making cordless tools corded

[DaveW]

I have the 18v Ryobi tools (from before they became One+), and they only get occasional use. Consequently, the batteries I have don't hold a charge all that long. With the drill/impact driver, they still work great, but with the saws, they last enough for me to kick up a bit of sawdust. Case in point, I got about 30-40 inches in cutting a sheet of 3/4" melamine with the circular saw.

So, I come to you, the gifted and creative members of BT3Central, to ask - has anyone come up with a corded adapter of some sort? This topic has come up on the Ryobi forums, but the last time I checked, Ryobi wasn't anywhere closer to making a real accessory to this end.

It doesn't seem that bad to me - 120VAC -> 18VDC, with something to make sure the resulting amperage was correct... but that's about as far as I can get - I don't know enough electronics to go further...

[Alex from Sac.]

I have been wondering the same thing since I have the same problem. Is this the same issue with other brands?? Dewalt, Ridgid, Milwaukee Craftsman???
I found that Dewalt made an adapter to convert to 120v but is discontinued and tagged at $120.00 when I found it. Awful expensive for an accessory but If anyone has a good answer let's hear it.
just my 2cents

[steve-u]

The problem would be finding a power supply and then connecting it to the tool. Assume the tool is doing the job that a 5 amp 120v tool is. That is about 600 watts which means you would need to find an 18v power supply that could supply about 33.3 amps and it would need a heavy duty cable to connect to the tool - say 10 guage wire as a top of my head guess. Even if my guess is high it is not easy to find am affordable high current 18v power supply. Some of my ham radio equipment works this way in that I can run it off of 120v or use a 12v power supply of which I have a 35 amp Astron. Users of 12v cordless tools could probably do fine connected to a car battery. I am not an electrical engineer but that is my take on the problem and I am sure some of those that know better/more than me will chime in.

As far as not getting much use I bought a Dewalt 9v cordless drill about 10 years ago and it still runs strong on the original battery with very occasional use. If you search previous posts on battery useage optimaization you will find some good tips on maximizing their potential and maybe even resurrecting them. If I remember correctly it is best to never charge a hot battery, use a "smart" type charger that cuts current to the battery after full charge, discharge a battery under normal load/use if it is going to be stored for a while, and not running battery to completely dead but charge when you notice a reduction in performance or measure that voltage is no less that .9v per cell. Divide your battery voltage by 1.2 to find the number of cells. I also undestand that we should not worry about the fabled battery memory problem with nicads that only applies if the battery is repeatedly discharged the same exact amount every time before recharge. --- Steve

[DaveW]

Steve:

I'm no electrical wizard but 33amps? would you really get that out of an 18v battery? Thanks for the general tips on battery usage/charging - I think I abide by most of them; but I'm still sitting here with dying batteries

Alex:

Supposedly, Milwaukee has/had something resembling an adapter.

In all honesty, I have severe doubts of Ryobi actually making and selling one - it would cut into the battery profit margins... that's why I posted here - in the hopes that there's a shopmade solution.

[steve-u]

My assumption/example is probably way high but I bet the saw draws several amps which means that something like a big wall wart would not power it. The drill would draw a lot less. --- Steve

[LCHIEN]

The problem would be finding a power supply and then connecting it to the tool. Assume the tool is doing the job that a 5 amp 120v tool is. That is about 600 watts which means you would need to find an 18v power supply that could supply about 33.3 amps and it would need a heavy duty cable to connect to the tool - say 10 guage wire as a top of my head guess. Even if my guess is high it is not easy to find am affordable high current 18v power supply. --- Steve

as an electrical engineer, I say steve has hit it right on the button.
To achieve the same power a 12V supply must supply ten times the current as a 120V unit, regardless of AC or DC issues.

The chargers supplied, even the fast ones, charge in an hour but you can drain the battery in 6 minutes of hard work. so there's roughly a 10:1 shortcomings in a battery charger. To provide full tool power the power pack would have to be ten times more powerful than the fastest chargers and the cables ten times bigger than the power cords used for 120V power cords. meaning stiff and heavy and unweildy OR huge compromises in performance.

Two configurations are possible - one a power pack that plugs into the wall directly (or with a normal 6-ft ac cord) and then probably a 0 or 0-0 gage cord (thats the gages that are bigger diameter than 2 which is a heck of a lot bigger than 8, 10, 12 or 14 gage) to the battery socket on the tool. OR, a normal AC cord to a 3"x3"x3" brick containing a 12-18V swicthing AC/DC converter capable of instantaneous 30-40 Amps, that plugged directly into the battery socket. which would run around $100 retail. (note a HV e.g. 120V motor in a drill needs small wire sizes and no conversion so they're cheap). The heavy wire is really way heavier than the 10 gage Steve proposed because voltage loss at 12 or 18V is a lot more cicritical than the same voltage loss at 110 where you might use 8 ga to carry 30 amps. Wire gages halve the resistance loss for every 4 gage numbers, very roughly. to get 1/2th the resistance or voltage loss that you experience with 16 gage wire would require 12 gage wire and so on. So just off the top of my head i suggest 0 or 0-0 wire - which is bigger stuff than most of you have ever used.

Nicads/NiMH are capable of very large current surges for short times, which is why low voltage portable battery tools can work. The wiring in the case is a matter of inches instead of 6 feet. And charging, even fast charging, is relatively slow compared to discharge rates.

NOte that PC's have the power supply box which most of us have seen or even replaced. They're big, provide around 3-4-500 watts, somewhat short of 600W that Steve rightly suggested is needed, and require a cooling fan. And PC supplies they cost around $30 because of the quantity and standarization/generic fit. Since it would require a custom plug to fit the tool, a power tool adapter custom-sole-supplier built by Ryobi or Dewalt would cost at least $100 as I said.

[ted van halen]

FWIW,
I had an old B&D 12v drill that with no battery. They refused to hold charge more than 4-5 minutes. I rigged a cord to the battery of my truck & bingo bango bongo, I was drilling again. I have since replaced it w/ an 18v ryobi refurb that was just a little more than 2 batteries would have cost at the time. I'm sure I defied ohm, newton & some other dudes too but I never studied law. If it dies, who cares. It was dead to me already.

[Wood_workur]

ted has a good Idea. Strap a car batery or two to your back, and run some wires. Then add an alternator.

[DaveW]

Steve: After I logged off and thought about the inversely-proportional math, the 33 amps made more sense...

Loring: 1) What's HV? 2) If someone were to go after the first configuration with the 0 gauge wire - how would that work if the garage/shop isn't wired with the same kind of wire? Or am I trying really hard to miss the implied point of "don't try it!"?

So I guess I need to figure out how to rig up a couple of computer power supplies to the shell of an old battery!

[LCHIEN]

Steve: After I logged off and thought about the inversely-proportional math, the 33 amps made more sense...

Loring: 1) What's HV? 2) If someone were to go after the first configuration with the 0 gauge wire - how would that work if the garage/shop isn't wired with the same kind of wire? Or am I trying really hard to miss the implied point of "don't try it!"?

So I guess I need to figure out how to rig up a couple of computer power supplies to the shell of an old battery!

HV= high voltage e.g. 120V
you only need heavy wire between the power supply and the battery.
I just did the calculations
you can use 10 ga. wire with a 12V 600W drill cerrying 50 Amps
and you'll lose 5% of the voltage in the wire, close to 10% of the power.
8 ga. or 6ga would be a lot better.

I guess i was too pessimistic and 0 gage wire is more than required.
Computer power supplies supply about 5 voltages, and the power capability is split between them. So a computer power supply won't actually work. I was just using them as a comparison for power per dollar and size.

[steve-u]

Dave.

I don't see an economical solution for 18v cordless tools. 12v cordless tools could be failry easily connected to a lead acid battery with deep cycle being the best bet. You could do a ton of drilling connected to one of those. Since you are failry happy with the performance of the drill still you might just want to buy a corded circular saw [it sounds like you might not have one?]. Even a cheap Skil saw will run circles around the Ryobi 18V saw with a fresh battery and I see them on sale all the time for under $35. -- Steve

[TheRic]

Being the froogle person I am (wifes words, I say I'm a tight @$$, lets call a spade a spade). I have an electrical, electronic, robotic, and computer science background. I love to make things work that others can't. I will work on something for hours / days just to get it to work. Knowing that I could spend $1.00 / hr. and by a new one, that is better. Yea I know I need to get a life!!

I will tell you, I have thought about this more then once, still have several old drills that I want to try it on, just to do it. But it still comes down to time, money, performance, SAFTY, etc to do it. Bottom line, it's just not worth it!!

[scorrpio]

Yeah, you'd need a 600W PSU to provide a 120V/5amp equivalent - and those aren't cheap. And you COULD use a computer PSU to power 12V tools - you'd just need to connect to several power rails. The wires coming out of a PC PSU are roughly 16ga, and in order to supply enough juice to a modern mobo and all components on it, there are four 12V leads, five 5V leads, four 3.3V leads and ten grounds. And even with that, many video cards require an additional connection. But fact remains that high-wattage PSUs are expensive, and are cumbersome.

So, my answer would be is just buy a corded saw - gonna be cheaper, far more convenient, and likely a lot safer.