Test application: 7A electric motor (peak 9A)
2 AA NiMH:
- 5+ year old Radio Shack 1600 mAh
- 1 year old LaCrosse 2 Ah
- new Noma 2 Ah
All were used by the motor for only 2-3 cycles before the test. Noma still being broken in.
LaCrosse Bc-900, charge 500 mA, discharge 250 mA
Before test capacity:
Radio Shack 1371 mAh, 1575 mAh
LaCrosse 1890 mAh, 1898 mAh
Noma 1928 mAh, 1745 mAh
All are close to spec, except RS1 is bit lower.
Charged,
Radio Shack 1466 mAh, 1751 mAh
LaCrosse 2.08 Ah, 2.11 Ah
Noma 1321 mAh, 1690 mAh
Hmmm, Nomas didn't take in enough charge, perhaps because still too new.
Rest for 32 days
Before test capacity:
Radio Shack
1250 mAh (*) vs 1371 mAh = 9% discharge
1108 mAh vs 1575 mAh = 30% discharge
LaCrosse
1613 mAh vs 1890 mAh = 15% discharge
1658 mAh vs 1898 mAh = 13% discharge
Noma
(**) 721 mAh vs 1321 mAh = 45% discharge
(**) 1063 mAh vs 1690 mAh = 59% discharge
(*) Guess as I lost the timing
(**) Charged current since it was less than capacity
Using SilverFox's graph the typical 0.7% discharge per day equals about 21% loss after 1 month. Radio Shack #2 is bit higher, but #1 and noth LaCrosse are better. Not sure what to make of Nomas. I guess they are still breaking in.
Old batteries have a high self discharge. Also, damaged batteries have a high SF rate as well (such as new Energizer 2500s with high SD). Therefore SD is a rough measure for cell age and/or damage.
I want to know if such a high current draw (7A or 3.5C) will kill AAs. I already lost several Energizer 2500s as many others. So higher capacity AAs are clearly not suitable. From reading different posts here, I thought that lower capacity cells may be more robust and I switched to 2Ah and lower capacity cells.
One Radio Shack seems to have a high SD. It is older cell so that is fine. LaCrosse cells are fine, low SD. Nomas are too new. Therefore, seems to me that 2Ah cells can handle such high current draw fine, with a minimum damage.
Therefore lower capacity NiMH cells are indeed more robuts and less damage prone.
2 AA NiMH:
- 5+ year old Radio Shack 1600 mAh
- 1 year old LaCrosse 2 Ah
- new Noma 2 Ah
All were used by the motor for only 2-3 cycles before the test. Noma still being broken in.
LaCrosse Bc-900, charge 500 mA, discharge 250 mA
Before test capacity:
Radio Shack 1371 mAh, 1575 mAh
LaCrosse 1890 mAh, 1898 mAh
Noma 1928 mAh, 1745 mAh
All are close to spec, except RS1 is bit lower.
Charged,
Radio Shack 1466 mAh, 1751 mAh
LaCrosse 2.08 Ah, 2.11 Ah
Noma 1321 mAh, 1690 mAh
Hmmm, Nomas didn't take in enough charge, perhaps because still too new.
Rest for 32 days
Before test capacity:
Radio Shack
1250 mAh (*) vs 1371 mAh = 9% discharge
1108 mAh vs 1575 mAh = 30% discharge
LaCrosse
1613 mAh vs 1890 mAh = 15% discharge
1658 mAh vs 1898 mAh = 13% discharge
Noma
(**) 721 mAh vs 1321 mAh = 45% discharge
(**) 1063 mAh vs 1690 mAh = 59% discharge
(*) Guess as I lost the timing
(**) Charged current since it was less than capacity
Using SilverFox's graph the typical 0.7% discharge per day equals about 21% loss after 1 month. Radio Shack #2 is bit higher, but #1 and noth LaCrosse are better. Not sure what to make of Nomas. I guess they are still breaking in.
Old batteries have a high self discharge. Also, damaged batteries have a high SF rate as well (such as new Energizer 2500s with high SD). Therefore SD is a rough measure for cell age and/or damage.
I want to know if such a high current draw (7A or 3.5C) will kill AAs. I already lost several Energizer 2500s as many others. So higher capacity AAs are clearly not suitable. From reading different posts here, I thought that lower capacity cells may be more robust and I switched to 2Ah and lower capacity cells.
One Radio Shack seems to have a high SD. It is older cell so that is fine. LaCrosse cells are fine, low SD. Nomas are too new. Therefore, seems to me that 2Ah cells can handle such high current draw fine, with a minimum damage.
Therefore lower capacity NiMH cells are indeed more robuts and less damage prone.
