stevem
Senior Heliman
Location: Oklahoma
| Depends on the cell really. Most of my AAA NiMH cells (700mah) are charged at 1.2A. How patient are you also is a consideration.
A new 700mah pack should be 'balanced' (or formated) by charging at 70ma for around 12 hours. While 70ma is enough to charge a cell from depletion to capacity in 10 hours, some of the cells will be at different states of discharge in a new pack. 70ma for a few extra hours would not hurt anything and will force some of the lazy cells to come up to capacity.
I know you don't have a 70ma option on the 250S, so first charge would be at 100ma until they peak, then do a gentle discharge. Recharge at 700ma and go fly.
No on future charges, try bumping the charge rate up 100ma or so and see how the pack responds. NiMH will get hotter than a nicad during charge due to the chemical processes. A NiCad will actually cool a bit when starting a charge. NiMH cells should be allowed to cool before a charge because they start to heat the moment you apply a charge current. So monitor the pack and see how hot they get. Warm is ok, hot is not of course. If it does well, then bump it up. Do a gentle discharge and 100mah charge ever 10-20 cycles and your packs will be happier and so will you.
Generally, I make my own packs from Energizer cells which work great at 1.2A charge rates - several hundred cycles at 6A discharges are the norm with my packs. 1.2A will get the cells pretty warm, but you will also find that a warm NiMH pack will perform much better than a cool one. In cold conditions, it is a good idea to peak charge the pack to get it to temp just before flying.
Hope this helps!
Steve |
