NiMh Battery Question - Page 1
Forum section: electronics / general

author: Terabyte2007
author_rank: Frequent Contributor
timestamp: March 16, 2015, 05:50:34 pm
content: I have Energizer NiMh rechargeable AA and AAA batteries I have been using for a couple years now and today I had one display "HIGH" in the smart charger. Never seeing that error before I checked the battery voltage and it was 2.10V. I removed the battery and resynced the charger placed it in another independent slot and it read 2.10V I then out of curiosity started the charge cycle again to see if I received the same error and it then all of a sudden reflected 1.38 to 1.4V and continued to finish the charge with no issues. I have never seen this before and I am a bit puzzled as to the error. Charger glitch? Battery glitch? Any ideas?Other batteries seem to charge fine after with no issues. The charger is a decent brand, PowerEx, one of their top line chargers.

author: IanB
author_rank: Super Contributor
timestamp: March 16, 2015, 06:00:01 pm
content: Is the charger a C9000?If so, this charger applies a high current pulse and measures the resulting voltage to test batteries for high resistance before attempting to charge them. This allows alkaline batteries to be rejected along with poor condition NiMH batteries (which would get too hot if charged at high rates).Most likely your battery is borderline and was failing the high resistance test. After a couple of attempts it probably warmed up, lowering its resistance enough to let it pass the test.Beware that Energizer NiMH batteries have had a poor reputation for quality (I personally wouldn't touch that brand with a 20 ft pole), so it is possible all your batteries are reaching end of life and becoming due for replacement.

author: MLXXXp
author_rank: Frequent Contributor
timestamp: March 16, 2015, 06:09:53 pm
content: The "HIGH" indication refers more to high internal resistance than high voltage. The smart charger initially tries to force a fairly high current through the cell to determine its internal resistance. If the voltage goes too high, it means it has developed a high internal resistance.A cell with a high resistance may appear to charge normally but it won't be able to supply enough current at the required voltage when powering devices that present a high load. Such a cell is probably at its end of life.I've had some luck recovering NiCd cells with a few cycles of discharging them and then charging them slowly with a low constant current source. I haven't had much luck restoring high resistance NiMH cells.

author: Terabyte2007
author_rank: Frequent Contributor
timestamp: March 16, 2015, 06:56:54 pm
content: Quote from: IanB on March 16, 2015, 06:00:01 pmYes, it is the C9000. Thanks for the info, makes sense. I have just never seen that before.

author: Terabyte2007
author_rank: Frequent Contributor
timestamp: March 16, 2015, 06:59:10 pm
content: Quote from: MLXXXp on March 16, 2015, 06:09:53 pmThanks for the info! I am starting to switch to Panasonic eneloop batteries, more costly but much better!

author: IanB
author_rank: Super Contributor
timestamp: March 16, 2015, 07:02:48 pm
content: Quote from: MLXXXp on March 16, 2015, 06:09:53 pmI think the high resistance is caused by irreversible changes to the internal state of the cell, including but not limited to drying out of the electrolyte. If the electrolyte becomes dry then only the replenishment of lost water will help.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 16, 2015, 08:06:36 pm
content: Quote from: Terabyte2007 on March 16, 2015, 05:50:34 pmCan you post a picture of your Energizer batteries? I'm curious if they are the low self discharge (LSD) variety or not? I'm also curious to see where they were made.A few years ago, in the race to higher mAH, a lot of non LSD batteries, developed a bad reputation for losing nearly 30% of their charge in 30 days (or more) and not charging properly. The Energizer AA 2500mAH developed such a reputation on some forums.I have 4 Energizer 2300mAH AA, made in Japan, but certainly its best days are over. They were purchased for a Canon camera and surely, but slowly they degraded.A pair of Eneloop AA, on the other hand, with probably over 400+ recharges is still working, but since I don't have a smart charger, I don't know the actual mAH. I do know this pair doesn't last as long as a new pair of Eneloops.

author: Terabyte2007
author_rank: Frequent Contributor
timestamp: March 16, 2015, 09:07:24 pm
content: Quote from: retiredcaps on March 16, 2015, 08:06:36 pmHere are the pics.I checked the offending battery with my battery impedance meter and it's 300+ mOhm! I would say it has issues...

author: IanB
author_rank: Super Contributor
timestamp: March 16, 2015, 09:32:59 pm
content: Quote from: Terabyte2007 on March 16, 2015, 09:07:24 pmYes. If the charger applies a 2 A current through the cell to test it that will produce a voltage rise of around 0.6 V. When added to the "normal" charging voltage of approx. 1.5 V it will get pretty close to the 2.1 V indicated by the charger when testing the cell.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 16, 2015, 09:35:41 pm
content: Quote from: Terabyte2007 on March 16, 2015, 09:07:24 pmThank you. I'm not up to date on this stuff anymore, but they look like the non LSD variety? Maybe someone else can confirm?

author: IanB
author_rank: Super Contributor
timestamp: March 16, 2015, 09:41:53 pm
content: Quote from: retiredcaps on March 16, 2015, 09:35:41 pmYes, I think just the regular kind of cell.

author: gregallenwarner
author_rank: Regular Contributor
timestamp: March 16, 2015, 10:55:44 pm
content: I had the exact same problem with the exact same charger and the exact same NiMH cell. Read HIGH when I tried to charge it. I also tried to discharge it in the smart charger, but it also refused to do that, also reading HIGH. To solve the problem, I noted that the cell wasn't fully discharged. So I stuck a resistor across the cell's terminals for a few hours till the voltage dropped to full discharged level, and stuck it back into the smart charger. Solved the problem and the cell took a complete charge again.

author: saturation
author_rank: Super Contributor
timestamp: March 18, 2015, 03:44:38 pm
content: Yes, you can 'restart' a dying NiMH by shorting the terminals briefly and it drops the internal resistance, and you can get it going again. You can cycle it 3x times on the Maha and if HIGH stops, you're successfully resuscitated the cell. If it persists, I discard it or you can keep cycling it 3x more to see if it helps. So far I've not had any such problems with LSD type NiMH from eneloop and Tenergy cells.I found that cells that start to show HIGH also have higher self discharge rates so even if the AH is decent, i.e., discharges in days to weeks. At some point the inconvenience of recharging it makes it impractical to keep, except for short high power applications like powering a photo strobe for a 1-2 hour session.In January each year, we do an inventory of stocked LSD cells unused for 1 year, we have about 15 eneloops AA and 20+ Tenergy AA and AAA. Sample testing showed eneloops had 91-97% of its remaining labeled AH using Maha C9000 discharging whereas the Tenergy cells had 75-85%. Of interest the oldest eneloop are from 2007 purchase date, and still have AH 'like new'. We 'topped' up the remaining cells and charge time correlated with the test samples, meaning it takes 10-20min to top eneloops off and at least twice as long for the Tenergy.Given the cost of eneloop vs Tenergy, is this difference worth it? I'm leaning towards all eneloop in the future because I fear the Tenergy's may worsen with age whereas the older eneloops are working like new at 8 years old, past the often published expected calendar life of NiMH of <= 5 years.Be careful buying eneloops, they are heavily counterfeited.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 19, 2015, 05:59:15 am
content: Quote from: saturation on March 18, 2015, 03:44:38 pmIn addition to counterfeits, you may want to look at the "Made in" label.As I said a bit earlier, I have not followed this market for a while now and I was surprised to see that Eneloop's new owner, Panasonic, is starting to make some Eneloops in China instead of Japan.As I was doing some initial research wrt to the above, some forums with published data indicate that the Made in China Eneloops are not as good as the Made in Japan ones. When buying my Eneloops or Duraloops (Eneloops rebranded for Duracell), I always made sure my packaging and labelling said Made in Japan.http://www.candlepowerforums.com/vb/showthread.php?392229-Japanese-Vs-Chinese-Eneloop-Cycle-Testing-ResultsI thought I went overboard buying 60 Duraloop Made in Japan cells about 18 months ago when Target Canada was clearing out old stock for about $1.25CDN/cell, but now I'm glad I got them since Target Canada is closing down.Obviously, one data point is not enough and it is still a bit early to say the Made in China cells are inferior.BTW, it took about 3 years to put 400+ recharges on my Eneloops. That number will go up since I'm now charging them almost every second day now. My current charge is a "dumb" Sanyo 250mAH charger.

author: saturation
author_rank: Super Contributor
timestamp: March 19, 2015, 11:08:58 am
content: ouch, retired caps, sounds like the glory days of eneloop are over. With that type of Performance vs cost, Tenergy becomes competitive once again.

author: IanB
author_rank: Super Contributor
timestamp: March 19, 2015, 02:23:19 pm
content: Quote from: mojo-chan on March 19, 2015, 02:12:14 pmUnfortunately the USA is one of those markets...