Re: Hybrid Lead/Lithium


Dean Gillies
 

Hi James,
Those are very sensible considerations. I am also a big fan of Gel's, except for their cost and energy density as you point out. I have happily used them in many military projects over the years where safety and ruggedness were paramount.

I cannot speak for every external BMS system, but my REC BMS and I'm sure the vast majority of others, do provide over-voltage protection against charge sources regardless of whether they are controlled and/or monitored by the BMS.  The BMS will disconnect the LFP battery when an over voltage is detected. 

With regard to the other safety issue you mention, where a short occurs in the lead battery of a directly-connected hybrid system, is mitigated by means of the series fusing provided on both the LFP and Lead batteries. In my system for example, 400A class T fuses protect both batteries.
I don't know what the fusing arrangement is on LFP batteries with internal BMS.

It's worth noting that most (if not all) external BMS units are fail-safe. The LFP is dis-connected by default and is only connected when all parameters are within spec.  In the event of a failure of the BMS, the LFP is disconnected. (Another reason that it's nice to have the lead component in the circuit to keep the lights on). 


cheers,
Dean
SV STELLA
A54-154

 

 

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