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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> Questions on A123 Batteries
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Questions on A123 Batteries - 4/8/2008 6:01:34 PM   
NorthernBoy


 

Posts: 122
Joined: 4/18/2003
From: Nellie Lake, ON, CANADA
Status: offline 		I am looking at converting my fleet over to A123 batteries and I have a few question. I plan to purchase a Dewalt 36v battery pack and making 5 packs, but will one charger be enough, and which charger is the best for detecting a fully charged battery? From what I have read they hold a charge longer without any trickle charger, so once they are charged up they are ready for the next session. And since you cannot measure the capacity left after flights, does the actually top them off and tell you how much mAH was used? Would it be relistic to top up every 3rd or 4th flight to make sure they are not down too much? Is there any other ways to measure how much is left in a pack before a flight? This is the only thing that bothers me, is it safe to fly or not. Also do they need to be recycled like Nicads or Nimh? If not seems like you could get away with alot less equipement.

Thanks
NB
       Post #: 1

RE: Questions on A123 Batteries - 4/8/2008 10:22:20 PM   
cwharper


 

Posts: 219
Joined: 2/18/2007
From: Ocilla, GA, USA
Status: offline 		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.

_____________________________

When you see the mushroom cloud, you will know then that I have finally achieved fusion.

(in reply to NorthernBoy)
       Post #: 2

RE: Questions on A123 Batteries - 4/9/2008 7:38:57 PM   
BocaBen


 

Posts: 160
Joined: 4/12/2002
From: Boca Raton, FL, USA
Status: offline 		I discharge my A123 (2s - 6.6V) from time to time using my Triton, setup to 2A discharge and 5V stop.
I go flying, make my 4 flights, come home and discharge them so I know what's left in there. I do that every 3 months or so.
I find that I roughly use 200mA per flight, meaning that the discharge is about 1300mAh on the Triton.
I then use the FMA Cellpro charger and it puts 2100mAh back in.

I am using switches with charger port and when done charging, I hang a small plug in there with red tape to remember that it was recharged. They hold the charge for a very long time, so all my fleet is ready to go at all time.

(in reply to cwharper)
       Post #: 3

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