Need Battery Advice

I have an old Makita drill I'd like to get working again.
The power source for the drill is 7.2 v. It runs at 600 rpm.
The battery charger says it outputs 7.2 vdc 300 mA.
The question I have is: Can I put another battery in the drill as long as it outputs 7.2 v and it physically fits?
I know how to solder.
Thanks,
Mike
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On Sat, 6 Nov 2004 21:23:21 -0600, Michael Hill put forth the notion that...

Yes. What you need is six 1.2 volt ni-cads.
--
Checkmate

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Michael Hill wrote:

Yes. Get batteries with as high an mAh rating as you can that will fit. Your drill will draw a LOT more current than the 300 mA the charger can provide to charge the battery pack.
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Michael Hill wrote:

Yes - it doesn't even have to fit as I have one drill I have modded to use a battery pack on my waist-belt. (Not all of us have the biceps to hold up a cordless drill with battery pack for more than a few seconds).
The only thing that you have to watch for is some cheap drills have inadequate heatsinks on their speed controllers. They are designed, IMO, to match the battery capacity - so the battery will go flat before the speed controller and its heatsink overheats. So maybe don't go too OTT on the capacity of the battery pack - even if you have the strength to hold car batteries up at arm's length for hours at a time..
--

Sue



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Sue,
So you have some kind of wire you run from the cells to your drill? It must be over 3 ft?
Mike
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Michael Hill wrote:

You can buy a new battery for it at real hardware stores or the makita web site. There are also 3rd party knockoffs. If you have the old dead battery for it, you can open it up and replace the internal batteries with fresh ones.
--Dale
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On Sat, 06 Nov 2004 21:23:21 -0600, Michael Hill wrote:

Shouldn't be a problem. Only thing to mention is make sure you use NiCads. TTYL
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Most battery operated tools use standard size cells. So once you figure out how to open the battery case it should be relatively easy to change the dead cells out for new ones.
I think Batteries plus has help for doing this. There are also many places on the web that will do it for you at a fixed price.

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Dale,
I do have the six cells it came with. How do I test which cells are bad?
Mike
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>

if it over 3 years old and if one cell is bad its better to replace all of them (in my experience).
to test the battery charge it with the correct current. a good nicad cell should show about 1.3 volts under charge and 1.25 volts just standing there with no load. (this might vary with type but true for most of what i see)
next place a load on the cell and determine how long it takes for the voltage to drop below a usable value (i.e. 80%)
multiply load current times time to get ampere-hours (or mA-h) then compare to the cell rating.
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