Batteries

[Stu Jackson]

There is some potentially misleading info in replies here. I say potentially because it really comes down to this related to the health of your alternator and a 1-2-B switch:


IT ALL DEPENDS ON HOW IT'S WIRED


If the alternator output goes to the C post of the 1-2-B then you shouldn't move the switch because of potential damage to the alternator from a sudden disconnect.


If, however, your alternator output (AO) goes directly to a battery bank, then once the engine is started you could turn your switch OFF and do no damage because the AO had "a place for the current to go."


As far as LiFePo is concerned folks don't feed the AO to the Lith bank because a sudden BMS disconnect would damage the alternator.


Also, limiting the input to the Lith bank via any means restricts the inherent advantage of lith, which is their high acceptance rate.


It would be helpful for you to learn more about the lith system's components and how they can best work well together.


Good luck.

[Pete7]

Originally Posted by Tocatta

Hi there I'm living on a mottel 33 and I bought 2 lithium batteries and a DCDC CHARGER

I would be interested in learning what you hope to achieve fitting LifePO4 that lead acid batteries can't?

Are they LifePO4 rather than one of the other lithium chemistries?

Pete

[sailingharry]

Adding a drop in lithium as a house bank on a boat with a one - two - both switch presents quite a dilemma.

I would use the lithium ba⁸nk as the everything bank. Put the switch on the lithium bank and leave it there. Since you are using drop-in batteries, you have to be concerned about the BMS disconnect killing the alternator. Hence the limitation of using a DC to DC charger. Hardware alternator to your lead acid battery to serve as a buffer for the alternator. The lead acid battery serves two purposes. First is to overcome the drop in battery limitation. The second is a backup if your lithium dies for any reason.

The only reason to use the lead acid as a start bank is if the drop in batteries have a weak BMS. Another limitation of drop-in batteries.

[Stu Jackson]

That's a pretty good summary, Harry.


To add details to a phrase like "weak BMS" and what that means, please read this:


https://marinehowto.com/drop-in-life...ated-consumer/


I've posted it a few times, and it seems some folks installing "drop-ins" still haven't gotten the memo.


Good luck.

[AKA-None]

If I may further ask
You can’t use an acr due to the different voltages required by the two battery chemistries?