We have just upgraded Anui’s battery bank from sealed Lead Acid batteries to Lithium. Why bother? Because it means we need fewer batteries or can have more in about the same space, and those batteries will last longer, cycle deeper, deliver more power, and weigh less.

It was a long time coming. Ever since we purchased Anui, we had the upgrade to lithium on our hit list. We were planning to tackle the change over at our haul out at the end of the year. The battery bank had been underperforming for a few weeks and we knew the end was near, just not that near! It all fell in a heap while we were at Lady Musgrave ready to head out to the Swain Reefs!

The boat originally had lithium batteries, but when we were about to put an offer on Anui, we noticed the batteries were swollen. We now think what blew the original lithium bank was that the existing 240 volt automatic battery charger had a lithium and AGM setting for 12 volts, and a setting for AGM 24 volts, but not a setting for lithium 24 volts. How do we know? Because we have just had to buy a new 240 volt Victron battery charger! The previous owners agreed to buy new batteries at the time… but went for cheaper AGMs which was disappointing but understandable.

The lithium bank does cost more than the AGM bank upfront. However when you consider the cycle count, the lithium battery bank will last 4 times longer than the AGM bank. Since we are on board for the long term, it is a no brainer for us.

Let’s get a bit nerdy

We have gone from 404amp of AGMs (6 batteries in 3 pairs) to 480amp LiFeP04 lithium batteries (8 in 4 pairs), stored in a slightly bigger space. These were supplied by EV Power in Western Australia. We had dealt with them before when we switched to Lithium on our previous boat Take It Easy and were happy with their service and pricing. We have also put four circuit breakers, one on each 24V string (two batteries in series) so the parallel strings (4 pairs) can be isolated from each other.

• Depth of discharge – or DoD, is how much of your battery bank’s stored energy can actually be used without dramatically reducing its life. For AGMs, it is typically 25-50%. Keep in mind that if you don’t have a sunny day to recharge your batteries after a day of use, the DoD will go down again the next day – so planning to use 25% per day will allow you to use less than the 50% maximum after two days of use. DoD on lithium-ion batteries is 80% or more, allowing you to use most or even all of the battery’s stored energy. As a result, the lithium battery bank can be smaller, or if as we have, you use the space to get a larger bank, you end up with much more useable power.
• Cycle count – Cycling a battery means discharging it to any amount and recharging it to a fully charged state. If you cycle your battery bank every day for a year, that’s 365 cycles. We used our AGMs for 4 ½ years – 1642 cycles… A standard sealed lead acid battery can have about 1200 cycles at 25% DoD. A typical lithium battery can have 5000+ cycles at up to 80% DoD. That is 4 times the cycles at over 3 times the DoD – a much longer-lived battery bank with lithium batteries.

The battery box had to be broadened to accommodate the extra two lithium batteries, and a new lid made, but Wade organised that the week prior to the change over. It looks quite neat.

The switchover is, however, not just a “drop-in” replacement. Solar Charge Controllers, Alternator, DC/DC Converter, 240volts Battery Charger, Battery Monitoring System all have to be lithium compatible and their profile altered to lithium. In some cases, it might mean replacing some components or the lot… so there are additional costs! We upgraded all components little by little as bits needed replacing, with the thought that eventually we would bite the bullet and upgrade.

The Battery Monitoring System (BMS) is critical and should have the ability to monitor both the individual batteries, and the whole bank. Watching more than just the voltage, but also how many amps go in and out of the battery bank and the temperature gives you a complete view of the health and state of charge of the entire set up. Our BMS and controllers were supplied by Victron and have Bluetooth connectivity which allows us to monitor everything from our phone. 

The installation was handled by Jason Twyman from Dan-Kel Electrical in Bundaberg. He was quick to respond when contacted from Lady Musgrave, able to schedule the installation swiftly, checked all our electrical systems on board prior to the batteries arriving to ensure we had everything we needed. After a bad run of dramas, we were feeling a bit apprehensive, but it all went smoothly. He did not take long: less than a day to get it all set up and everything checked. We were impressed.

Meanwhile one stressed cat was just sunbaking in the cockpit!

Sailing away again

We have now headed offshore knowing we can use power with abandon. Captain Wadie might be able to relax his tight monitoring other than to marvel at the amount of battery power we now have. And Chris can stop saying “we haven’t spent an insane amount of money on Anui to have to choose between using the toilet pump or the laptop.” A game changer!

We left the Bundaberg Port Marina on Wednesday, made it back to Lady Musgrave, and left the lagoon on Thursday afternoon for an overnight sail to the Swain Reefs. No mucking about… time for some well earned fun.

We are now out of internet and phone coverage, but have scheduled a few posts including this one in advance so it is not total silence. You can track us on our satellite system on PredictWind at the bottom of this page.