AW14500+WF-139 4.8V off the charger!

[MetalZone]

Yesterday night I was charging my two AW14500 Protected cells. I kept a close eye for the green light and removed the cells once it is complete. They didn't feel obnormally hot. 10 mins later (was busy), I tested my cells voltage as I always do, both showed up at 4.8+V !!! I was alarmed. I put them into my nitecores (NDI and D10) went to the bathroom (in case I need to bail and evacuate) and turned them on high. After about a minute, i turned them off and took out the cells, neither felt hot or anything. Tested them and they both read about 4.1V.

Please enlighten me on what happened here?
To my knowledge, AW's cells protection circuit are supposed to cut off at 4.35V.

Looks like I need to find another charger. But it seems even the Pila IBC has it's own issues? Someone mentioned the performance is inconsistent.

 

[mdocod]

I'm not sure about IBC inconsistency problems, maybe in regards to variations in termination based on cell size yes, which is normal when using cells on a charger that has 1 charge rate and 1 termination method and winds up getting used for cells from 600-2400mAH capacity. It's consistent in that it will not charge a cell above 4.20V in my experience, but on smaller cells termination may be lower than 4.20V, which is perfectly acceptable.

As for your 4.8V AW 14500s. I'd be tempted to say that something else entirely was going on there, like a DMM screwed up, or something to that effect. I doubt the cell ever reached 4.8V. Especially if it only took 1 minute in the flashlight to get down to 4.1V.

FYI: LiCo goes into thermal runaway when charged to ~4.5V. You wouldn't be able to show me a cell in-tact that was measured at 4.8V.

 

[AW]

Here is two things you need to do : 1) Check the accuracy of your meter. 2) check the output voltage of your charger with a battery in there. If you really sees 4.8V with a LiIon battery, it won't be pretty.

 

[MetalZone]

1) my multimeter isn't anything high end but i doubt it would make such a huge error.
2) There was once I monitored the charging process with a meter attached. It read 4.25V before shooting up to about 4.9V. The light didn't turn green to indicate it had finished charging. I waiting a while before pulling it out of the charger. It measured 4.18V. After 10 mins it rested at 4.14V. What can you deduce about this? I'm guessing the cell's PCB kicked in and thus the sudden rise in the voltage reading? My WF-139 is the newer version reading 5V open circuit.

I'm puzzled. How is it even possible that I saw it read 4.8V....:thinking: not once. but twice... maybe it's my eyes... you both mentioned the accuracy of the meter, is it possible for it to make that huge an error? It's just a budget multimeter actually but decent enough to make rough measurements.

I think I might consider the Pila IBC. Are there any other chargers I should consider?

 

[seaside]

I am no expert on this matter, but for the embrassment you experienced...

My wf-139 is new one reading at 5.3V open circuit. When I took the battery out of the charger at green light, it usually is 4.21V at battery side. But I always use protected battery with this charger after I noticed mine puts out 4.38V at the end of charging process.

WF-139 is not known as the best charger, so it is too early to tell it is the battery or the charger. Can you check the charger behavior with other brand betteries and see if it does the same thing? That may help you find where the problem lies at.

 

[MetalZone]

No embarrassment experienced, but I'm perplexed nonetheless. XD
Unfortunately (but also fortunately) I only use AW brand batteries. I don't trust anything cheaper. I will monitor another charging process the next time I charge my batteries.

I don't feel so comfortable with my WF-139 now. I'll probably get a better charger.

 

[LuxLuthor]

I have to agree with the others who have said that if this is a voltage on a cell removed from the charger, it really almost has to be your DMM.

I think you are right to be skeptical at this point with the charger, but my first step would be to get another slightly better quality DMM and check again with that...because we are all saying that these cells cannot tolerate that high of voltage, as well as AW's protection limit would have kicked in and broken the circuit.

Nothing wrong with using a Pila IBC as a better quality charger, but my $ is on the DMM screwing up.

 

[lctorana]

I strongly suggest that while you measured 4.8V, the battery wasn't making firm contact in the charger, and you were actually measuring the OC charger voltage, despite appearances.

 

[mdocod]

I strongly suggest that while you measured 4.8V, the battery wasn't making firm contact in the charger, and you were actually measuring the OC charger voltage, despite appearances.

I would argue the same except that in the original post, MetalZone describes physical removal from the charger.