| 摘要 |
The present invention relates to emergency lighting ballasts having rechargeable batteries, usually of the nickel-cadmium type and more specifically to an apparatus to facilitate the charging of the battery pack at temperatures generally below normal operating ranges of the batteries (such as below 0° C) without damaging the battery. The apparatus includes such as a reverse-biased zener diode which has a breakdown voltage in the reverse mode which is at or below the maximum allowable charging voltage for the battery. Accordingly, when ambient conditions would otherwise allow the charging current of the battery to exceed the allowable level, the clamping zener diode breaks down shunting the excess current away from the battery. |
