Do I own the worlds most gentle li-ion charger?

[andrewnewman]

...or do I own a broken charger? I recently took receipt of a brand new AW RCR123a battery and one of those inexpensive little Nano 3.7V chargers. I know that there are threads about this charger that are a few years old with helpful information but I still have questions.

I started charging the battery last night. It got a little warm over a 2 hour period after which the battery voltage was around 4.05V. With no load the charger appears to produce 4.14-4.15V. I put the battery back in and after another 4 hours the "charge complete" light never went from red to green. I left it overnight and in the morning the light was still red. Battery voltage was around 4.11V.

I unplugged the charger and battery and took them both to work with me so I could keep an eye on them. The charger is plugged in under my desk right now (still red).

Is it plausible that the light will some day turn green? If so, how long might I wait? I'm not too upset as I spent about as much on this charger as a large burrito. Even so...

/Andy

 

[45/70]

I would return the charger, if you can.

It is not good for Li-Ion cells to spend more time than necessary, charging at voltages over 4.0 Volts. Metallic lithium, which is very unstable, can be deposited onto the anode under these conditions. This can make the chemistry unstable, and while it's not certain this will happen, it's not worth taking the chance, IMO.

Dave

 

[andrewnewman]

Ok folks...10 hours and the red light never turned green. I'm giving up. I think I'm going to send this less-than-impressive piece of engineering back to the good folks at 4sevens as defective and consider a slightly more costly charger unless someone else has any re-mediation I might be able to try. Sort of too bad as the form factor is quite appealing.

/Andy

 

[kramer5150]

Make sure you have the right one for the type of cell you are trying to charge... they are identical besides the label. With no output specs anywhere on the product. 10+ hours something is wrong with the charger. 16340 cells are only 400-500 mah capacity, and mine charge in about 75 minutes in a WF-139.

heres a thread from before.

http://www.candlepowerforums.com/vb/showthread.php?t=240075

 

[madmook]

Haha thanks for that link, kramer. I just recently ordered and bought one of those nano 3v chargers with some AW LiFePO4's from lighthound, and was also somewhat wary of the weird labelling. There were just some small circular stickers on the packaging with "3v" on them.

Anyways, they seem to have charged up the LiFePO4's just fine, as the charging indicator light goes from red at plug-in to green after a couple hours.

I think OP got a dud unit.

 

[andrewnewman]

I think OP got a dud unit.

Yup. That's my conclusion. I considered the possibility that I might have the 3.0V charger but my DVM reads 4.15V at the terminals when the charger is plugged in. I think that is low but I think it is a dud, not a mis-labeled 3.0V unit.

 

[moldyoldy]

correct - you have a bad Nano charger. The Nano build quality is not high, and the unit is plagued by DOA and preemie failures. Never turning green is one of the failures, usually because of too-low a charging voltage. The open circuit voltage should be in the 4.2-4.25 range. 4.15 open circuit volts is too low.

I have worked thru to maybe a dozen good Nano chargers, for which I rejected about half of those received for some reason. Not a good percentage. however if you are willing to tolerate the initial failures, the Nano chargers actually seem to be relatively long-lived. I cycle them for a few months to provide reasonable testing, then pass them on to maintenance personnel.

however a retained voltage of 4.15v after charge completion out of the charger is about correct for long life and safety.

 

[hoongern]

Yup - I bought the Ultrafire WF-138 chargers (2 charging bays), and only one bay was charging. Dealer sent me a second one for free, and it came, and again only 1 bay working. But that's fine, since I now basically have effectively "one working unit" (2 working bays) :thumbsup: I imagine the same sorta thing is happening with yours.