Is There A Way To Check Battery's Health?

Witterings

Enlightened
Joined
Dec 15, 2015
Messages
282
Is there a way to check a battery's health, I've certainly at leat one that if I charge it still takes a good percentage of it's original mah but if I put a torch on high / turbo it almost immediately switches to a lower setting ... I'm guessing this is because the battery is old / in poor health and can't cope with the current draw.

Be good if there was some way I could measure and see which batteries are getting "tired" and maybe best retired ... be especially useful as I do quite a lot of cycling and go out in the winters evenings, you're suddenly grabbing a torch / battery that hasn't been touched for 6 months and don't fancy getting to the furthest point and finding both batteries (carry a spare) have failed.

A secondary question but for the same reason ... a 14500 / 18650 that has sat unused for a while and seems a depleted, are they like NiMH that if they get used again / cycled they can recover to a degree or does the different chemistry just mean they're dead?
 

alpg88

Flashlight Enthusiast
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Apr 19, 2005
Messages
5,228
Internal resistance, measure it when the battery is fully charged, you need a charger that has this function.
Depends how low they self discharged, if to 0 then trash it, if 2.5 and up most likely still good
 

Witterings

Enlightened
Joined
Dec 15, 2015
Messages
282
Internal resistance, measure it when the battery is fully charged, you need a charger that has this function.
Depends how low they self discharged, if to 0 then trash it, if 2.5 and up most likely still good

OK - I've just googled and found my Miboxer C4-12 does this but one review said it's inconsistent / not accurate.

I do have a high quality charger in a cupboard somewhere from when I used to fly RC things many moons ago .... I'd have to get a battery holder and knock up some wires with 4mm banana plugs for the charger but is certainly doable.

Any idea what sort of readings would be seen as good / acceptable and what are bad?
 

vicv

Flashlight Enthusiast
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Mar 22, 2013
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2,746
Location
Southern Ontario
Yeah, I would not rely on the chargers internal resistance measurement. They are not accurate. Basically I do a discharge of the battery. If it's below 70% of its original capacity, it's tired and ready to be tossed.
 

alpg88

Flashlight Enthusiast
Joined
Apr 19, 2005
Messages
5,228
They maybe not 100% accurate, but it would give you an idea which cell out of 2 or more is in better health. if t is off by 50 mohm, or even 100, it would apply equally to all cells it measures.
 
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