Cordless drill: Runs off of a 12V Nicad pack. Will it survive 14.4V of wholesom Li-ion goodness?

[Jeff7]

I've got a Bosch 3054VSR drill here, a hand-me-down gift from my grandfather. It's pretty old - I've had it for over a year, and before that, I have no idea how long my grandfather had it. The NiCad battery packs were starting to deteriorate significantly. I took the worst one apart (all battery packs seem to be glued together, it's like they want to keep consumers from creating fire hazards or something), and checked it out. One cell was registering 0.03V, and it had crystals all over the positive terminal. I'm charging the pack cell-by-cell now, and interestingly enough, this zombie cell is taking a charge. Whether or not it will retain it is another story.

Now, I could buy new sub-C NiMH's to stick in there, but I've already got some Li-ion cells here, from laptop batteries that stopped holding a charge. They were fun - it'd show a charge of 98%, about 1hr 45 minutes left. Then I'd start watching a movie. Suddenly I was at 2% charge and the system was shutting down. The only way to get decent battery life out of the things was to throttle back the CPU to 600MHz (default speed is 2GHz). Then I could get 2hrs.
Opened up those packs - the damn things use adhesive everywhere, or else an ultrasonic welding machine. Same problem, one cell in each was dead.

Anywho, I've got a bunch of decent Li-ion cells here. 3 in series powers the drill alright, though a bit slowly, as it's only 10.8V. But 4 in series would give it 14.4V. Generally, how tolerant should it be of this 20% overvoltage? Or do I just play it safe and stick with 10.8V?


And yes yes, I know that Li-ion's aren't to be taken lightly, I know that I can't use them with the original charger, etc etc. I have a charger that can charge Lithium-ion batteries safely.

 

[thecoolnessrune]

GO FOR IT DUUUUDE!

 

[wedi42]

14.4 will be fine.
just a mild overclock!

 

[PottedMeat]

Its probably ok. Are you sure those aren't 4.2V cells in the laptop?

 

[slpaulson]

What's the worst that could happen?


I wouldn't do it....

 

[Jeff7]

Originally posted by: PottedMeat
Its probably ok. Are you sure those aren't 4.2V cells in the laptop?

3.6V. For sure.
Pack is rated 14.4V. There are 8 cells, comprised of 4 pairs in series, and each pair consisting of two cells in parallel.
14.4/4 = 3.6V.
A voltmeter confirms this.

 

[NoShangriLa]

It should work just fine, however how are you going to recharge them batteries?

 

[Jeff7]

Originally posted by: NoShangriLa
It should work just fine, however how are you going to recharge them batteries?

As I mentioned in the OP I have a charger that can charge Li-ion cells and packs - the Triton charger.
Only the Triton I though.

 

[alfa147x]

Post back on how its goes

 

[Rubycon]

Does the drill have an electric brake? (i.e. when you release the trigger does it stop abruptly?) The speed controller may not like the overvoltage and do strange things. If you're using unprotected cells (18650's from lappy packs are NOT protected) bad things can happen quickly if the tool's speed controller shunts suddenly placing a crowbar across your pack! At the very least use a fuse.

BTW if a cell has shown signs of leakage you should NEVER try to charge it. NiCad's operate under rather high pressures compared to other parts and their rupture mechanism is so equipped to handle such pressures. What this means is when it does engage the sudden release of kinetic energy can be as dramatic as a firearm.

Which in the case of a rogue drill with out of control lithium ion cells may give you - a fire arm! :laugh:

But yes it can be serious. Don't take it lightly.

Originally posted by: PottedMeat
Its probably ok. Are you sure those aren't 4.2V cells in the laptop?

The 4.2 is the finish charge which settles down to 3.6-4VDC quickly and holds 3.6 under load. Typically 3.0V is the termination of cycle point for those cells. Discharging to below 3.0V will drastically reduce the cycle life of the cell and in some cases permanently damage them!

 

[Jeff7]

Originally posted by: Rubycon
Does the drill have an electric brake? (i.e. when you release the trigger does it stop abruptly?) The speed controller may not like the overvoltage and do strange things. If you're using unprotected cells (18650's from lappy packs are NOT protected) bad things can happen quickly if the tool's speed controller shunts suddenly placing a crowbar across your pack! At the very least use a fuse.

BTW if a cell has shown signs of leakage you should NEVER try to charge it. NiCad's operate under rather high pressures compared to other parts and their rupture mechanism is so equipped to handle such pressures. What this means is when it does engage the sudden release of kinetic energy can be as dramatic as a firearm.

Which in the case of a rogue drill with out of control lithium ion cells may give you - a fire arm! :laugh:

But yes it can be serious. Don't take it lightly.

Either a brake, or else really really sucky bearings.
Yes, it does stop rather quickly when the trigger is let off.

Hm, so the crystals are leakage? I've seen those things form on a number of older Nicads. Ok, I guess the pack is toast then. I'll check out the other cells with a voltmeter and see if they're ok. It's only the one cell that had the crystals on it.

I'll try it out first then at just 10.8V and see how I like it.
I do have another pack here with 3.7V cells, which would give me a marginal increase to 11.1V. I haven't yet fully disassembled it though - just enough to get a voltmeter in to see which cell was bad.

 

[dug777]

I don't know that it will work that great anyway...there's a reason they still use NiCads in high drain applications

 

[Jeff7]

Originally posted by: dug777
I don't know that it will work that great anyway...there's a reason they still use NiCads in high drain applications

Yeah, but of course, I can't test that all right now - the only test leads I have here are very thin, and probably wouldn't handle the higher current drain if I'd test the drill's torque. Tomorrow I plan to get some thicker wiring, and some more alligator clips. Then I'll really be able to see what it's capable of.

Maybe I'll have to pick up one of these bad boys.
I wish I had a little spot welder, too - I could tab my own cells then. Oh well.

Here's the datasheet for this circuit.
I see where to attach the battery pack and cells. Where do I hook up the load then? Do I just attach it straight across the B- and B+ terminals?
And what the heck does that mean, "You need chose either two of P- point become the Charge-/out- terminal" bit mean? Anyone speak Poor Chinese Translation? Do both P- pads get wired together, or can I just pick one?



Damn Li-ion chemistry, I'm pondering just rebuilding the pack (or maybe both of them) with NiMH's instead. I wish I had a little spot welder, too - I could tab my own cells then. Oh well.
If high current draw is just going to kill off the Li-ions, that really wouldn't make good use of them, despite the fact that they're already getting old.
Hopefully that new silicon nanofiber lithium battery technology is a bit less tempermental than standard Li-ion cells.

 

[Rubycon]

Originally posted by: Jeff7

Damn Li-ion chemistry, I'm pondering just rebuilding the pack (or maybe both of them) with NiMH's instead. I wish I had a little spot welder, too - I could tab my own cells then. Oh well.
If high current draw is just going to kill off the Li-ions, that really wouldn't make good use of them, despite the fact that they're already getting old.
Hopefully that new silicon nanofiber lithium battery technology is a bit less tempermental than standard Li-ion cells.

Those resistance tab welders are expensive! Get some copper tape, cut a piece 2X the electrode diameter so you can stick it to the neg of one and the pos of the adjoining cells, fold and put them together! Works like a charm. Not the physical connection of welded tabs however if you shrink wrap the packs with a good 50% polyolefin based tube (the best have glue on the innards but are REAL hard to remove if needed) you're good to go!

New Li cells with higher capacities and potentially higher discharge rates due to extremely low internal resistances will likely need more protection especially from shorting. Think Polapulse on steroids. Those did 50+ amps in dead short - paper clip across the terms = fire in 1sec! That was those packs used in Polaroid "one step" cameras. 10 pics in a pack and the pack was tossed. I'd fetch those out of wastebaskets at theme parks in the day and had a stack of those 3 feet high. Wired 40 in series (240V) and ran a blow dryer!

 

[alfa147x]

So how did it go?

 

[runzwithsizorz]

Gosh OP, thanks for making me feel reeeeealy old! My father barely knows what a cordless drill is. When I was young, and used my dads' metal cased electric drill, it shorted, OUCH!
When I told my dad about it, he just said, "oh thats just random, try it again". I then used my grandfathers' hand crank auger, which was all he had, for he had yet to aquire that new fangled invention called,---- electricity.
Recently, and after many years use, my Craftsman 19.2 quit, rats! and I just bought 4 new batteries. A new motor from the Sears web site was $50+ shipping, however, a new one, with case, 2 batteries, and a flashlight is $99 at the local Sears store, quess which one I chose?
Hint, I now have 6 batteries. You OP, seem to have alot of time on your hands, good luck with your experiment.
I'd rather be drillin, n chillin

 

[waffleironhead]

Screw that plan, just attach leads from your car battery and drill away. 20 foot jumper cable should work nicely.

 

[StageLeft]

Originally posted by: Jeff7

Originally posted by: PottedMeat
Its probably ok. Are you sure those aren't 4.2V cells in the laptop?

3.6V. For sure.
Pack is rated 14.4V. There are 8 cells, comprised of 4 pairs in series, and each pair consisting of two cells in parallel.
14.4/4 = 3.6V.
A voltmeter confirms this.

If a voltmeter confirms their resting, not nominal voltage is indeed 3.6, then that's not too bad. A nicd pack rated at 12v would probably be 10 cells anyway with a resting voltage of about 14.4 or 14.5.

The best cells out now, bar none, for what you want are A123 brand cells. You can buy Black & Decker VPX Packs for $18/pop at walmart, each with two 1100 cells. They have a resting voltage of 3.6 and though that capacity is not high they can handle a continous 30+ amps and they can be charged in 15 minutes or less. They can take far more cycles than any other lithium technology, too

Ltihiums like in a laptop or cellphone are not ideal for high drain. Lithium polymer like radio control vehicles use can handle high drain, but if you're actually buying cells, I'd really look at the A123 ones. Far less fragile and more capable than any lipo battery. Their only drawback is weight, which is not a concern for a power tool.

You could use NiMH cells and not bother with a new charger, since they can take a trickle charge without blowing (unlike lithium, which will raise volts until a fire starts). cheapbatterypacks.com sells spare cells.

 

[Jeff7]

Originally posted by: alfa147x
So how did it go?

Very slowly.

I bought a protection PCB, but I accidentally got the wrong one - it had too low a current limit, and in tests, it shut down the current flow when the drill was putting out its maximum torque. So I ordered another one with a higher limit. Even if it reduces the life of the Li-ion cells, it's not huge loss - they're already in their second life, as they're salvages from old laptop batteries.
Maybe I'll start asking for "donations" of old laptop batteries.
In my experience with two packs, it's only been one pair of cells in each pack that was really bad. Such is the problem with battery packs that lack cell balancing - but cell balancing PCBs are expensive - for 14.4V packs, a protection circuit will cost you $6-$13. One with a balancing function is $43. Sure it'll keep your Li-ions healthy as the day they were born, and it'll even shine their contacts and buff their casings, but it'll cost ya. A generic protection circuit is good enough for salvaged cells.



Anyhow, the drill - at the time, I was more interested in having a functioning drill, with proven technology, so I replaced the Nicads in one of the packs with NiMH cells. They're cheap Powerizer things, but in my tests they did put out their rated capacity. So that one's working fine.

The Li-ion pack will take more work for what I want to do to it. I have to figure out an idea physical configuration for the cells inside the pack, as well as a place for the protection PCB, and a way of integrating the fuel gauge circuitboard so that it's visible on the pack. At the rate it's going, that might not be until spring break.
These projects I get into tend to take awhile, with a little work here and there, kind of like watching a Tivo'd show while you're otherwise busy.

Originally posted by: waffleironhead
Screw that plan, just attach leads from your car battery and drill away. 20 foot jumper cable should work nicely.

While I had both Nicad packs disassembled, I did need to drill something, so I hooked it up to a 12V lead acid battery.

Originally posted by: Skoorb
If a voltmeter confirms their resting, not nominal voltage is indeed 3.6, then that's not too bad. A nicd pack rated at 12v would probably be 10 cells anyway with a resting voltage of about 14.4 or 14.5.

The best cells out now, bar none, for what you want are A123 brand cells. You can buy Black & Decker VPX Packs for $18/pop at walmart, each with two 1100 cells. They have a resting voltage of 3.6 and though that capacity is not high they can handle a continous 30+ amps and they can be charged in 15 minutes or less. They can take far more cycles than any other lithium technology, too

Ltihiums like in a laptop or cellphone are not ideal for high drain. Lithium polymer like radio control vehicles use can handle high drain, but if you're actually buying cells, I'd really look at the A123 ones. Far less fragile and more capable than any lipo battery. Their only drawback is weight, which is not a concern for a power tool.

You could use NiMH cells and not bother with a new charger, since they can take a trickle charge without blowing (unlike lithium, which will raise volts until a fire starts). cheapbatterypacks.com sells spare cells.

1100mAH? Heck, that's probably about what the Nicads could put out anyway, and there's the Li-ion weight advantage.

 

[StageLeft]

1100mAH? Heck, that's probably about what the Nicads could put out anyway, and there's the Li-ion weight advantage.

There's a reason hybrids haven't been using lithium and the new ones will be--A123, to be specific. The batteries have a very flat power curve. All batteries offer less volts with load, but the A123 bats will have the voltage drop as all batteries have but it basically remains very flat until the battery is all used up. They are far less volatile than any other lithium bat, many times the number of useable cycles, many times the charging rate.

You can buy a small NiMH battery at Walmart with a capacity of about 3000 but it's useless in this application because it has no ability to deliver current quickly. Similar thing for regular lithium. Lithium polymer will give you the current you need at the lowest energy density available (which is why it's used in radio control vehicles), but its power:weight ratio is important in a power tool (this is why power tools continue to use NiCD despite the fact that in most gadgets the newer NiMH is a superior chemistry, lacking memory effect and having better capacity) and the power--the ability to supply requested amps--is as good in A123 as anything else. You don't have to worry about the particulars of lithium storage as much or be careful not to bring its volts too low, causing permanent loss of capacity in the battery.

 

[flxnimprtmscl]

Originally posted by: slpaulson
What's the worst that could happen?


I wouldn't do it....

The joining of the drill and the Li-ion batteries could form a singularity that would destroy the planet Earth?

 

[Jeff7]

Originally posted by: Skoorb

1100mAH? Heck, that's probably about what the Nicads could put out anyway, and there's the Li-ion weight advantage.

There's a reason hybrids haven't been using lithium and the new ones will be--A123, to be specific. The batteries have a very flat power curve. All batteries offer less volts with load, but the A123 bats will have the voltage drop as all batteries have but it basically remains very flat until the battery is all used up. They are far less volatile than any other lithium bat, many times the number of useable cycles, many times the charging rate.

You can buy a small NiMH battery at Walmart with a capacity of about 3000 but it's useless in this application because it has no ability to deliver current quickly. Similar thing for regular lithium. Lithium polymer will give you the current you need at the lowest energy density available (which is why it's used in radio control vehicles), but its power:weight ratio is important in a power tool (this is why power tools continue to use NiCD despite the fact that in most gadgets the newer NiMH is a superior chemistry, lacking memory effect and having better capacity) and the power--the ability to supply requested amps--is as good in A123 as anything else. You don't have to worry about the particulars of lithium storage as much or be careful not to bring its volts too low, causing permanent loss of capacity in the battery.

You can't buy tabbed Sub-C NiMH's at Walmart though.


And in my tests, the lithium cells are capable of delivering the required amperage. The limiting factor in the first test was the protection circuitry's low current limit. The new circuit has a higher limit. It can't be good for the longevity of the cells, but as I mentioned, they've already served their primary purpose. Now they're in my own personal battery hell. :evil:

Those A123's look interesting. 3.3V per cell though? I wonder why it's lower like that.
The price sure isn't low. :Q

 

[alfa147x]

Can we get an update, how did the build go
Was there a build ?

 

[Jeff7]

It's been Syringered, at least for now.

Once I put a pack together with new Sub-C NiMH cells, I was sufficiently placated as far as battery pack needs were concerned.

I did however get a new multimeter, and characterized the behavior of the Li-Ion cells I had. I found out why the pack was being read as bad by the laptop.

Link

The "Time" is not quite accurate - each tick was actually 2 seconds, so "200" on Time is actually 400 seconds. I think that was at a drain rate of .5A or .5C, I don't remember which. Check out the one cell though, 412-2. BIG dip in voltage right at the start, but then it normalizes.
And all of these cells were from the same pack, charged individually to the same peak voltage before the test, and run at the same drain rate.


But I had plans to add in a drain meter on the pack, which would involve the Dremel, and, well, I tend to spend more time neffing or doing homework or working than getting involved in a day-long project. Over the summer, I should be back to having a regular full-time job, and so should have lots more time at home than I have now.

Unfortunately, a lot of my projects turn out this way. I plan it out, see where it might go, figure out what the outcome will likely be, and by that time, all the interest has gone out of it. I feel like I've already seen the end product, and so there is not so much point in doing it anymore. That, and I really don't like starting on something unless I know I've got enough time to finish it. I hate putting a project down when it's not yet finished.


I didn't know my projects had any loyal fans though.