Quote:
Originally Posted by super__dan
I firmly believe the problems are caused by the enormous variation rates of self discharge on modern cells. I think equalising before charge is vital and with this your chances of problems are enormously reduced.
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I agree. If a cell does develop a small internal short (called a 'soft' short) then the Self Discharge will be worse for that cell. this means that guy has a lower state of charge and will be discharged first when you are discharging the pack, it also stands a higher chance of being forced to zero or being driven negative. This can lead to development of hydrogen gas which cannot be recombined. When the pack is then charged again this guy lags behind the others in the pack and never reaches top of charge.. it is then forced lower on the next cycle.. it is a downward spiral... Yes, equalisation is good.
Ideally your discharger should have a 0.9V-1.0V per cell cutoff but if it doesnt then you are still better using it and maybe suffering some irrecoverable capacity loss than never equalising. I will confess that my equaliser does not have a low voltage cutoff (shock horror!) but I dont leave it connected for long after all the lights have gone out. It is keeping NiMH cells shorted down that kills them, not doing it for a few minutes.
Im off to rebuild buy bx now... Need to beat Mike, Jeff and Ash and Kidi tomorrow..
Neil