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

[darrylcapulla]

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

 

[KlausST]

Hi,

There are charger ICs.
Look at www.linear.com or other manufacturers.


Klaus

 

[darrylcapulla]

Here is another circuit, but i think this is not a charger for my battery.

 

[Audioguru]

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.

 

[darrylcapulla]

@KlausST

We don't have any SMD in our market, It takes a week if i

order it online.
Parts is very limited.

 

[kam1787]

Kumasta [again], Darryl,

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

See
and
https://en.wikipedia.org/wiki/Lithium-ion_battery#Charging_procedure
and
https://www.powerstream.com/li.htm
and
**broken link removed**


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