kx250ryder

OK so I got sick of my 1400mAh 2/3A ni-mh receiver pack always dying on me. So over the last two nights I built a 2650 mAh AA receiver pack with some Duracells because they had highest rating out (more than I could even find online), and were cheaper than Energizers.

I don't know that it matters but I built the pack with some scraps lying around. I used 14 gauge braided Dynamite wire with the insulation removed as battery bars. I used a 18 gauge receiver leads with the signal wire pulled out, and a deans micro 2r connector. Since its in a wierd shape, I couldn't use shrink wrap, and so I wrapped the whole thing in electrical tape.

In any case, I was lazy and I blew off form charging the pack at C/10. I am cycling it on my Super Brain 977 right now at work using a 1 amp charge rate, and on my second charge it says it took 2875mAh and finished at 7.19 volts. I actually screwed up and set my delta peak at 20mV which is 5mV per cell for only 4 cells. So if I would have set the delta peak threshold to 25mV per cell (the recommended setting for 5 cells), it would have even registered higher! I am in an air conditioned building, and the fan that cools my charger was blowing on the pack, could this have been the reason for the extra capacity?

I know that batteries typically charge to higher voltage than what they say, but I thought that usually you should only expect about 90% of rated capacity. This charged to well over 100%. Not only that, but this is only the battery's second charge. I have heard that they take several charges before they get to full capacity. I am not complaining, just wondering if this is normal, if I got lucky, or if I am misunderstanding the data.

Also, I was wondering if 18 gauge wire will stand up to charging this thing at 1C (2.65 amps) since charging at 1 amp is taking me forever.

hunter306

I have a couple sets of AA reciever packs that I regularly charge on my Super Brain 977.. an 8cell 2500mah pack regularly fits about 3100mah in during a normal charge.

Similarly, I live in the basement, so it's cool and I have a custom built cooling rig for my batteries. I would say that it's not unusual.

kx250ryder

OK, what about charge rates? I am using 18 gauge wire, which is the thickness of the wires that you plug into your receiver. Does anyone know if thin gauge wire and these AAs will stand up to a 1C charge rate on a regular basis?

guver

My Feedback: (325)

Yes, both set-ups sound pretty normal to me, I don't buy into the idea that cells take a few cycles to come up to capacity. Ok maybe 2 but I believe that every cycle dimishes capacity a certain amount. Your cells maybe are formed at factory.

kx250ryder

Thanks, as soon as this discharge cycle finishes and the pack cools off, I will give it a shot at 1C. Now that I think about it, I charge my 2300 mAh radio batteries at 1C and if that plastic holder they sit in can handle that rate, my battery pack should be able to as well.

guver

My Feedback: (325)

The wire and holders are ok, but I have always used a max rate of a half amp for AA batts. cuz they got hot.

kx250ryder

I realized I do my radio batteries at .5C (1.2 amps). After discharging my new receiver pack at 1 amp, I got 5.45 volts and drained 2545 mAh. When I re-charged them at 1C (2.6 amps) I got 2745 mAh into them, finishing at 7.11 volts. Took 64 minutes, and yeah, they were hot. I guess I will just plod along with .5C from now on. I am surprised how much more resilent to fast charging sub C cells are than AA cells.

guver

My Feedback: (325)

My theory is that it is in the diameter of the cell. It's only an idea, but the larger diameter delivers better discharge current and the longer length gives better capacity.