Lifepo4 - CA - LVC

[Danos]

Have i got this right re my Lifepo4 A123 9.2Ah (16s4p) pack and LVC setting, and interpreting the info.

I understand Lifepo4 cell voltage ranges from 3.6 - 2.0 volts. 2v = empty or 100% DOD. So fully charged i should see 16 x 3.6 = 57.6v on my CA. If i discharge the pack 100% the CA would read 16 x 2 = 32v on the CA.

If i want to restrict my battery pack to 50% DOD i should set the LVC on the CA to 16 x 2.8 = 44.8v...is my understanding of this and application to LVC correct?

If this logic is correct i could set the LVC to 44.8v, ride until it cuts out and i should see consumption of 4.6Ah on the CA...is that how it works? If i ride to LVC and the Ah consumed is more (or less) than this figure i adjust the Rshunt value in the CA until i have it spot on.

I'm trying to work this out as i don't know the exact shunt resistance of my 9 fet 30A Infineon controller and i want my CA to give me as close to exact consumption figures as possible.

Thanks for any advice.

 

[dogman dan]

Since lifepo4 has such a flat discharge curve, then drops off a cliff at the end, your dod needs to be measured by wh used, or ah used, not by voltage.

Lvc cutoff should be set pretty close to 48v, for 16s. Perhaps about 46-47v, or even 48v. Then ride, see what your real world ah is, to the point of cutoff. If you see the voltage really dive off the cliff before cutoff, I'd raise the cutoff some more. To make cells last, you don't go anywhere near the steep drop in voltage for a typical discharge.

I'd say, you have about 7-8 ah of usable pack size. (about 80% dod) 50% dod would be 4.5 ah of course. Riding till you use 5 ah should be fine.