High capacity NiMH premature failure

[itsme000]

I've got about a dozen 2500mAh+ batteries sitting here that still hold 80%+ mAh capacity, but are faulty, because the internal resistance is too high and can't sustain adequate voltage at current draw level used in digital cameras.

They're Made in Japan 2500 and 2650mAh cells with Kodak and Duracell labels. Once fully charged, they "hold" charge ok, and maintains 1.35v for months, but under load, voltage plummets. Short circuit current is around 4A at room temperature while a healthy cell is around 12-20A. They've got less than 100 cycles and although after a few cycles, they perform better, the problem relapse after a week or so.

Depending on how bad the internal resistance build-up is, you'll end up with batteries that will work on warm days, but won't work on slightly colder days.

These batteries work when they're held shorted until they get hot enough for current to rise to 10A.

From reliability stand point, this is unacceptable.

[webworld]

You should recondition your NiCd and NiMH battery packs once a month and/or when your run time is significantly reduced. Do not recondition more than prescribed or expose the battery to high heat.
Lithium Ion battery pack have no memory effect like NiCD does, but by properly taking care of your battery you can maximize its life. Use your Lithium Ion battery in area’s that temperature does not vary widely and do not expose it to excessive heat.

[a-beginner]

[QUOTE=itsme000;1007870]I've got about a dozen 2500mAh+ batteries sitting here that still hold 80%+ mAh capacity, but are faulty, because the internal resistance is too high and can't sustain adequate voltage at current draw level used in digital cameras.


You might want to get a good charger like a La Crosse BC-900 or a Maha 9000 that has a Refresh function - the charger discharges and charges your batteries until they have attained maximum capacity. Then the charger will tell you the capacity it was able to restore your batteries to.

I had a set of 2600mAH that took about a day to recondition on a BC-900.

[skyquipin]

Originally Posted by itsme000

I've got about a dozen 2500mAh+ batteries sitting here that still hold 80%+ mAh capacity, but are faulty, because the internal resistance is too high and can't sustain adequate voltage at current draw level used in digital cameras.

They're Made in Japan 2500 and 2650mAh cells with Kodak and Duracell labels. Once fully charged, they "hold" charge ok, and maintains 1.35v for months, but under load, voltage plummets. Short circuit current is around 4A at room temperature while a healthy cell is around 12-20A. They've got less than 100 cycles and although after a few cycles, they perform better, the problem relapse after a week or so.

Depending on how bad the internal resistance build-up is, you'll end up with batteries that will work on warm days, but won't work on slightly colder days.

These batteries work when they're held shorted until they get hot enough for current to rise to 10A.

From reliability stand point, this is unacceptable.

wonderful! thanks for the info..
However I think you should vary more examples to your writing much more interesting !
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[itsme000]

Originally Posted by a-beginner

You might want to get a good charger like a La Crosse BC-900 or a Maha 9000 that has a Refresh function - the charger discharges and charges your batteries until they have attained maximum capacity. Then the charger will tell you the capacity it was able to restore your batteries to.

I had a set of 2600mAH that took about a day to recondition on a BC-900.

The MH-C9000 is a one of the better analyzers available on the consumer market, but its algorithm has serious flaws.

It is not capable of providing true programmed current that is needed for "training" and testing the batteries.

It loads the battery at 1,000mA and measures voltage under load no matter what setting you use. When it is set for 100mA, it loads it at 1,000mA, @ 0.5Hz and 10% duty cycle. The problem with this is that batteries that developed a high internal resistance will drop voltage enough to cause it to terminate the discharge cycle even if it's nearly fully charged. Regardless of current setting, the voltage reading during discharge is the voltage at 1,000mA load.

As for "break-in" cycle, it doesn't quite provide true constant current either. Batteries don't respond the same to constant 200mA charge vs 10% on @ 2A, 90% off.

So, MH-C9000 is practically useless for reconditioning cells with elevated internal resistance as it's unable to complete the process without premature termination.