Why does my charger charge to 4.19v?

[rades]

Maybe it's a safety mechanism so not to overcharge but I thought I'd ask anyways, how come my charger charges to 4.19 volts instead of 4.2v? I have the xstar 4 slot charger..

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[NemesisVaper]

0.01 of a volt is within margin of error, it's not a safety consideration. I've had cells come off the charger anywhere from 4.18 to 4.21V. The spec for a 4.2V liion is usually 4.2V +/- 0.05V. While not ideal, a 4.25V charge or a 4.15V charge are both within spec.

Under charging by 0.1V may get you more cycles, under charging by 0.02 is likely to achieve nothing. It's a miniscule amount.

 

[NemesisVaper]

It does seem strange, I notice the behaviour too. It's due to how the charger is charging the cell. It's programmed to tail off charge current.

It'll give the cell 4.2V at up to the max charge current, and over time it goes down and down on a curve. The cut off current for 1A charging is 100mA, so on my efest, the cell voltage might be 4.2V but it won't stop until current tails to 100mA.

Ive also noticed that applying a charge to a cell will instantly raise cell voltage. Remove the charge current quickly enough and the cell voltage falls again. Nit by a lot, but if the charger rounds the displayed voltage it's enough to appear like to cell is getting hammered by the charger unnecessarily.

It's more complicated than that, there are different charging phases etc, but the deeper you go into it... Well.. It gets fucking boring.

 

[Slurp812]

.01 volts? Kinda splitting hairs?

 

[rades]

I don't care, I was just wondering why


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[Lefty]

It's most likely a design parameter. Leaving room for the error margin and leaving room on the low side since going over puts more wear and tear on the cell. It's only because the charger displays to the hundredth that it's noticeable. A display that only shows to the tenth would round it to show 4.2V.

 

[Slurp812]

Nothing is perfect. The charger, the meter being used to measure the batteries voltage, and the battery itself. They will also drain slowly over time. Its close enough for rock -n- roll!