Is my Xtar WP2II charger defective?

[userofnames]

I recently bought an Xtar WP2II charger and two Enerpower 18650 3400mAh (Panasonic NCR18650B) batteries. The first time I charged them everything went fine. It took a few hours, but eventually the indicator light on the charger changed from red to green, indicating that the batteries were fully charged. I have used them a few times in my Fenix TK15 S2. After charging one of the batteries for a few hours, I got curious about why the light didn't turn green, so I took it out, the light changed to green (indicating standby), and then I put it back in and the light stayed green, indicating that the battery was fully charged. I have tried a few times, and this seems to happen every time with both batteries. I am worried that the charger is not properly detecting that the batteries are fully charged and is attempting to overcharge the batteries (although they do have protection circuits). The batteries do not get hot, the charger just gets slightly warm. Unfortunately, I do not have a multimeter yet, but I will be buying one soon. What might be the cause of this odd behavior? Is it possible that my charger, or my batteries, is defective? Please advise.

 

[ChrisGarrett]

I always rotate my batteries/cells, while in my chargers, a couple of times during their charging cycle. By "rotate," I mean turn them maybe a few millimeters, or an eighth of an inch, to break up any contact resistance at the +/- points between the batteries/cells and the charger.

On my 'recalled' VP2, I noticed I had to do this moreso, than on other chargers, since it seemed that the charger wasn't turning green when I thought it would/should. As soon as I 'turned' the cells, the resistance dropped and the charger (I guess) recognized the cells as in fact, being full.

My replacement VP2 doesn't do this and my two and a half year old WP2 II has done this on on a few cells.

I even rotate the batteries on my Maha C-9000, LaCrosse BC-700 and NC i4 v.2, mostly out of habit.

If you're playing with li-ions, you need to get a DMM (voltage meter) and see where things are measuring at, when you initially pull them off the charger, before it goes green.

Chris

 

[CyclingSalmon14]

Buddy its fine, I had the same "issue" but it wont overcharge them, I have a DMM and took them out thinking it was overchargeing them, they were not charged was all, if I put them back in it will say there charged but I think the turning thing will help I dont know why it dosent turn green but I have left them in when I think they should have gone green but havent and if you just leave them in for a bit longer say another hour they WILL go green eventualy, and they will be 4.18/19/2 never had them overcharged and I have left them chargeing overnight by mistake once and they did not over charge. Its never missed termination for me. but as said sometimes it fails to say its charged when it is....but it is a cheap charger so meh, im going to get a VP2 soon.

 

[userofnames]

Thank you both for the responses.

@CyclingSalmon14: But is it not overcharged because of the protection circuit (which the li-ion battery guide on CPF told me not to rely on) or because the charger stopped charging? :-/

I just ordered a multimeter online and I should get it early next week.

 

[userofnames]

Sorry for the doublepost, but I forgot to add this to the other post.

@ChrisGarrett: I tried turning the battery like you described a couple of times during charging, but it didn't seem to work.

 

[CyclingSalmon14]

Good point, dont rely on protection but its nice to have, its the charger buddy, I have charged IMR 16340's as well, same issue, still not over charged as I cheack with Multimeter fresh of charger and then again after a couple of hours restring to make sure, never more than 4.18/19, infact I very rearly even see it get to 4.2, its very rare if it dose. If you are worried charge in a LIPO bag from hobbyking or a local hobby shop, but IMO I just never leave them on when I am not in the house, NEVER EVER and just come and cheack on them once an hour to make sure there not getting to hot or anything, which they never have.

 

[THE_dAY]

Welcome userofnames, here is a similar thread regarding your issue with the WP2II that explains the issue:

http://www.candlepowerforums.com/vb...agleTac-3400-amp-Xtar-WP2-II-strange-behavior!!

Basically by turning the cell while charging you are increasing the contact resistance which ends full charge slightly early.