[Shop-talk] Recharging a Ni-Cad Battery

[jibjib at att.net]

Karl,

I did say very occassionally and I do not believe that NiCad packs will have an issue with it, especially at the 1/10 C rate I also discussed. 

I would not do this with NiMH and certainly not any Lithium chemistry. which defnitely require balanced charging or regular balancing.  I only use balanced chargers on Lithium cells, but simple 1/10 C charging on everything else.  

Complete discharging of NiCad (and only NiCad) packs is not an uncommon practice in the RC world.

Jack
-------------- Original message from "Karl Vacek" <kvacek at ameritech.net>: -------------- 


> 
> > Also, NiCads, unlike many other batteries, have no issue and may benefit 
> > from a very occassional, full and complete discharge. 
> > 
> > Jack 
> 
> 
> This is a little off from Eric's dive light question, but... 
> 
> As an R/C pilot you can't mean that. You have a potentially lethal weapon, 
> and an investment of hundreds (or thousands) of dollars flying around 
> completely dependent upon the health of your radio batteries. 
> 
> If you're referring to completely discharging a nicad back as opposed to one 
> individual cell, DO NOT do it. 
> 
> Maybe one or two complete discharges won't do any noticeable harm, but more 
> than a few will begin to destroy the weakest cell in the pack. As the cells 
> discharge, one reaches 0 volts first, and the current from the others 
> flowing through it as they continue to discharge will reverse-charge that 
> weakest cell, reversing its polarity. Then the second-weakest cell will 
> reach 0 volts and reverse polarity, and so forth, till only one cell is left 
> with any voltage. 
> 
> Do that a few times and you've ruined one or more cells and thus ruined the 
> pack. That's why there are smart chargers and dischargers and 
> expanded-scale voltmeters to monitor the state of charge and discharge of 
> nicad cells and battery packs and exercise them as well. 
> 
> Karl