Newbie Ni-Cd to Ni-Mh Battery Question

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Hi all,

I have a cordless drill here that the battery pack has died on. After
cracking it open (dead anyway) it's just filled with 12 x 1.2V 1200mAh
Ni-Cd batteries to total 14.4V.

My question is if I replace them with higher rated 1.2V Ni-Mh batteries,
say 2000 or 2200mAh will the original charger for the drill be ok?

The output on the chargers label is 15.0V DC 400MA.

PS I know cordless drills are as cheap as chips these days or I could
get them refilled at a battery joint, but it's more of a Cup Day project
than anything else...

This page was quite helpful http://www.greenbatteries.com/bachfa.html
I'm just not sure about the 15V charger and 14.4V total (or is it 1.2V?)

Any assistance appreciated.

Cheers

Re: Newbie Ni-Cd to Ni-Mh Battery Question


I've just changed the NiCd batteries in my "Bostik" soldering iron with
NiMH. Runs and charges like a beauty, and I can get even more heat out of it
now.

It had two 1200mAh C cells and they were changed to 2700mAh. The original
plug-pack charger works happily without getting too hot.

Hope this helps,
Peter

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Re: Newbie Ni-Cd to Ni-Mh Battery Question


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Don't use NiMh. NiCd have much lower internal resistance than NiMh so
are more suited to high current devices like drills.

Also, NiCd are much more robust and tolerant when it comes to charging.
NiMh cells are exothermic during charging so they can get hot real
quick and hence get damaged more easily.

Stick with NiCd.
 
Dave :)


Re: Newbie Ni-Cd to Ni-Mh Battery Question



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My 14.4V cordless drill recently lost performance due to a couple of shorted
cells, this in turn popped the thermal fuse in the wall wart charger. There
was no safe way to bodge the charger transformer other than find another
wall wart transformer with the same ratings, the shorted cells were cleared
by using a 12V lead battery with both filaments of a H4 bulb in parallel to
limit the current and immediately giving the pack a full charge on the
repaired charger - its worked good as new since.



Re: Newbie Ni-Cd to Ni-Mh Battery Question


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no. most NiCd chargers can't correctly charce NiMh cells.


Bye.
   Jasen

Re: Newbie Ni-Cd to Ni-Mh Battery Question


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Ta for that, probably a good thing I did go the NiMh route then.

Cheers

Re: Newbie Ni-Cd to Ni-Mh Battery Question


Thanks for the replies, much appreciated.

I looked for NiCd's without success, seems NiMh are now the only readily
available rechargeables available from the department stores / Jaycar /
DSE / etc..

With concerns about the charger too, in the end I decided against
refreshing them ;) Thanks again for the advice.

Cheers

Re: Newbie Ni-Cd to Ni-Mh Battery Question



Han wrote:
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Jaycar have plenty of NiCD cells!
Solder tab versions are available in AA,Sub C, 1/2 Sub C, 4/5 Sub C,
and 2/3A
Page 196 in the catalog.

Dave :)


Re: Newbie Ni-Cd to Ni-Mh Battery Question


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My local store didn't have any stock of the ones I thought I needed. The
1.8AH SUB C were what I thought would be ok and better, the other 1.3AH
would be much the same as the original batteries I thought and very
little point in replacing given the cost.

I was even going to try higher rated AA (as they would physically fit)
but the highest in stock were 1000mAh.

I guess it's probably safer anyway that someone like me didn't do it ;)

Thanks all again.

Re: Newbie Ni-Cd to Ni-Mh Battery Question


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go to a battery place. not a toy shop.


Bye.
   Jasen

Re: Newbie Ni-Cd to Ni-Mh Battery Question



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Actually, model toy shops would most likely have the high-performance NiMH
batteries that he wants.

I'm curious though, do these drill packs still use temperature sensing for
charge cutoff? Or do they use delta V with temperature as a safety backup?
If they still use temperature, would the temperature change of a NiMH pack
be close enough to that of NiCads?




Re: Newbie Ni-Cd to Ni-Mh Battery Question



Poxy wrote:
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No, NiMH have an exothermic charging process and generate a lot more
heat (and internal pressure) during and at the end of charging, totally
different to NiCd.

Only the expensive drills have any sort of proper charging design. The
cheap $15-$50 Bunnings drills have no cutout at all.

Dave :)


Re: Newbie Ni-Cd to Ni-Mh Battery Question


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NiCd charging is endothermic, so the increase when they fill up and go
endothermic is more pronounced.

it could work.

Bye.
   Jasen

Re: Newbie Ni-Cd to Ni-Mh Battery Question


On 2006-11-08, I

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  ~~~~~~~~~~
 eXothermic
 

Bye.
   Jasen

Re: Newbie Ni-Cd to Ni-Mh Battery Question


Have a look at the next (December) issue of Silicon Chip - this exact
topic is covered in a feature and also a charger controller to stop you
coooking the batteries in the future.

Ross Tester

Han wrote:
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