CloudSkipper

First: Is it totally OK to charge a 5 cell NiMH with a wallwart for 4 cell packs?

The reason why: I bought this 5 cell RX NiMH pack over a year ago. I never touched it until now. When I tried to charge it with my accucycle charger, it told me after a few minutes of charging "voltage too low". I checked and the whole 5 cell pack has a voltage of 1.3 volts [X(] ... The only other charger I have is a wallwart for 4 cell RX packs. Can I use that to kick start this 5 cell pack (it charges at 60 mah)? Will it do any good or will the too low charge voltage do anything wierd to it?

p.s. come to think of it, if the above is ok to do, then I could use the accucycle to charge the 5 cell as a "one cell"... then as a "two cell" and so on until it's back up to proper volts again... ???

Thanks

Highflight

My Feedback: (4)

A 5-cell Nimh pack that reads 1.3 volts is pretty much a lost cause. Let it go.

CloudSkipper

Bummer. It was new, but bought it over a year ago. So it drained in that time. Didn't think it could go that low in that time.

So even if it's not cycled at all, not an old pack, you cannot bring it back up?

Thanks

MetallicaJunkie

i would bump it up with your wallwart overnight then try putting it on your elite charger.... i have left the switch on a couple of times on different battery packs and brought them back to life with out any issues....after its charged cycle it and see how it goes

CloudSkipper

Got it charging on the 4 cell wallwart now. Then I guess I'll cycle it a couple of times on the accucycle to check that it performs normally.

But wow I didn't think a new, unused pack could drain that low.

Cheers

Rodney

Both NiCad and NiMh have a rather high self discharge rate and both will eventually discharge to the point that, if you put a conventional VOM on them, they will read very low. In fact, one of NASA's papers recommend that NiCad's be stored completely discharged with a shorting bar across each cell and kept at a low temperature (right around 30 degrees); when ready to use, warm and charge at 0.1C for 16 hours. And, yes, you can fully charge a 5 cell battery with the typical wall wart made for the 4.8 (4 cell) batteries. It will just take a lot longer as the current will be less when charging a 5 cell rather than a 4 cell.

ericyao22

there are some low self discharge nimh batteries on the market.So do our manufactory.

CloudSkipper

It's working out fine with the 6V pack (1600 mah). Interesting though the steps I had to take...

1) I charged for some 20 hours on the 4C wallwart. That got it to 2.9V. It just leveled off there and wouldn't go higher.

2) Then I tried it on the accucycle on 5C charge mode @150mah. Got the "too low voltage".

3) Then tried on accucycle on 4C mode @150mah. That got it charging. It leveled off again at 3.6V and wouldn't go higher.

4) Then tried on 5C mode @150mah. That got the voltage going higher again, but it leveled off at I think it was just over 4V.

5) After that getting the volts to increase required repeated increases in mah up from 150mah. It got up to 7V only after increasing to 550mah charging. Soon after that the accucycle indicated that charging was done.

6) Then I did a 200mah discharge. It went down to 5.5V in only 10 minutes.

7) Then I started a charge at 300mah. It put in about 1800mah without detecting the peak. I stopped it manually and started a 250mah discharge.

The above discharge is ongoing and the pack is behaving normally maintaining a under-load volt level above 6V (last checked @1000mah discharged).

Cheers

ericyao22

Normal nimh battery self discharge rate is very high ,when you put them in a corner for a long time,the voltage will bedroped very quickly.
For solve this problem,lowself discharge rate nimh battery was born .The voltage of the lowself discharge rate nimh battery will be droped very slowly.
Maybe you will found the voltage of 5 cell is 4.8V after one year you don't touch it ,it justreduced 1.2V .