Necessity is truly the mother of all inventions....and my case was no different. About a year ago, I found myself with a dead battery for my Ryobi 18V cordless tools and no means of getting a new one as I was working overseas. So I came up with a setup to run my tools off AC (household current) safely and with no worries of my tools dying halfway into the job.
Now I enjoy all the benefits of battery operated power tools just as much as the next guy....They're convenient, flexible, and you can usually get quite an assortment of tools that run off the same battery. Then the inevitable happens....you get the dreaded blinking set of lights on your charger and the batteries die out almost instantly. Your faced with two options.....Drop $50-$100 on a new set of batteries or try rebuilding them yourself. Neither one of those two options appealed to me nor did I have the time to order the parts from overseas. As anyone in my situation might do, I scoured the internet for an alternative solution. I found guys connecting car batteries to their drill...ummmm no thanks. Then I came across the idea of using an old laptop power supply in place of the battery.....The voltage seemed right, but alas the wattage was too small. Even at 180 watts, the biggest pc power supplies couldn't provide enough to overcome the start-up current of my battery operated circular saw or angle grinder.
The principal of the pc power supply was sound, I just needed something bigger. After a little more research I found that the common everyday laptop power supply is what they call a "switch power supply". Turns out, switching power supplies are very common everywhere in the world, affordable and come in a variety of voltage and power ratings... I eventually chose a 350w AC/DC power supply produced by a reputable company called Meanwell with a voltage range of 15-18volts DC.
Wiring of the power supply to a dead battery is very straightforward, but the following instructable goes through the details step-by-step.
Now I enjoy all the benefits of battery operated power tools just as much as the next guy....They're convenient, flexible, and you can usually get quite an assortment of tools that run off the same battery. Then the inevitable happens....you get the dreaded blinking set of lights on your charger and the batteries die out almost instantly. Your faced with two options.....Drop $50-$100 on a new set of batteries or try rebuilding them yourself. Neither one of those two options appealed to me nor did I have the time to order the parts from overseas. As anyone in my situation might do, I scoured the internet for an alternative solution. I found guys connecting car batteries to their drill...ummmm no thanks. Then I came across the idea of using an old laptop power supply in place of the battery.....The voltage seemed right, but alas the wattage was too small. Even at 180 watts, the biggest pc power supplies couldn't provide enough to overcome the start-up current of my battery operated circular saw or angle grinder.
The principal of the pc power supply was sound, I just needed something bigger. After a little more research I found that the common everyday laptop power supply is what they call a "switch power supply". Turns out, switching power supplies are very common everywhere in the world, affordable and come in a variety of voltage and power ratings... I eventually chose a 350w AC/DC power supply produced by a reputable company called Meanwell with a voltage range of 15-18volts DC.
Wiring of the power supply to a dead battery is very straightforward, but the following instructable goes through the details step-by-step.
Remove these ads by
Signing UpStep 1: Electrical Warning
Before starting please understand you have a power supply capable of discharging 20Amps. Although the setup is fairly simple, if you are not comfortable working with electronics, please seek professional help on this Instructable.
The cable exiting the battery and connector of the DC outlet from the power supply are made from an standard 120VAC wall plug. The plug and cable was selected for ease of availability and to allow me to use a standard extension cable if needed. For my case, I will be the only individual using this setup.
Under no circumstances would I plug an AC powered appliance, tool or otherwise, into this power supply. If you choose to make this setup please think ahead who might be using it. If there is the remote possibility of someone not trained to using this setup, I would suggest using a different type of connector and cable. Something more unique but capable of handling the amps.
One recommended cable is that of a twist lock generator plug.
The cable exiting the battery and connector of the DC outlet from the power supply are made from an standard 120VAC wall plug. The plug and cable was selected for ease of availability and to allow me to use a standard extension cable if needed. For my case, I will be the only individual using this setup.
Under no circumstances would I plug an AC powered appliance, tool or otherwise, into this power supply. If you choose to make this setup please think ahead who might be using it. If there is the remote possibility of someone not trained to using this setup, I would suggest using a different type of connector and cable. Something more unique but capable of handling the amps.
One recommended cable is that of a twist lock generator plug.
Visit Our Store »
Go Pro Today »
The cheapest source of suitable batteries is those sold for (serious) radio control models.
Take a cheap RC model battery pack with compatible voltage and capacity, and a matching plug. Then make a five foot lead from the plug to the power tool terminals.
Then just drop the battery pack in your pocket, and conveniently use the power tool with much less weight in your hand.
And if it is a reasonably compatible voltage, and with an appropriate socket fitted, run it from a car battery charger when in the workshop.
If the car battery charger is a slightly lower voltage, the tool will run a bit slow.
If it's a higher voltage, the tool runs faster, but give it regular breaks to cool down or it will overheat !
Somebody please tell me if anything in italics was wrong, because I suspect that it was.
The "C" rating tells you how much current relative to capacity, "mil Amp hour", that is safe to draw or charge your battery.
Amps = C * m A h / 1000 ( the /1000 is to go from mil amps to amps)
So a 1200mAh 10C battery is good for 12A (10 x 1200mA/1000)
A 1200mAh 15C battery would be good for 18A (15 x 1200mA/1000)
Exceed this rating for to long and excessive heat and catastrophic failure will surly follow.
The C rate is the highest rate at which the cell (or pack) can be drained per the manufacturer's spec. In this case, 20 C. This means that the max drain is 20 times the capacity rating of the battery. 3A * 20C = 60 Amps. It only has a capacity of 3 Ah, so its theoretical capacity limits it to 3 minutes (1 hour = 60 minutes, 60 minutes/20C = 3 minutes). The reality of cell chemistries is that you cannot get the full useable capacity of the cell/pack at discharge rates higher than 1C due to internal series resistance and other factors.
Please can anyone provide a link to a table of those RC pack codes ? That would be extremely useful.
What are RC pack codes?
The only pack codes that I know of are the ones that describe the construction (# of cells, negative electrode, positive electrode, shape of cell, size (diameter, width, height)) as given in IEC 61960. This is a standard for secondary (rechargeable) cells for portable applications.
You have a right to your opinion and I respect that, but to each their own. I'm sure there are guys out there that can make use of what I've instructed and that's why I did it. My needs overseas dictated I have a set of cordless tools. You might not be aware of this little fact, but consumers in the U.S. are privileged when it comes to availability and price of products. In southeast Asia where I'm currently working, you can't get a decent set of 18v tools for less than $1000!!! So I when I needed tools I brought them from the U.S. and I didn't want to drop a wad of $$$ on something that might get stolen on the job site. When the battery died, I improvised. Enough said.
I value and appreciate good well made tools just as much as the next guy, but my Dewalts, Porter Cables and yes....Milwakees stay home.
Sorry for the long winded reply & if I offended. I have been wiped out of tools several times in a 30 year career but if I can't use my tools for the purpose I purchased them they are waste of money. I have worked for contractors using my tools since the 1st theft and refusal of my employer at the time to replace them. I continue to supply my own tools with my employer supplying consumables. On the occasion I was relieved of a tool the cost of consumables increases accordingly. Maybe underhanded but have had no complaints from employers. Their insurance may not replace lost personal tools but they haven't seemed to mind replacing said tools through unexplained increases in consumable's cost even when my drill bit, blade purchases, etc. briefly rise to match cost of stolen tools. I guess I'm fortunate to be employed by persons appreciative of the fact I always have the required tool available without searching an entire job-site. I still believe purchase of cheap (Ryobi) tools beats the adaptation of PWM power supplies of adequate output to power a cordless tool. Please accept my apology,
Zappenfusen
Go one or both. I've corded Milwaukee's 30 yrs. old and like new, as I've complete cordless Makita's which are unbeatable. The time is coming when this debate shall be moot. I remember the thrill of my 1st 14.4 V DeWalt drill. Amazing!
Zapp
Sounds like a great idea but you might find it hard to fit hard to fit a powersupply big enough into the confined space. Good luck and drop me a line if you can get it done. Loved to see it work.
Frank
http://www.radioshack.com/product/index.jsp?productId=2103293
http://www.radioshack.com/product/index.jsp?productId=2103250
Your definitely right about using a unique DC receptacle that can not be confused with a standard wall receptacle. Because this is a DIY setup I assume the builder will be the end user and will know well enough how to use the supply. For me it was out of convenience but I'll definitely make mention about the labeling the socket and recommending people use something more unique.
Thanks
As for the risk of DC....There's always a risk, but the power supply is fuse protected internally. Also, you might want to label the receptacle "For DC use Only". I personally used an AC receptacle out of convenience, but you can use any 2 prong connector that is rated for the amps.
Hope that helps.
F
I voted for your idea - there have been many times i had wished I had one of these. I just never had the time to get one built/engineered. I always hated wasting the old cordless drills b/c the new one with battery was the same cost as the battery itself.
Thanks for the kudos...As I mentioned in my instructable, I tried this setup with a 180w laptop power supply originally. I couldn't get enough amps for the startup. I took an educated guess and figured double the horsepower should do the trick. Luckily it did and I don't have any issues with startup or heavy loading, even with my big motored tools.
Your idea about adding some capacitors sounds like a great idea. You can probably get by with a smaller power supply for startup but you might run into some issues during a high load situation. The power supply I used was less than $40 so I didn't see the need to do any fancy electronics to get it to work. But if this works with an used laptop supply you can probably cut your cost by half at least.
Anyways, good luck on it.....Drop me a line if you can get it up and running.