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Where to buy replacement batteries?

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Lowlife

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Anyone know the best place to get replacement batteries for my 12v Bosch drill? The past couple of months they've taken progressively longer to charge and less time to discharge so are clearly on their way out. In the past I've bought loose tagged cells and fitted them in the old case, this works well as they're generally cheaper than a complete replacement battery, and the new cells are usually greater capacity than the originals too, but I was just wondering if anywhere does good quality replacements cheap enough that it wouldn't be worth the effort of doing this?
 

Andrewf

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I also was looking at replacing batteries for couple of Bosch drills, is it easy to obtain replacement cells and fit into old cases. Where would one find the info on cells required.
 

Lowlife

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Thanks guys I'll check out those two.

I also was looking at replacing batteries for couple of Bosch drills, is it easy to obtain replacement cells and fit into old cases. Where would one find the info on cells required.
It's not difficult to do, just replace the existing ones with the same physical size cells, as I mentioned you'll probably find that you can get new ones with a greater capacity than the originals which is a bonus. If the old ones are NiCad or NiMH then they're 1.2v, new replacement ones will be the same so you need the same number, try to get tagged cells as they're much easier to solder together, if they don't have tags it's easy to damage the cell if you're not careful by overheating it with the soldering iron.

I buy my cells from places that sell stuff for electric model planes, they usually have good quality tagged ones, but shop around as prices vary considerably.
 

bosshogg

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Unfortunately there's a bit more to it than just replacing cells size for size, unless the cells are identical.
First the obvious, cell size must be the same,as must be be the chemical composition, fortunately in all power tools , the size in question is always "sub C" unfortunately these are also used for other applications than just power tools. same size cells must also be same configuration, that is high density (Ah) and high discharge, this makes them a bit special.
Less high spec cells, of the same size, can indeed be replaced, but the performance of these will both likely be woeful and short lived. Another thing, Makita Battery packs normally include a heat sensitive diode in the matrix, without this included in the rebuild, the packs can, and often do, explode whilst being charged.
Better in reality to buy after market replacement packs, these can provide a guarantee, if you shop around.
By the way, I used to own a co. (Energen AH) to build replacement power tool battery packs, Makita ni-cads were one of the most regular ones I worked on.
If you wish to PM me with the model No. Chemistry etc. of the Makitas you have, I'll do my best to find you a good deal...bosshogg :)

I never teach my pupils. I only attempt to provide the conditions in which they can learn.
Albert Einstein 8)
 

Lowlife

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That's why I use the type of cells used for electric model flight, it's a very demanding application so cells tend to be of very high quality, built for fast charge and high discharge.

You're right about heat sensitive diodes of course, I thought it went without saying that you would replace just the cells and retain any other existing components, but maybe it is worth mentioning just in case!

I've replaced old NiCads with NiMHs with no real problem, NiMHs tend to deliver slightly less current so performance isn't quite as good, but size for size they have a greater capacity so last longer between charges, again I think it goes without saying that you don't mix cells of different chemistry.

NiCads and NiMHs will charge perfectly well using the same charger, but other types of battery require more specialised chargers.
 
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