Woody Norwood":2u4pwzmn said:
I have a 2021 Cutwater 24 Coupe. I'm thinking of replacing the lead-acid original house batteries with lithium-ion ones for their lighter weight and superior performance. Here are the questions: (1) in charging and recharging, is the original recharging unit compatible with the installed alternator and the separate charging unit? (2) If the other batteries are not Lithium Ion, does this affect the charging dynamics? (3) What other precautions are advised when replacing the house batteries with Lithium-ion? Woody Norwood
I too am interested in converting to either Firefly or Lithium batteries when my house bank goes end of life.
In order to get maximum benefit from lithium batteries, you need to find a way to push lots of amps to them in the charging cycle. Lithium batteries can take 50%-80% of rated capacity until they are nearly fully charged. All lithium batteries need a battery management system to manage that flow.
There are 3 ways to get more amps.....(1)A big engine alternator with a smart voltage regulator that is programmed for LifePO4, (2) A bigger charger (or more time) plugged into shore power and (3) More solar panels. Since you have an outboard, then your options are shore power charger and solar. As far as I can tell, the charger/inverters standard on our boats can not be programmed for lithium, so you're going to need a new charger that can handle lithium, and/or more solar panels. A new programmable charger can charge separate banks of lithium and SLA batteries.
12V Lithium batteries are actually 4 3.2V cells wired in series to get 12.8V. There are drop in replacement lithium batteries, which have a bms integrated into them. these types of bms are very sort of on-off, but don't manage balancing the individual cells within the actual battery case. An external BMS cna handle cell charge balancing.
Flooded batteries can only take about 20% of rated capacity (a 200 amp/hr bank can only take about 40 amps in bulk mode, then it tapers to lower rates as they go into absorption, the float mode.)
A different option with similar benefits but much lower cost of entry (best bang for the buck) would be Carbon Foam AGM (Firefly) batteries. They have much higher capacity, but they play well with the FLA system that's on your boat now.
Martin Nethkin (Channel Surfing) has been down the road you are about to step onto. You could learn a lot from his experience.
Hope this halps.
Patrick
