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Ii want to display the battery charge of a flashlight? Answered

I am looking for a way to display the charge level and possible even control the light out put of a flashlight. It would be kind of neat to get one to control several.


There ARE standard "Fuel gauge" ICs that can do this for you.
Take a look at the Maxim DS2788 - which has all you need, on chip.


Impressive standing chip to study but it needs a micro to set up.

Yes, but you could bang it from a parallel port - I bet Maxim have an app-note to that effect.


Makes sense and maybe Maxim makes a non lithium version


Yes, there are some for NiMh as well. That said, you get coulombs and volts out, the rest is maths.



6 years ago

Most battery remaining displays are computed by subtracting amp-hours
as they are delivered which takes a micro processor.
Lead acid batteries are a breed that telegraph their state of discharge
by the cell voltage and an op-amp can be used to announce the charge.


Thank you for the info iceng. Every bit of knowledge helps. Would I need a arduino and if so which one. I wanted to buy a uno to play around with. Would this get the job done.

Yes that would do the job but not fit very neatly inside a torch (flashlight). Perhaps you could get an uno to prototype it on, then once you've taught yourself you could switch over to one of the AtTiny microcontrollers. They're, as the name suggests, tiny.

Another, perhaps simpler method would be to use one of those "tester strips" that once came with batteries. You would place your fingers on two contact points and the battery level would display between green, yellow or red (good, weak, dead). Since the strip required your fingers to activate the display, you could essentially leave it on the battery, or in this case, wire the strip ends to the battery on the inside and leave the indicator strip on the outside.

Honestly I've never tried this myself, but I don't see why it couldn't work, perhaps you could give that a go, if you don't need to display a constant reading.

Im assuming you wsnt to know how, dedpite never having asked a question. Try google for existing circuits first. How much do you know about electronics? This will give those of us willing to help, a starting point.