The story of how we converted from Lead Acid to LiFePo4 will be told in a series of posts. This is the first post talking about our thoughts about the conversion and sourcing the right components. From battery cells to BMS and all other essential parts.

Lacking battery capacity

When we bought our Jeanneau SO 42.1 in 2021, the boat was in overall very good condition. But soon after sailing, we realized that the battery capacity was not very good. 

Even though the previous owner had recently put in 3x95AH lead acid batteries for consumption, it seemed that the actual capacity was significantly lower. 

I did not do an actual capacity test. But after installing a Victron Smartshunt we could get an excellent indication of the capacity state.

As we bought the boat with long-distance cruising in mind, we knew that the batteries had to be changed. We did not plan further but decided to wait because we knew the project would also be followed by other upgrades. 

Fast forward to the summer of 2022, we sailed off towards Sweden on our 4 weak summer trip. We had plans about being at anchor as much as possible and had just upgraded our anchor chain so that we could anchor on more and deeper locations (from 22 meters of chain to 75 meters) - But when arriving on Anholt (A small danish island) something ‘’fishy’’ happened. We found out that one of our lead acid batteries had gone bad and started smelling. Having removed the battery we could see our capacity drop to almost nothing, we decided that now was the time to switch batteries. 

Lead acid or LiFePo4

The first, and the most logical option was to install new lead acid batteries with higher capacity - But when measuring the battery compartment we found out that we could maximum fit the physical size of 3x95AH batteries. 

We quickly ruled the traditional lead acid batteries out as an option - Not only because of lacking physical space - but also because we knew we wanted to make some other big upgrades to our sailboat. 

1. Solar arch and min 600W solar panels. 

2. New charger and inverter

3. An overall upgrade of the electrical system (fuses, breaker, and a dedicated battery to our anchor winch)

Furthermore, we had just upgraded the navigational equipment and installed brand new B&G chart plotters, displays, and autopilot system. 

We also had a look into our consumption by looking at each of the electrical instruments/lamps e.g. and then calculating our max kwh need per 24 hrs. 

When we looked at the combined need our boat would have, when all was installed - there was not much of a discussion. 

Upsides of Lithium: 

• Recharging cycles / Up 10.000 depending on type/brand. 

• Low weight (up to 70% lighter depending on type/brand)

• No lead and no acid fluids

• Faster charging time

• More useable capacity (up to 95% discharge compared to 50% discharge in lead acid)

• Low self-discharge

Downsides of Lithium: 

• Price 

• More complicated chemistry and required monitoring

• requires upgrades to existing electrical systems (Charger, monitoring, protection to alternator e.g.)

Even though the price is higher and the installation of lithium requires an upgrade to the existing system it was quite easy to make the decision. 

We had to convert to LiFePo4 / Lithium. 

Drop-in or DIY build

There are a lot of different options to choose from when doing a lithium conversion. 

Our main priority was to make a conversion where safety was our number one priority - It is logical as we knew, that within a year our boat would be our permanent home. And in that matter, neither of us would be able to get a good night's sleep if we did not feel sure about our electrical system. 

Converting to Lithium would also open a good option for us, to have an overall look at our installation and ensuring we had the right wire size, fuses, and breakers e.g. to handle the loads we would be putting on the system. 

Drop in

First of all, the term ‘’drop-in’’ is not an option when looking at Lithium. It is simply not possible to take your old lead acid batteries and replace them with lithium WITHOUT having to look at other components of your electrical system. The chemistry in a lithium battery required a lot more monitoring as the cell within the battery is capable of absorbing much more power than your regular lead acid battery.

But we looked at different options when speaking about the ‘’drop in’’ batteries. But common for all the options (except a few discount brands) was the price tag. 

We knew that we wanted to put in between 4.5 kwh and 5 kwh (appr. 400 AH at 12V) and the price tag of the batteries we would buy was just too high. Furthermore, many of the batteries that were within our budget and had the right amount of amp hours would simply be too big to fit in our battery compartment. 

Upsides of a ‘’drop-in’’:

• Proven quality (Among the brands we would have chosen)

• Closed cabinet

• No or very little configuration

• Internal BMS (not exposed to the salty environment in a sailboat)

Downsides of a ‘’drop-in’’:

• Unknown BMS quality

• Fixed-size = fewer mounting possibilities

• Higher price

• Uncertainty about charging cycles

• Flexibility in capacity size (DIY has more capacity options compared to the physical dimensions)

The biggest downside to drop-in batteries for us was the physical size. Many of the solutions we looked at, were simply either too large in relation to the capacity and thereby not giving us the kwh we were looking to achieve. 

We could, therefore, relatively quickly, exclude using an existing drop-in brand - The pursuit for a suitable DIY setup had therefore begun. 

The right cells

Since we had chosen to build our batteries, this meant we had to find the right Lithium cells for our setup. 

If you are not yet aware - a Lithium battery consists of several 3.3V cells that, when combined, create a 12V battery. As the chemistry of a Lithium battery can absorb almost any power you give it, the cells need to be protected in order not to overcharge or discharge to levels unhealthy to the chemistry. 

The protection is done by a BMS (Battery Management System) - It measures the current levels of each of the battery cells and cut’s off if the current or e.g temperature is above or under its ‘’healthy’’ levels.

(That’s the ‘’basics’’ of a Lithium battery - it’s much more complicated than that)

The most important factor for us when searching for battery cells, was build quality, proven discharge capacity, and safety. The cells had to be manufactured by a well-known brand/supplier and to very high standards. 

As we very often use youtube as inspiration for our projects and how to do things, we scrolled the endless library of DIY LiFePo4 youtube videos. 

And on several occasions, we came across Winston Thundersky cells. 

Through a European supplier (GWL.eu) we found some very promising tests of the cells proving their quality and were able to find cells of the right physical dimensions and capacity. 

Initially, we wanted to buy the batteries through GWL but found the prices a bit too high. 

We, therefore, contacted Sky Power Int. in Hong Kong where we received a very competitive offer and ended up purchasing through them. 

We bought 12 - 130AH 3.3V cells - Put in series of 4 giving us 130AH at 12V (13.2V) and a total of 390AH at 12V in parallel. 

BMS

As we had chosen to use Winston battery cells, we needed to find a suitable BMS to control the cells. We knew we wanted as simple a system as possible but also with proven quality and reliability. As each of our batteries would be 130AH at 12V we had to find a BMS that could handle that amount of capacity. 

From several blogs and youtube channels, we found out that the Overkill Solar 120AH 12V BMS was a very reliable solution with specifications that matched our setup and needs. 

An additional benefit is that the app available for iOS and Android works really well and has an integrated balancing tool. 

We bought 3 units so that we can monitor each of our 12V 130AH Winston batteries. 

Additional upgrades

As described, upgrading from Lead Acid batteries to Lithium can not be done without ensuring that the electrical system can cope with the increased battery capabilities. 

Our charger could only charge Lead Acid batteries plus we wanted to option of using 230V when off-grid. Furthermore, we needed to protect our alternator from the lithium batteries. It would be too much of a risk letting our alternator charge the new batteries and then ending up frying the alternator. 

It was also important for us, to be able to monitor the battery state and SOC level and to future-proof our system for new installations we might want to make. 

We choose to buy Victron products as much as possible. 

The charger/Inverter ended up being a Victron Multiplus Compact 12/1600/70. We would have loved to have a larger inverter, but our budget just did not allow it. And most important for us, was to be able to run our coffee machine and smaller electrical appliances while on the way. 

To protect our alternator, we bought the Victron Orion Tr-Smart 12/12-18a DC/DC which is connected as a charger from the alternator to the Lithium batteries. 

In order to monitor our lithium bank, besides the 3 Overkill Solar BMS’ we bought a Victron 1000A Smart Shunt. Even though we would be able to monitor the cells of the 3 batteries from the BMS App - The Victron Smart Shunt would enable us to connect the shunt to the rest of our Victron appliances and make a total system monitoring system through the Cerbo Gx and the Victron Gx Touch. 

Another addition to the setup is the Victron MPPT 150/45 for our upcoming solar panels. Here we will install 3x200Watt. But more about that in a later post. 

To sum it all up: 

Charger/Inverter: Victron Multiplus Compact 12/1600/70

DC/DC: Victron Orion Tr-Smart 12/12-18a DC/DC

Shunt: Victron 1000A Smart Shunt

Solar charger: Victron MPPT 150/45 Smart

Whats next?

When we got back from our summer sailing trip, we finally had time to start setting up our new system. That meant preparing the Lithium cell’s for assebly, building a new battery holder, installing new wires and a lot of other fun stuff.

It will all be described in our next blog post.

If you have any questions or comments to our installation, please feel free to reach out.

You can get in tough on both Instagram and Facebook.

Disclaimer

I am not an electrician or professional within the field. Any of the installations I have done is made from the research I have made and should not be ‘’copied’’ unless you do your research. 

Using any of our methods, materials e.g. is at own risk. 

Working with electrics is dangerous and can cause fatalities - Ask a professional if in doubt!