I did some load testing on the 6-Cell RC battery packs from http://www.batteryspace.com because I am anticipating using them to replace lead-acid batteries in my motorcycle. I just need to work out how to build a BMS and charge them.
NiMH 3ah 7.2v test http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=70
After Connector cut off
Charged at 2 amps for few minutes before test
Open C. 7.8v
30 amps: 5.83
50 amps: 5.10
75 amps: 3.174
The load test was only momentary
NiCad 1.7 ah 7.2v test http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=89
Battery 1 after overcharge for about 20 hrs at 250 ma (oops!)
After Connector cut off
Battery feels warm to hot
Open C. 8.41v
30 amps: 6.5
50 amps: 5.42
80 amps: 3.61
The load was only momentary.
Battery 2 after charge at 250 ma for 7hrs
Connector cut off
Battery feels slightly warmer than room temp
Open C. 8.47v
30 amps: 6.61
50 amps: 5.53
80 amps: 3.75
How short was momentary? I'm surprised you could draw 25C from their NiMH with out problems. 63 milliohms @ 30A for either of their packs = 10 milliohm per cell with interconnects.
I'm using Batteryspace 24V sub-C packs (mine are the earlier 3.3AH version):
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2759
I measured 120 milliohm resistance in these packs. That would be 3.6V sag @ 30A.
circuitsmith,
I'd cut the Tamiya connector as I found they add considerable resistance.
Each load test was for about 2 sec, and I did the lower rates first. I was surprised I got 47C out of the NiCad pack. That "sintered" electrode must do something. Note that the NiCads have 16 AWG wire, while the NiMH has 14 AWG.
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