What the heck is wrong with these things.
They show 1.1V but my charger refuses to charge them.
If I load it I get 35mA max....

Is there any way to revive them

 

Hi R!f@@, Have had some sucess by flashing 12V dc across single cells, seems to shock them into life again.

 

Like defibrillation?

"Clear!"
Zapf!
"Wait... wait...waaaaait. We got a live one here! YES!!! Give him room. Okay, next. Clear!"
Zapf!

Zapf!

"I think this one got away. Clear"

ZapfZapfZapfZapfZapfZapfZapf!

"Umh, Now he's gone"

Sorry about that.

 

Hello,

I made a reflex battery charger once.
That can "breath" the health back into the batteries.

Here is an other thread wich talkes about this type of batter charger:
http://www.edaboard.com/thread106948-4.html

Bertus

 

But they can die from old age.

 

NiMH are 1.1-1.2V fully charged
edit: i think hydrogen is used as an active ingredient so be careful zapping it

 

If u here any news about a hydrogen bomb going off in Maldives.

You should know it's me, fiddling with the unknown

 

They aren't old Bill..

Daryl.....are u talking about clearing the memory effect of these cells..
how long should I apply 12V.

Is it 12V /cell?

 

Batteries of that type will behave that way if allowed to overheat while charging. They never again can deliver current. (I think it boils away too much of the liquid portion of the electrolyte)

 

Hello,

On the Amtel Products - AVR Solutions page, in the block Battery Management, you can find application note AVR450.

Bertus

 

Too many beans last night and the gas went the wrong way. You have Ni-MH, Not Nickel-Cadmium. Duh...at this end.

 

Hello,

On the Amtel Products - AVR Solutions page, in the block Battery Management, you can find application note AVR450.

Bertus

Bertus....
The note is for a charger right ?

My actual problem is that the cells are not charging. My charger is OK.
I can charge new ones but these old ones are not that old, may be a year or so but at first they charged pretty well, now the darn thing just won't hold or charge.

 

Hello,

In the first post in this thread I gave a thread from an other forum that shows the reflex method.
It uses discharge cyles during charging.
The discharge is to remove the gass bubbles on the electrodes.
With the reflexcharger I have revived several old Nicd and Nimh cells.

Bertus

 

Hello,

In the first post in this thread I gave a thread from an other forum that shows the reflex method.
It uses discharge cyles during charging.
The discharge is to remove the gass bubbles on the electrodes.
With the reflexcharger I have revived several old Nicd and Nimh cells.

Bertus

I can't seem to access any links there bertus

 

NiMH are 1.1-1.2V fully charged

Please look at the datasheet of a Ni-MH battery cell before making incorrect remarks.

 

http://data.energizer.com/PDFs/nh15-2000.pdf
Nominal voltage: 1.2V.

 

Does NiMH goes above 1.2V..?

 

Does NiMH goes above 1.2V..?

The graph I posted shows 1.5V when fully charged at a high current.
It is 1.4V when fully charged at a low current.

I just measured the voltage of some Ni-MH cells I fully charged a couple of weeks ago and they measure 1.34V without a load.

Here is a discharge graph:

 

Rifaa,
During charging, yes - it can go above 1.2v. See the plot that Audioguru posted.

"Zapping" can work for NiCD batteries (I've fixed some that way) - but it is hardly ever effective for NiMH cells. "Zapping" is inherently hazardous, which is why I haven't discussed it before now. It is all too easy to "zap" too much, and have the battery rupture forcefully, sending shrapnel and chemicals in various directions. Temperatures and pressures inside the battery shell can and do skyrocket unpredictably. I advise against attempting to "zap" your NiMH batteries; your safety is worth much more than a pair of batteries.

If you decide to attempt it despite my advice, wear suitable protective gear:
1) Eye protection - complete coverage.
2) Face protection - At least several layers of heavy cardboard stock.
3) Hand protection - leather gloves.
4) Body protection - wear a leather or thick denim jacket, and a leather shop apron.
5) Do not hold the battery in your hand(s).

It sometimes works on NiCD's that have not experienced cell reversal.
NiMH cells have a shorter service life than NiCDs, and are more easily damaged by improper charging. High temps will kill them quickly.

 

I agree with the sarge. While zapping batteries in my past, I used a camping cooler for a "blast chamber".

I use the same cooler for capacitors when working on high charge/discharges projects.

Dont play around. You have enough experience to know how to be safe, but the amount of money you would have to spend to be safe is MANY times the price of a set of batteries.. Not to mention the amount of money you would loose while mending your injuries.