Charging your LifeP04 battery banks in a marine environment

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knotbehavin asked Jun 2, '22

Charging your LifeP04 battery banks in a marine environment

I am adding Lithium LifeP04 batteries to my boat this year. The boat is a 2000 Searay Sundancer which has to two Merc 7.4 V8 engines. I purchased a Pronautic 60amp charger to handle the shore power charging needs and it does have a LifeP04 program. Each battery bank consists of two Banshee 12V 100ah LifeP04 batteries connected in parallel to double the ah. There is a port and starboard battery bank that power the boat and also providing starting current for the engines. My concerns are the two alternators on the boat. From what I can tell they are original equipment to the boat. Banshee suggests that as long as the alternators produce between 13v and 15v while running (3000 rpm) that should be fine. "should" is what concerns me. I really don't want to blow up my alternators. I believe I'm need an alternator that is a smart alternator with the correct amps but I don't have the budget to replace them at this time. In doing some research I believe the Orion Tr Smart 12/12-30A (360W) might be the way to go. I believe the negatives have a common ground so I think the non isolated would do the trick. Most of my boating is at cruising speeds @3000 rpm producing about 13.7A. Would two of the Orion's do the trick?

Any advise would be most appreciated.

orion-tr smart

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Answer 1 · 2022-06-03T18:01:24Z

Mike Dorsett answered · Jun 03, 2022 at 06:01 PM

The caution with charging lithium ion batteries from an alternator is the maximum voltage - the current is much less of an issue, as this is source limited by the alternator in normal operation. If the Alternator charges to 14.4V, which is normal for a lead acid battery, then as Banshee states, this should be ok for the lithium batteries. This relates to 3.6V per cell for a 4 cell battery, and typically the max is at 3.65V (depending on chemistry of the cell). If the voltage rises above 15V, then this will stress the battery and cause a reduction in lifetime due to increased corrosion.

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Answer 2 · 2022-06-03T19:24:25Z

johanndo answered · Jun 03, 2022 at 07:24 PM

We are on a Lagoon 400S2 cruising cat with 2 Yanmar 3JH5E 40Hp engines and 120A Vaneo stock alternators, house bank is a DIY 1000AH Winston Thundersky 12V battery, REC ABMS, we use a Victron BMV and the charge relay settings to produce signals based on SOC for a BlueSea ML-RBS 7700 500A bi-stable solenoid, we turn on alternators below 85% and off at 98% SOC, we switch the Lines behind the battery distribution diodes / FET blocks, the start batteries remain connected.

Don't worry about the current, it is in a range of 40A only per alternator, as LiFePO4 batteries have a higher voltage then LA batteries, there is less voltage difference to push a high current to the bank, also typically house batteries are not installed in the hot engine compartments, so there are long wires to the battery that contribute to voltage drops. Alternators and batteries are safe with such setups, no need for fancy external regulators.

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