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Author Topic: Reviving an old NiMh pack  (Read 2630 times)

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Offline TrickyNekroTopic starter

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Reviving an old NiMh pack
« on: May 24, 2009, 03:06:03 PM »
Hello guys, I recently got a very old (i386) laptop and I want to explore it for a little fun....
First of all... I want to revive it's battery pack.... and use it for my own...
It's a 12V (somewhere near....) NiMh pack...
It's seems that it's around 0.2V and the smart charger does no good....
I'm currently zapping the pack with a 12V source to lower the cell resistance....
Is that any good???
Have you something else to offer??? :P
It's not that I'm in need of the pack.... but.... why not... I want to play.... not just go out and buy a new....
It seems that it's currently letting 10mA through which means the resistance is somewhere to 1K to 1K5...
That's bad...
Anyway... have to offer any other methods???
I read about freezing methods.... but.... hey.... don't really agree with that stuff..... (ok it might work... but too ghetto....)


Thanks in advance,
Lefteris,
Greece
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline SmAsH

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Re: Reviving an old NiMh pack
« Reply #1 on: May 24, 2009, 03:10:42 PM »
get a 12v 500mA adapter and charge the battery for no more than 3 seconds and see if its voltage has increased..
if it hasn't it is most likely a dead cell.
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Offline TrickyNekroTopic starter

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Re: Reviving an old NiMh pack
« Reply #2 on: May 24, 2009, 03:22:37 PM »
I'm using an ATX 12V supply to zap her...
After some time it was held at ~7V....
But with no charge at all....
I think I need a greater voltage to do that... around 24V let's say... for about an hour and measure self resistance...
ATX can give you 24V so I might try it soon enough... :P
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline SmAsH

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Re: Reviving an old NiMh pack
« Reply #3 on: May 24, 2009, 03:25:27 PM »
just don't let her explode on you ;)
that would be bad...
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Offline TrickyNekroTopic starter

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Re: Reviving an old NiMh pack
« Reply #4 on: May 24, 2009, 04:02:36 PM »
Ok..... I started zapping with 24V.... and wait for what it may happen...
And so far.... I almost get a current of 120mA.... Wow.....
Temperature is still good...

And by the end of the post it should reach 200mA meaning a 120Ω internal resistance...
I'll continue to 300mA to get a >100Ω resistance... then rey a normal charge...

And hey... I'll video the fireworks if there are any... :P


Regards,
Lefteris...

PS: James... don't worry...... I'll try to survive even if I turn my room to vietnam.... :D
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline Soeren

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Re: Reviving an old NiMh pack
« Reply #5 on: May 24, 2009, 05:33:24 PM »
Hi,

You might try slow charging for a couple of days (a week?) and then discharge by 2C to 3C (where C = original nominal capacity) until 0.9V/cell is reached and then repeat. It may build capacity over some cycles.

The freezing method, I'm not too sure about either (only tried a few times with no luck), but don't discard it solely for being Ghetto :)

Personally, I'd open the pack, as there is nearly allways 1 or a few cell that is dead. Either exchange them with better ones or try to zap them alone - zapping rarely gives anything substantial on a battery with that many cells.


Good luck - and if it fails, you might at least get some good cells out of the bundle.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline TrickyNekroTopic starter

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Re: Reviving an old NiMh pack
« Reply #6 on: May 24, 2009, 06:44:06 PM »
Thing is that the pack was working.... But haven't been used for years....
That's why I did prefer the zapping method...
I'll try building a 13V8 steady supply tomorrow with a LM317 and the ATX I have...
Then select with a resistor the C/10 charge rate and see what happens after one day or so...
Good thing is that the pack has build in thermal protector...
Just a two metal wire thermostat but will do the hard work for me...

I charged at 24V.... until the battery was hot (didn't wait for the thermostat of course...)
I gave around 100mA, and assuming most of it was heat.... It did indeed moved a moter for some seconds (30 - 40 seconds)
with a huge voltage drop, but still this is positive... Gotta think that it WILL wake up.... but still I can only hope....


So thanks guys for the ideas so far.... I'll try updating as soon as possible!!!

Regards, Lefteris
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

Offline SmAsH

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Re: Reviving an old NiMh pack
« Reply #7 on: May 25, 2009, 01:07:21 AM »
PS: James... don't worry...... I'll try to survive even if I turn my room to vietnam.... :D
don't you go trying anything...

just out of curiosity, what voltage does the motor run off?
Howdy

Offline TrickyNekroTopic starter

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Re: Reviving an old NiMh pack
« Reply #8 on: May 25, 2009, 11:50:11 AM »
It starts running from 7 to react 1 point something volts.... when finally stops...
I zapped her for some time... it should be ok....
Just need a charger now....
Bad thing I have exams.... So I'll delay testing that's for sure....
Plus I have may things to do.... So I'll just keep being busy until the end of the next month....
I have other projects I must finish too....

So... thanks so far....
I'll update as soon as possible.... (may write a tutorial.... why not???)

Regards, Lefteris
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

Cheers!

 


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