[SOLVED] need help with battery charging circuit, and how to turn off when battery is at 1.65V

[Michael Weaser]

I need a circuit that can turn the battery charging circuit off when the battery gets to about 1.65 volts, or i need a circuit that turns a LED on, when the battery is at 1.65 volts. Can someone please help me? I believe you can use a pnp transistor to turn off when the battery gets to a certain voltage, but i have no idea on how to do it. I already designed the charger, i am making a pulsed charging circuit for different battery types , that are rechargable, i use a 555 to make the pulse at a certain duty cycle and than at a certain frequency, just need the turning off part or tell me when the battery gets to the correct voltage of 1.65 volts.

 

[KlausST]

Hi,

There are comparators. They compare two voltages.
You could use a 1.25V reference at one input and a 1.65V to 1.25V voltage divider at the other input.
The comparator output can control a bjt, a fet, or a led.

Klaus

 

[Audioguru]

What type of battery is fully charged when its voltage is 1.65V? Not lead-acid, not Ni-Cad, not Ni-MH and not Lithium.
Do you have a new battery chemistry that you invented?

 

[Michael Weaser]

no this is for rechargable alkaline , that is not not recommended to go over 110%, charged, which is about 1.65 volts

 

[Audioguru]

Wikipedia says a rechargeable alkaline battery cell can be charged for only a few dozen cycles to only 1.32V if it has been discharged less that 50% which is pretty bad for a rechargeable battery cell.
It says that if you barely discharge it 25% or less then "it can be recharged for hundreds of cycles to about 1.42 V." They do not say 1.65V.
Then why bother trying to use it?