Bob said:

> We went thru a whole deal on this NiMH battery charge system.

> The most important factor is battery temperature.
> As the NiMH cell tops off, battery temp rises
> to 45C or so. For the most part, charge level can
> be determined simply by the temperature.

> As a general rule, charging without monitoring temperature
> is a good way to have a fire.

> As the cell is approaching full charge, the cell voltage rises to
> 1.50V per cell. Cut it off there, if you can. The knee is softer on
> NiMH and more difficult to read.

> ... and DON'T trickle-charge NiMH cells, they don't like it.
> Charge at a rate of C/5 for good cell life.

> Good documentation is hard to find. But Tynergy Batteries

Maybe Tenergy ???

>  has V-I charts that are accurate.

All good stuff where you have essentially unlimited charging energy 
available and "normal" temperatures apply.

Just to add perspective: In my main applications energy source is limited 
energy solar and ambient temperature may be as high or even above Bob's  end 
point temperature. (The latter is not good for battery life!).

NimH long term low rate charge end point voltages are lower than under 
typical conditions. Maximum end point voltage / cell would typically be 
never above 1.45V/cell and may even be less so a 1.5V end point would never 
be reached..

My available charge rates vary with application but are in the C/4 - C/8 
range at full rate and can be anything below that when the enerrgy source 
decides to hide behind clouds or increasing amounts of the atmosphere.


            Russell.


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