New charger DOA

[KarlMaldensNose]

Well, sort of. It's a Cytac dual independent bay charger... the 139-type jobbers from 4Sevens. First cells I threw in were new AW's -- a protected 18650 (2600mAH) and a protected R123A (750mAH). The 123 went green within an hour but the 18650 was still red eight or nine hours later. Didn't seem right since I thought AW sent his cells near full, so I popped it in my P-Rocket and it worked magnificently. I then put it in the other bay (the one that successfully charged the 123) and it immediately showed green. I tried some other cells which I knew to be full in the seemingly faulty bay and they all indicated red.

Since I haven't got a multimeter yet I don't know if the bay is actually dead or if it is just the indicator light that is defective. Either way, it has to go back... and I don't plan on replacing it with another Cytac, but that's beside the point. What I'm curious about is the possible "damage" the 18650 could have incurred due to being in the charger for nearly ten hours after it was already (near?) full. Despite manufacturer and retailer claims, it has been proven to not terminate charge when complete; it trickles and trickles and trickles... or at least that's how I understood its operation as explained in the 'Consumer Li-Ion "cradle" charger roundup' thread.

The 18650 seems to work fine right now, but could this episode have contributed to a shorter overall life, i.e. able to sustain fewer overall charge cycles, or maybe decrease the cell's capacity somewhat? I'm trying to determine if I have a legitimate claim to a new replacement 18650 from the retailer who sold me this defective charger. Don't get me wrong, I'm not "lookin' for free $h!t" here, it's just that I'm new to this game and honestly have no idea if the cell in question has been compromised or not. Thanks.

 

[mdocod]

Hello KarlMalkensNose,

Your cell is almost certainly fine, I would not worry about that too much. The Cytac sliding bay charger has a clamped voltage output (well, it's supposed to, hehe). The "trickle" charge effect is really more like a float charge effect where it just holds the voltage of the cell at a particular level. The exact point could vary from unit to unit. As you may recall from that roundup thread, I measured mine around 4.25V or higher (IIRC).

Assuming that the charging taking place was working as expected, but the charger failed to report a finished charge by switching to a green light, then all that happened is some brand new cells may have been charged above 4.20V at a very slow pace and then held there.

Brand spanking new cells are pretty tolerant to this type of charge. It's when the cells get older that such a charge routine can start to cause unnecessary and potentially hazardous wear.

My biggest fear is for folks who have both a junk charger and junk cells, not when they are brand new, but a few years down the road. having one of the 2 of good quality probably improves the safety margin by an order of magnitude.

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Of course, we'll never really know what's going on with that cytac without a DMM... Sometimes harbor freight sells their cheapo model for like $3 on special.

Eric

 

[KarlMaldensNose]

Thanks, Eric. That's encouraging to know. You're right, I do need a DMM, and I have no problem paying ~$100 for one, so the Harbor Freight econo model isn't an issue. What is is me finding a compromise between the high-end Flukes and those ubiquitous (and purportedly useless) budget DMMs. And understanding how and why to use one.

 

[mdocod]

Hard to go wrong with a $20-50 Mastech or one of the re-badges. I own 2 of them, one is very old and still works great. They aren't FLuke but they are more than adequate for most peoples needs here. There are some guides to using multi-meters right here on CPF and all over the net as well.

Eric

 

[Black Rose]

Thanks, Eric. That's encouraging to know. You're right, I do need a DMM, and I have no problem paying ~$100 for one, so the Harbor Freight econo model isn't an issue.

Keep an eye on the weekly Canadian Tire flyer.

They routinely have DMMs from Innova/Equus on sale at least once a month.

 

[a1penguin]

I found these to be useful and entertaining. There's also a video that talks about what to look for in a DMM as well as some reviews for fancier DMMs. Worth watching.

$50 DMM shootout:
http://www.eevblog.com/2010/06/04/eevblog-91-50-multimeter-shootout/

$100 DMM shootout:
http://www.eevblog.com/2010/07/11/e...probe-bk-precision-ideal-uei-uni-t-part-1of2/