How can I replace a power tool battery with an ac adapter?

Question

I have several old power tool batteries that have died over the years... I really don't like buying them over and over.
I got the bright idea (oh no), if I could find an ac adapter with the same volt and amp output, and I could fit it inside a battery case (take the batteries out of the housing), then I wouldn't need more than one or two batteries while I'm away from an outlet. (Most of what I do, I do close to an outlet. Having cordless tools are just very nice.)
Anyway, I found an adapter with the spec I needed on eBay. Got it home and checked it out on my meter (right on the money for volts; less than 1/2 amp higher than the batteries).
I emptied out a worthless battery, fit the adapter in, carved a hole for the cord and fit the wires inside to connect to the "battery" terminals. Now it looks just like a regular battery, test the same, it just has a cord hanging out.
When I put it in any of my tools, however, the tool runs in VERY short bursts.
What did I do wrong?

New information.... (I'm still trying to figure it out)

If I plug the "battery" into a tool that is variable speed and sloooowly squeeze the trigger, THE TOOL RUNS GREAT!
If I squeeze too fast, though, it sounds just like a non variable speed tool.
rumm... rumm... rumm... about once per second.

Well... I thought it ran great. It only SOUNDED like it was running great. When you put it under a load, it dies. At full clutch, I can stop the drill with minimal effort with one hand. With a good battery and at full clutch, this drill is a wrist-breaker if it jams a bit in something!
What's going on?!

If you read a bit closer, you'll see I'm talking about a thing I made. Not a gimmick... I created it. It's not a battery, but an ac adapter that I put in a battery housing.

DOES NOBODY KNOW?!

It is an ac to dc adapter.
And it was not an easy fit into the battery housing; it's sitting at a sharp angle and a little carving on the battery housing was needed to get the top screwed down. (ryobi 18v)

As every test I've learned to do says it doesn't have enough amps, my next plan is to replace the adapter with a laptop adapter at 18.5V and 6.5 amps.
That will either be enough, burn the motor up or tell me it isn't going to work no matter what.

I really hope someone has a better idea.

Answer 1

Well,
I think its fabulous that someone else has an idea like me. Back in 1995 I had thought of this very idea. It was not until two years ago I invested over $10,000 and applied for a patent on this product. Back in June after 1-1/2 long years I received patent pending status. But anyway. What your problem is, is this. You have overlooked how much milliamps you need to efficiently drive your cordless tool. You are on the right path. Most cordless tools need at least a minimum of 1200 milliamps. I guarantee your transformer is only putting out around 400 milliamps. (I had this same problem in my first proto. You can find this on the label of one of the batteries.) Then you have to find a AC to DC transformer that will put out the milliamps you need. Remember Volts are like horse power and milliamps are like Torque. This my friend will correct your problem. Please do me a favor and don't manufacture and sell this.

Answer 2

I have never seen the unit you are talking about, but it sounds like it is a battery with a built in charger. Leave this plugged in for an hour, if it runs longer ( like a battery ) this may be true. Sounds like a Gimmick to get you to buy. Sorry. The purpose of cordless drills is to use where power is not available. I have 2 cordless drills and 1 corded drill. Each is designed for a specific use. If you are using near a power source often, I would recommend a corded drill, they are more powerful anyway, and come pretty cheap these days

Answer 3

suprised the thing runs at all.

consider most battery's, lets saya 12 volt at 2.5 amp hour, it puts out 12 volts at 2.5 amps for an hour before it dies. most adapters that could physically fit into a battery housing are small and deliver at most 12 volts at .5 amp hours - not enough for serious usage and chances are you're going to burn out the adapter anytime soon.


btw, you are using a AC to DC adapter? and not an AC to AC adapter

Answer 4

By using the transformer to power the tool you have changed the amperage of the power supply , in a nut shell - this won't work effectively . I'd suggest buying one that has available option for ac power . Very inventive idea though .

Answer 5

Either the connector on the motherboard is bad (repair), the charger is bad (replace), or the battery is entirely dead (replace). Does it not boot with the charger plugged in? Do you get any lights like the power from the charger is getting into the computer?