evtlfp20 via EV wrote:
I recived a shipment of NMC battery pack with zero volts across 12s ,
and yes they all showed zero.
I read about bumping the cells with nicad setting to get them to 3 volts
so the normal charging could begin and most of them charged to Storage
voltage and have held with in 4/100 of a volt ( 3.70 ) 1 week now .
theses are 30amhr 10C rated.
I was warned that metal based dendrits that have formed becuse of below
zero volts could cause the cells to go blastic .
most of the cells show an Internal Impendance of 17 - 22 meg.
Should I put them into a light test use and do a few lights cycles or
solud I just slowly bleed them to zero then send to recycling?
I like to get come use and No Fires
Hi evtlfp20,
I would be very wary of those cells!
First, the seller cheated you. Send them back, and demand replacements
or a refund!
Second, don't expect them to ever deliver their rated capacity or
current again. You might be able to recover some capacity from them, but
they will almost certainly be damaged by being run dead.
Third, if you were able to charge them, check their internal resistance.
It cannot be the "17-22 meg" that you said. Did you mis-type, and it's
really 17-22 milli-ohms (0.017 to 0.022 ohms)? How did you measure it?
A 30 amphour cell good for 10C would have to deliver 300 amps. To do
this, it can't have an internal resistance more than about 5 milliohms
(0.005 ohms). So even if yours are 17-22 milliohms, they are bad.
The danger with damaged cells is that they become resistors at high
charge or discharge currents. The resistance produces heat, which starts
a runaway reaction leading to a fire. The other danger is that they can
spontaneously short, dumping all of the charge in them, also causing a fire.
--
Any intelligent fool can make things bigger, more complex, and more
violent. It takes a touch of genius, and a lot of courage, to move
in the opposite direction. -- Albert Einstein
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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