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

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Michael Weaser

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Aug 4, 2015
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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.


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.


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?

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

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?

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