Are my mAh calculations flawed ?

[reman]

Hi all,
I just got a 2500mAh battery to replace the 700mAh ni-cd in my futaba TX.
The sticker on the 2500mAh battery says to "charge it for 14/16 hours at 250mAh"
So does that mean that using the 70mAh charger the 2500 will take up to 57.15 hours to charge ?
What would the maximum "C" rating for ni-mh batteries ? (can you get fast chargers for the TX ?)

Also, I have a charger kicking about from an rc systems minicopter, It's 9v and 350mAh, would this kill the pack ? ( either by being .6v to low or 100mAh higher than recommended )

[DavidH]

No the 70 mah charger will not have enough power to fully charge the 2500 mah battery. It could be used as a charger to trickle charge the battery all the time.

Yes you can fast charge TX batteries. Some transmitters have a diode that prevent charging the battery while it is in the TX. If you use a charger that has to read the battery. You will have to take the battery out of the TX to charge it. If theTX has a diode installed.

Yes the 9 volt charger would NOTt work well charging the 9.6 battery pack.
David

[Pinecone]

I have a 2000mAH TX battery I picked up at RCX 05. I needed charging the other day, so I popped it onteh Triton at 2A charge rate (nice 1C), and it took 149 mAH. Hmm, this doesn't make sense, so I hit it again and it took another 149 mAH, Ahh, at least consistancy.

So I dropped the chrage rate down to 0.5A and it took 1000 mAH. Dropped it to 0.2A and it took almost 600 mAH. So after 4 charges it took just under 2000mAH.

So not ALL high cap TX batteries will take a fast charge.

[DavidH]

Nickle Metal Hydride batteries need to be cycled several times before they reach rated capacity.
When I have bought and used Nimh cells. I charge and discharge them several times on a cycler before I use them. The first few times cycling them, they get closer to the rated capacity each time. Finally after several cycles, they will exceed rated capacity by a few hundred mahs.

David

[Pinecone]

These have been cycled. They just don't seem to like to be fast charged.

[DavidH]

Yes there is certain batteries that do not liked to be charged at 1C or higher. The charger will usually false peak due the heat build up in the cell.

David

[reman]

I had to do something about the TX charge time so I bit the bullet about a week ago and got a Multiplex LN-5014 charger.
Like lots of 'um these days it does everything I need and somethings I didn't know I needed, like when it cycles a pack it lets me know how much power it put out ( the original 700mAh pack only held 550 mAh on the first cycle, by the 4th it was up to 720 !!! ). The 2500 pack charged in 10 hours ( had three flights + a lot of testing on it so far and its still reading over 10 volts, with the old one the second flight always had to end early when the TX starts bleeping at me )

All I need now is a 3 cell balancer for for it and then I can use it on the lipo's to