CCCV Charging of NiMH Cells
Is it possible to charge Ni-MH cells using CCCV algorithm? How good or bad it is and how does it affect the cells’ cycle life? Let’s find out…
Test Objects
Panasonic Ni-MH 2700 performs poorly in life cycle tests. CCCV could be more gentle to NiMH cells and could yield more cycles at the expense of capacity.
Test Method
I don’t have any charger that could CCCV charge Ni-MH cells. The closest I have is the RAM charging algorithm on SkyRC MC3000 charger. I am going to use it with with these parameters:
- charge current: 1A
- target voltage: 1.45V
- terminate charging at 100mA
- discharge current: 0.5A
- terminate discharge at 0.9V
Test Result
Here are the measured CCCV results and the -dV results as reference
| BK-3HGAE | CCCV A | CCCV B | -dV A | -dV B |
|---|---|---|---|---|
| Capacity [mAh] | 2117 | 2128 | 2470 | 2495 |
| Cycles to 100 mOhm | 183 | 102 | 57 | 48 |
| Cycles to 80% | 177 | 135 | 84 | 82 |
Conclusion
Charging Panasonic Ni-MH 2700 cells with CCCV algorithm more than doubles the cycle count, but fails to charge the cells fully. The higher the internal resistance the sooner the target charge voltage is reached and the less capacity is put into the cell.
Cheers,
AA Cycler