how to design a protect circuit for Li-battery

[xiaofeixia]

i want to design a protect circuit for 3.8V Li-battery using only ordianry analog device like transisters and resistance to limit it's voltage above 3 V, who can lend me a help, many thanks.

 

[xxargs]

i want to design a protect circuit for 3.8V Li-battery using only ordianry analog device like transisters and resistance to limit it's voltage above 3 V, who can lend me a help, many thanks.

hmm, look around after protection circurit on maxim, linjear technology etc.

is not simple to built itself depend of protection must work both low voltage (around 3 Volt) and over voltage (around 4.5 Volt) and no draw current from battery in protected mode or using mode (for long storage without discharge)
ie. using FET-transistors and very precise tresholds

Now sell rechargeable 650 mAh LitiumIon-battery CR123 (look at google) with embedd protect circurit (button weld on battery for same size as normal CR123-battey) to camera and LED-flashlight market - try use this battey directly or use this protection button from dissmantle battery. (take very care and stay alert on risk for explode, fire and poison smoke on this dismantle moment...)

 

[sunking]

Use diode and Resistor to generate a low voltage as supply voltage

R---R---R--GND
|-D---D--GND
|---Supply

 

[xiaofeixia]

thanks
but i have selected a Li-battery of 3.8V and 145mah, and the ciucuit need a voltage above 2.4v, i wanna a protect circuit of lower power consume.

 

[sunking]

then the best way is a LDO