Xtar VC4 Charging problem

Wurkkos

Spudnuts

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Hello forum members
i quick question about the Xtar VC4 charger. For the owners of this charger, have you tried this?
after the charger shows that the batteries are fully charged, have you tested them to see if they are fully charged by trying to charge them in another charger like a wall charger?

Ive only just received mine so ive been testing it out. With mine, after the Xtar shows Full i then try to charge the batteries in a wall charger and they continue to charge so it looks like the Xtar is not charging them to 100% the batteries im using are the BTY batteries which you can get on ebay and also some Energiser batteries. The batteries are new.

has anyone else tried this? What was the result?
thanks
 

WalkIntoTheLight

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I'm assuming you're charging NiMH cells. What you're describing sounds normal. NiMH cells will lose some of their resting voltage, very soon after charging. So, depending on the charger you use, they may be able to be "topped up" right away. However, if it's a smart charger, they should terminate fairly quickly (within about 10 minutes).

That said, make sure your "other charger" is indeed a smart charger, and isn't just dumping charge into an already-charged cell.
 

Spudnuts

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Thanks for your response, yes they are NIMH batteries. My other charger isnt a smart charger. I tested it to see if the red light came on meaning its not fully charged. But like you said it’s normal. I also tried with another AA NIMH when it showed that is was full, i removed the battery from the VC4 and put it back in the same slot. It then charged another 300 to 400 ma into the battery. That seemed to be quite a bit.
 

WalkIntoTheLight

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Yeah, that seems like a long time to detect the cell is already full. But, it may be that the charger couldn't use the "normal" method of detection (which is a slight drop in voltage during the last part of charge). Perhaps it then resorted to another method to detect the charge is finished, such as a upper voltage limit, or temperature of the cell.

In any case, I wouldn't worry about it. Just don't re-charge cells that are already charged.
 

Spudnuts

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Thats a good point about the multimeter. Im thinking if the reading is 1.2v there is still a fair bit of fluctuation. What i mean is that even if it reads as 1.2 it may not be 100% charge and it may be just at 1.2v ill google if the amps can be measured on a battery, that’s something I haven’t done before. If i know how many amps are in it then i know if its 100% charged.
 

WalkIntoTheLight

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Thats a good point about the multimeter. Im thinking if the reading is 1.2v there is still a fair bit of fluctuation. What i mean is that even if it reads as 1.2 it may not be 100% charge and it may be just at 1.2v ill google if the amps can be measured on a battery, that’s something I haven’t done before. If i know how many amps are in it then i know if its 100% charged.

When finished charging, a NiMH cell should read at least 1.40v. And, that's assuming you didn't check it as soon as it's done. If you check it right away, it should read closer to 1.50v, perhaps a bit higher.

1.20v is the average nominal voltage under load. If you measure 1.20v when the cell is resting, then it's almost empty.
 

Spudnuts

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Sorry for the late reply, on occasions the charger says a battery is fully charged but has only charged it with a few hundred mAs then I disconnect the battery and plug it back in again and it will charger for another 400mA approx so im not too sure if its working like it should.
 

NiOOH

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Even a fully charged cell will take some time to be detected on another charger. How long, it depends on how big of a signal the charger needs to terminate. -dV chargers need to put enough charge in order to heat the cell, which in turn, produces the -dV signal for termination. It may take anything from 4-5 to 20-30 min to do so. During this time, the cell is being overcharged.
 

Spudnuts

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On previous occasions, it will charge for about 10 mins before it detects thats its charged then it switches to Full. It would charge maybe 12mA during that time. Then i know it was already charged.
 

jm79

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Hello about to buy XTAR VC4 and its USB plug is a separate buy with output of 5V 2.1A and input of 0.40A (Left picture attached).

I have at home two cellphone chargers that has a rating of
1. Output 5V 2A / Input 0.30A (Black Charger)
2. Output 5V=2A OR 4.5V=5A OR 5V=4.5A / Input 0.75A (White Charger)

Can i use my cellphone chargers to charge the VC4 or need to buy a separate one with the same rating as of the device.

Thanks in advance for the assistance.
 

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