Xtar VP2 Overcharging

Marquis07

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I recently noticed my charger is overcharging cells.
It has done 2 so far. I panicked with the first one a few weeks ago, and quickly lowered the voltage using turbo on my light. Not sure what to do with the current battery.

I bought the charger this fall, and have taken good care of it, what should I do? Is there a way to "reset" it? I don't have the funds to replace it anytime soon.

IMG_20240305_140357_872.jpg


Thanks guys,
mark
 

Marquis07

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Hmm, figured out there's a switch on the back for 3.2, 3.6, and 3.8 volts, so I did some research. I had it set on 3.8v, not knowing the difference and that would charge the cells to 4.35v. I'm sorry to waste your time.
 

slumber

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Yep, thought it was the switch as I read your original post. Mine is very old and the display is really dim now, but it's been a really great charger. It does an excellent job of topping off small cells like 16340's.
 

aznsx

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I have 3 of them, and they're quite handy.

However, speaking of 'overcharging', do not leave LFP cells in the original VP2 charger for many hours following charge termination. Under those specific conditions, it will overcharge those cells. I've tested it myself. (It happened to / was reported by someone else.) I doubt those reading this do such things, but just in case, don't. I documented this elsewhere, but won't link to it, because Mr. Ed might bust me;-)
 

Marquis07

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I have 3 of them, and they're quite handy.

However, speaking of 'overcharging', do not leave LFP cells in the original VP2 charger for many hours following charge termination. Under those specific conditions, it will overcharge those cells. I've tested it myself. (It happened to / was reported by someone else.) I doubt those reading this do such things, but just in case, don't. I documented this elsewhere, but won't link to it, because Mr. Ed might bust me;-)
*Removes charged cell from charger... 😬

I assume It's bad practice for li ion cells too?
Thanks for the advice!
 

aznsx

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*Removes charged cell from charger... 😬

I assume It's bad practice for li ion cells too?
Thanks for the advice!
You're welcome. I guess I should clarify too: This 'issue' is a defect in design or manufacture, and the charger should not do this, regardless of how long the cells are left in the charger following termination. In most cases, such chargers will actually likely draw a very small amount of current from cells left in a charger following charge cycle termination, if anything. In this specific case however, as the cell's voltage settles to some threshold, it will begin very slowly charging the cell, as if to 'top it off', which should not occur, and to make matters worse it will ultimately charge it to ~4.2V then, not the correct 3.6V it initially charged them to. To make matters even worse, the display will not reflect this, but instead remains showing 3.6V from the initial termination. It can be measured / verified with a voltmeter though. It's a little twisted.

That said, the scenario requires both that defect, combined with bad practice to ever occur. The user reporting it had left the cells in the charger for many hours (until some time the following day), and it takes several hours (I forget exactly how many) for it to become an issue at all.

I continue to use the VP2s I have, including for LFPs, as they're otherwise good chargers for what they do. it's effectively a non-issue for me, I just wanted to mention it, because if one charges LFPs and just forgets about them / leaves them in the charger, it will happen. Unless someone does something silly, it's a non-issue in practice. I'll call it a defect with a 'workaround' - common sense;-)
 

Diatom

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Hmm, figured out there's a switch on the back for 3.2, 3.6, and 3.8 volts, so I did some research. I had it set on 3.8v, not knowing the difference and that would charge the cells to 4.35v. I'm sorry to waste your time.
That switch is a muddle. I still use my Xtar VP2, and I was grateful to be reminded of the switch.
 

lyyyghtey

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I'm one of the people this LFP overcharging happened to. In my case, I left two 16340 LFP cells in the VP2, set to 3.2 V, and forgot them for a week. Normally this should be no problem. Even if the cell voltage drops over time and the charger tops it off within a week, that's not ideal but is no problem. However, at least some VP2 copies will just keep going, not stopping at the usual 3.6~3.65V. In my case the cells were at a whopping 4.49 and 4.57V 😳 Somewhere in there the charger channel for the higher V one reverted to showing the nominal cell voltage, I believe this must happen at 4.50 V or slightly above, and the lower cell hadn't quite reached it yet. The 4.49V one was still showing the (also erroneous) 3.6V normal termination voltage.

In terms of regular Li Ion, I don't know if the charger would do that to them too. I'm assuming it does, but would take a lot longer than a week except for the tiniest cells perhaps, because of the voltages Xtar chose to activate the topping off being a lot further down the regular Li Ion discharge curve.
 
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