cell testing help needed

[rcracer]

I was wondering if someone can tell me what procedures to test a pack to see which cell or cells are bad.

I have a 6 cell NiCad 2400mah pack that doesn't hold a charge too good anymore. It's about 2 yrs old with light use and instead of throwing it out I was hoping to scavange 4 good cells from it.

I have tested each cell and they are all around 1.2 volt range. I also tested the amps at no load and they were anywhere from 2.29 to 1.6 and they all dropped about .01 per second, is that normal?

thanks

[Jeckler]

What kind of cells are they? Brand name or cardboard?
What kind of charger are you using?
How often do you use the pack?
Does each cell get warm once the pack is charged?
Are any cells hotter than others when the pack is charged or after it's used?
Do you discharge the pack before recharging?
When you're done with it and put it away, do you discharge it first?

I have 5 Sanyo RC2400 packs, the oldest of which is about 5 years old. They still work pretty good. I manually discharge them to 5.4v using a 6 bulb discharger and a voltmeter. When they're not going to being used for more than a few days, I put Gecko's on them after discharging.
At one point I hadn't used them for about 6 months, and it took a couple charge/disharge cycles to bring them back up.

[rcracer]

Originally Posted by Jeckler

What kind of cells are they? Brand name or cardboard?
What kind of charger are you using?
How often do you use the pack?
Does each cell get warm once the pack is charged?
Are any cells hotter than others when the pack is charged or after it's used?
Do you discharge the pack before recharging?
When you're done with it and put it away, do you discharge it first?

I have 5 Sanyo RC2400 packs, the oldest of which is about 5 years old. They still work pretty good. I manually discharge them to 5.4v using a 6 bulb discharger and a voltmeter. When they're not going to being used for more than a few days, I put Gecko's on them after discharging.
At one point I hadn't used them for about 6 months, and it took a couple charge/disharge cycles to bring them back up.

They are sanyo 2400.
battery is used maybe once a month at most.
duratrax intellipeak pulse charger model DTXP4100 charging at 3amps; before this charger I used a manual 15min discharge and duratrax peak charger.
I haven't noticed it get warm after a charge.
it does get alittle warm after use.
I do a discharge before charging.
I don't discharge it when I'm done using it.

I did a cycle with my charger once but not back to back, should I?

seems like after the first couple months of use it just doesn't hold a charge like it should and now I'm lucky if I get 4 mins of run time on a 2.2 with 55T lathe motor when I should be getting 30 mins. I still hope I can find 4 good cells in the pack to use.

thanks guys

[Jeckler]

Originally Posted by rcracer

I haven't noticed it get warm after a charge.
I don't discharge it when I'm done using it.

I did a cycle with my charger once but not back to back, should I?

seems like after the first couple months of use it just doesn't hold a charge like it should and now I'm lucky if I get 4 mins of run time on a 2.2 with 55T lathe motor when I should be getting 30 mins. I still hope I can find 4 good cells in the pack to use.

thanks guys

Sounds like it has some memory in it, and it's not charging all the way. It should get warm after charging. Not blistering, but it should warm your hands.
Charge it up, let it peak, then just hit start again. Even a couple times. It's false peaking.
Now discharge it using bulbs or whatever.
Let it sit for an hour or so.
Discharge it again. BTW: How do you discharge it?
Charge it again.
At 3 amps, it should take around 30-40 minutes to charge it, depending on the level of charge it has in it. If it's totally dead, math says it should take 8/10ths of an hour.
I charge mine at 4.5 amps.
Mine usually false peak around 1400mah if they haven't been used all week. If it's been over a week, they'll false around 400, and maybe once more before they'll go all the way.
Even if you don't use it for a while, do a charge/discharge once a day for 3-4 days and see if it comes back.
I bought an old Frog a few years ago that came with a 1500mah NiCd. It was completely dead when I got it (showing lessa than .5v on the multimeter). I let it slow charge overnight, then charged it at 2 amps. After about 3 cycles, I could get about 1300mah into it. I'm still using that pack to this day.

If it does come back up, you can either use it, or you'll have 6 good cells for other projects.

[rcracer]

much appreciated!! I use my 15 min dial discharger that has a meter and I don't let it get down below 2 volts. I continue as you suggested and hope this thing comes to life, it has been false peaking after about 5 mins then i just unplug and hit charge again.

thanks

[rcracer]

Originally Posted by Jeckler

After about 3 cycles, I could get about 1300mah into it. I'm still using that pack to this day.

If it does come back up, you can either use it, or you'll have 6 good cells for other projects.

how do you calculate how much mah it is retaining?

[Jeckler]

I use an Intellipeak Digital. It has the display on it that shows how much is being put into the battery.
BTW: 2 volts is way too low for a 6 cell pack in a stick configuration (.33v per cell) Big danger of reversing a cell that way, since you can't monitor an individual cell (easily).
Discharge it to 5.4v or thereabouts (.9v per cell). That's about the industry norm.
I don't even use the built in discharger on my Digital, as it would take the cells down to 2.6v, or some odd value.
You may have already done some damage to the pack, but an overnight trickle charge might help as well.

[rcracer]

your right, my duratrax discharger takes the pack down to 2.6 volts so I thought that was normal, didn't know about the .9 V per cell.

Thanks again

[rcracer]

After a few days of charging and discharging the pack is showing signs of positive life.

thanks again