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


Arno Luijten
 

Hi Sheriffdep,

It depends what you call a LiFePO battery. But I can tell you without a doubt that the (prismatic) cells you can buy at AliExpress and other sites have no BMS build in.
Having a BMS overseeing the full battery bank is useful for cell balancing. Mastervolt is/was using Chinese Wilson cells in their batteries with a proprietary BMS on top of it enabling it to communicate with other Mastervolt stuff across the Masterbus interface. Very nice but very expensive.

This is my biggest problem with Battle Born batteries. You cannot have sensible interfacing with other systems.
Lithium batteries like to be kept between 20 and 75% state of charge if you have extended charging facilities (i.e. shore power) . The voltage alone makes it very hard to determine the state of charge when a system is at use. Basically you need a Coulomb counter to see the SOC at any point in time. Ideally your BMS should provide you with this information and adjust the float voltage of any charging device in such way it can maintain a desired SOC after bulk charging. Given the different sources of charge you can have on a boat this is not so simple.

Personally  I'm still looking for a BMS that can handle this task without me having to reconfigure everything every time I go out sailing. But I'm on shore power most of the time.

Kind Regards,

Arno Luijten
SV Luna,
A54-121

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