battery discharging circuit/ battery full charge detection

Discussion in 'Power Electronics' started by haneef, Mar 18, 2010.

1. haneef

2
0
Mar 18, 2010
Hello...I want to build a circuit for battery discharging...or even to detect a battery when it is fully charged.....can anyone please help me??

2. neon

1,325
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Oct 21, 2006
to discharge a battery all you need is a load. If you want to discharge it at a certain rate just put a power transistor across and vary the base. to detect a fully charge battery a comparator will do it or even a LED if designed carefully

3. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,849
Jan 21, 2010
It also depends on the battery type (a lot).

Detecting discharge is usually based on voltage (but that voltage varies with load)

Detecting a full charge is sometimes based on voltage alone, sometimes often there's a top-up charge applies after reaching a certain voltage. Other battery types a full charge is indicated by the rate of change of temperature, or even a small dip in the voltage.

4. haneef

2
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Mar 18, 2010
Hi der...thanx alot for your reply..actually i am a little weak in practicals..can you guys please tell me how to attach the load...i want to discharge the battery after it is fully charged or i want to connnect an led showing full charge...can you please show me the circuit..please...u can email it to me at [email protected]

5. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
2,849
Jan 21, 2010
A load is anything that you connect to the battery causing current to be drawn. It could be a lamp, a resistor, or some fancy electronics. Here is a simple example.

To determine when the battery is fully discharged you need to know (at a minimum) what type of battery and what nominal voltage it has.

To connect a LED showing full charge, well, that is a complex topic...

6. GreenGiant

842
7
Feb 9, 2012
Not entirely correct, you can check a battery's true voltage while it is charging if the voltage reading comes directly from the tabs of the batteries

This should yield the voltage of the battery, rather than a charge/discharge voltage, though you will sometimes get discrepancies when close to fully charged/discharged

7. BobK

7,682
1,689
Jan 5, 2010
Plus the internal resistance times the charging current.

Bob