cordless drill batteries

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Re: cordless drill batteries

Postby RichardLaw » Tue Feb 15, 2011 8:45 am

This is beginning to sound rather good. I'll be wiring the whole of Strid Wood to my spare Land Rover battery soon, forge blower, cordedcordless drill, popcorn popper, video player ... (Steady on - Ed)
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Re: cordless drill batteries

Postby Stellan Vert » Tue Feb 15, 2011 1:04 pm

Brian
The battery i gutted was a 12volt bosch battery (cordless drill) (Screwfix sell them for £41), the hardest part was getting the case apart with out damaging it.
Inside there was 10 1.2volt nicad cells (Maplins do a similar sized cell, 10 would cost about £30)). The cells were connected in series, 8 were dead 2 wuold still accept charge.

With a nifty bit of soldering It would be possible to replace the 8 dead ones, however two big leads and a car battery would be a lot easier and possibly longer lasting.

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Re: cordless drill batteries

Postby Shankar » Tue Feb 15, 2011 10:39 pm

If the car is close by it is possible to use the lighter socket or a special power socket to power a corded drill.
You need an inverter to change DC to AC with a 3 pin plug which can be bought fairly cheap and a extension cord.
Need to check how many Watts you need.
I don't know how long it takes to deplete a car battery but worth running the engine once in a while if you are drilling a lot of holes.

DeWalt are a good make and recently treated myself to a drill with a spare battery (18V - 1.3Ah) for £95 from B&Q.

Hope that helps

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Re: cordless drill batteries

Postby Stellan Vert » Wed Feb 16, 2011 12:56 am

Hi Bob

"Nice one Sean
Here's the next step

drill lathe.jpg (6.67 KiB) Viewed 35 times

Association of Portable Turners etc........"

Don't knock axminsters little lathe, that where I started (in my ignorance), good little tool I have had happy hours learning how to use a roughing gouge/scew chisel.
(my Wife liked it as I was not in "chapel with handles ont prayer books)

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Re: cordless drill batteries

Postby jrccaim » Fri Feb 18, 2011 4:27 am

One thing about rechargeable batteries that I forgot to put in my post: run them down all the way to complete discharge. This applies to any rechargeable battery of the crodless drill, cell phone and related persuasions. If you recharge your battery say at the halfway mark, the battery develops a "knee," as it is called, at that point. You will not be able to discharge it past the knee. So if you recharge at the halfway point, you've lost half the battery. Voltage fine, amp-hours reduced. If you have a lead-acid battery, as in a car, it does not develop this knee. However, there are two kinds of lead-acid batteries: those sold for cars, which deliver a lot of amps in a hurry and then charge right back up, and the "deep discharge" batteries sold for boats and trailers (caravans). These will give you steady amps untill the battery gives up, at which point you recharge it. If you are thinking of solar or wind power charging a battery bank this is what you want. For a cordless drill I don't think it matters much what you use!

And (since I had to recharge my cordless drills today, right on cue) I had a look at where the battery connects into the drill itself. There are two terminals clearly visible. Very close quarters for a soldering iron, but I think it can be done. So you wouldn't even have to take the thing apart! Be careful you don't burn the plastic housing.
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Re: cordless drill batteries

Postby Brian Williamson » Fri Feb 18, 2011 7:13 am

jrccaim wrote:One thing about rechargeable batteries that I forgot to put in my post: run them down all the way to complete discharge. This applies to any rechargeable battery of the crodless drill, cell phone and related persuasions.


Could you confirm that statement for me please, jrccaim? I've been trawling around on the net for info, and one of the themes that has emerged is that you DON'T run them to complete discharge. Run them until the power is obviously low or you can't drill yes, but not to complete discharge. I've tried to do this in the past by tying a string round the trigger so that all power is consumed, but there are suggestions that this is too much and has a bad effect on the battery.

Can you (or anyone else) be absolutely positive on this point - and back it up with the science?

Thanks,

Brian.
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Re: cordless drill batteries

Postby Brian Williamson » Sat Feb 19, 2011 9:20 am

For the curious, here is the inside of my 12v Black and Decker battery.

battery.JPG
battery.JPG (62.21 KiB) Viewed 5121 times


This one was easy to get inside because it was screwed together. I think most will be glued/pressed/moulded and therefore harder to access. As Stellan found, there are ten separate 1.2v cells, all soldered together. There are three blade connectors, only two of which go to the drill. The third presumably relates to the charger.

I'm planning to hook this one up to an old 12v car battery. With my more modern, 9.6v, Bosch I might try replacing the individual cells.

More photos and reports to follow!

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Re: cordless drill batteries

Postby Brian Williamson » Sat Feb 19, 2011 9:45 am

This one shows the battery 'unit' better. I've just cut off the black plastic band.

battery2.JPG
battery2.JPG (40.02 KiB) Viewed 5119 times


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Re: cordless drill batteries

Postby RichardLaw » Sat Feb 19, 2011 10:28 am

Brian Williamson wrote:
jrccaim wrote:One thing about rechargeable batteries that I forgot to put in my post: run them down all the way to complete discharge. This applies to any rechargeable battery of the crodless drill, cell phone and related persuasions.


Could you confirm that statement for me please, jrccaim? I've been trawling around on the net for info, and one of the themes that has emerged is that you DON'T run them to complete discharge. Run them until the power is obviously low or you can't drill yes, but not to complete discharge. I've tried to do this in the past by tying a string round the trigger so that all power is consumed, but there are suggestions that this is too much and has a bad effect on the battery.

Can you (or anyone else) be absolutely positive on this point - and back it up with the science?.


Here's all you need to know about batteries: http://batteryuniversity.com/learn/article/charging_nickel_based_batteries
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Re: cordless drill batteries

Postby Mike Abbott » Sat Feb 19, 2011 7:58 pm

I think it's just brilliant that this issue has aroused so many replies in such a short time. What does this say about the APT?
I find all the details a bit hard to take in and I still hope we can discuss it in real life at the BBall. Any chance of our friend coming over from Alaska? I'll give you some free books!
All the best, Mike
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Re: cordless drill batteries

Postby jrccaim » Sun Feb 20, 2011 5:32 am

RichardLaw wrote:
Brian Williamson wrote:
jrccaim wrote:One thing about rechargeable batteries that I forgot to put in my post: run them down all the way to complete discharge. This applies to any rechargeable battery of the crodless drill, cell phone and related persuasions.


Could you confirm that statement for me please, jrccaim? I've been trawling around on the net for info, and one of the themes that has emerged is that you DON'T run them to complete discharge. Run them until the power is obviously low or you can't drill yes, but not to complete discharge. I've tried to do this in the past by tying a string round the trigger so that all power is consumed, but there are suggestions that this is too much and has a bad effect on the battery.

Can you (or anyone else) be absolutely positive on this point - and back it up with the science?.


Here's all you need to know about batteries: http://batteryuniversity.com/learn/article/charging_nickel_based_batteries


Piling quote upon quote, I am. OK, I read the link above. It confirmed my previous reading: Nicads (Nickel-Cadmium) batts are very complex animals. The artcicle cited does not mention the knee (I read about that in an engineering magazine, so probably true). I have a very direct interest in this subject so I'll do some more research. And a lot of the stuff you read on the net is hearsay at best. Sounds authoritative but isn't. However, the cited article has a good feel to it -- no obvious technical howlers.

As to deep discharge: OK, take it down to where it won't drill any more. In fact that's what I do. But don't recharge at halfway points. I don't struggle to drain the last microamp out of the battery. The suggestions for charge rates in the article are interesting. But most people who buy cordless whatevers are stuck with whatever the manufacturers provide. Manufacturers are torn. In the one hand, there are the pro users. They want a quick recharge so they have no down time on a job. On the other hand there are us bodgers. We cannot afford to purchase a new battery frequently, and even if we could, we decry the waste. So we want, in the words of a former US President, a "kinder, gentler" charge. I suspect we get the short end of the shaft. But that is merely suspicion. And, come to think of it, a lot of the yuppies (hardly pros) also want a good fast charge. My suspicions have just been strengthened.
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Re: cordless drill batteries

Postby jrccaim » Sun Feb 20, 2011 5:57 am

Oddball wrote:
RichardLaw wrote:
This sounds interesting. Is it possible to run various voltage tools from a 12v vehicle battery?


If I can remember back to my college days correctly, then if you assume the average 12v drill battery is say 3 amp it will produce 36 watts of power. Even the smallest 12v car battery will be 40 amps which equates to 480 watts of power, therefore several things could happen. It will turn a lot quicker, if using small drill bits they could break a lot more frequently, if using large bits & it jams then could pull the drill from your hands or rapidly strip the clutch in the drill. The lower the voltage below 12 the quicker it will burn out, conversely above 12 it should last longer but have less power. Basically I would go for the lowest amp car battery you can find, maybe a caravan battery which are designed for low power consumption over a long period of time. Or find ten people to all run power tools off one battery at the same time :roll:


Erm, I don't want to pick nits or insult anyone. But the size of the battery has nothing to do with it (mostly). A car battery will deliver 40 amps and up, true. But there is nothing that says it has to do so, except the load. If you crank a car with it, why maybe you need those 40 amps. But if you put a drill across the battery, it will draw 3 amps from the battery, using your figures. So a car battery will run a cordless for a long time! Now, if you tried using flashlight batteries to run your cordless, well, you wouldn't have a very deep hole. The batteries will drain in no time at all. This is why batteries are rated in ampere-hours. For instance suppose you had a 600 A-h batt, This would deliver 3 amps for 200 hours. (At whatever the voltage might be, say 12V). I could drill a lot of holes in 200 hours :)
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Re: cordless drill batteries

Postby jrccaim » Sun Feb 20, 2011 5:59 am

Mike Abbott wrote:I think it's just brilliant that this issue has aroused so many replies in such a short time. What does this say about the APT?
I find all the details a bit hard to take in and I still hope we can discuss it in real life at the BBall. Any chance of our friend coming over from Alaska? I'll give you some free books!
All the best, Mike


Sigh. I'd love it. But it is not in the cards at this time. Keep it in mind, though!
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Re: cordless drill batteries

Postby Mark Allery » Sun Feb 20, 2011 12:41 pm

Brian Williamson wrote:
jrccaim wrote:One thing about rechargeable batteries that I forgot to put in my post: run them down all the way to complete discharge. This applies to any rechargeable battery of the crodless drill, cell phone and related persuasions.


Could you confirm that statement for me please, jrccaim? I've been trawling around on the net for info, and one of the themes that has emerged is that you DON'T run them to complete discharge. Run them until the power is obviously low or you can't drill yes, but not to complete discharge. I've tried to do this in the past by tying a string round the trigger so that all power is consumed, but there are suggestions that this is too much and has a bad effect on the battery.

Can you (or anyone else) be absolutely positive on this point - and back it up with the science?

Thanks,

Brian.


Errr. I'll try. First a couple of definitions might help. Cell = individual 1.2 (or 1.5)volt accumulator of charge. Battery = collection of individual cells in both series and/or parallel to attain required terminal voltage and amp characteristics. NiCd - outdated (I mean really outdated) nickel cadmium cell design with several problems in terms of lifetime. Li-Ion - modern lithium cell design with higher storage density and improvement in cycles reliability - though it does suffer from a limited and predicatable cycle lifetime! A cycle is one discharge and recharge of a cell. NiMH is the joker in the pack - far better than the old NiCd and without the cadmium whisker problems it achieves storage capacity fairly similar or in higher than nonrechargable alkanlines and without Li-Ion lifetime limits. No one should be using NiCd's any longer in my view. Cycle lifetime is the number of times you can repeat the charge/discharge without losing a certain amount of storage capacity and depth of discharge is the amount of charge you take from the battery relative to its rated capacity. ie for a 1 AH (amphour) cell taking out 0.5AH is 50% depth of discharge. An Amp Hour is a load running at one amp for one hour. Most cells and batteries have a rated capcity in Amp Hours (AH) which is the faceplate capacity -actually capacities vary.

Right now to answer Brians question which is extremely relevant. For each cell you should treat it as gently as you can. Maintain it at full charge by trickling if you can and when in use recharge as often as possible to limit the depth of discharge. Running cells down to flat is generally a bad thing and is more likely to induce chemical change in the cell reducing its capacity. This applies to virtually all battery chemistries but is particularly bad for some types of cell design where the ability to withstand complete discharge is limited. Further cycles to a similar depth of discharge are then actually increasing this effect as the effective depth of discharge increases. Always running your battery to flat will cause it to have minimum lifetime.

So why does it occasionally need a deep discharge (running to flat). That's often because its a battery and not a cell. When you take a certain capacity from cells with different actual capacities their terminal voltages will vary and during the charge and discharge cycles the weakest (lowest capacity cell) will flatten first whilst the highest capacity cell will still have charge. If this continues then the actual state of charge in each cell will diverge further, the power you can extract from the battery will fall and so will the cycle lifetime. A quick way to resolve this is to flatten the battery completely normally across a power load or equivalent which will extract all the energy then recharge. This deep discharge cycle may need to be repeated occasionally. However the problem may not be divergent cells as NiCds have a load of chemical problems, one of which is growing Cd whiskers. A virtually short circuit of the cell can blow off whiskers and restore the cell -but it's clearly not good for the cell. A last resort. NiMH and Li-Ion do not have these problems but may suffer from diverging cells in the battery.

The knee referred to is a particularly pronounced effect in NiCd's where as the cell discharges it runs down from 1.5 to 1.2 volts rapidly and then stabilises falling very little (the plateau) until it starts to fall rapidly (the knee) towards complete discharge. This effect often causes NiCd run equipment to stop working very rapidly. Li-Ion and NiMH have much smoother discharge curves with a less pronounced plateau and hence less of a knee.

There is loads more, but I hope I've made a stab at answering the question. Summary - be nice to your batteries. Do not flatten them regularly and charge them as often as possible - though not so you are wasting energy all the time. If capacity appears to be falling a deep discharge may help to recondition the cells in the battery, though not always. It's not rocket science is it? Well it used to be for me, having run a 12V 4AH NiCd pack in one satellite for over 20,000 cycles by limiting depth of discharge to 20% with a discharge cycle every 90 minutes and fast charging in between with a deep discharge reconditioning cycle every few thousand cycles.

cheers

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Re: cordless drill batteries

Postby Mark Allery » Sun Feb 20, 2011 12:53 pm

I really like the old car battery idea. I occasionally have old 12 volt tractor or landrover batteries which are no longer good for cold weather starting but not poor enough to throw away and could continue to give a level of service for years which might power a cordless drill - I shall be trying this one ! Likewise an old car battery may no longer be any good at 12volts but might give good service at 10.5 volts with a dead cell depends upon the internal resistance-o f the cell. I don't know but I shall try this.

Another point worth noting - check its really the battery that's gone. Sometimes cheap chargers seem to blow up as well so it's worth trying an alternative power source on the battery - a car battery charger should give something into the battery just to test it out if you don't have a handy bench power supply.

If you are planning to buy a new battery for this purpose do not buy a cheap car battery. These are high cycle lifetime batteries with limited deep discharge capacity. They do this by making the cell plates thinner, so a cheap car battery can only be fully discharged a few times before it will become seriously damaged. So called heavy duty batteries - truck, tractor and recreational are designed to be regularly deep discharged, so the same size of battery has a lower starting (cold cranking amps) capacity. The cells plates are much thicker.

cheers

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