Ni-MH Rechargeable Batteries
Cycle
and
Battery
Life
(cont.)
Charge rate and amount of charge input during overcharging are also important factors affecting cycle life. If the battery is charged at a rate that exceeds the oxygen recombination rate, oxygen that is generated during overcharge will not react, causing a build up in gas pressure and a rise in temperature which will have damaging effects on battery and cycle life. Prompt use of an effective charge termination method when deleterious overcharge begins will lessen the effect
on cycle life.
Cycle life is also affected by the depth of dis- charge. Depending upon the charge termination method, up to 500 cycles can be obtained with the battery being fully discharged on each cycle (100 percent depth of dis- charge, or “DOD”). Considerably higher cycle life can be obtained if the battery is cycled at shallower charge/ discharges.
7.2 Battery Life
The same factors that affect cycle life affect overall battery life. Operation or storage at extreme temperatures, overcharging, cell venting and abusive use will reduce battery life. Operation and storage of
batteries at or about room temperature (20°C or 68°F) will maximize battery life. Recommended and permissi- ble temperature limits are shown in Table 7.2.1.
Table 7.2.1
| Recommended | Permissible |
|
|
|
Low Rate Charge | 15°C to 30°C (59°F to 86°F) | 0°C to 45°C (32°F to 113°F) |
|
|
|
Quick Charge | 10°C to 30°C (50°F to 86°F) | 10°C to 45°C (50°F to 113°F) |
|
|
|
Fast Charge | 10°C to 30°C (50°F to 86°F) | 10°C to 45°C (50°F to 113°F) |
|
|
|
Trickle Charge | 10°C to 30°C (50°F to 86°F) | 10°C to 35°C (50°F to 95°F) |
|
|
|
Discharge | 0°C to 40°C (32°F to 104°F) | - 20°C to 50°C |
|
|
|
Storage, Short Term | 10°C to 30°C (50°F to 86°F) | - 20°C to 50°C |
|
|
|
Storage, Long Term | 10°C to 30°C (50°F to 86°F) | - 20°C to 35°C |
|
|
|
Table 7.2.1 Recommended and permissible temperature limits for operation and storage of DURACELL
18