question

Ceki Gabay avatar image
Ceki Gabay asked

Partial migration from agm to lifepo batteries.

I am planning to migrate from agm to lifepo batteries on my boat.

Current configuration is

640Ah battery bank

Feeders are two smart mppts 100/30 and 100/20, an inverter/charger 12/1600, an alternator 12/125.

Replacing all bank will cost alot as it will cause changing the alternator as well.


The question is about phase by phase replacement is possible by doing something like below.

Extract one agm battery.

Drop to 480ah.

Then put a seperate lifepo battery. Lets say a superpack 25.6/50

Disconnect solar mppts from agm bank.

Connect them to the new lifepo battery.

Place a new smart mppt 100/30 with max current setting 25A.

Connect new lifepo to the new mppt’s solar ports. And battery port to the old agm bank.

So working scenario is... Everything on the bot draws power from old agm bank. Lifepo will be the charger of that bank. Alternator and shorepower charging will also be avalable at old bank.


Is it possible that works fine? Or do you see any showstopper?


Thanks in advance,



battery charging
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1 Answer
boekel avatar image
boekel answered ·

so you want to change to 24 Volts?

If you are 'electrically saffy' you could even try connecting the Lithium battery in parallel with the AGM's (if you go for 12V lithium batteries).

Set all voltages to the LiFePO4 values, the AGM's might not get fully charged, but the batteries will help each other during discharge.

This is only to be attempted if you have the skills to check if there aren't unwanted current flows during charge / discharge (checking with clamp meter etc.) Also make sure the lithium battery is capable of handling all loads on it's own.

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