Should I leave LiPO4 batteries partially charged?

[MikeCondor]

Hi- I have a Mastervolt Lithium house battery system, 200Ahr on our 38 ft sailboat. While on the marina, which is most of the time, shore power keeps them at 100% via the Mastervolt charge controller.

I've read Lithium lasts longer if partially charged, reference friends with electric cars.

I am hesitant to leave shore power disconnected in case some drain drops the Lithium below salvageable level = $$. The only loads should be bilge pump (zero draw), phantom loads, unless inverter came on with shore power outage.

When away from the boat I leave a dehumidifier running off AC, which is shore power fed. If advised to leave batteries partially charged, I'd have to figure how to leave shore power on for the dehumidifer, but block the charge controller.

[Jorddarb]

Car batteries such as Tesla are a different chemistry than your house battery. That said there is no reason to leave them partially charged or to take the boat off shore power.

[Flod]

I have installed a switch that makes me able to manually operate the high voltage relay where all my charge sources go. This way I can be on shore power without charging the lifepo4 bank. As far as I know they should be stored at around 50% and you shouldn’t be on shore power with a charger connected for longer periods. The lifepo4 is sensitive to overcharging just as they are to low voltages.

[GordMay]

Greetings and welcome aboard the CF, Jorddarb.

Accelerated degradation of LiFePO4 batteries when stored fully charged
➥ https://www.cruisersforum.com/forums...ed-209661.html

[Jorddarb]

Thanks for the link! I have not see that information before. I’m not sure what kind of charger the OP has, but many like my multiplus have the ability to set the appropriate charge profile for the batteries as mentioned in the link.

[facciatosta]

What about novel idea of going to the source and ask the vendor/manufacturer of the batteries for clear and intelligent instructions instead of listening to the sailing community folklore?

Unlike flooded acid/AGM/Gel batteries lithium batteries needed to be taken seriously. They are fairly new on the market and have some reputation.

[CapnBazza]

Originally Posted by MikeCondor

Hi- I have a Mastervolt Lithium house battery system, 200Ahr on our 38 ft sailboat. While on the marina, which is most of the time, shore power keeps them at 100% via the Mastervolt charge controller.

I've read Lithium lasts longer if partially charged, reference friends with electric cars.

I am hesitant to leave shore power disconnected in case some drain drops the Lithium below salvageable level = $$. The only loads should be bilge pump (zero draw), phantom loads, unless inverter came on with shore power outage.

When away from the boat I leave a dehumidifier running off AC, which is shore power fed. If advised to leave batteries partially charged, I'd have to figure how to leave shore power on for the dehumidifer, but block the charge controller.

Someone switched off my shore power and the fridge took the batteries down to the point where the BMS shut them down. When I turned the switch back on a few weeks later, the battery charger just recharged the batteries. No dramas although no cold beer.