Electric Drill-drivers with dead batteries

I have two electric drill-drivers with dead battery packs, one 9.6V, the other 12V. The motor & everything other than the battery works perfectly. It seems a criminal waste to throw the things away without at least trying to do something with them. I'm also not keen on buying another as I know my way of using them kills Ni-Cads in short order. The drill-driver will be unused for a month or more, then used heavily (90-100 2" screws). This is almost the worst usage profile you could imagine for Ni-Cads, and kills the batteries in under 2 years. I would prefer a mains powered alternative power supply that avoids waste & getting a new drill every 2 years. So, investigating mains supplies...

I realised I had a dead computer (motherboard dead, PSU fine) so decided to use the PSU to power the 12V drill driver. First problem was that the PSU needs extra components to make it work (A 5W resistor to simulate the motherboard load and a switch to simulate the computer on/off button). After fitting these bits, the PSU fired up & produced the correct voltages at the correct places.

So, I made a wooden block with brass plates to fit the battery compartment, and used the first available flex to hand, a bit of loud speaker cable. And, as a proof of concept it worked. The drill-driver operated very slowly, obviously limited by the high resistance wire. So, got a higher current rating wire and... stopped the PSU dead in its tracks. It switched off every time I pulled the drill-driver's trigger. It seems the start-up current draw of the drill-driver's motor triggers a crowbar circuit in the PSU.

So, next attempt, a car battery charger: Insufficient oomph at low speeds, safety cutout did its job and no power to the drill-driver.

Does anyone have any suggestions I could try before I end up throwing away a perfectly good drill-driver & buying another whose battery pack will be just as dead before the end of 2019? I have a 2.4Ah nearly dead Moped battery that could possibly be used as a buffer for the battery charger. This battery was used for the starter motor until it decided to do what happens to all old car batteries. May hold some charge still.

I just hate the waste, and want to avoid throwing away something that works. Alternative uses for the motor will be interesting too. But it whatever the alternative use is, it needs to be powered somehow.

Regards,

Richard.

Edited By richardandtracy on 16/01/2017 09:48:17

I also have a couple of dead nicad drills wanting re-powering. Interesting that a computer PSUs is not up to it. But they would be a cheap solution. I was pondering trying some of the really hefty ones intended for powering servers - e.g. this one is rated at 36A, 12V for £6.99 inc postage - or this one with 12.1V, 69A, £8.54 inc postage! Often there are instructions on the web for hooking them up e.g. here. Was thinking that the extra capacity might let them cope with the start-up current... anyone tried it?

PS most new drill/drivers, even cheapish ones, now use lithium batteries - might they survive your usage better than nicads?

Edited By Bikepete on 16/01/2017 10:18:48

I should point out the majority of replacements for Ni-Cd batteries are now NiMH. This has been largely brought about for two reasons. Partly to remove Cadmium from the environment and also because NiMH batteries are a far superior technology. They overcome/minimise many of the weaknesses of the older Ni-Cd technology you describe. They also have a far greater energy/volume profile. I would suggest you consult "the Bay" to find an equivalent. For all practical purposes the charging regime for NiMH technology is no different from Ni-Cd so you may almost certainly continue to use your existing charger.

Several ideas-- I used a 12V car battery for a couple of years, worked well on all drills 12V or less. A friend pointed out that I might as well buy a mains drill. You can get the battery pack rebuilt, look on-line, quite pricey. Re-build the battery pack yourself, can be cost effective. Buy a new drill, my new one has Lithium -Ion battery 4Ahrs and does not seem to suffer like the old ones. I've put in several hundred 4" wood screws with no problems on new roof so it's paid for itself already. I now use old one on 12V car battery in the w/shop were the cable does not matter.

Gordon has all the answers there ^^^

Summary recommendation: Power the dud drills from a car battery, and buy a Li-ion powered drill if you need true portability.

MichaelG.

Edited By Michael Gilligan on 16/01/2017 10:27:00

The PSU I used was a 200W Dell unit. It could well be under powered. Must admit I didn't try very hard to take the drill-driver apart yesterday to see the motor wattage. We still had snow on the ground and my workshop is unheated. To call it 'parky' would be an understatement, so when something got a bit sticky when taking it apart, I decided I'd had enough and retreated to the house.

Regards,

Richard.

In theory, 200W should be more than adequate for what was a battery powered hand drill.

[at least, all the ones I've seen]

But you may find that the peak 'inrush current' is upsetting the PSU ... hence the recommendation to use a car battery.

MichaelG.

Just thought of a little, rarely used, transformer I have with a bit of oomph.

My 150A Screwfix MMA welder. It's not very good as a welder because the duty cycle is so low and it doesn't make as stable an arc as my Boxford 240/415V MMA welder, so the Boxford gets used exclusively and I'd half forgotten the Screwfix one. It would be wise to check the no load voltage though...

I like the suggestion of using an old lead acid battery. Will give it a go. I have a feeling our car battery needs changing this winter, and it'll be alive enough to provide all the oomph I need for a screwdriver.

Regards,

Richard

The new drills with 18v lithium-ion batteries have more capacity and do not have a memory problem like ni-cad batteries and do not have to be completely drained before charging. Your problem of "will be unused for a month or more, then used heavily (90-100 2" screws)" will not be as big a problem.

I've re-celled battery packs a few times which normally works fine.Try and find cells with tags ready welded on if possible as it makes the job easier. If not and you need to solder directly to the cells, clean with a fibreglass pencil and use as big an iron as possible to minimise the heating time.

N.B. Make sure the cells you use are capable of fast re-charge. I can remember "Fixing" a Skill battery pack a good few years ago. I was assured the cells I bought would take the requisite fast charge.

I used it for a quite while without issue, but only following a slow charge. In need of a few more holes without waiting too long I pressed the FC button and went for a brew. A while later there was a seriously loud bang upstairs, one of the cells had blown the end out and looked like Zeberdee off the Magic Roundabout.

It took me a while to find one of the other cells, It was perfectly fine, but had been blown clean through the plastic casing and put a dent in the bedroom ceiling.

I have looked at one of my 200W PC Power supplies .... from the label -

5v @ 18Amps, 12v @ 6A, 3.3v @ 10A

Is 6Amps at 12v (72 Watts) enough to start and run a drill??

Dave

Edited By Steambuff on 16/01/2017 11:16:46

Might be enough to run, but not start, the motor.

Must admit there is no similar label on the Dell PSU I tried. It would have been very useful right at the beginning!

Regards,

Richard

.

Very likely to run it ... once you get it started

Years ago, when 35mm slide projectors were popular, there were electronic devices for them to provide 'slow start' ... I suspect that this also may be a good approach for drills.

MichaelG.

.

Richard beat me to it.

Edited By Michael Gilligan on 16/01/2017 11:45:01

I don't know if it'd be possible to rebuild the pack using eneloop packs.. as far as i know the largest are only AA so a mix of series/parallel if they'd fir in there. BUT they are supposed to hold a charge for many months between use 85% charge retention for a year and as much as 75% after 3 years

I used some old alarm 12 volt batteries to power 3 battery drills lasted ages then when they were played out used an old car battery, keep it on a trickle charger and bobs yer uncle,lugging a battery around no worse than using a 110 volt transformer, incidentally there are useful little gearboxes in the drills-- waste nothing

Mick

Hi chaps,

Using a PC Power supply in this fashion will never work well. The problem is that the power supply, being a PWM Switchmode type, uses one of it's output supply voltages to regulate the output voltage against. In most/all cases this would be, in the case of the 'older' PC's, the +5V rail, and the 'newer generation' PC, the 3.3v rail. For the PSU to regulate , it requires some form of load on that rail, hence the resistor you fitted Richard. However, since the other supply voltages are in effect 'unregulated' , they end up at a nominal value, close to the rated value, ONLY when the regulated rail is loaded to its specified wattage load. Since you are loading the main rail very lightly, the +12V rail will drop radically when you load it ( as the main rail is loaded to little), and then the undervoltage protection circuit in the PSU kills the supply...

If you load the main rail to around 60 to 70% of the rated value, say maybe 15 to 18 amps, then the +12v should drive a drill fine - unless its driving a 30mm auger in Ebony....

What to do with the 100 watts or so of heat from the +5V @ 20amps ---, well that should keep the Tea water on the ready...

I have a few drills that suffered the same battery demise - I just purchased some 4 cell 8amp/hour LIPO cells, the type used extensively by RC modellers, and they work a treat. Can discharge them very hard, charge quickly, and one pack has lasted 2 years with really extensive use.

Th PC supply is not really a great option..

Regards

joe

Ahh. Thanks for the explanation, Joe. Makes sense of a situation that didn't really appear to follow the rules of simple electrics. So... what I really need is a new 5V drill-driver, so when its batteries die, I can use the PSU. Ho hum.

I'm not keen on buying replacement batteries, I have never found ones that give a life anything like as good as the dreadful OEM ones. Probably my usage is just too intermittent. I will try the car battery route. I had a Lithium battery electric screwdriver (3.6V) and that died in 2.5 years, so I've had no more success with Lithium batteries.

Regards,

Richard

Edited By richardandtracy on 16/01/2017 15:49:46

.

+1

MichaelG.

Hi for drilling underground in potholes for safety bolts, I wanting to have longer battery life I replaced the battery with a pair of motorcycle sealed batteries in an ammunition box with an XLR connector on the lid and fitted a cable with said connector to suit. This worked quite well just remember to open the lid when charging. I have many times replaced the batteries in the original case of other drills, you can get replacements with the solder tabs from RS components.

David