Published July 9th, 2006 by Jim O'Halloran
Charging NiMH AA’s
I recently bought a set of 8 Energizer NiMH rechargables to run in my transmitter (the awsome Futaba 2PL). I didn’t buy the Energizer charger because I’ve got my Integy 16×5. I’ve had the Integy for a coupla years now and like it a lot. Its done an excelleny job of looking after my cheapo 3300 packs I use for racing, and I figured it’ll do a much better job of AA’s than some $20 charger from Bunnings.
Of course, that left me with one problem! Charging current… I know the AA’s and AAA’s are sensitive to charging current, you certainly don’t force feed ‘em at 5amps like you would a racing pack. But I didn’t necessarily want to charge them at 0.2 amps (the slowest rate the Integy can charge at) because it would take all day!
The Energizer site had a datasheet for my batteries, but it doesn’t mention what current to charge at (they probably want you to buy their chargers). Elsewhere on the net I found plenty of discussion about which brand of AA’s are best, but nothing that answers my question about how fast they can/should be charged. Finally, this RC Tech forum thread gave me the info I needed. One forum post suggested 0.5 - 1.5 amps.
I’ve always chaged on the low end of the amp range (I charge my racing packs at 4.5 amps), so I went with 0.5. The trade off you get with different charging currents is “punch” vs runtime and battery life. Charge at a high amperage and you’ll get a little more punch, but at the expense of a little bit of runtime and potentially a lot of battery life. Lower amperage carges give you a less punchy pack, but slightly longer runtime, and considerably better overall battery life. As a guy who can’t spend much money on my racing gear, I definately wanna look after my batteries, they’re to expensice to replace often!
I’ve soldered up a 4 cell AA holder to a deans plug so I can charge 4 of my AA’s at a time, and set up a program on the Integy to charge at 0.5A and discuarge at 1A. When I connected it all up and set the batteries to charge the charger immediately started beeping and reporting “Open Curcuit Error” on the screen. I tested all of the solder joints and cabling with the multimeter and they were fine. However, when I tested the batteries themselves, they reported voltages suggesting they were almost fully charged. When I slapped them in the TX, the voltage dropped rapidly, and once the TX reported low battery I took them out again and put the first 4 on charge, and this time they started charging normally.
Heh, now that I’ve figured out how to work around an “Open Cuircuit Error”, I might have to revive my plans to charge my nitro glow warmer off of the Integy. When I last tried that I got the same error and couldn’t work out why it was happening! One charger to charge them all! I’ll also be interested to see how the rechargables go in the Digital Camera too.
Jez Says
G’day Jim,
Regarding the Energizer NiMH AA’s in a camera, I have an Olympus C-370Z which requires two AA’s, so I picked up an Energizer charger with two NiMH AA’s which have served me well for almost a year now.
While the charge cycle lasts fourteen hours I can say without a doubt that it’s the best $20 I’ve ever spent on batteries in my life. Because the camera’s preview panel is always active the drain on the batteries is constant, include the drain from the flash and you can see it’s not hard to chew through AA’s like Sunday’s roast.
I’ve just picked up a second set of the same NiMH AA’s and now I’m giving the camera a real workout, luckily the charger handles four AA’s in the same fourteen hour cycle.
I’m going to get a set of eight AA’s and a 9V for my son’s R/C car, and a couple more chargers!
Jez (0:
Dec 22nd, 2006 at 8:48 pm