from the front of the engine room to the back, along the port side of the boat, and then crossed over to starboard where the main DC distribution is. I estimate this was about 35-40 feet of length. I was able to cut this down to 10 feet by going directly from the new distribution to the DC panel. This reduction in cable from the house bank to the panel, and the higher voltages that the LiFePO4 batteries output in general meant a more consistent and higher overall voltage to all DC devices, which is a good thing for pumps and compressors and lights which all should last a bit longer and perform a bit better with this more stable supply.

One big change was how AC wiring was handled. Those devices running off of the inverter were on a separate neutral bus which was combined with the non-inverted devices when needed depending on the original Magnum inverter and its current state. This is pretty easy to achieve in theory, but I found 4 different plugs/devices on the boat when I bought her that were not on the right neutral bus. That meant that either those devices didn’t work, or in one case, it worked very weirdly/poorly. Having all AC power run through the inverter means that split bus could be eliminated, simplifying the entire system for any future changes.


The biggest result has been the increased capacity of 600 amp hours provided by the Battle Born batteries. We have doubled the time we can be at anchor without major charging.

This has meant less time charging with the generator while at anchor, and more peace of mind – I don’t have to keep nagging people. With the old system, we could barely get a day at anchor, mainly due to the size of the bank, but also given that we were never really able to charge it fully. While we had 420 amp hours with that design, we rarely were able to use more than about 300 amp hours on  trips without having to charge excessively long to get those last few amp hours. With the Battle Born batteries, we’re able to use that whole 600 amp hours of capacity.

Victron VRM app showing deep state of discharge for the warmer days

Several times this summer on one of my longer trips, it was 90F outside during the day, and we had the primary fridge/freezer, secondary freezer, ice machine, and lots of other smaller loads all running off of the inverter. Because the boat got so warm inside, those appliances ate up tons of power keeping their contents cool, which we all appreciated. Several times we went through a whopping 400 amp hours of power in a day because of those appliances plus all of the electronics, TV, coffee and espresso machines, lighting, and deep-into-the-night activities with the music, etc. That is definitely not the norm for our usage, but it didn’t pose a huge problem the next morning – we always had at least a 2 hour journey on that trip, which meant things were charged back up very quickly. The main reason this was possible was the higher output alternators combined with the Wakespeed WS-500 regulators.

Having come from sailboats for the last 20+ years, seeing a boat draw 200 amp hours a day, let alone 440 is still quite a shock to me! Even though I have a very convenient and quiet generator that can charge things quickly and keep my floating apartment comfortable, I am still, and will likely always be, a power miser, and always looking for ways to improve overall electrical performance and reduce what we use. Still, 440 amp hours!?

Victron VRM showing 320 amps of charging for a bit over an hour

The second biggest change is the charging time, which is directly linked to the Wakespeed setup + larger alternators + house bank charging. It has been simply amazing how efficient the Wakespeed regulators are, combined with the 170 amp dual alternator setup. We can go from an almost completely depleted bank to a fully charged house bank in around 2 hours of motoring time. If you throw in the generator as well, which uses the Victron inverter/charger to send 120 amps into the mix, it cuts that down even more. We routinely would be running the generator anyhow to power the water maker, and my preference is to load up the generator as much as possible to get the best result out of using it, so it was adding to the charging as well.

I can’t understate the night-and-day difference of the Battle Born batteries combined with the Wakespeed regulators + Balmar alternators. What used to be a system that I would monitor constantly – watching usage during the day, yelling at the random person for leaving a light on, running the generator extra long, and urging the charger to get that last 10% on the flooded batteries – all of that is gone. I now know that regardless of how low we get our house bank, it can get back to a day’s capacity in less than an hour of motoring, or a bit more with the generator. That is a huge weight of my mind, and allows me to focus on having more fun!

SIgnalK dashboard showing various things including data from Color Control GX

The visibility is also exactly what I wanted, with the Color Control GX showing me everything I need to know about the house system, and keeping an eye on the voltages and health of the start and generator banks as well. Having this information in real-time while on the boat, and remotely via the Victron Remote Monitoring Portal is perfect. I’ve also configured various alarms both on-board within the BMV-712, and in the VRM system so I am always aware of critical situations wherever I am. I’m used to this from other Victron projects both on Grace, Jammy, at my family cabin, and for other customers, but it is still nice to have it again, after 6+ months without!

You can view Rendezvous live data on Victron’s VRM Portal here. When I’m at the dock, it is pretty uninteresting, so change the date range to see times away from the dock, charging rates, etc.

The peace of mind in isolating the start and generator batteries is also very appreciated. Instead of having multiple charge sources for these critical banks, everything is simplified and treating the batteries very nicely.

Overall, I feel that this system has addressed my goals of having more capacity, better monitoring, redundancy, and more simplicity than some of the other LiFePO4 systems I’ve worked on and installed. I’m looking forward to more time away from the dock without worrying about my power system! ?


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38 thoughts on “Victron + Wakespeed + Battle Born power system”

  1. Another great project write-up: thanks Steve. I had not heard of the Wakespeed regulators before but have read up on them now. Looking forward to your dedicated write-up about these. I have Balmar MC614 regs with a CenterFielder II, putting the charge from my two different alts to my House bank. The Wakespeed looks like an attractive option if one of these three components fails. In place of dedicated Start batteries, I have a ‘cranking bank’, comprising a pair of Optima Spiral Wound AGMs. This bank starts the propulsion engines and runs the windlass, davit and bow thruster. I have a single identical Optima for the genset Start….though I often combine this to make a 3-Optima cranking bank. The cranking bank and genset Start are charged by 2 x Balmar DuoChargers: not as good as your Sterling solution, but OK.

    I was also interested to see you chose to stay with the Victron battery monitors. I am a Victron fan and like the ColorControl GX and their remote portal, but were you tempted to also bring in the Balmar SG200 gauge, which seems to have more smarts??

  2. Steve: I also took a look at your Victron Remote monitoring page. What is the load that is switching on regularly (every 3 hours?) that creates that uptick?

    • It is a great app you can install within SignalK called signalk-venus-plugin that is written and maintained by Scott Bender. You can see details on the project at….

      The install steps include changing a configuration file on your Color Control GX, rebooting it, and then putting it’s IP address into the SignalK plugin.


      I have been using this plugin since it came out 2+ years ago and am always shocked at how much data there is in the CCGX. It’s nice to have an option to have it all show up locally on other displays. In addition, using some additional plugins in SignalK, you can take some of this data and put it back out onto NMEA 2000 so that other chart plotters and instruments can use it. This saves me having to buy a NMEA 2000 interface for the CCGX, and also allows me to put some data on the bus that Victron doesn’t currently support.

      You can also combine it with another plugin for InfluxDB and Grafana and end up with a local database of all of the data, along with beautiful dashboards that include graphs and many other things.

      Scott actually is the author of another project directly for Victron that combines all of this together in a quick-to-install package on a Linux machine. It is essentially a way of having a lot of the data from VRM locally on your own system and can be found at

      I run it as well, and it has beautiful dashboards too.

  3. Hi Steve-your comprehensive write up on your electrical upgrades was a good read and review. It was interesting to read your issues with the Pronautic charger as I had replaced my factory installed Cristec charger last year (after it stayed in boost mode for over extended period frying multiple batteries) with a new Pronautic. I have new wet cell deep cycles and This past summer I have been plagued with the Pronautic going into and staying in a high charge(14.6-14.8 v) for extended periods. A reset of the AC to the charger puts the unit back in float mode but it is disappointing a less than 1 year old item is not functioning properly. rgs. RC

    • Sorry you’re having problems with your charger! Just to be clear, my problematic charger was a ProMariner system that was 10-20 years old. It had issues with overcharging that were apparently something that happened to it as it got old, as others have documented.

      I had a ProNautic charger that I used to replace it, and never had any issues with it. In fact, I’ve used ProNautic chargers in the last 3 boats I’ve owned, and in other installs without any issues, and consider them to be one of the best chargers on the market. I would definitely contact the manufacturer or store you purchased it from as they have a great warranty and customer support.

  4. Hi Steve – Very interesting article, and some interesting hardware that I don’t see much about from other sources. So many questions!

    1) Your genset – is it 8kw or 9kw? The original listing data on your Rendezvous webpage shows it as 8kw. Either way, I’m curious, as you say the boat has only a single, 30A shore connection. Typically that configuration would be sized with a much smaller genset, as even an 8kw unit outputs 66A of AC current – which is pretty hard to take advantage of through a single, 30A AC Main breaker. Have you thought about this?

    2) Also concerning the genset – you have obviously gone to great lengths to design a system that provides accurate charging profiles for all banks, without “odd voltages or other badness that you would see with less accurate regulators, automatic charging relays” or different sources “fighting each other”. I applaud you for that, and I share that goal, as I see a lot of systems where those issues are ignored. But did you forget about the genset’s built-in DC charging? In your case with the Onan, I believe its an alternator with an external, fixed-voltage regulator – and any time the gensets running, it’s trying to re-charge it’s connected battery with some amount of DC charging current. So that’s “fighting” whatever the Sterling DC-DC charger is doing, isn’t it? I’ve thought about this before, and the obvious workaround seems to be to disable the generators alternator output – probably as simple as removing a fuse – but you don’t mention that in your write up…

    3) Costs – most of your articles are pretty good at considering the cost/benefit – but I don’t see anything here. Am I correct in assuming yoru batteries alone were close to $7,000 including tax and shipping?? That’s some serious coin, at least for some of us.. I get the unique advantages of LiFePO4 technologies, but I’m not sure many of us will be alive long enough to take advantage of 5,000 cycles, etc…

    • Hi Grant,

      Thanks for your questions, let me see if I can answer below:

      1. The generator is actually 8Kw – thanks for catching that. I’ve updated the text in the article, and will update the diagram when I next do revisions. While I have a 30 amp shore connection and separate breaker, I have a 70 amp AC breaker for the generator, and between those two a selector switch rated at 100 amps AC.

      The only manual things I have to do is to change the selector switch to generator while out and about, and change the maximum current in the Color Control GX to allow a higher amount for the generator. I am considering automating this later this year, but it doesn’t happen that often, so….

      2. I have disconnected the generator alternator circuit from charging the generator start battery. I rely on the DC-to-DC charger to do this. In an emergency, I can reconnect this if I want to. However, I’ve found that older generators aren’t the nicest things to charge their own starting batteries.

      3. When it comes to LiFePO4, there can be much higher costs than traditional battery systems. I think I talked about some of it with Grace, my sailboat that had a big Victron system as well.

      While cycle count is definitely something to consider with LiFePO4, there are many, many other things to factor in to a decision around this battery chemistry type. Weight and space are usually a big factor. In my case, another set of factors is charge rate and total charge time.

      Taking into account both charge cycles, even if they are only half of what is advertised, constant voltage being supplied, much higher charge rates, and a fast charge time, that makes it financially worth it to me, as I spend a lot less time fussing with things while using the boat.

      I think as we see LiFePO4 banks age, we won’t see them go for 5000 cycles because of other factors – overcharging, heat, or just general use – just like flooded batteries don’t last as long as the specifications cite. However, I do expect that these will last a lot more cycles than flooded, and provide a more consistent, predictable result.

      In terms of costs, I spent around $6500 on the batteries, easily $2000 in wire, fuses, switches, and other things, about $500 on Sterling stuff, and around $2000 on Victron equipment. I’ll detail out costs on the Balmar+Wakespeed stuff in a future article.

      Hope this helps!

      • OK Steve, thanks for the quick reply, as always. Obviously you had already considered the genset alternator charging issue, and disabled it. That’s what I would have done as well.
        The Battleborn batteries are impressive in many aspects, no doubt. The GC2 form factor is going to make them really attractive to anyone considering a retrofit. I’m still leaning towards the Group 31 Firefly’s, at about 1/2 the cost, but my needs are not anywhere near what yours are. I’m curious – do you plan on going to 100% DOD with the LiFePO4 bank? I know they advertise that – not sure it’s necessarily a good thing…
        I’ll look forward to future postings on your complete system. Still not sure how the AC sources are wired. You mentioned a 70A breaker for the genset, but the diagram shows a 50A breaker – which I believe is the maximum recommended for the Victron’s AC input. Still seems odd to me that OA would install that large a genset, when the boats original AC panel could only accommodate a single, 30A main breaker and bus. Maybe it was retrofitted along the way somewhere….

        • I absolutely will be discharging them to near 100% – that’s one of the main reasons I purchased LiFePO4. On Grace, I had a 300 amp hour Victron battery, and discharged it very deep all the time. That’s one of the main attractions to LiFePO4. There’s nothing wrong with doing it, as long as you understand how to charge them correctly.

          The generator and panel are original, along with the breakers. OA put a 30 amp 110VAC shore breaker because that was the most popular at the time. Any bigger and you need to go to 220VAC which adds its own issues. The main AC panel can handle far more than 30 amps. The only 30 amp piece is the shore breaker. The generator has either a 50 or 70 amp breaker (now you have me wondering if I got the amperage wrong) but I only run it to 50 amps regularly.

          This isn’t unusual – I’ve seen this config on other boats of this era. What many people have done is wired in a second 30 amp shore connection for non-essential loads, and left the first 30 amp connection for the inverter/etc. I don’t like that as it creates some challenging issues for neutrals, grounds, etc. Maybe in the future I will put in a bigger shore connection, but I haven’t needed one yet. It is also nice because it is a smaller cable than a 50 amp connection.

  5. On the negative side of this diagram, are your starter batteries tied into the same negative as your house? I’m trying to implement something very similar to this, but I get very divergent suggestions on isolating the battery banks and having them on the same system. I like the idea of DC-DC charger which sort of treats them as a subsystem. Just wondering if they are combinable.

    Separately, but related, where do you wire your windlass into?

  6. Great job on this write up Steve! Can you tell us more on the battery wire crimping? What tool do you use? I remember you used to order them online?

  7. Great articles! I’m considering switching my house bank to lithium. I have a 190 amp alternator and the original 90 amp alternator on my single Perkins diesel. Would it be beneficial enough to have those two just charging the house bank in a similar way to how you have done it, or would it be simpler to have one charge the house and the other charge the start?

    • It really depends on a number of things – here’s what I can think of off the top of my head:

      Bank sizes – can your new house bank handle 190+90 amps?

      Chemistries – is your start bank going to remain some other chemistry? It might be easier to use a DC-to-DC charger like I have since your start battery bank likely won’t need a full 90 amps of charging capability all the time.

      Charge control of alternators – are you planning on using a Wakespeed, Balmar or other system to control both of the alternators? If not, you may not get much benefit in combining both of them to charge one bank, or they may be inefficient. Worst case you could be charging at funky voltages if you don’t.

      Also can your engine handle that much on the alternator side? How big is it? You might not be able to do either route depending on it’s size…

      In theory my configuration could work for anyone’s setup, but you want to step through a bunch of the pros and cons to make sure they all apply to your engine and bank sizes.

  8. My potential setup is very similar. but in addition I have a AGM battery for my thrusters. How much charging output can those Sterling DC to DC chargers output?
    I want to recharge that thruster quickly after use. Generally they dont recommend putting the thursters on the same house battery setup as the voltage drop off on use can damage or turn off other electronics like the chart plotter – otherwise I could bin the thruster battery and just build a bigger house lithium setup. perhaps this is a non issue with a decent lithium? – it would certainly simplify my boat setup: 3 house battle borns + 1 AGM start with the Sterling charger.

    • reading victron website: they suggest not putting the thruster on the house with BMS and lithium as sudden disconnects can be a problem for manoevering and also thruster power spikes are bad for the electronics. therefore I have left with 1 engine, 2 house, 1 thruster. it looks like the Sterling battery charges can charge about 25-18Amps 12v to 12v. thats a pretty heathly charge rate. with your set up do you see the watthours flowing on the control GX due to the sterling chargers? i assume yes because they are wired downstream of the shunts and not direct to the batteries?

      • If you’re using Victron batteries and their BMS, I could see how that might be more likely. The safe way would be to have a separate thruster battery – it could even be LiFePO4 so that you could charge it at higher rates. I’d get a bigger DC to DC charger if that was the case, even the 60 amp one, and that way it could charge back up quickly so while you’re maneuvering, it would catch back up as quickly as possible.

        You also should think about your charge sources while maneuvering or underway – are your alternators big enough to charge the house bank at say 100 amps, so that the DC to DC charger can use 60 amps of that and send it along to the thruster battery. Doesn’t have to be that way, but if you have smaller alternators, you could be taking quite a bit of house power capacity.

        I have my windlass connected to my house bank (it was wired this way originally) and I’ve used the Orion DC-to-DC converters to provide a stable voltage to critical electronics. That was required with the older flooded battery bank as it would sag to 10v when the windlass was under load. With the LiFePO4 bank it isn’t required anymore.

        Everything is wired downstream of the main shunt. I always recommend that, and all of the manufacturers do too. Without that, I could have devices pulling power from the bank and not know my total amp hour draw which would mean potentially taking the batteries down lower than I would want, and having the BMS’es trip and disconnect things.

        So yes, I can see the power flowing from my house bank to the start/generator banks via the DC to DC chargers. It’s really not that much because the start batteries for both are only used a tiny amount when you’re starting things, and then at that point I either have alternators spinning (main engines) or an AC charger alive charging (generator) and they offset anything being taken by the DC to DC chargers.

        I just helped someone locally add several DC to DC chargers for two thruster banks and they see the draw a bit more of course while they are using the thrusters, but are much happier with the setup compared to their original design.

    • I know a number of people who use DC to DC chargers specifically for thruster and windlass battery banks. In fact, the first time I ever saw them was in that application years ago. Sterling has quite a lot of different options for DC to DC chargers, including other voltages besides 12v – . They have one that goes up to 60 amps which is equivalent to a very big AC battery charger, which would work well with a quick discharge bank like a thruster.

      Victron also came out with something similar recently, although I have not used one. They don’t appear to have as high amperage though.

      I could see combining a house bank and thruster bank, but the trend is definitely to keep them separate. You may still have sags and spikes, although with LiFePO4 not anywhere near as much. I run my windlass off of my house bank, and compared to what it was like with traditional batteries, it is super stable now. Previously, I would have things rebooting everywhere.

      • Steve, what is the victron product you would have used instead of the battery to battery charger? What about Blue Sea ACR? Do you think it would have been bad for your starting batteries?

        • Victron has a series of DC to DC chargers at but they weren’t released when I built my system, or the one that had a 3 stage charger had just come out. They are also pretty small in terms of overall amperage for those looking for a larger unit.

          An ACR has a number of downsides in this situation. First, it does not have a charge profile and just connects the banks together. This would mean that the start batteries would be charged the same way as the LiFePO4 house bank or vice versa, which I wanted to avoid. Second, the ACR just combines the banks, so the current could flow either way. If the house bank got super low, it could steal capacity off of the starting batteries, which I was trying to avoid with my design. The DC to DC charger only allows current to flow one way – from the source battery – in this case my house bank – to the bank to be charged – the start bank.

  9. Hi Steve. Great writeup. I’m wondering how you handle the back EMF if the lithium batteries cut out under load? You have protection for your alternators for when they cut out at full charge. Is there some protection you have for your electronics if they cut out from excess load from a back EMF prone load like a windlass or a water pressure pump? Obviously you have the load capacity from the batteries but maybe not if you were running them to the floor and then your water pump kicked in as you were bringing up the dingy.

    • I’ve never really had a problem with this, as I designed the system where full cut out would only happen in a catastrophic situation. The two most likely I can think about right away are either if I deplete the entire battery bank, or if I draw more than 600 amps from the bank continuously.

      Drawing more than 600 amps (6x batteries each with 100 amp capability) would be hard to do for a couple of reasons. First, my inverter could never exceed 350 I believe (I don’t have the details in front of me) and the rest of my loads aboard couldn’t get to 600. Second, I have a 500 amp fuse between the main battery bank and anything external, so that would blow.

      If I draw the batteries down to near dead and they cut out, they would cut out one at a time, not all at once, due to how they are wired, and not only that, but alarms would be blaring for quite a bit before then as I have them set to go off at 5% SOC. That includes remote alarms, emails, etc.

      Even so, I have most of the critical electronics on voltage regulators already, so they would likely be protected.

    • One other thing to note – since they are lithium, even if they are at 5% SOC and I pull a ton of amps from them with the windlass and other loads, they’re not going to sag or cause other issues similar to traditional batteries. Even so, with the size of the bank I have, I doubt I’d ever have 600 amps of continuous load for any amount of time to cause this.

      • I think what you are saying is if your were at a low but not alarm level SOC one morning and you fire up the 120A anchor winch and then the 40A water pump kicks in that the discharge profile of a lithium battery is such that it won’t trigger a cutout of one battery that cascades into the rest. The other source of such an event would be the early morning espresso machine/toaster combo on a low but not alarm level SOC but the low voltage cutout of the inverter should be set to shut the inverter down before the last battery decides to say goodbye.

        • That is correct – it should not cascade as far as I can see, but anything is possible, and I have been wrong before!

          The inverter is set to shut off before SOC reaches 0%, and the inverter itself can’t draw the maximum from the batteries anyhow. It would have to be the espresso machine + microwave + both electric heads + windlass to even get close.

  10. Because of the high voltage of lithium batteries most dc to dc chargers will be always on and act as a parasitic load at anchor since the voltage needs to drop below 13v for them to go into sleep mode. Did you put In a switch that would turn them on with ignition when cruising versus full auto for when you leave the boat at the dock with the ignition off and the chargers on?

    Another question is what do you think of hybrid lithium SLA battery setups? One example would be adding a small SLA in parallel to your battleborns instead of the sterling alternator protection as a way of always having a battery in the system regardless of the lithium connection state. I’ve seen this recommended but the issue of having a full SLA seeng 14+v charging current from an inverter that can’t see CAR like the WA500s can is not discussed and would seem an issue.

    • I am using DC to DC chargers that you can program more specifically. I don’t have them keyed off of ignition because I am OK with them continuing to charge the start and generator batteries to make sure those are always ready to go. The draw from them is minimal when float charging.

      I did look at using a battery of some type instead of an alternator protection device, but it got more complicated, as you mention. I felt with the WS500s being able to control the alternators very aggressively, combined with the APD, that I had a good solution with minimal complexity. A lot of the Lithium designs out there are very complex (see my previous sailboat and it’s setup at that there are more problems with various components failing or in other ways as a result of the complexity.

  11. Do you see much in the way of voltage fluctuations from sudden loads when the battleborn’s are offline because they are full so your hotel load is supported from the alternators or the alternators and the inverter? Do those charge devices do a good job keeping constant voltage under quickly changing loads? Or is it the case that, like agms, battleborns rarely get full and go offline except at the dock when they’ve got hours to get that last little bit in.

    • The Battle Born batteries are true LiFePO4, so they don’t have the same properties as AGM or flooded batteries where they take much longer to charge the last few percentage points. They charge right up to 100% very quickly. They never take hours to top off, which is part of the reason people choose LiFePO4 and other similar technologies – the ability to charge up quickly, and not keep things running for hours afterwards charging at very low levels.

      The WS500 has software/behavior built in that watches that final run up, and will of course adjust the charging profile based on the manufacturers recommendations, which in turn modifies how the alternators behave. There is also the Zero Output feature which will supply house loads from the alternators instead of discharging the batteries. I’ve seen no voltage drops or dips in combination with that feature, the WS500 in general, and the alternators. In fact, I did some testing with larger loads and noticed no issues at all, and quick response from the alternators ramping up to cover that load. I’m sure the batteries were covering the initial few seconds while the alternators spun up for the larger tests I did, but I noticed no voltage fluctuation at all.

      • Wow! I”m impressed how well your setup works and how much of the complexity you’ve cut out. Nice design job.

  12. Just ran across this and took in a lot of information; excellent and thank you.
    We have been planning a Lithium/Victron fully integrated system very similar to yours however using two Victron Quattros in split phase to provide our needed 240VAC to run the two forward AC units. Integrated also with our design is an AGS which will operate the Onan generator based upon the vessel loads and SOC when off shore power.
    The question I have is why didn’t you also use the BattleBorn batteries for start batteries? It seems as you have a capability of 1200 amps for 30 seconds (provided the cabling could support) these could easily be utilized for starting thus greatly simplifying the alternator charging system. We have two Cummins QSM11 660HP engines and the measured cranking amperage is 360 amps with an average start time less than 5 seconds.

    • Hi Tom,
      It sounds like you have a nice system planned.

      I didn’t use my house bank for starting the engines for a few reasons. I did that on two other boats and wasn’t happy with the potential issues using the house to start brings – mainly that you could potentially run the house down so far that starting the mains would be impossible, or require charging from the generator to get to a point of being usable. There were also more opportunities with one bank to have voltage drops when too many things were going on – starting things while using the windlass, etc.

      Building a LiFePO4 start bank that was big enough to be safe to be used for starting would be expensive. The two Group 31 Lifeline AGM starting batteries I have were about $450 each, which is less than half a 100ah LiFePO4 battery, so I really couldn’t justify that cost just for starting batteries.

      I did the same calculations you did for my 1988 vintage Volvo Penta TAMD61A engines, and it is pretty similar. They generally start almost immediately, but I was also concerned about having to crank them a lot if I was, say, bleeding the diesel lines, or had some other unexpected problem. Having that dedicated bank makes me feel pretty good, and also a dedicated G31 for the generator that is never touched.

      There are some folks I’ve chatted with who are looking at or actually using capacitive power supplies to do the starting side of things, which charge off of the house bank and offer a lot of cranking amps for a short period of time, and are a lot smaller, cheaper, and more reliable than a battery. I haven’t looked into those much myself, but that seems like something I could add in later on.

      I don’t think the charging system is that complicated – I think it’s easier and simpler than some of the dual alternator, dual bank charging setups I’ve had before, with echo chargers, combiners, ACRs, and other things in between. Now all I have are two DC-to-DC chargers that pull power one way only to the two battery banks, and there’s really no way to have them do something stupid, where combiners and switches in the past actually did more in my case…

      I definitely would love one big bank for everything if I could guarantee not draining it too low or not having some sort of failure that left me without any battery capacity at all.

      • Thank you; valued data.
        Regarding use of cap banks for starting; we looked at Maxwell Start Modules and also had technical discussions with them. They are a good option however only good for about a 20 second crank then they need recharging which takes between 20 and 30 minutes. Not really good for those fuel purging times…. They are, however, good for millions of cycles.
        We will have a rather large battery bank at 1000Ah and the system will start the generator (which is on a separate Gp27 lead acid battery) at 80% DOD. My calculation provides for an emergency margin of 10% of the battery bank for starting (80% DOD to 90% DOD) which is essentially about 100Ah without any significant voltage drop. The inverters will cut off at 80% DOD as the generator will be providing power. If the generator fails to start the inverters will still cut out. This should give a total crank time (in my case) of around 500 seconds (1Ah per 5 seconds at 360 amps cranking).
        Good point on the windlass current; we never pull the anchor up without the mains running, however, I have let out more chain without them running so I need to account for that current; I don’t think running chain out is much however.
        Again, Thanks

    • Hi Owen,
      I mention one of the main reasons why in the article – simplification. When using traditional (non drop-in) LiFePO4 batteries, they require a BMS and other components for a successful install. You’ll see those in the design and install on Grace. In particular, the safety cut offs that had to be everywhere on the loads and charge sources increased the complexity and wiring. Drop-in batteries like the Battle Borns have that built in to each battery.

      There are many debates as to which approach is better – both have merit, and I wanted something simpler.

      In addition, Victron batteries are funky sizes, not really conforming to any marine standard. I had existing GC2 (golf cart sized) 6V batteries, and Battle Born makes a drop in replacement size-wise, which made things a lot easier in the physical design.


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