# Converting dead cordless tools with an external battery pack



## manygoatsnmore (Feb 12, 2005)

I picked up some issues of a new to me magazine at the library the other day and just had to share. The magazine is *BackHome Magazine*, not Backwoods Home, that I've read for ages. In the January issue for this year, they had a 2 page article on making an external battery pack adaptor to use with dead cordless batteries. As most of us have found out, the batteries on cordless tools a) don't hold a charge long enough to finish most jobs, and b) eventually no longer recharge at all. 

Rather than taking them to Lowe's to the battery recycling bin, it is possible to take them apart and remove the old batteries, solder wires to the connector to the tool, using a long cord like a vacuum cleaner cord, epoxy it all into place, then attach battery clips to the other end of the cord and clip them to a deep cycle battery, so that you can use the power of the deep cycle dc battery to run the tool. The battery can be recharged with a solar charger, giving you power tools when there is no electricity. It also means that you can be on the lookout for dead cordless tools and batteries at garage sales and thrift shops, and can return them to usefulness. I just thought this was an idea worth sharing.  

I plan to keep using my cordless tools until the batteries won't hold a charge and then make my adaptor, and in the meantime, I'll be on the hunt for dead cordless tools to practice on. I would imagine that I could also take my (working) batteries to Lowe's and ask them if I can look in the recycling bin for matching dead ones so that I could make an adaptor now. After all, better to make it when you still have grid power to run the solder gun.

If you have access to that article, maybe from your library (interlibrary loan, if your local library doesn't subscribe) or can buy a back copy - looks like they charge 3.50 for the copy, the article has a lot of good pictures and is clearly written. If *I* can understand it, anyone can, lol. I checked the website to see if the article was available on line, but it just referred me to buying a back issue. I photocopied the article on my printer so I'll have it to refer to when I build my adaptor.


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## mellowguy (Jul 8, 2009)

Years ago, I saw a guy carrying a 12V deep cycle battery to power his 12V drill on a job site. He had a short cord (maybe 10'), which didn't make the tool that "portable", but still better than a generator + drill combo. That was when batteries didn't last "as long" as they do today. I think you'd want to stick to a 12V tool though (or an 18V with 3 x 6V cells). Anything less than 12V would get a burnt motor, and anything above would be underpowered.

There aren't cheap power adaptors adjusting DC power (to, say, 12 V to 9.6V)


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## Harry Chickpea (Dec 19, 2008)

I would add a fuse, but that is a good idea. Remember that cordless screwdrivers and drills can also be repurposed. Insert a threaded rod into the cordless screwdriver chuck and you have a powered worm drive shaft you can use to open hard-to-reach windows, and so forth.


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## Ed Norman (Jun 8, 2002)

How do you tell + and - on the battery? I have a dead 12V battery that I've been wanting to do this with. I guess if it turns the wrong way, I reverse poles, but the battery has 3 contacts. I planned to put a cigarette lighter plug on the cord and then install a lighter socket in the golf cart.


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## TnAndy (Sep 15, 2005)

You know you don't HAVE to make an adapter....you can simply rebuild the battery pack.....all most of them are is AA or AAA re-chargeable cells wired together in a pack, then put in a plastic case. There are several places you can send you old battery pack for a "rebuild"....but the above is all they do. Take yours apart, see what size and amp/hr rating the cells have, order new cells and put it back together.....seems to me that would beat a Rube Goldberg adapter.


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## dezingg (Feb 25, 2010)

Not a bad idea! I have some 18v Dewalt tools. You'd want to consider if the new battery pack supplies too much power and causes heat damage in the tool. Although I guess that if you had several stock battery packs you could be putting plenty of heat producing power into the tool with stock batteries.

I'd love to get a better flashlight for the 18v pack. The DeWalt one is adjustable for the angle, but it isn't anything like a good Mag Lite flashlight.

Ed Norman - do you know anyone who has a similar battery that works. You could measure a working battery with a volt meter. Or maybe use a volt meter on the battery charger?

I once built a four D cell pack that clipped on my belt and a wooden plug with metal contacts to replace four AA batteries in a camera flash. It worked well, as that particular flash unit ate batteries like crazy.


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## texican (Oct 4, 2003)

I've done this back when I had a 12v drill... Had a small solar panel just a little larger than a milk crate, with a smallish 12v battery in the crate... had it all attached together... worked great.

Now I'd love to be able to jury rig an 18v setup. Might have to get some backup 12v tools, just so I can have tools to use years into the future (I have ridgid and ryobi tools, and the battery life of both is lacking.) I've looked at the lithium batteries and sheesh upwards of 70bucks a piece... Maybe someone will have some available on Black Friday!


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## manygoatsnmore (Feb 12, 2005)

The article did state that an 18v cordless tool would be a little underpowered with a 12 volt battery, but that it would still work. Using 3 6v batteries in a line would work, although probably less portable. The cord from any AC appliance could be used to connect the tool to the battery, but the article's author recommended using something like a vacuum cleaner cord, as it is generally pretty long and would let you move around more with the tools. I would think an extension cord could also be used. 

How do you tell the + from the -? The article said something about trying to note when you took it apart which was which - I'm thinking you could probably tell from the way it's wired inside? It also said something along the lines of it not being that important, but didn't go into why that would be. I guess if you are using battery clips on the ends and it isn't the right way the first time, you'd switch poles? Would that work, any of you electrical geniouses? I'm NOT one, so I'm just thinking and wondering this myself.

As to having the battery rebuilt, what happens when the rebuilt batteries also die? I know a deep cycle battery is going to last a very long time, and with a solar charger, will be available power even if the grid is gone. Also, having a battery rebuilt is a bit expensive. This is a relatively cheap method to provide a more permanent solution. A vacuum cleaner can usually be found at a garage sale for under $5, or if you ask on freecycle for a non-working one, you can probably find one for free.

I just thought it was a pretty good idea, if a bit "Rube Goldberg". :shrug: 


eta: I'm not an electrical engineer, nor do I play one on TV, so I have another question. Can a 12v and a 6v battery be wired together to provide 18v of power, or do you have to use 3 6v batteries? In other words, do all the batteries in the series have to be the same voltage?


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## EDDIE BUCK (Jul 17, 2005)

You can find lots of info here [ame]http://www.youtube.com/watch?v=ig2fbI2jejM[/ame] Plus many more battery videos here to.

And Here http://www.ehow.com/how_5431955_rebuild-battery-pack.html

Here's something that I haven't tried,but I believe it works.Zap with a wielder to restore power [ame]http://www.youtube.com/watch?v=g0JbNX4K4fQ[/ame] I'm not telling you to try it,but.well you get the message.

I have in the past,with an 18 volt flashlight, when cells started dying in my drills and other tools,drop to a 16volt bulb,then 14 volt bulb,ect.Now that you can find fairly cheep cells on line,I just rebuild the packs.And don't throw away those wall chargers.You can find many uses for them.Just make sure its the proper A/C or D/C and Volt output for what you need,and determine the pos and neg wires,then I replace the jack with alligator clips,and paint the pos clip red.

A 12volt dc wall charger will charge a 12 volt auto battery,takes a little longer,but it will charge it.Mower batteries to.Theres lots of ways around that 50 bucks for a new pack,plus that 50 bucks will be handy to buy this outrageously high gas we are having to buy and the price rising everyday lol eb Hope this helps.


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## ||Downhome|| (Jan 12, 2009)

battery banks should be of the same type. and at the least voltage.

you can wire 2 -12v for the 24 or do the 3- 6v for 18 

those 6 extra volts wont matter to much but if you where worried about it you could put some resistors in the circuit.

I myself would rebuild the battery pack,theres a few diy battery pack rebuild howtos on the web. I figured it could be even simpler if you used some battery holders instead of soldering your cells together.

though it would be nice to have the corded pack adapter for the what if scenario. 
with low volt dc though the smaller the wire and the longer the run/wire the more loss. loss=heat not to mention the heat is you battery reserv being changed into that heat. you will be limited on wire length unless you go with a proper sized cable. wich I dont see. dont think it to super practical.

and if Im stuck useing a wired tool, I might as well hook up the gen or inverter and be able to run a few hundred feet of wire. A/C does not have the loss issues of low voltage D/C. 

http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel


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## texican (Oct 4, 2003)

To determine which is positive and which is negative on the batteries, I probed the three prongs inside the charger... one is +, one is -, and the other one is for some kind of charge monitoring function. When I hotwired my tool, I simply soldered on some wire to the + and - sides of a completely dead battery, connected to the 12v battery, and slid it in... worked like a charm.

I'd never thought about three six volt batteries. {ding ding ding ... learned something today.... IF I had to have my 18v tools, and the grid had been down for a year, I would have sat down, and used Grandpas calculus formulas and probably figured it out} I keep several of my old six volt deep cycle batteries around. Of course, if I tied three of them together, I'd have to put them on a cart, as they weigh what, ~60 to 70lbs each.


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## Ed Norman (Jun 8, 2002)

They are making 8V golf cart batteries now in case someone has some strange voltage they need to reach. I've seem some 14V tools that would work with two 8V batteries. They would also do good on 18V tools.


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