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Keep Those Old Cordless Tools Going

How I converted my old coldless drills to run on my RC LiPo batteries

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Gary Manuel21/02/2018 20:41:24
2276 forum posts
1552 photos

I have a pair of Makita cordless drills that I have owned for many years. They came in a heavy duty storage box with a charger and a pair of NiCad batteries. A couple of years ago, I noticed that the batteries were failing, so I replaced the NiCad's with a set of high capacity NiMh's I bought from eBay.

The battery packs worked well for a while but every time I go to use the drills, the batteries have self discharged and it is a continuous battle to keep them charged up.

I started looking at alternatives. Should I buy new NiCad batteries, because there is nothing wrong with my drills? Should I buy a new drill / combo? Can I convert them to run on modern Makita Lithium Ion (LXT) batteries? All options looked expensive baring in mind that my days of heavy duty DIY are numbered.

But then I realised that I already have a supply of batteries which could be ideal for this application - my R/C LiPo's!

Here's what the old battery packs look like.


And here's what I've done to them. The XT60 plug is wired directly to the battery pack "+" and "-" terminals.


The cutout and velcro nicely match the 1000mAh 4S 65C Graphene batteries that I use for most of my small models.


The drills feel far more punchy than they ever did . Old NiCad's were 14.4V. New LiPo's are 14.8V.


It doesn't look too good, but it appears to work very well.

I'll take them from my RC battery box when needed and charge them using my normal Hobbyking Quattro as I would after flying.

Note that I wouldn't recommend this for heavy duty work as the batteries do not have any in-built safety features in case of an overworked / stalled motor. For keeping a DIY drill running at minimal (NO) cost however, it appears to be a winner.

I've not used it in anger yet (i.e. hammer drilling or screwing) but I have used it for drilling and the 1000mAh batteries are easily large enough.

If more capacity is needed, there is plenty of space for a bigger battery. This is an out of service swollen 3 cell but if this fits, a decent 4 cell 2200mAh should easily fit.


John Rudd21/02/2018 21:05:26
96 forum posts
2 photos

What about the issue of depleting the batteries below a safe level? No lvc?

Gary Manuel21/02/2018 21:09:07
2276 forum posts
1552 photos


I'll take the same approach that I do when flying.

When performance starts to deteriorate, it's time to change batteries.

Jez Saunders21/02/2018 21:32:49
111 forum posts

Put one of those cheap low battery warning indicators on.

John Robertson 321/02/2018 23:05:49
192 forum posts
5 photos

Gary - Thanks for posting this. For some reason It never crossed my mind to use LiPos for the job - I'm in exactly the same position as you were, with decent machines and old NiCads. Majik.

KiwiKid21/02/2018 23:55:51
492 forum posts
479 photos

Well done Gary, it's great when hobby experience helps you out in real life.

I had a similar problem seven years ago and I was sitting down contemplating the horror of soldering up a bunch of ni-cads when I suddenly thought "hold the bus a lipo could do this". Worked a treat and the drill is still soldiering on to this day.



onetenor22/02/2018 02:45:56
1901 forum posts

You could have jolted the Nimhs back to life with a flash contact from a welder. or any other higher voltage Really works.

Edited By onetenor on 22/02/2018 02:48:16

Trevor Crook22/02/2018 07:47:10
990 forum posts
71 photos

I've wondered about doing something similar with my older drill. I've got a Li Ion one for d.i.y. The main advantage over the old Nickel cells is that it keeps its charge between uses, my old cordless drills always needed a charge before they were ready to use.

I'd been concerned about lack of over-discharge protection, but I guess for light use tnis would be less of a problem, and a cheap cell monitor could always be fitted.

It would be ideal to house the LiPo in a nice hard protective case though, in case you dropped the drill.

Stuart Z22/02/2018 12:42:01
394 forum posts


I got replacement batteries (pattern replacement) on Amazon for my Bosch cordless. Much better amp hour rating and fit the drill and the original case perfectly. Uses the standard charger supplied with the drill.

Just mentioned for what it’s worth.


MaL22/02/2018 13:48:52
140 forum posts
13 photos

I have replaced all my old ni-mh drill batteries with a 1300mAh li-po so it fits inside the existing battery case. I recharge using a cheap HK balance charger so only the balance port socket needs to be accessible. (the main power socket is connected to the case terminals. The only problem is you must stop and charge the battery AS SOON AS you detect the drill or whatever is slowing down, if you carry on for another 5 seconds I find one cell is usually too low for the charger to allow a charge and I end up having to 'flash' the cell to bring it up to a voltage that the charger will accept. OK... I know it is no way to treat a li-po, it is either that or throw it away.

Former Member22/02/2018 15:29:52

[This posting has been removed]

Steve Hargreaves - Moderator22/02/2018 19:42:48
6765 forum posts
197 photos

Did exactly the same with my cordless drills a few years ago (7 or 8 maybe) using some old packs that were passed their best. I managed to fit them into the battery holder where the NiMHs used to sit. They are still going strong & it's the best modification I ever made....they are always ready to go & have far more power than they ever did on NiMH cells.....For sure I run the risk of ruining a battery by running it too low but so far that's not happened.....

A very worthwhile modification....thumbs up

kc23/02/2018 11:46:00
6576 forum posts
173 photos

It is good idea to buy all cordless tools with the same type of battery - e.g. buy a drill with same fitting battery as hedgetrimmer etc so that the battery is interchangeable and gets used all the year round. Also works the other way - when one charger fails then there is another that will work. As often as not it's the charger that fails.

Toni Reynaud23/02/2018 12:33:51
424 forum posts
58 photos

I made up replacement battery packs from ex-laptop battery li-ion 18650 cells. 3.6V per cell nominal insted of 3.7V. A 4s2p battery works well in a 14.8V drill, and doesn't self discharcge. I do also use a 4S LiPo on a cordless circular saw which I feel needs just a little more punch.

David Ovenden23/02/2018 18:33:17
362 forum posts
17 photos

Well you can still buy replacement Sanyo 2500SCR NICADS on ebay from Germany!

Gary Manuel10/03/2018 18:01:55
2276 forum posts
1552 photos

Just a bit of feedback to report how my battery conversion has worked in practice.

I've used the pair of drills for drilling hard engineering bricks, screwing heavy duty rawlplugs and hole saw cutting and I'm well impressed by how much power a small 1000mAh battery can deliver. So much better than the NiCad's or NiMh's ever performed.

After hammer drilling a couple of dozen holes the battery took 467 mAh, so it was at about 50% capacity. The other battery used for screwing took much less.

The best thing is that the battery worked straight out of by flight box without having to charge them up before use.

Well pleased and happy to carry on using them for DIY use.

fly boy301/02/2019 11:55:29
3688 forum posts
22 photos

Great idea Gary. I only use cordless drill to drill ply. I am not into electrics but do have a 1500 mah 3cell spare for my e glider. Would one of these be ok. Cheers

Gary Manuel01/02/2019 14:46:33
2276 forum posts
1552 photos

fly boy3

I've just tried mine with a 3cell 2200mAh 65c Graphene LiPo and surprisingly, it feels like it's got plenty of power.

I would say it's well worth having a go with your 3 cell LiPo if you keep the mounting arrangement fairly universal so that you can switch to 4 cell when / if one becomes available.

fly boy301/02/2019 14:52:05
3688 forum posts
22 photos

Thanks Gary, you have been a great help and money saver lol. Hobby King here I come. Cheers, ps As I said only for ply and wood. My mains Bosch does the heavy stuff.

Edited By fly boy3 on 01/02/2019 14:53:47

Bruce Collinson02/02/2019 10:20:47
543 forum posts

Didn’t see this first time round, wish I had but for reference there’s a bloke outside Rotherham who will replace original batteries inside the casing for sensible money. He did two of the three my Makita came with and it’s better than new as he was able to smuggle larger capacity cells in. I had already bought a new third cell.

Yes it’s perfectly possible to diy but I made a bit of a mess getting the first one open. His was neat, everything fits like it did before. Ex modeller, I’m sure. Can’t recall precise details, advertises on web.


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