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Li-Ion 18650 question

mathyou9

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Mods, move this elsewhere if need be.  Anyway--

Do Li-Ion 18650 batteries ever peak higher than the norm of 3.7V.  I ask because I have two 18650s that my multimeter shows are well above 4V.  One reads 4.15V and the other at 4.25V.

I tested numerous other batteries whose voltage were within spec; i.e., some AAA reading 1.48V and 1.32V; a AA at 1.48V; some [dying] Li-Ion 123 at 3.3V and last, a different [dying] 18650 at 3.15V.

I'm confident I've got my multimeter hooked up right; black is plugged into COM and red is plugged into V[omega]mA, right?
 

chido

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They all peak higher after they're done recharging or when you buy them. When you you start using them they'll drop to about 3.7v and then keep dropping slowly, recaharge them before they reach 3v.
 

Morepower

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It may also depend on whether they have protection circuits in them or not. I know these circuits prevent over voltage(charging) and under voltage, they don't just run down like normal batteries, the appliance you are using just suddenly stops working. If your not used to it it freaks you out the first couple of times because you end up thinking the laser, or whatever, just died !!! But yeah rechargeable Lithium batts charge up to about 4.2V and go down to about 2.75V
 

mathyou9

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thanks for the replies

Tangentially, I know the batteries in question have protection circuits; my laser has done exactly as you described; i.e., it just stopped working with drained batteries. And just today, using the 3.15V-18650, my laser appeared to just stop working (perhaps I'll recharge it.) :)

So to verify: the freshly charged 18650s (w/ protection circuit) reading 4+ volts is normal then?
 

Gazoo

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mathyou9 said:
thanks for the replies

Tangentially, I know the batteries in question have protection circuits; my laser has done exactly as you described; i.e., it just stopped working with drained batteries. And just today, using the 3.15V-18650, my laser appeared to just stop working (perhaps I'll recharge it.) :)

So to verify: the freshly charged 18650s (w/ protection circuit) reading 4+ volts is normal then?
The cutoff voltage of the charger is supposed to be exactly 4.2 volts. Some cheaper chargers tend to overcharge or undercharge a bit which is not healthy for the battery. As long as it is staying within .05 volts..I don't think it matters that much.
 




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