NimH batteries

Archived from groups: rec.photo.digital (More info?)

I get very confused about NiMh batteries. On the one hand we are told that
you don't have to have them fully discharged before recharging because they
don't have a memory. But on the other hand I understand that if you don't
have an expensive charger that knows when full charge has been reached and
automatically switches off, your batteries can overheat and deteriorate.
I think I have hit on a simple solution. I remove the batteries before they
are fully exhausted. Then I put them into a torch, switch the torch on and
leave it on until the light dies. I then give the batteries a full timed
charge as if for first charge.
Is there anything wrong with this idea please? Thanks.

Archived from groups: rec.photo.digital (More info?)

"John Lee" <jandj.lee@ntlworld.com> wrote in message
news:Z31Re.1877$76.668@newsfe5-gui.ntli.net...
>I get very confused about NiMh batteries. On the one hand we are told that
> you don't have to have them fully discharged before recharging because
> they
> don't have a memory. But on the other hand I understand that if you don't
> have an expensive charger that knows when full charge has been reached and
> automatically switches off, your batteries can overheat and deteriorate.
> I think I have hit on a simple solution. I remove the batteries before
> they
> are fully exhausted. Then I put them into a torch, switch the torch on and
> leave it on until the light dies. I then give the batteries a full timed
> charge as if for first charge.
> Is there anything wrong with this idea please? Thanks.
>

www.batteryuniversity.com will tell you all you want to know ..

full discharge will be indicated by a minimum cell voltage of approx. 0.9 V
... a lower discharge may damage the cells ..
investing in an "intelligent" charger is worth every penny ..

Archived from groups: rec.photo.digital (More info?)

I found a cheap and safe way to discharge any NiMh or NiCd batteries down to
0.9V. You must be a little bit "electronically inclined".
Needed parts: a battery holder, one NPN 2N3055 transistor, one 1K resistor,
one Scottky diode like 1N5817 and one load resistor like 5 ohms or 10 ohms
1/2W.

1) battery (-) and transistor emitter to ground
2) transistor base to battery (+) through a 1K reistor and a Schottky diode
3) load resistor appropriate for the battery capacity from battery (+) to
transistor collector

The transistor will drive the load resistor until the battery voltage falls
down to arround 1.0V. As the battery voltage "tries" to go lower, the
transistor turns off and the load is removed. Only leak current remains
which is negligeable.

Jerry

"imbsysop" <imbsysop@yahoo.com> wrote in message
news:4314c0e2$0$11881$ba620e4c@news.skynet.be...
>
> "John Lee" <jandj.lee@ntlworld.com> wrote in message
> news:Z31Re.1877$76.668@newsfe5-gui.ntli.net...
>>I get very confused about NiMh batteries. On the one hand we are told that
>> you don't have to have them fully discharged before recharging because
>> they
>> don't have a memory. But on the other hand I understand that if you don't
>> have an expensive charger that knows when full charge has been reached
>> and
>> automatically switches off, your batteries can overheat and deteriorate.
>> I think I have hit on a simple solution. I remove the batteries before
>> they
>> are fully exhausted. Then I put them into a torch, switch the torch on
>> and
>> leave it on until the light dies. I then give the batteries a full timed
>> charge as if for first charge.
>> Is there anything wrong with this idea please? Thanks.
>>
>
> www.batteryuniversity.com will tell you all you want to know ..
>
> full discharge will be indicated by a minimum cell voltage of approx. 0.9
> V .. a lower discharge may damage the cells ..
> investing in an "intelligent" charger is worth every penny ..
>