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I am building charging system for 12v tool batters ( drills, lights, etc. ). I found a 12v a/c adapter and I cut the end off the but bullet connectors that hook up to a wire with a shielded female spade connector. The shade fits the 12v battery. My question is - is there a way to design a circuit that will let me know when its charged, like with a red and green light. Any help or schematic would me greatly appreciated

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It depends on what type of battery you have. To charge batteries you need a constant current source, but the method of charge termination varies from chemistry to chemistry. Lead acid batteries charge with a constant current then need a float voltage top off. NiCads and NiMH need a change in voltage with time charge (or temperature). Lithiums need an extremely accurate charge termination (to 100mV accuracy).

Look at the MAX712/713 datasheet from Maxim for NiMH and NiCads.

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It depends on what type of battery you have. To charge batteries you need a constant current source, but the method of charge termination varies from chemistry to chemistry. Lead acid batteries charge with a constant current then need a float voltage top off. NiCads and NiMH need a change in voltage with time charge (or temperature). Lithiums need an extremely accurate charge termination (to 100mV accuracy).

Look at the MAX712/713 datasheet from Maxim for NiMH and NiCads.




Lead-acid-batteries are charged with constant voltage e.g. 13.8V. Their charging current decreases while they approach full charging voltage.

NiCads are charged with constant current.
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  • 3 weeks later...

A lead acid battery will charge very slowly if charged to 13.8V.

If it's charged to 14.5V and reduced to 13.8V when the current drops below a certain level, it will charge much quicker.


OK! Partially agreed.  :D

Subtract 0.1V for a final charge voltage of 14.4V to make it safe!  ;)

Beyond 14.4V any lead-acid battery starts gasing (Hoffman's electrolytic gas production facility)  ???  ???

H + O mixed make a beautiful firework if touched off by the spark of a switch.  ;D

HtG
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