Vela Nautica goes lithium

We are going to switch Vela Nautica to lithium power!

There are some very obvious points that convinced us to switch Vela Nautica to lithium power and abandon our old lead acid batterie system.

  • charging efficency is near 100%
  • significant reduction of generator times
  • the weight reduction of 60%
  • the size is about 60% smaller against lead acid
  • energy usage of 80 to 90% without damage
  • long lasting (15 years or more) deep cycle
  • price competetive to common AGM
  • posibility to extend capacity on the fly

In this first episode about lithium power on a yacht, we show our motivation and the process to get the batteries to the boat.

For us it gets time to change our old AGM lead acid batteries, unitl now they did not fail but they are nearly 3 years old now. AMEL suggests to change batteries after 1.5 to 2 years so we are good with them. The old batteries where 12 Pcs 12 volt 100 Ah EXITE marine batteries. SetUp as 6 parallel 2 series to gain 24V 600Ah as house batterie bank.

To change them will be a mayor investment and in my eyes the new lithiums technologie, that is no more that new, offers much more advantages that it´s time to switch.

Lithium has a linear charging curve. That means we charge with high charging current like 120A all the time, until the batteries are full. The general direction is to reduce our generator times, when anchored, from about 3 hours plus a day, down to max. 1 hour.

As charging device we use a Victron Charger / Inverter 120A / 5000W.

As we are online, you can see our batterie performance on VRM Portal – Victron Energy

Our lead acid batteries have an asymptotic charging curve: they start to charge with 100A, 5 mins later current goes down to 75A, an other 5 mins later current is down to 60A and an other 10 mins later current is down to 30 A and so on.

We end up with 3 to 4 hours generator time to bring them up to maybe 95 percent. So the longer it takes to charge the less power goes into the batteries. What is bad when we run our generator to charge, the last 10% before the batteries are full lets the generator run for hours, ideling around, but charging is very ineffective. This will be gone with lithium batteries!

  • Lithium batteries last way longer than old fashoned lead acid technologie.
  • The LiFePo4 cells we bought last >3000 cycles until their capacity is down to 90% of their nominal capacity.
  • The LiFeYPo4 cells last >5000 to 8000 cycles until their capacity is down to 80% of their nominal capacity.

And they are not dead by then, they still provide 90% of their original capacity.

  • To compare, lead acid has a life expectaion of only 500 to 1000 cycles and after that, or mostly earlier, they are dead.
  • Wight of lithium batteries is less than 50% of lead acid batteries.
  • Space of lithium batteries is 2/3 of lead acid batteries
  • It is possible to use 80% or more of the capacity of lithium batteries without damaging them. Lead acid allows only to use 40 to 50 % of their capacity without killing the cells.

There is also a downside of lithium batteries:


  • They are more expensive and we need to change the complete setup including charger and Batteriemanagement.

Our LiFePo4 batterie is permanent monitored by PowerBMS. The PowerBMS protects the batterie from overcharge or undercharge and temperature hazards. It is fully configurable. It will also inform us with acoustic Alarms.

From safty point, it looks like we are good with LiFePo4 or LiFeYPo4 cells, if you short them they start steaming, they get 180 degrees celsus hot but they don`t give up in flames.


Therefore that we are under a budget in money wise of view, we decided to get the batterie cells, from china. We did not find any affordable offer in europe or US and in the end these very expensive batteries you get here come probably from chinese production as well. (in fact they do)

In this first post about getting and installing the LiFePo4 batteries in the boat you see the process until they are in their batterie compartment.

Next Part

The next part about changeing the energie system of Vela Nautica we will give you more specific technical details and show our experiance and how the new batteries perform

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