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  • Adam Morris

Connie's Lithium Powered Electrical System to WFB (Work from Boat)

Updated: Dec 2, 2023

Note: I/we are not sponsored by any companies mentioned in this article. We cruise full time on our test bed, SV Confianza, and we enjoy sharing our tests and opinions to give back to the community.

In order to work from boat, we need a stable power system that gives us household like reliability.

After publishing this (and a few comments from readers), I realized that it's quite the long post, so I've added a table of contents:

Original Lead Acid Setup Nowhere Near Adequate

Our 2004 Privilege 435 came equipped with traditional lead acid batteries. 5 100ah lead acid for the house bank and two LA starter batteries. We had a northern lights generator that had roughly a million hours on it, and was acting up.

The two stock alternators would give us some charge, but quite slowly. The problem with charging lead acid is that it takes forever to reach full charge because of the absorption phase.

Since LA batteries should only be discharged to 50%, our house bank capacity for all of our electronics was only 250 amp hours. The fridge and the freezer alone could easily chew through this, and our limited solar was definitely not enough to keep up.

Then when you add 3-4 laptops, 2 iPads, 3-4 cell phones, wireless earbuds, etc, we could chew up our whole bank in a half a day.

Before the transformation, we could be in the middle of a video call, low battery light on the inverter clicks on, and be figuring out whether our calls were "starting the engine" friendly.

Additionally, many of Connie's systems were wired straight to the generator (or shore power) and required 220v @ 50hz. That means, in the USA, we could only run the air conditioners, the water maker, the washing machine, and the hot water heater when the generator was running.

We wouldn't dare use any high loads off the batteries. Toast was made in a pan instead of a basic toaster.

Time to rethink the whole system!

The New System

I know many folks reading might already have done a decent amount of research around lithium conversion projects. If that's you, we'll dig right into what we're using. And, if that's not you, keep reading for further explanation of why we made the choices we made.

System Main Components

4x 100ah 12v Battleborn Lithium Iron Phosphate (LFP)

1x 100ah 12v Zooms Lithium Iron Phosphate (LFP)

2x Standard Marine Starter Batteries

2x Balmar XT170 Alternators

2x Wakespeed WS500 Alternator Regulators with Shunt and Temperature add-ons

2x 150amp Load Dump Protection & Stay Alive Relay Solenoid

4x Littelfuse High Amp fuses with holder

2x Sterling Alternator Protection Device

2x Victron SmartShunt

1x Victron Multiplus 3000

2x Victron MPPT 100/30

14x 50watt Sunpower Flexible Solar Panels

Other Accessories of Note

6x Legrand Radiant Tamper Resistant Ultra Fast USB C Outlet

Wiring Diagram

Attached is a PDF Diagram of the main components for reference

Confianza DC schematic
Download PDF • 677KB

Household-like Power Version 1.0

Staying with 12 volts

There are many advantages to upgrading to 24 volts or even 48, including more efficient charging, lower cable gauges, and reducing amperage / risk of heat, to name a few.

However, the goal was to keep the system simple as we experiment with what works and what doesn't. We may outgrow this system at some point and switch to a combination 12/24 volt or 12/48 volt system in the future, but for now, we are very happy with the setup.

Why Lithium instead of Lead Acid, AGM, or Gel?

1. Fast charging capability - There is no long absorption phase. The batteries take as much energy as you can give them immediately (as long as you stay below the recommended C rating). We charge at 0.25C to maximize the life of the batteries and minimize complexity, even though Battleborn says up to a 0.5C rate is fine.

If we wanted to go up to a 0.5C rate, we would have had to go with large frame alternators, and thus more modifications.

2. Higher capacity - Lithium Batteries can be discharged at least 80%, while lead acid batteries should only be discharged to 50% to prevent damage. That means for the same number of batteries, we get 400 usable AH vs 250 usable AH. This allowed us to keep the same battery boxes in the same location and still provided a 60% increase in usable capacity!

3. Charging cycles - Working from boat means that we are cycling these batteries a lot. And the Battleborns are rated for 3000-5000 cycles. If we drained the batteries every single day, we should have over 8 years out of these batteries. Lead acid batteries, on the other hand, are usually rated for 1000 cycles, and that's only if you treat them properly.

4. Voltage drop - If your traditional lead acid batteries are not anywhere near full, a high load such as a windlass or even a toaster will sag the voltage low enough that it could effect certain electronics. I've had my chart plotter restart a few times with traditional batteries at very inopportune times.

Are There any Negatives?

As you can see, upgrading to Lithium is the best way to achieve the household-like power that we required for working from boat full time. To make this happen, we've got to make a number of upgrades to accommodate the LFPs. So let's examine the negatives of an LFP setup.

Cost - The batteries themselves are basically a wash because of the extra long life, but it is a higher initial investment. A Battleborn 100ah will run about $875 each.

I am experimenting with a MUCH cheaper direct from China brand called Zooms for the 5th battery in an attempt to do a long term comparison test. I picked it up on Amazon for $325. I chose the Zooms battery based on a good tear down done by Will Prowse -

So at $325, the cost should be settled, but now we'll have to look at the additional modifications and equipment that we will need to deal with the LFPs

Upgrading to Lithium Requires Multiple Changes to the Charging Systems

Don't be misled by the companies that advertise their batteries as "drop in replacements." That might simply refer to the size of the battery and the cabling, but that's where the "drop in" part ends.

LFPs can not use stock alternators to charge as they are set up. The original 60amp stock alternators were not set up for external regulation and would burn up.

Because the LFPs do not have internal resistance like Lead Acid, the alternators run too hard and the diodes burn up. I've torched a few alternators in my experiments.

So, you could take your stock alternators to an alternator shop and have them modified for external regulation for pretty cheap. Or, if you're so included, you can do this yourself.

However, two 60amp chargers that are regularly down regulated to likely 30amps continuous duty would not meet our needs for charging efficiently. If the bank was depleted, I would have to run one engine for almost 17 hours to fully charge.

Let's bring in some bigger fire power.

Balmar XT-170s

We originally tried the CMI AMP-IT 100 amp ERV. Rod, who runs CMI, is an absolute legend in the space, even mentioned that these might be a little light for our needs. We decided to give them a try anyway thinking they were just augmentation for the solar.

Turns out he was right. We were still running the engine too long, and under low loads (terrible for Diesel engines!).

When we repowered Connie from our tired Volvo MD2040's to new Beta 38s, we also decided to upgrade the alternators to the Balmar XT-170s. These are still a small case alternator, so no custom brackets or dual belts required. Again, keeping it simple.

The Balmars are much better for charging LFP since they have dual fan cooling. The issue with alternators is that they are mechanically cooled based on the RPM of the engine. They also only produce anywhere near the rated power at full RPM.

The Balmars, on the other hand, have a much higher output at lower RPM and much better cooling.

We can effectively charge our batteries now at a pretty consistent 90amps per engine. That means 1 engine will charge an empty bank in 5.5 hours. That's not nearly as good as the crazy 48v systems with large case alternators charging 1000ah banks in like 45 minutes, but it's plenty to augment our solar.

One thing I wish I realized is that the Balmar XT-170s come in an isolated ground version. With the case ground version, we can't use the Victron Smart Shunts to measure just the output of the alternator. The Smart Shunts are only set up to work on the negative side, and the negative side is a common negative with the case ground.

The Balmars still need a brain to keep them from burning up and maximizing their charging capability, so we'll need an alternator regulator that can handle LFP batteries.

The Wakespeed WS500

We need the regulator to do a few things.

  1. Monitor the alternator temperature and pull back the charging when it gets too hot, while still maximizing the amount of amps it's producing

  2. Communicate with another regulator to maximize charging between the two engines

When we designed this system, there was only one regulator smart enough to work with two engines, the Wakespeed WS500. Otherwise, the alternators would confuse each other into thinking the battery was full, and we would only get the output of one.

Now Balmar has come out with their own option, the MC-618. Would we have bought that one today? Maybe.

The Wakespeed WS500 is incredibly customizable, and that also means incredibly complex. There are a very limited number of installers available that will understand how to program it. So, unless you're technically inclined, and comfortable working with Terminal or Putty command line, it could be a challenge.

Programming the regulator will take significant learning and effort, and monitoring what it's doing is not easy either.

Dragonfly Energy has bought Wakespeed, so we will see if they plan on bringing any more user friendly software to the market. The provided app is neat, but it doesn't really give the best insight into what your program is actually doing.

There is software made by Offgrid Software Solutions that we've had good luck with for programming and monitoring, but it is still cumbersome and now has trouble updating the regulator firmware. Also, you'll need your computer to be plugged into the regulator via usb to do either. And that's also a pain in the you know what on our boat.

Offgrid Software Solutions WS500 Configuration and Monitoring Tool Home Screen
Offgrid Software Solutions WS500 Configuration and Monitoring Tool

With all this said, the Wakespeed WS500 is incredibly customizable and intelligent.

It has a pretty good algorithm that understands the speed a which the alternator temp is increasing and anticipates by lowering the field (output). This prevents a jerky on/off cycle that would put more stress on the components (like the belt).

It also connects via can bus to the second WS500 and should work in tandem to maximize charging. I am still finding that I don't have things set right to take advantage of this well, and am still experiment. It's quite complicated. And I have to take the bed apart to get into the engine compartment every time I want to play with it, so I don't play with it that often.

I am thinking about getting some MC-618s to install to do a side by side comparison. More on that in the future!

Now let's figure out which batteries we're going to charge and how to deal with two different battery chemistries.

How to Charge LFP House Bank as Well as LA Starter Bank

Now that we have two different battery chemistries on the boat, charging becomes a bit more complicated. Both chemistries charge in completely different fashions.

The most proper way to do it for our configuration would be to have all charging sources charge the LFP bank (the house bank) and then use DC to DC chargers (like from Victron or other manufacturers) to properly charge the two independent starter batteries.

Keeping with our theme for simplicity, we decided against that and instead went with stay alive relays that parallel the battery banks when the ignition switch is on.

When the engine is running, the starter batteries now get on the bus (in parellel), and they are seeing the same voltage as the house bank batteries. And, since starter batteries use very little charge from each start, if they're topped off each time, float voltage is about the same as what the rest of the bus is charging. So the theory is that the starter batteries will be topped off and then just be at float voltage.

If you surf Cruiser Forum, you can see that this theory is quite controversial. It is endorsed by Rod from CMI, and we chose this method for simplicity. Three years in, and our starter batteries are doing fine. I will update if we have any problems with this method.

Now that we're charging, let's do something with all that power.

Victron Multiplus Inverter Charger 3000 Watt

The inverter will be powering all of our household (110v) electrical needs. Being that this is a critical part of our system, we went with the top brand: Victron.

Rather than drone on about why Victron makes better inverters than the competitors that offer them for 1/3rd of the price, I can easily just refer you to this video: Inside the Victron MultiPlus & a Detailed Explanation of How It Works.

3000 Watts has been plenty for us to run the toaster, microwave, vacuum cleaner, an electric heater, and even a Dyson Airwrap Hairdryer (not all at the same time mind you...).

We may want to expand the system some day to add capability for another 3000 watts, and Victron makes it very easy to add another 3000 watt Inverter in Parallel to achieve this.

And now that we're using all that power, let's talk solar

Solar Power Setup

Connie is a Privilege 435 Catamaran with a nice hard top over the cockpit with a good amount of room for solar.

The initial design was to be able to run the fridge and the freezer indefinitely. And the decision to move aboard full time and work from boat came later. So the solar setup is already inadequate, especially as we had already made the decision to remove the generator.

While we have 700 watts of solar and wired in a way to help with shading, half our our solar is often covered by the boom and sail bag, drastically reducing our solar harnessing ability.

Side note here, it's important to understand how wiring in parallel vs series will affect shading. Gone with the Wynns did a fantastic demonstration that is easy to understand here:

We used Sunpower flexible panels at 50w each. The 50w rather than 100w allowed us to pack more watts up there given the rounded shape of the hard top. However, the 50 watt panels alone would often not have a high enough voltage to give to the SmartSolar controllers to turn into charging, so 50 watt panels would be wired in pairs as series, doubling their voltage output. Those pairs would then be wired in parallel before going to the controller to maximize shading resistance.

While Sunpower makes some of the very best solar cells on the market, their panels have not lasted. Flexible panels have the reputation of a short life, but our panels were even on the short end of that.

We later learned from a solar dealer at the Annapolis Boat show that Sunpower was using their B cells to create their own cheaper panels that could compete with the direct from Chinese brands that were also buying up Sunpower's B cells. And, unfortunately, I think this cheapened their brand. I believe Sunpower realized that as well, since their panels are now discontinued.

Since the install, we also learned about the importance of the lack of airflow that flexible panels experience, and the degradation that causes. The most innovate and simple solution that I've seen to the problem is to put the panels on top of corrugated plastic sheets. This puts a good amount of air space (cooling!) under the panels.

Time for new panels, and more power!

Why not wind power?

The power produced per dollar just doesn't add up. If I was going to get one, my research points me to the D400 for its industry leading noise level and power output. However, even after visiting many owners of different wind generators, even the best of the bunch doesn't seem to hold a candle to a good solar setup. Yes in the off chance we have many rainy days, we will chew through batteries, but that's why we have two engine charging sources ready to go.

I also still hate the sound of these things, even the D400.

Why not hydro power?

The dollars don't add up here as well, but the bigger problem is the drag. We go through great time and expense to own and maintain maxprop feathering propellers to give us an extra 0.5 to 1 knot under sail. And we would ruin that and then some with a hydro generator.

Next Phase

We are having a solar arch made to hopefully add another 1000 watts of solar, in addition to replacing the 700 watts on the hard top. Based on our experience, 1700 watts will be plenty of solar, especially with much less shading of the panels on the solar arch.

The solar arch also has the added benefit of providing shade to the dinghy, so we won't have to buy bespoke dinghy chaps to prolong its life.

As you can see by now, there's a lot to consider when trying to upgrade a boat to household like power. Hope this writeup gives some useful guidance and ideas. If you have any questions, feel free to drop a comment!




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