locked Re: Batteries starting to get weak - MMM - What to do -

Arno Luijten

Mark, Scott,

Thanks for the links and additional information.  Very interesting and helpful.

My point with using voltage to determine SOC is that the whole system on a boat in “action” is not stable. Your fridges turn on and off all the time. There is a cloud in front of your solar panel, a windgust for your windgenerator, you run a sheet winch, etc etc. So the voltage varies quite a bit because of fluctuating current draw and we just determined the voltage curve on Lithium is quite flat. How is your BMS to determine the SOC? This is why you really need a coulomb counter and some way to make it control your charging sources. Mastervolt has this mastershunt thing and some other stuff to make that happen but it quickly becomes very complex and maybe too complex for a bue water boat. I don’t know.
Anyway, for my usecase I think (as Scott rightfully says) it is not worth the trouble. I’m first going to try Firefly carbon foam batteries and in a few years we will see what the next best is. For those who spend most of the time off-grid lithium is much more attractive.


SV Luna,

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