# 12VDC Battery Question

Discussion in 'General Electronics Chat' started by mpcotuong, Mar 6, 2012.

1. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
Hi All,

I am using 12VDC battery for my circuit. How do I know when I need to recharge the battery? Do you have any circuit to tell that the battery need to recharge by display LED?

Thanks,
Kevin

2. ### crutschow Expert

Mar 14, 2008
13,501
3,375
What type of battery?

Aug 26, 2010
170
0

Thanks,
Kevin

4. ### crutschow Expert

Mar 14, 2008
13,501
3,375
Then you just use a comparator set to trip at about 12V (12.6V is full charge). That will indicate a discharge of the battery to about the 50% point. Going lower than that will tend to shorten the life of the battery.

5. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
What is the voltage need to recharge? can you more specific? Anh if you have the circuit is great.

Thanks,
Kevin

6. ### Vahe Member

Mar 3, 2011
75
9
If this is an automotive lead acid battery, then you may be able to use the technique that is used there. The alternator voltage is regulated at about 14.2V or so that the terminal voltage at the battery is about 13.5V. This is to account for the voltage drops along cables. So I think if you can have the terminal voltage at about 13.5V, you can push current into the battery to charge it. The open-circuit voltage of the automotive lead-acid battery is about 12.6-12.8V (2.1-2.15V per lead acid cell, 6 cells per battery pack).

7. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
Thanks, Vahe for explain but I need circuit to tell once need recharge the battery?

Kevin

Nov 23, 2010
230
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9. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
Thanks, Stanman11. It help. I will try it.

Kevin

Nov 23, 2010
230
4

11. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Kevin, I think you have a low battery warning ckt mixed in with weight dpop ckt. composed of a LM 393 comp, V divider, precision ref Lm 385Z- 1.233 V, & red LED.

12. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
Thanks, Bernard. You mean the reference circuit you sent to me last time?

Kevin

13. ### Bernard AAC Fanatic!

Aug 7, 2008
4,240
414
Before that- think it may be in picture file

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14. ### mpcotuong Thread Starter Member

Aug 26, 2010
170
0
Thanks, Bernard so much.

Kevin.