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[HELP] Build Automatic Cut off Charger for 7.4 Volts Battery

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darrylcapulla

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Hello, can anyone help me build Automatic Cut off Charger or
Smart Battery Charger for 7.4 Volts - 2 x 3.7volts Lithium Polymer Battery 3500mah.

Charger will automatically turn off when its 8.2volts(safe voltage) or 8.4 volts - fully charged.

I try to search from the internet,and i found this one.
when i simulate it, output voltage is 8.2 volts.
I don't know if this charger is good or not, should i use this one?
please, help. thanks

Capture.JPG
 

Audioguru

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The charger circuits you found are for charging an old fashioned lead-acid battery.
Modern Lithium battery chargers use balanced charging of each cell to avoid overcharging one cell and causing a fire.
 

kam1787

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Kumasta [again], Darryl,

As AudioGuru stated Lithium type batteries need a rather specialized charger.

See http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
and
http://en.wikipedia.org/wiki/Lithium-ion_battery#Charging_procedure
and
http://www.powerstream.com/li.htm
and
http://www.digikey.com/en/articles/techzone/2012/sep/a-designers-guide-to-lithium-battery-charging


You can try searching for a "Lithium-Ion Battery Charger" but there does seem to be quite a few junk circuits out there.
 
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