IMAX B6-AC Question

[ThirstyTurtle]

Here's a question for someone with more experience than me.

I've always used my Ultrafire WF-139 2-bay charger for charging all of my Li-Ion cells. It's 500mA which is fine but I was wanting to charge some of my 18650s a bit faster so I pulled out my IMAX B6-AC hobby charger that I use for my RC Li-Po batteries. This is not the genuine model but rather the knock off version and the circuitry isn't as nice as the real thing apparently.

Anyways, I put one of my NCR18650PF's (2900mAh) onI (using magnets in gator clips) and set it to 1.0A and let it go. It finished 30 minutes or so later (battery wasn't all the way dead) and the charger was reading 4.2V so I took it off and double checked with my multimeter. Well I was only getting about 3.9v. So I put it back on and after about 30 seconds it said it was done again. So I tried many different cells and charging amperages from 0.1A to 2.0A and no matter what I could never get a cell charged above about 4.0v.

So I think the problem is this, when it starts charging, the voltage readout is correct, but as soon as it applies current, the voltage spikes up to the max allowable for Li-Ion (4.2v) and after it sits there for a little while, it thinks it's done. I was able to get more charge at 0.1A than 1.0A+ because the voltage wasn't spiking as much. I tried it on the NiMh setting (which seems to pulse current between 0A and your selected peak, so it got the correct voltage reading at the 0A resting state) and was able to get it up to 4.1V but still it stopped automatically and wouldn't go any further.

So I'm nearly certain the charger is just a dud which is a bummer because I was excited to have the option to fast charge a cell if I wanted.

But what do you all think? Am I doing something wrong? Is this normal behavior?

 

[ThirstyTurtle]

Additionally, I've tried the "discharge" mode on a fully-charged cell where it's supposed to drain it to 3.0v and tell you the capacity. When it said it was done (discharging at 1.0A) I checked it with my multimeter and it said 3.8V...i guess this thing is just a hunk of junk :-(

 

[vicv]

I have the same basic charger except mine is a genuine imax b6 which itself is a knockoff of a bantam. For the nimh setting where it cycles from 0A to the set amps mine also does this. It's not supposed to though. Your nimh part of the charger is broken as is mine and will grossly overcharge the cells. As far as the li ion charge part mine charges cells from 4.16-4.2 so Ya yours isn't working right. With the discharge part when it stops the cell at 3v that's under load and will bounce back to about 3.5v after it shuts off but yes 3.8 is too high. That charger is done

 

[ThirstyTurtle]

I have the same basic charger except mine is a genuine imax b6 which itself is a knockoff of a bantam. For the nimh setting where it cycles from 0A to the set amps mine also does this. It's not supposed to though. Your nimh part of the charger is broken as is mine and will grossly overcharge the cells. As far as the li ion charge part mine charges cells from 4.16-4.2 so Ya yours isn't working right. With the discharge part when it stops the cell at 3v that's under load and will bounce back to about 3.5v after it shuts off but yes 3.8 is too high. That charger is done

Boo!

You pretty much confirmed my worry. It's not that big of a deal as I've sold my RC stuff other than this charger and I already have a decent charger for my flashlights cells. Just would've been nice to have the option. I hate to just TRASH it but if it don't work it don't work :-(

 

[vicv]

Ya. I still use mine for periodically checking the capacity of my cells for matching them for series lights. Even my 18650s I just charge at 500ma on my xtar wp2 even though it has a 1 amp setting. I'm in no rush and I have enough cells. One thing I use my b6 that only in can do is charging my a123 cells which it works well for