Cordless drills with cords

[mklotz]

Probably one of the most frustrating tools in the hobbyist's arsenal is the cordless electric drill. It's undeniably handy but, if you're like me, dealing with the batteries is enough to make you wish that Maxwell and Faraday had just kept their discoveries to themselves.

I wanted to drill a single hole out on the patio. Not wishing to deal with stringing an extension cord through a window, etc., I reached for the Craftsman 12V drill my daughter gave me a few years ago. No the battery wasn't dead - it managed to revolve the chuck at a stately 33-1/3 rpm for about ten seconds. Then it was dead. The backup battery that came with the drill hasn't been able to hold a charge since its second recharge. I reached for the backup cheapy drill from HF and it could spin its chuck but only if I didn't hold on to it. I hadn't used it in about a month so, of course, the battery had run down.

After exhausting my repertoire of curse words in three languages I started thinking about the problem. The real advantage (at least to me, an occasional user) is not that they're cordless but that one doesn't have to string (110 VAC) extension cords to use them. (Sounds confusing but stick with me.) I wouldn't mind if the thing had a short cord attached to a battery if that battery was more dependable than the ones supplied with these drills.

The typical NiCd supplied has all sorts of "memory" problems that can interfere with it taking and holding a decent charge. The manufacturers don't supply charging instructions and the chargers they supply have no "smarts".

But 12V Sealed Lead Acid (SLA) are widely available in small size packages, have decent capacity, and can hold a charge.

So, I opened up the drill and found the battery contacts...

Attached a hunk of speaker cable with some brass screws...

and, voila, a corded cordless drill...

Now the thing spins like a banshee and has torque to spare. The drill draws about 1.5 A at top speed and the battery is a 5 A-hr so it should last for at least an hour or two of use. I've never done anything with a cordless that took longer than a few minutes of drill run time so I think I'm in good shape there.

Lead-acid technology is well understood and smart chargers are widely available and inexpensive. Mine delivers 0.75A so it should be able to recharge the battery in 6+ hours. I intend to leave it on trickle charge most of the time so it's always ready to go.

 

[Dan Rowe]

I have the same problem with cordless equipment and that is a cool easy fix.

You need a more catchy name how about power lanyard?

Dan

 

[bentprop]

Are you going to get the horse and cart out today,Marv ?:big: :big: :big:
I have 3 cordless drills,and usually at least 1 on the charger.But you're right,they do seem to run out of puff at the most inopportune moment.
The price of progress.............

 

[Twmaster]

And what really sucks is how cheap a decent new drill is making the purchase of a battery more than a whole new drill.

I have standardised my cordless power tools around the Black & Decker 12V Firestorm line. I have 5 batteries for the three tools I own.

Just last week I took three perfectly good drills apart and gutted them for the motors and chucks as the battery for any of them is more than a new drill.

 

[milotrain]

I've used cordless and corded drills a lot and I've found that while I'm in my own shop I like corded drills better. That's partially because I have power everywhere, and partially because I can easily afford a pair of corded drills, and most of the time I'm using a hand drill I'm doing a two step process. I'd much rather have a pair of drills around, one doing the piloting and the other doing the driving than mess with those horrible quick change tool heads. Also because I use the pair of corded more often than the cordless there is always a stack of fresh batteries charged for the cordless.

You can also get a pair of really nice corded drills for less than a single cordless drill.

TWmaster, make sure there isn't another tool on sale that uses the same batteries. I recently wanted a new pair of batteries for my DeWalt 18v set (someone at a shop I worked poached one of mine ) so I went to HD where a single battery was $80 or something. However a 1/2" cordless Impact Wrench was on sale for $225, so I got an Impact Wrench for $65. Also if you do any work on cars at all, especially if you go to junkyards go get a 1/2" cordless Impact Wrench, it's like freeking fairy dust, totally magic.

 

[kf2qd]

You have a case of old - old style batteries. This lack of ability to hold a charge is a characteristic of old NiCad batteries. If they had been used in low discharge rate applications they wopuld show less of that tendancy, but because you are using them in a higher current application this is the way they get after a few years. Basically your batteries are getiing tired/worn out.

Newer cordless tools are using LiPo (lithium Polymer) technology and these batteries seems to hold up better under high current applications. I have a Makita set that seems to last forever and they also hold a charge nearly forever. Best way to store a LiPo is half discharged.

I have a 7 yerar old DeWalt drill that stioll works fine - IF ii remeber to charge the battery before I use it. Otherwise the battery is always dead. Needless to say, for the last couple years it hasn't seen much use because of the newer technology Makita.

You might look into whether there is a LiPo replacement for your current drill, or go get a new one with the LiPo packs.

 

[mklotz]

Basically your batteries are getiing tired/worn out.

Kf,

I'm nearly seventy years old. You can just bet my batteries are worn out.

Seriously, I'm sure you're correct. However, I don't use a cordless drill often enough to justify much effort or expense in updating batteries/charger. All I want is something reliable when SWMBO wants a hole drilled in the pergola to suspend the latest decoration.

Having a 12 V SLA always on charge has other benefits. Our emergency lantern for power outages uses two 6 volt batteries in series. I just know the next time we need it they'll be dead. But the SLA will attach to it quite easily.

 

[milotrain]

Having a 12 V SLA always on charge has other benefits.

You aren't kidding. A friend in college always had a 12V SLA on a trickle, I can't tell you how often it bailed us out of very odd problems. That's one of those things that you never think of doing until someone else does it and then you wonder how everyone doesn't just always have a 12V SLA ready to go. It's also often easier to hook up a 12V to some random electronic (especially car parts that need testing on a bench) than it is to mess about unhooking the variable power supply that's hooked up to the real project.

 

[TroyO]

I seem to recall reading once that corded drills (And many other home appliances... IE, your shop vac) run on "Universal motors" which are also capable of running from DC. I'm not certain that the speed control circuits work equally well though... I think they use diodes and/or triacs to vary the speeds.

In theory though, you can take a simple on/off AC corded drill (Which wouldn't have the above diodes or triacs in it) and run it from a battery array.

Not sure how much value this adds to the discussion, more a point on interest I guess.

 

[picclock]

The problem with NiCads is that with higher capacity and smaller size the self discharge rates are poor. However, there is a new type of rechargeable cell (Hybrio) developed by Uniross and licensed to various other manufacturers which has very low self discharge. A fully charged cell will retain 85% of its charge after 1 year of storage (so they say). I have some in a beard trimmer and they do seem to work as advertised. They are generally sold as 'pre charged' rechargeables.

I have been unable to find out the technical details of the cell changes, which probably involve some clever chemistry.

The AA sizes go up to 2100mAH, so it would not be difficult to construct a suitable pack.

Whilst Li-ion batteries have a higher cell voltage and similar long self discharge, they suffer from an insulating film build up on the battery anode, resulting in the cell being high impedance after long storage. With use the insulating barrier will reduce returning the cell to its former lower impedance state, but during that period the energy available is limited.

Just my 2 cents worth

picclock

 

[jpeter]

Here's my solution. Taped on is a 3s1p 2200 mah 30c Lipo battery from my model helicopter. A new one would cost about $25. It cranks this drill great.

 

[mklotz]

Your solution is better than mine, Jim. Mine lacks the duct tape cachet.

 

[Twmaster]

Milo, I have a Firestorm impact driver. It's the most often used tool of the three 12V B&D tools I have.

Nice thing when you have 5 batteries and three tools is workflow. One set up to drill holes, one to countersink and the other to drive the screws.

I'd be careful of that Lipo pack. Make sure you are not pulling too much current else you let the magic FIRE out of them.

Marv, Curious. how much current does that drill draw under something like a heavy drilling load?

Otherwise I think your solution is pretty good. Portable enough and plenty of capacity.

 

[Foozer]

Fanny pack, I have something similar for camera usage.

Robert

 

[Twmaster]

The AA sizes go up to 2100mAH, so it would not be difficult to construct a suitable pack.

I'd be wary of a small cell like the AA. Even thought it -says- 2100mA that does not take into account the C rating. C is how many times it's own current it can supply. Most AA batteries are intended for consumer electronic devices and cannot deliver high C numbers like physically larger cells can due to higher cell impedance. They are not intended for power tools with high demands on cells. Every cordless drill I ever dissected had sub-C sized cells inside (Sub C is a physical size that is 2/3 the height of a standard C sized battery). I've seen 1800 mA nicad cells dump 100A of current and survive. Try that with an AA cell. Go ahead. I dare ya.... (Speaking of batteries, who remembers that commercial?)

Dang, I'll hush up now. I could go on and on...

 

[dgjessing]

Last spring I broke down and treated myself to one of the new-fangled lithium-ion jobs - this one: http://www.hitachipowertools.com/index/main-navigation/tools.aspx?d=2,307&p=684

I love it! The batteries put out pretty much full power till the end, and don't take long to charge. And a charged battery stays that way on the shelf. Can't recommend it highly enough...

 

[Kmot]

I did the same as you. I wired up a Powerpole connector and now I can quickly plug in any number of NiMh packs I have. I also did the same to a small cordless house vacuum cleaner I use for touchup between the main super Hoover corded version. It came with 600 mAh NiCd batteries and it required using both batteries to do my house and each one was running slow from the load. Now I connect a 4200 mAh NiMh and it is much more powerful on suction and easily lasts the entire house.

 

[mklotz]

I haven't bothered to measure the current drain when the drill is under load but yesterday I drilled six one inch diameter one inch deep holes in a 2 x 4 using a spade drill. When done, the battery voltage was the same as when I started. I don't think this lashup is likely to have any problems with the typically wimpy jobs I'm likely to throw its way.

 

[te_gui]

Something else to consider if you are in the market for cordless tools, Home Depots brand Rigid has a lifetime guarantee on their batteries. I was able to swap out my last one at the local tool repair shop. I have no connection other then a satisfied customer who has thrown away his share of prior cordless equipment due to the batteries dying.

Brian