Trickle Charging LSD Cells
Common knowledge says trickle charging is bad for low self discharge NiMH cells. But how bad? Should one care? This test is to give us some answers.
Test Objects
- “0mA” control cell - no trickle charge
- “20mA” test cell - trickle charged with 20mA
- “50mA” test cell - trickle charged with 50mA
- “100mA” test cell - trickle charged with 100mA
Test Method
Test performed on SkyRC MC3000 for its accuracy and ability to terminate on 0dV and Fujitsu White cells for their consistency. The test consists of these steps
- discharge the cells at 1.0 Amp (about 2 hours)
- charge the cells at 1.0 Amp, terminate at 0dV (another 2 hours)
- trickle charge the cells for the remaining 2 days (44 hours) with 0mA, 20mA, 50mA, and 100mA respectively
- repeat steps 1-3 until feasable
This test is going to take months to finish…
Test Result
Conclusion
This test took 87 weeks (1 year 8 months) to finish.
I am going to assess the impact of trickle charge based on how the internal resistance developed in each cell. The controll cell without trickle charge defines the baseline.
| Cell | Cycles to 100 mOhm | % | Change |
|---|---|---|---|
| 0mA control | 248 | 100% | 0% |
| 20mA test | 210 | 85% | -15% |
| 50mA test | 190 | 77% | -23% |
| 100mA test | 160 | 65% | -35% |
Even the smallest 20mA trickle charge causes 15% drop in cycle count.
Conclusion: don’t trickle charge LSD NiMH cells, or do so with less than 20mA current.
Cheers,
AA Cycler