[Need For Advice] Xtar PB2 charger - irregular voltage drop

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Lux-Perpetua
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[Need For Advice] Xtar PB2 charger - irregular voltage drop

Hello everyone,

Many of you may be familiar with the Xtar PB2 charger that came out in 2018. I was one of the first buyers of this tiny little device. So far, I was quite happy about it. But lately it behaves more and more suspicious. Normally, the PB2 should charge both batteries in parallel, i.e. no matter what voltage, what brand or capacity each cell has - they will be charged in a "balanced" way. I have asked about this charging process before ► here ◄ and I got very helpful answers.

 

So far so good. Now, after a couple of months using this charger I get totally different termination voltages when I take out the batteries. I made a picture to illustrate the issue I'm facing right now.

 

The big question is: Why do I get overcharged batteries in bay #1 (left) while batteries in bay #2 (right) will not be fully charged? I thought this patented safe technology should prevent situations like this, or am I totally wrong about it? If there was a "balanced" charging, all cells should have the same voltage once they are taken from the charger. Instead, the voltage differs by 0.08V.

Any ideas? Is this charger subject to be regarded as defective? Maybe it's worth to file a warranty claim at Xtar?

 

Thanks a lot for any help!

Cheers,

Thomas

Edited by: Lux-Perpetua on 03/06/2019 - 03:58
USA
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I don’t own this charger and don’t know the history or any product reviews. But, depending on how the voltages are measured, this could simply be the result of varying resistances, differences in the cells used and simply standard deviation.

Does this happen with every cell brand used?
If you change the cells around – do you get the same voltages regardless of which cell is charged in which slot?

MascaratumB
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I normally use the same type of cells (Sony VTC6) in this charger, and I always get 4.20V charge (confirmed on OPUS charger)!
Supposedly the charger should be “different battery proof”, but maybe it has to do with that?

Lux-Perpetua
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USA wrote:
I don’t own this charger and don’t know the history or any product reviews. But, depending on how the voltages are measured, this could simply be the result of varying resistances, differences in the cells used and simply standard deviation.

Does this happen with every cell brand used?
If you change the cells around – do you get the same voltages regardless of which cell is charged in which slot?

I must admit I never paid any attention to a single-variety charging process, so I mixed both 35E and VTC6 all the time. Anyway, I followed your question and changed the order, i.e. the VTC6 into the left bay and the 35E into the right bay.

Result:
Both batteries were terminated with 4.23V right after the PB2 reached 100%. 12 hours later the VTC6 has dropped to 4.19V while the 35E still holds 4.22V. I presume the VTC6’s voltage will rest at 4.15V another 12 hours later and the 35E will keep indicating 4.22V. I wonder what that’s supposed to mean. Is this just normal for a high drain cell’s voltage to drop that much and fast while the high capacity cell remains as is? Since the termination current is the same for both charging bays I have no clue about the root cause. The VTC6 is about 1 year old and has probably 30 charge/discharge cycles which is not that much. Internal resistance looks still fine, though.

USA
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sounds like your charger is fine.

My cells also drop after charging, they are all different but they do drop in voltage.

Lux-Perpetua
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Thank you USA! Beer
If you or anyone here can give me some hints about the significant voltage drop on this VTC6 battery, I’d be very happy. As far as I know, the amount of the voltage drop depends on the termination current in the CV-phase, i.e. the lower the current the lower the voltage drop and the longer the duration to charge the battery.

USA
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You can read up on batteries on http://lygte-info.dk/ or in the batteries forum. I, unfortunately, don’t know too much about discharge curves on this model. There are a lot of variables when it comes to battery/chemistry/age/cycles /..

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Lux-Perpetua wrote:
Thank you USA! Beer
If you or anyone here can give me some hints about the significant voltage drop on this VTC6 battery, I’d be very happy. As far as I know, the amount of the voltage drop depends on the termination current in the CV-phase, i.e. the lower the current the lower the voltage drop and the longer the duration to charge the battery.

Wolfdog (capo) has confirmed that the vtc6 battery’s go down hill fast compared to other cells.