Klas Strandberg wrote:
>
> Vicky,
>
> the little mysterious thing is a temperature swith, swithing off the
> charging when the cells have reach a certain temperature.
>
> This little device can have different functions in different systems:
>
> 1/ The entire system (cells, charger and temp switch) is so calculated, that
> the batteries are fully charged at a certain temperature, and that the
> switch then disconnects the charging.
>
> 2/ That the charging process is controlled by electronics, and that the temp
> switch is only a "fuse", giving extra protection to prevent overcharging.
>
> I don't know which system Sony used, probably 1/
>
> This means that you cannot just put in new cells, and then use the original
> Sony charger! Without the temperature switch you may blow the new cells, and
> with it you may blow them anyway, as the switch may allow too high
> temperature for your new cells.
>
> Make a new battery pack, that's okay, but check carefully that the cells
> don't get hot when you charge them. "Luke warm" is okay.
One of the differences in NIMH Cells is that they are much hotter than
Nicads at the end of a fast charge that is correct for them. Often hot
enough you would not want to close your hand on them just as they
finish. A fast charge to Luke warm would leave them way undercharged. If
this pac is of your first type, and the original thermal switch is left
in while changing to NIMH it may create a problem of undercharge using
the original charger unless it's a slow charge type.
The thing to do if setting up the battery pac, if you are not replacing
the exact same cell model is to go with the charge recommendations for
the new batteries. Use of the original charger may or may not match
this. The best would be to use a newer design computerized charger that
can do 5 cell voltages. Then the thermal sensing system is not really needed.
The other choice is simply to only slow charge the modified pac.
Walt
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