LOW_BATTERY_WARNING_DISCONNECTOR

Published:2009/7/6 5:59:00 Author:May | From:SeekIC

NiCad batteries are excellent rechargeable power sources for portable equipment, but care must be taken to ensure that the batteries are not damaged by overdischarge. Specifically, a NiCad battery should not be discharged to the point where the polarity of the cell is reversed and is reverse-charged by the higher-capacity cells. This reverse charging will dramatically reduce the life of a NiCad battery. This circuit both prevents reverse charging and also gives a low-battery warning. A typical low-battery warning voltage is 1 V per cell. Since a NiCad, 9-V battery is ordinarily made up of six cells with a nominal voltage of 7.2 V, a low-battery waming of 6 V is appropriate, with a small hysteresis of 100 mV. To prevent overdischarge of a battery, the load should be disconnected when the battery voltage is 1 V x (,N- 1), where N = number of cells. In this case, the low-battery load disconnect should occur at 5 V. Since the battery voltage will rise when the load is disconnected, 800 mV of hysteresis is used to prevent repeated on-off cycling.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Basic_Circuit/LOW_BATTERY_WARNING_DISCONNECTOR.html

Print this Page | Comments | Reading(3)