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cwharper -> RE: Questions on A123 Batteries (4/8/2008 10:22:20 PM)
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For my small A123 packs 5s or less I now use a Thunder Power 1010C. It can charge a 5s or less pack at 10 amps in about 15 minutes. It will charge up to a 10s pack but the charge time increases. This charger will only tell you how many MAH you put back in. I don't think there is a charger out there that can tell you how much is left in a pack other than looking at voltage, but the resting voltage can be misleading on A123's. I guess you could finish discharging your packs after a flight or two to see what was left. Stop at 2v/cell. Once you charge A123's they stay charged. In my own experience for as long a 2 months (that's how long I left a pack sit that I know was fully charged the last time I dealt with it).
A123's are charged using constant current/constant voltage method kind of like charging a lipo but NOT peak detection like nimh or nicd. So there is not a problem in detecting a full charge, the voltage of the A123 tells the charger when to stop. Of course the charger must be A123 capable. An A123 cell is fully charged at 3.6 - 3.7v/cell. After you remove it from the charger it will eventually settle to around 3.45v/cell.
Not sure what you mean about topping up every 3rd or 4th flight, which brings to mind how long are you planning on flying? If you've forgetten what state of charge you left them in from the last session, then throw them back on the charger and find out.
Best recommended method for determining how long you can fly is to fly for say five minutes, land, and recharge measuring how much you put back in, then fly again for a little longer if you had the capacity to spare. One A123 cell is rated for 2300mah. In reality you will get about 2200mah out of it so go with that.
The recycling issue hasn't been brought up because a very good majority of the cells that were the first to make it into rc are still being used and still perform very well at least ALL of the cells I started with are still functional.
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