Can I measure voltage of batteries/packs while charging?

[sygyzy]

Hi,

What would happen if I am charging a pack (say FiveMega's 6xAA or 9xAA) and I try to measure voltage with a DMM. Would this be trouble?

 

[VidPro]

no problem, definatly do that. just dont set it on amps and short it, but reading the voltage without shorting anything is just fine.

 

[AlexLED]

No problem, Sygyzy !

Just don't be alarmed that the voltage per cell will be significantly higher than the nominal NiMH voltage of 1.2 volts. And the voltage will increase during charge. Once the voltage stops rising and starts to decline, the charge(r) should stop.

 

[Fallingwater]

IIRC, voltage only stops rising in NiMH cells. It's NiCD ones where it starts declining.

 

[clintb]

IIRC, voltage only stops rising in NiMH cells. It's NiCD ones where it starts declining.

Both chemistries have voltage drop at the end of a charge cycle; the difference is how large of a drop the charger detects. Generally, a smaller drop for NiMh and larger for NiCd. There are some chargers that do a zero delta V detection as well.

 

[sygyzy]

Thanks for your help fellas. AlexLED - Thanks for the heads up. I have a hard time keeping track of stuff but I do know that NiMH batteries are often > 1.2 volts off the charger

 

[AlexLED]

Both chemistries have voltage drop at the end of a charge cycle; the difference is how large of a drop the charger detects. Generally, a smaller drop for NiMh and larger for NiCd. There are some chargers that do a zero delta V detection as well.

Fully correct !

Just for the record:
Decent chargers should detect a voltage drop of about 4 mV per NiMH and 8 mV per NiCd cell respectively.
Even better if they would detect when the rise stops, but this is technically more challenging.

 

[Fallingwater]

Both chemistries have voltage drop at the end of a charge cycle; the difference is how large of a drop the charger detects. Generally, a smaller drop for NiMh and larger for NiCd. There are some chargers that do a zero delta V detection as well.

Well, I did say IIRC. Obviously IDRC (I Don't Remember Correctly).