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Old 03-28-2004, 01:48 PM   #1
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Default how do i find a bad cell?

i think have a bad cell in one of my packs.fully discharged my millenium pro says that the pack has over 6 volts. and will only charge it for about 20 seconds. when i put my multi meter across each cell they all read the same. what gives? and how can i figure out wich one it is? (4cell nicad)
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Old 03-28-2004, 04:59 PM   #2
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Default Re: how do i find a bad cell?

The easy way is to put them in a turbomatcher .

There are a couple of other ways though. Often when a cell goes bad, it will get extremely hot while it charging or discharging, so keep an eye out for that. Assuming that doesn't work, a more tedius method is to disassemble the 4 cell pack in question. Take a 4 cell pack that works, remove one cell from the working 4 cell pack and replace it from one from the faulty pack, try cycling the pack, if it fails, there's your bad cell, if not, keep trying to you find it.

John


Quote:
Originally posted by sean
i think have a bad cell in one of my packs.fully discharged my millenium pro says that the pack has over 6 volts. and will only charge it for about 20 seconds. when i put my multi meter across each cell they all read the same. what gives? and how can i figure out wich one it is? (4cell nicad)
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Old 03-28-2004, 05:09 PM   #3
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Default Re: how do i find a bad cell?

Quote:
Originally posted by sean
i think have a bad cell in one of my packs.fully discharged my millenium pro says that the pack has over 6 volts. and will only charge it for about 20 seconds. when i put my multi meter across each cell they all read the same. what gives? and how can i figure out wich one it is? (4cell nicad)
Usually when you discharge it voltage check each cell during discharge and it should be apparent. Heat is another indicator..

coop
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Old 03-28-2004, 05:52 PM   #4
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Lightbulb More help I hope

The best way is to put the pack in a tray then read the voltage of each cell. A bad one will be 0 volts or really low. Most will be in the 1.2 range.

Some signs:

Heat shrink or label blurred,
Heat shrink or label coming off cell
leakage at the + end will look like acid on one cell


Charge the pack as much as you can. put on a load like bulbs or a discharger or a tray. Read the voltage of each individual cell as it is discharging. I f you have a bad one it will be obvious.

David Root

Or you could send the pack with the motors
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Old 03-28-2004, 08:02 PM   #5
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Default

my 2 cents.

try chargiong the cell, then put it in a tray iwth an individual resistor like the trinity real time 2, the bad cell will show immediately as the indicator will show that the bad cell has no charge in it by not lighting up.

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Old 03-29-2004, 01:19 AM   #6
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It gets hotter than the other cells while charging, easiest test.
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Old 03-29-2004, 05:05 AM   #7
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Default Re: how do i find a bad cell?

Quote:
Originally posted by sean
i think have a bad cell in one of my packs.fully discharged my millenium pro says that the pack has over 6 volts. and will only charge it for about 20 seconds. when i put my multi meter across each cell they all read the same. what gives? and how can i figure out wich one it is? (4cell nicad)
I'm not familiar with the Millenium, but maybe it simply wont charge because the voltage is too low.

With some of my older packs, I've experienced that if they have rested for several weeks (discharged), my Eagle CDC 6.0 try to charge. After a couple of minutes, the charger stops, with the error message: Batt. voltage too low (or something like that).

If I afterwards pot a few miliamps in the pack with a 7,2 volt power supply, the voltage raises and the CDC charges normally.

But if it's a bad cell, GCoopers methods is good.
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