Author Topic: Cordless drill battery packs  (Read 3314 times)

Cordless drill battery packs
« on: June 04, 2015, 09:25:29 pm »
My Makita 18v packs have reached the end of the road, and I'm contemplating what to do.

Options:
Buy new Makita batteries like this from china or this in the UK (almost cheaper to buy new tools )
Buy clone batteries like this
Rebuild the battery pack - must be reasonably standard cells inside there?
Turn a battery into corded using something like this


Anybody done any of the above?

Is there any way of ID'ing which of the cells are duff? if it is only a limited number (ok, unlikely), I could combine the three into one or two.

Kim

  • Timelord
Re: Cordless drill battery packs
« Reply #1 on: June 04, 2015, 09:34:04 pm »
I've got a clone of a Makita BL1830 (so a differently-shaped 18V Li+ battery) as well as one of the genuine article.  Subjectively the only difference is that the clone is a bit sloppy with the physical tolerances, so is a bit stiffer at sliding into the tools/charger.  I haven't attempted to measure the capacity, thoguh.

If you can hack your way into the pack in a non-destructive way, then you might be able to rebuild it.  The trick is going to be finding cells you can solder to...
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Re: Cordless drill battery packs
« Reply #3 on: June 04, 2015, 09:52:58 pm »
Different battery, but I bought a Dewalt 14.4 clone on Ebay from a seller called Koo-Power a couple of months ago and am very happy with the item. 

The claimed 3AH does some to last longer than the original Dewalt 2AH.

Re: Cordless drill battery packs
« Reply #4 on: June 04, 2015, 09:58:52 pm »
I replaced my Bosch ones from buyspares.co.uk with uprated versions, and they've been very good.
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Re: Cordless drill battery packs
« Reply #5 on: June 05, 2015, 09:59:34 am »
Is there any way of ID'ing which of the cells are duff? if it is only a limited number (ok, unlikely), I could combine the three into one or two.

Yes, by measuring the voltage or noticing differences of temperature.  It's not too unlikely that just one or two cells per pack will be duff.  Worth a try anyway.

If you need/want new cells after all, the cheapest way might be to buy a new battery intended for some other drill that contains the same cells - like this: https://youtu.be/96foswY1m58   Edit: I'm not convinced this is cheaper, but see the video anyway.
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Re: Cordless drill battery packs
« Reply #6 on: June 05, 2015, 10:14:17 am »
Turns out that instead of being a relatively recent purchase, it is 10 years old..... how time flies.

I'm thinking of going with the Koo-power for 2 @ £58, I will probably convert one of the old to corded (battery was never much cop for the jigsaw) and play with the others.

Biggsy

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Re: Cordless drill battery packs
« Reply #7 on: June 05, 2015, 10:23:16 am »
I still think your cannibalism plan is good.
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Re: Cordless drill battery packs
« Reply #8 on: June 05, 2015, 10:48:32 am »
Well, I'm buying 1 ( buying 2 x 1 is cheaper than 1 x 2, go figger - think it is a feature of the trend to "free" postage), as I CBA not to have at least one functioning battery, I will then bugger around with the three old ones, see what can be salvaged. I wonder if there will be issues trying to charge individual cells from a hacked AA charger.

Kim

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Re: Cordless drill battery packs
« Reply #9 on: June 05, 2015, 12:19:20 pm »
I will probably convert one of the old to corded (battery was never much cop for the jigsaw) and play with the others.

I forgot to mention this:  In a fit of battery frustration I did once resort to running my old drill from a bench power supply.  It worked, but it is a very beefy bench power supply, and even then it would panic a bit every time the drill started.  So if you're going to use a SMPSU with short-circuit protection, make sure you over-spec the current rating by a healthy margin.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Cordless drill battery packs
« Reply #10 on: June 05, 2015, 05:33:35 pm »
If you use a simple transformer and rectifier that will stand big peak loads without panicking. If the transformer is overloaded by the drill starting, the voltage will dip on starting but that really won't matter.

Can you now get Li-Ion batteries for that drill? That would need a different charger, as Li_Ion batteries need a different charging circuit, which might well mean that a new drill is cheaper.

I have found Li-Ion batteries to be much better in all regards, except cost, than the NiMh batteries.

Quote from: Kim
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Kim

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Re: Cordless drill battery packs
« Reply #11 on: June 05, 2015, 05:53:45 pm »
If you use a simple transformer and rectifier that will stand big peak loads without panicking. If the transformer is overloaded by the drill starting, the voltage will dip on starting but that really won't matter.

Indeed.  No real need to get posh for this application, unless it works out cheaper.



Quote
I have found Li-Ion batteries to be much better in all regards, except cost, than the NiMh batteries.

Not least - when applied to infrequently used power tools - that they tend to still have some charge in them when you come to do a quick one-off job.

I also note that whatever the Makita charger is that I've got will charge the afore-mentioned 3Ah lithium battery in about 20 minutes (and then play a little tune to announce the fact, which is more useful than it sounds).  Which, unless you're really going at it with an angle grinder or something, is probably less time than it'll take you to deplete the spare.
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Cordless drill battery packs
« Reply #12 on: June 05, 2015, 05:59:03 pm »
Oooooo now then, that has reminded me of something I have hidded in TEH SEEKRET, a little fossicking is called for

Re: Cordless drill battery packs
« Reply #13 on: June 05, 2015, 06:14:41 pm »
<back>

That was easy. I present what everyone should have hanging around...tada!




A brand new, unused 250va 12v IP68 toroidal transformer.

Now, I make 12v full wave rectified about 19v, so that should do NICELY

Now to find a BFO rectifier, and possibly a capacitor across the output.... anybody care to guess what I should use?

ETA - one of these? http://www.maplin.co.uk/p/kbpc3501-35a-bridge-rectifier-ar86t

Re: Cordless drill battery packs
« Reply #14 on: June 05, 2015, 07:02:43 pm »
I wouldn't have recognised the transformer.

The capacitor is not needed. It might increase the average voltage but it will be big and expensive.

Do you want me to have a rummage for unused BFO rectifiers? I probably have one or two around.
Quote from: Kim
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Re: Cordless drill battery packs
« Reply #15 on: June 10, 2015, 10:11:02 am »
OK, so koo-power battery has arrived, seems to be OK to start with, charges, fits, all good.

Now, on with the show.

Here's the guts of the Makita



With 14v output, I reckon that's 4 duff cells or thereabouts, I have already found 3. Before I strip off everything, I was looking at the additional components. The bit on the side of the top two cells is a heat sensor, the one cemented on the top of the pack looks like a  tantalum capacitor and appears to be wired across the output ("20K" is the printing on it), but why cement it in place? Anyhow that cell it is cemented to is OK and the two top ones are duff so it isn't that important as I shouldn't have to take it off.

More to follow, but it is looking interesting.

Re: Cordless drill battery packs
« Reply #16 on: June 10, 2015, 10:46:30 am »


So there's another tantalum stuck down the middle - odd. Also, note that the contacts are spot welded!

All ded cells accounted for.

Re: Cordless drill battery packs
« Reply #17 on: June 10, 2015, 11:11:37 am »
Also, note that the contacts are spot welded!

Unless the batteries have solder tabs, they are usually spot welded to form packs. Both electrodes placed on nickel strip outside the battery -

Soldering batteries isn't recommended - as the heat can damage the battery / the battery has a high thermal mass which makes it awkward to solder.

You can make a spot welder for batteries from a bunch of capacitors ( http://zeva.com.au/Projects/SpotWelderV2/) and mosfets or a repurposed microwave oven transformer but that might be a bit much for a one off job  :) You can get the nickel strip on ebay.

If I were going to solder them I'd clean and pre-tin everything, use short, thick insulated wire and apply heat for a limited time. Wear some goggles  8)

Re: Cordless drill battery packs
« Reply #18 on: June 10, 2015, 11:48:19 am »
My current intention (oops  :demon:) is to cut the welded tabs, clean with dremel and solder those together with about 6mm overlap, probably trying to use a pair of long nose pliers as a heat sink, only I may run out of hands.

Re: Cordless drill battery packs
« Reply #19 on: June 10, 2015, 04:47:03 pm »
Right. All batteries stripped with the following conclusion:

The worst battery has 4 duff cells
The median battery has two duff cells, but ....2 weak cells, too (defining weak as anything less than 1.2V
The best battery has 3 duff cells, but the remainder are charged to 1.3v! (or thereabouts), one of the cells to be replaced is under the thermistor

The additional components are linked to the charging circuit. The blue thing stuck to the top of one of the cells appears to be a 20Kohm thermistor, but why cement it to one cell?

I reckon my best bet is to use the worst to repair the median as a first experiment, changing all 4 batteries.

Re: Cordless drill battery packs
« Reply #20 on: June 11, 2015, 05:26:56 am »
If you buy batteries (claimed genuine or mot) from China via unofficial channels like eBay, you are quite likely to get a casing containing old-school NiCd cells and some concrete to make up the weight.  Been there, done that.  In some cases the low price justifies it (e.g. if you want to get an old laptop going and aren't intending to use it untethered for more than an hour at a time) but they're unlikely to have passed any leakage or safety tests.

The laptop battery I bought lasted about 1 hour and then went from 40% to 0% in about 2 minutes.  There are lots of photos out there of these opened up to show the makeweight masonry inside!
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Re: Cordless drill battery packs
« Reply #21 on: June 11, 2015, 07:15:31 am »
...which is why I bought a clone from a recommended source, the Koo Power seems OK.

As I'm looking at the cells themselves, that shouldn't be an issue, but I just don't believe these can push out 6A for any useful period

http://www.ebay.co.uk/itm/12x-Sub-C-SubC-With-Tab-6000mAh-1-2V-Ni-MH-Rechargeable-Battery-White-High-Power-/390848434931?pt=LH_DefaultDomain_3&hash=item5b0061d2f3

Re: Cordless drill battery packs
« Reply #22 on: June 11, 2015, 07:35:07 am »
Yes 6000mAh is a bit hopeful for capacity.

This site http://lygte-info.dk/ does great battery tests and reviews - mainly Li-Ion although some NiMH etc

Also does flashlight and charger reviews.

A lot of capacity claims - for example the *fire Li-Ion 18650's - are absolute nonsense.

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Re: Cordless drill battery packs
« Reply #23 on: June 12, 2015, 02:11:55 am »
I have a few dead or dying Dewalt cells, I was going to recell them but then noticed I could buy the koopower ones for the same price. Question is, I now have the replacement batteries and they are working great. But I still have 4 old Dewalt batteries lol.

I'm half tempted to strip them out and replace the cells with decent 18650s such as the VTC4s, HE2s or likewise, 35+ amps of discharge per cell should make for a silly amount of grunt. 4 of them would give me 14.8v and 2.5ah.
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Re: Cordless drill battery packs
« Reply #24 on: June 13, 2015, 12:08:15 pm »
Battery #1 now has 19.5 voles at the terminals!

Sliced through the strips with Dremel cut-off, cut some 0.2mm shim brass for the strips. Learned that I REALLY needed to throw out that old solder....

All good.