Wierd Eneloop behaviour

[x2x3x2]

While doing a runtime tests for the Hyperion CE-R, I noticed that one of my Eneloop AA cells was behaving wierd.

Let's call the normal working Cell A and the faulty(?) one Cell B.

On high mode,
both Cell A and Cell B produced similar runtimes of about 2 hours to 50%

But on low mode,
Cell A produced a runtime of about 9 hours to 50%
Cell B produced a runtime of about 4 hours to 50%

Repeated test twice to confirm finding. Any ideas?

 

[koala]

Hey have you tried the eneloop in other lights?

NiMH perform better when they are warm, it could be cell B having a cold during the low mode

 

[monkeyboy]

Sounds like a bad cell to me. I find that bad cells are quite common with AAs even with good brand names such as Sanyo.

 

[parnass]

I observed some odd Eneloop behavior, too.

I charged 4 new AAA Eneloops and installed them in in series in an old Princeton Tec Impact II LED flashlight. After 13 hours use, the open circuit voltage on 2 of the cells was noticeably lower than the other 2 cells.

This was their first charge and usage. Perhaps they will "even out" after a few charge/discharge cycles.

 

[BlackDecker]

I've bought 3 packs of Eneloop AA's from Circuit City, and all of mine seem to be charging to higher levels each time I charge them.

I charged 4 yesterday on my LaCrosse BC-900 and now they are charging up to 2200mah. This is the third discharge/recharge cycle on the cells.

I use the 350mah discharge / 700mah recharge setting on my BC-900 if that makes any difference.

 

[x2x3x2]

koala,
That's something new, I didn't know that NiMH perform better when warm thanks for the info.

parnass,
Yes, my wierd Cell B does charge up to a slightly lower voltage comapred to my other cells, but not by much. Fresh off the charger Cell A measured 1.42V, and Cell B measure 1.38V. I'm using a Sony 15 min charger.

But still, if Cell B is indeed faulty. How come it's giving similar runtimes on the high mode? It's really puzzling...
SilverFox, please come and save the day! hehe!

 

[koala]

hey x2x3x2,
Please read this NiMh Battery Shoot Out by Tom. He mention a few times NiMH perform better when hot. Also check out the high current discharge graphs, they start off low then go up high, that's because they got hot after a while.

Most professional electric car racers will time-charge their battery packs so they come out hot right before the competition. There are also things like cell warmers that heats up cells before they are put to use. Tamiya makes a few.

koala,
That's something new, I didn't know that NiMH perform better when warm thanks for the info.

 

[VidPro]

also your 15min charger might be harsher on the cells than would normally occur, and if it terminated differentally , as shown by your different voltages, it may not be "as" charged.
dont even 15 minute chargers "top -off" as you leave them in the unit? getting to ~80% or so the fast hard way, then continuing if you leave it on?.

if i had that situation, i would use a different set of cells, not ever charged on any 15 min charger, and do the same test.
as robust and durable as the cell is, a "15 min" charger and a charger that does not have seperate "channels" for each cell, would be the last thing i would "test" it with, even if i used a 15min charger to get things going fast.

when total relability and capacity are needed OVER the speed of recharging, i would not use 15 or even 1hr chargers, IMO they are to mean :devil: to my precious batteries.

 

[lyyyghtmaster]

The behavior you described could possibly result if the B cell somehow developed a very high self-discharge rate (damage from 15-min charging?). Have you tried just letting both cells sit around for 9 hours and do a remaining capacity test?

 

[x2x3x2]

Ok i'll try letting them sit overnite and do runtime again.

Btw, if Cel B indeed was giving higher self discharge, would the light output be higher as well?

 

[lyyyghtmaster]

Nah, it just means the cell would be "leaky", and lose its charge rapidly from just sitting around. You could think about it as the cell having a permanent internal load that you can't shut off. This is specifically the thing Eneloops are NOT supposed to do very much, so it would have to be pretty damaged. If it's self-discharging this fast, you might even be able to detect a very slight temperature difference between it and a good cell just from leaving them sitting around a couple hours in the same spot (with no breeze blowing on them) but separated by half a foot or so. The power dissipated might only be around 1/4 Watt or so, but it would all be in the cell, so it may be just barely detectable.

 

[jezzyp]

My camera has been dead twice when I have come to use it. It takes 4 x AA. Twice it was the same eneloop that was flat - all the others have the same charge. All my eneloops are numbered.
I have the maha 9000 so I am now trying a break in.

Has anyone else had a bad eneloop and can it be recovered?

 

[VidPro]

its not having a bad enloop its Making it bad

when you put them 4 in series, and the thing your running it with will discharge one completly and still continue to operate, then you can cause a reverse charge and that will damage about any rechargable battery.

say like in a incadesecent flashlight, run till there is 0 light comming out, or a device that takes 4 batteries , but will still operate on 3v.

after this one battery gets a reverse charge, it will become the bad apple of the bunch and have even less capacity, and still be the one that gets damaged each time, making it worse and worse.

if it wasnt a charge issue (didnt get charged) and its weak and lower in capacity, even if you can get it to limp along , it wouldnt be good to have it be in series with others that are working great still.

the best thing you could have done for batteries in seires, is pull them when the device is weak, like say in a digicam, when the flash starts taking to long to charge. or in a flashlight when it starts lowering in output.

with rechargables you can always have a second set, and change out when they are mostly discharged, you can always recharge it.

i am not saying you did reverse charge it, i am just saying, that can get things bad faster than anything, and 4x series is a good place to get that to happen.

reguardless if you have a bad cell, and it didnt do what it is supposed to do, good brand name manufactures will replace it.

 

[jezzyp]

I think they are parallel - two up two down. Its a fuji S7000

 

[Anders]

[FONT=arial,helvetica][FONT=Verdana, Arial, Helvetica]AC-5V AC Adapter is an optional [/FONT][/FONT][FONT=arial,helvetica][FONT=Verdana, Arial, Helvetica]accessorie so I doubt they are paralell [/FONT][/FONT]jezzyp.

"all the others have the same charge"
Did you do a discharge with the other cells that where "good"?

If you did you could see if your camera:s system for detection of low battery was defect and therefore it didn't shut it off in time?




Anders

 

[jezzyp]

One of the eneloops was flat - the others measured around 1800mah on the maha - what I would have expected as I hadn't used the camera for a month or so.
Low battery indicator seems to be normal (as tested with some old alkalines).
I have put another set of eneloops in the camera to see what happens.

Thanks for your advice.