Charger Malfunction or Battery Failure or Misuse?

I have 5 Eneloop Pro AAA batteries that I am using alternately for my Surefire Titan Plus. While one of them is in the flashlight, another one awaits duty in fully charged condition for about a week. The others await their turn in discharged condition. My routine is to discharge at .5A to 0.9V the one that powers the flashlight during the week, after replacing it with the one that waited fully charged during this period. I recharge one of the resting ones at .4A for duty every week so I always have three empty and two fully charged batteries, one of the latter being in the Titan Plus. I repeat a break-in cycle for all of them every six months or so. My MH-C9000 takes care of this routine. The batteries are two years old and none of them drop to below 900mAh during the .2C discharge cycle of the break-in mode. When discharged at .5A, they all deliver 840+mAh.

Yesterday, however, my MH-C9000 refused to discharge the one that powered the flashlight during the week. My usage was very limited, this week. In fact, according to my DMM, the battery's voltage was 1.298V out of the flashlight. When I set the discharge rate to .5A, the MH-C9000 screen read "1.30V, DONE, AVAILABLE CAPACITY: 0 mAh". All the slots repeated the same, even when I lowered the discharge rate to .2A. I tried the charge mode to see if this was due to excessive internal resistance. It seemed so. Following the momentary initial test result of 2.14V, the screen read "HIGH" and refused to charge as well. I put the battery back into my Titan Plus and ran it at max for a while. The flashlight did not hesitate to enter Turbo mode. The rest voltage dropped to 1.247V. Then, the MH-C9000 discharged the battery, as usual.

Once the battery was empty, I ran a Refresh and Analyze cycle at .4A charge and .5A discharge rates, resulting in 820 mAh capacity, slightly lower than usual at this current rate. Then, I discharged the battery at .2A and its capacity improved to 863 mAh, again slightly lower than usual for .2A discharge rate.

I am actually running a break-in cycle for this battery. The charge cycle started by the momentary test result of 1.63V. It seems the internal resistance improved somewhat but I wonder why it was that high after waiting fully charged for a week, followed by light use for another week, after 3 weeks of rest time in discharged condition. Why did it improve by simply further using the flashlight? What can I expect from the ongoing break-in cycle? What else shall I do to keep my set of 5 batteries healthy for a few more years? After all, the batteries have less than 30 cycles each.

I would be grateful to charger/battery gurus who would like to comment. Thanks.

Very strange.

Though the C9000 charger has a problem with the slots dying one by one, failure to charge or discharge happens to most of them eventually that`s what killed my last C9000, I bough a new one as you cannot beat it for NiMh AA and AAA cells.

John.

Hello Bucur,

Interesting...

It appears that your cell experienced an increase in internal resistance momentarily, and then things went back to normal. This could be a chemical breakdown of the electrolyte or just a fluke.

Keep an eye on the cell. If it happens again the cell may be "going south" and you will have to replace it. Exercising it may help but I am not sure.

Tom

Thank you both for your replies.

The break-in cycle yielded a slightly reduced capacity of 876mAh but when I tried to discharge it again, the battery failed completely. Neither .5A nor .2A discharge rate was possible. It sagged terribly before delivering a few mAh. I recycled it.

I understand from your replies that this was as weird as I think. Maybe the battery was injured when I dropped the flashlight. I don't know. This rarely happens and I do not keep track of which battery was in the flashlight when I drop it.

I am keeping an eye on the other 4.

UPDATE:

It is now clear that my MH-C9000 is kaput, as John suggested.

It did not properly discharge another battery that was fully charged a week ago and not used since then. At 0.5A discharge rate; voltage dropped to 0.9V within a few seconds, available capacity being a few mAh. At 0.2A discharge rate, the same happened within a few minutes.

When I discharged the same battery in my Sky RC MC3000 at 0.5A, it worked as usual. Voltage dropped gradually as available capacity accumulated and finally, it showed 860mAh when the discharge cycle stopped at 0.9V.

I repeated the same procedure with another nearly full battery and the results were the same: at 0.5A discharge rate, almost instant drop to 0.9V with the MH-C9000 with a capacity of few mAh, whereas with the MC3000, the same battery revealed 790mAh without fuss, again at 0.5A discharge rate.

I am so sorry for my loss! The MH-C9000 was my favorite NiMH charger but … :mecry:

The C9000 does not have reverse polarity protection supposedly, I read a review on Amazon and saw a photo of the positive contact on the charger was burnt, The guy said he had put a battery in the wrong way around, I do this myself now and then when loading battery`s in low light, All my other charger have protection i just have to be careful with my new C9000.

Just buy a replacement C9000 i did as i prefer it to my MC3000 when i am only charging NiMh AA and AAA cells.

John.

Just as an fyi, you can store those eneloop pros at full charge. They also tend to not handle deep discharges as well as normal eneloops suffering degredation more quickly on full cycles. Your maintenance of those batteries would be ideal for nicds, not nimh.

John, I know why you prefer the MH-C9000 to the MC3000 for NiMH. I was in the same boat but I no longer am. I no longer can entrust my Eneloops to another MH-C9000 because there is no way I know when and why it will start demolishing them rather than up keeping.

Herektir, you may be quite right on my maintenance routine. Deep discharge may not be the way to go, indeed, but I would still refrain from storing them at full charge either. Maybe I should store them half discharged, top off before use, and “exercise” them every few months.

As another has mentioned I never fully discharge the Eneloop Pro cells all the time as they'll degrade faster than the regular white Eneloops. The only time I would cycle Eneloops in general is to get capacity readings, typically if I don't regularly use them or I question the cells run time.

For an example I got a set of Goal Zero batteries and one of them has higher voltage than the others when discharged in the GZ unit. 2 of the cells has high internal resistance and I know one cell is older due to the manufacture date. But the older cell is performing good in a cycle on the BC1000 charger. I found 2 cells that are slightly underperforming but they are still cycling at the moment. (ALL those cells are cycling still).

I have found that Eneloops don't require cycling like the traditional NiMh cells do or the hybrids (and generally any cheap cell). Also I just store my Eneloops at 80-90% using the C9000 charger, they do fine. The Eneloop Pro I use a little here and there to keep them active.