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Replacing my AGM's with Lithium

I like to replace my 520AH AGM bank with lithium batteries and have the following questions:

1) What AH lithium battery do I need to replace my 520Ah AGM's to have at least the same output?

2) Which of the batteries cells are the right ones to be used on a yacht and what do I have to watch for?

3) Can your BMS be used for any type of Lithium ( Lifep04) cells?


Hi Frits,

In theory you can take half the AGM capacity but with fridge, freezer... and considering the size of your boat I am wondering if 520Ah AGM is not a bit just?  What is the SOC / voltage in the morning when sailing?  Do you have a generator and how often do you use it?

As a reference I have 600Ah on Tao, but I run the 100l/h watermaker and the 230V water heater on the batteries and I have not used the generator for a very long time.  I can be 24 hours without sun at anchor (less when sailing).  I would need more information on your installation, but unless you have large loads, 400Ah should be plenty and not have to worry if there is no sun for one day.

I would go for the cells you assemble to create the battery that suits you.  For example 8 x 200Ah cells in a configuration 2P4S (groups of 2 cells in parallel and 4 groups in series) would make a 12V 400Ah battery.

Looking at the link you sent I am surprised I did not see 400Ah cells! For the example above the 200Ah cell ref RJ-LFP54174201-202 would be fine.  I would just question the weight of those cells: 4.1kg considering that the same 200Ah from Winston weights 8kg and those from GBS 6.5kg.  What is the difference?  less active material and/or thinner electrodes (maybe that could also explain the internal resistance of 0.5mohm while Winston is 0.35mohm?)

And yes, the TaoBMS can be used for those cells.

Have a nice evening