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Can anyone here recommend a good, simple 12v low-voltage cutoff? (lemmy.fmhy.ml)
submitted 2 years ago by chick3n@lemmy.fmhy.ml to c/askelectronics@discuss.tchncs.de
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I've been looking for a simple low-voltage cutoff circuit for a 12v SLA battery, but many of the ones I find have reviews saying that the protection circuit itself drains the battery slowly as well. Is this just inherent in the design, where it has to draw a little to measure the voltage, or are there low-voltage cutoffs that don't draw anything until the battery is recharged?

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[–] Saigonauticon@voltage.vn 1 points 2 years ago

No, it's not possible to do it without current draw. You can do it with really, really low current draw though.

Ignoring MOSFET stages for the moment, I could design a system that could do this, with a power consumption of under 0.1 uA when in the low-voltage cutoff state.

I'd use a TPL5110 and an Attiny10 to do that.

Alternatively, if ~50 uA is OK (it really should be), then I'd just use the Attiny10 on watchdog timer, and save the cost of the TPL5110.

If I absolutely did not want to use the SLA to power that system (as an academic exercise), I'd use a separate CR2032 coin cell. That ought to last 3-5 years. Or if there's ambient light, a calculator solar cell and a supercapacitor would make it self-powered. I could design a system that could last overnight on just a few hours of ambient light during the day. Modern microcontrollers are a marvel!

The amount of power drawn by a reasonably designed system should be many orders of magnitude less than the self-discharge of the battery. So not worth worrying about unless it's very poorly designed for some reason.