Cranking LifePo4 Battery BMS needed...

[golfmonke]

I've built several LifePo4 batteries and they have been great, a lot cheaper, lighter and last about twice as long as similar size lead acids.

I'd like to build a LifePo4 Cranking battery, but can't seem to find a BMS that will suit my needs...

I plan to use 120AH or 135AH cells.

The cranking battery will be used sometimes in below freezing temps on an outboard, so want to be able to protect the battery from the alternator. I plan to put heating pads to warm it up on cold days so it can take a charge, but still needs to protect against charging below freezing.

I need to find a BMS that is suitable for cranking (i'm assuming a relay BMS) but I can't find one with low temp disconnect.

The specs on my engine call for a battery that can provide 750CCA's.

Anybody know where I can find one?

 

[FilterGuy]

Anybody know where I can find one?

No but..... What if you completely bypassed the BMS while cranking the engine.

The BMS would be there for charging and maintaining the battery but when cranking the engine you could hook it directly to the negative rather than running the current through the BMS.

 

[Xhumeka]

How about using an automotive relay switch? Like this guy describes:

 

[golfmonke]

How about using an automotive relay switch? Like this guy describes:

Wouldn't the charging circuiit not have any low temp protection/short circuit protection/overcharge as it appears would not be going through the BMS?

 

[golfmonke]

No but..... What if you completely bypassed the BMS while cranking the engine.

The BMS would be there for charging and maintaining the battery but when cranking the engine you could hook it directly to the negative rather than running the current through the BMS.

I believe there is only one set of power cables running from the engine to the battery.

But I think the Alternator + could be split out and run separately.

I'm not an electronics guy... what would the wiring look like?

BMS to neg of battery, other side to engine block ground?

Separate Alternator + going to battery +?

Main Power Cables as is going from battery to engine?

 

[golfmonke]

I believe there is only one set of power cables running from the engine to the battery.

But I think the Alternator + could be split out and run separately.

I'm not an electronics guy... what would the wiring look like?

BMS B- to neg of battery, C- to engine block ground?

Separate Alternator + going to battery +?

Main Power Cables as is going from battery to engine?

I guess the only thing i'd lose is disconnecting the battery if low voltage?

 

[golfmonke]

I guess the only thing i'd lose is disconnecting the battery if low voltage and high temp disconnect?