Lithium conversion setup

[Brian Cope]

I have a 12v starter and 2 pair of 6v house batteries. A 150 amp alternator and a balmar mc614 regulator. The batteries are combined by a BEP voltage regulator. I also have a 1800w inverter which is not lithium compatible, so I am upgrading that to a 3000w.

I am not sure the best way to charge starting battery with the new system. The balmar can switch to charge the lithium no problem, but then the starter battery will need power. I'm trying to figure a way to put enough power to the starter battery for it to have enough power and the rest get dumped into the lithium.

[hlev00]

The typical setup today is to charge your house bank with alternator, solar, etc. Then use a DCDC charger to charge the start battery which can remain lead acid based. Install an alternator protection device from either Balmar or Sterling to protect the alternator in case the BMS shuts down the lithium bank.

[Brian Cope]

how do you determine how man amps your dc/dc need to keep starter battery charged? My balmar regulator can get set up for Lithium profile so that shouldn't require new hardware. I'd run alternator to balmar regulator to house. then dc/dc to starter.

[hlev00]

Most factory alternators are around 60A for something like a 50hp diesel. They seldom put out more than half of that and that is when charging house batteries too. I would expect something like a Victron 12/12/18 DCDC charger would work if starting is all the battery needs to do. Starting uses very little power and the start batteries charge quickly.

The only other consideration is whether you have a windlass or bow thruster that will run off of the start battery. If so, going up one size to a 30A model might make sense.

Check with a Victron distributor and they can probably help size for you.