Posted on Aug 8, 2012

Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery`s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage of 1 Vi cell. Measure the discharge time ofthe cells and perform a simple calculation to obtain the battery`s capacity. Set the drain current (!D) to 0.5C (C = battery capacity in mA/hr) by selecting an appropriate value for R4. Choose R5 such that: ID x R5 = 1 V. VREF is set so the comparator turns off the drain current and timer when the battery reaches its depleted voltage, V8 (usually 1 V/cell).

Click here to download the full size of the above Circuit.

With the battery in place, activate the circuit by grounding VREF with the momentary switch. The battery drains at ID until it reaches V8, turning off the drain circuit and the timer. Hysteresis keeps the circuit from restarting. The circuit shown tests 4.8 V, 180 mA/hr batteries. ID is 100 mA and V8 is 4 V.

Leave Comment

characters left:

New Circuits



Popular Circuits

Plants Humidity Sensor
Precision LED Blinker
Lead-Acid Battery Charger Circuit
ic 7812 dual regulator power supply
Solar Panel Based Charger And Small LED Lamp
Synchronous Camera Flash Trigger Using IGBT
DECL Documentation
Bipolar Tesla Coil Radiant Energy Collector
Crystal-Oscillator Circuits
FM IF amplifier circuit composed of ceramic filters
A simple control circuit Lantern
The MAX4104 4105 4304 4305 as the driving capacitive loads