arcarle

right now I have only 2 6 cell nimh packs @ 3300mah. The question is: I just got my hyperion charger. When I charge at 1 amp it takes 4+ hours to get a full charge and the readings are 8.56 volts and 3800mah. Does that mean its over charging it or just that my battery was underated by the manufacturer? I did just do a discharge the night before down to 5.8 volts since i had run the packs close to twenty times.

Now the second battery i tried to charge it at 3.3 amps and it only got to 6.5 volts and the charger said it was finished in like 20 minutes. I forget what the mah was. Was this maybe too high of a charge rate?

I'm just wondering do I have to use the 1 amp charge rate for 4-5 hours to get a good charge or is there another better rate that someone else has experimented with and found to work well already that they wouldnt mind sharing the knowledge with me?

Thanks for any answers, theories, responses in general.

Trips

iTrader: (16)

When I was running 3300mah NIMH cells I used to charge at 4.5 to 5 amps. This was with matched cells. If you're running sport type "stick" packs, you might want to go at a lower rate, say 3.5 to 4 amps or so.

THe 3800 reading you got wasn't what went into the cells, that was what came out of the charger. Some of the energy coming out of the charger gets converted to heat. That's why the mah reading for the charge can be higher than the expected capacity of the battery.

arcarle

That makes sense since heat IS energy. What about the low end voltage though? After that "low" charge I set it up on the 1 amp rate and even though it took longer the voltage came back up significantly.

I guess what I am asking is by charging at a higher amperage rate am I sacrificing a full quality charge for a fast one?

trailranger

Delta-Peak chargers know when to stop charging the cells even when charging at a fast rate. There is minimal difference in total capacity in the cells when charging at 1C or charging at up to 6amps. There will be lower voltage under load when charging at low C rates. Only charge at high amps if the cells are in good working order.

Since you said that you have 3300 packs, I would have to assume these are old cells or stick packs which would limit the charge rate becuase of the chances of one of the cells not being fully functional. I suspect the pack that only charges for 20min has a dead cell or the remaining capacities in each cell vary greatly.

If you can tray your pack on an equalizer before charging your packs would not false peack as much and should take a full charge. If you can not discharge on a tray, discharge the pack untill the no load voltage is 5.4V
peak charge at 4A. Once peak allow the pack to trickle charge @ 100mA untill the total MAH reaches 3600~4000. This is about the only way to equalize a sealed pack.

arcarle

Thanks man I'll try that. I was starting to think it was maybe just a false peak.