26650 overcharging?

TovinoThomas said:

Hi all, I recently picked up a D4S and threw the included LiitoKala 3.7V 5000 mAh 26650 into my old model Nitecore i2 charger. I took it off when it was indicated at about 2/3 charge and put it in my D4S, then was surprised to see that the battery check feature indicated a charge of 4.2V already. I thought that the battery was supposed to be full once it hit 4.2V but I put it back on the i2 to let it charge for another hour since it's supposed to stop it from overcharging. I used the D4S batt check again and it registered it at 4.3V. Is my D4S off or is my i2 overcharging my batteries?? Do I need to pick up a multimeter and verify all of my battery charges as they go? Also, I've been using it for a while to charge up unprotected 18650's until it registers them as fully charged - am I to assume that I may have been overcharging those too?

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WalkIntoTheLight said:

Charging specs usually give a max charge of 4.2v +/- 0.05v. So, it's possible for the charger to charge as high as 4.25v, and still be within spec. Your light's built-in voltage meter likely isn't too accurate, so it could be reading 4.25v as 4.3v.

As said, best bet is to get a DMM and read the battery voltage. A cheap one is only about $10 and it will be much more accurate than what you're doing now.

4.25v is a little high for a maximum charge, IMO, though it's within spec. At that charge, you'll get about 5% more capacity out of the cell, but probably 20% less cycles overall. If you charge it daily, the reduced cycles might be an issue. Like a smartphone (which usually over-charges to exaggerate runtimes when you first buy it), you'll probably notice it getting less run-time in a year.

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