Not sure how better to title this... But basically, I want to try to convert one of my old ryobi 18v batteries into a wall plug. I want to strip the guts of the battery, attach some components and a heavy duty cable to be able to plug the "battery" into the wall so I can have continuous power to a "cordless" tool.

enter image description here

In other words, I want to make a plug-in cord to make any of my cordless tools into a corded tool.

I know Ryobi has tools that have both battery and cord hookups. I'm wondering if I could just take the guts from one of those and put it into the old battery casing, so everything plugs in just fine.

Question: Is it possible, and is it as simple as creating an AC/DC converter

  • \$\begingroup\$ In theory it is possible. I don't know much about the design of these batteries, but if there is some sort of communication between the battery and the tool (there probably isn't), simple AC/DC probably won't cut it. If you replace the battery portion of the pack with an AC/DC converter, be aware that drills typically have heavily inductive loads, and you may need to provide protection against an inductive kickback. Also, you may be surprised by the amount of current the drill is taking, and the power supply will need to be sized accordingly. \$\endgroup\$ – Scott Winder May 4 '15 at 18:28
  • \$\begingroup\$ Also, see instructables.com/id/… \$\endgroup\$ – Scott Winder May 4 '15 at 18:34
  • \$\begingroup\$ @ScottWinder, Great comment. Many things I didn't think about. I was only into EE as a hobby for a short time but want to get back into it. Thank you for the link! \$\endgroup\$ – ntgCleaner May 4 '15 at 18:38

Get a 18 V power supply that is rated at least for the current that the batteries were able to put out (a couple amps minimum, probably). Gut the battery module you have and connect the 18 V wires from the power supply to the battery connector internally. Be really careful to make sure the +18 V goes to where the battery + went, and the power supply return goes to where the battery - went.

There is a off chance that it still won't work if this was a "smart" battery module. In that case, there will be some communication going on between the drill and the module. However, this is unlikely in a volume product like this where consumers largely buy on price.

  • \$\begingroup\$ Great answer Olin. It seems safer and easier to purchase a converter for this specific task. Thank you \$\endgroup\$ – ntgCleaner May 4 '15 at 19:27

You can certainly do this but you may be surprised at the current requirement of the supply.

One of the reasons that portable power tool manufacturers use NiCd or NiMh cells in their battery packs is that those cells can supply relatively enormous amounts of current for short periods of time.

You should insert a low-value current shunt in series with the battery as close to the drill (or whatever the tool is) as possible and measure the current while you are loading the tool almost to the stall point.

There is a very good chance that you will see current values well in excess of 10 Amps - possibly even exceeding 20 Amps.

The power supply that you build (or purchase) has to be capable of supplying that much current if you want the tool to work as well when running from your AC adapter as it does when running from a fresh, fully-charged battery pack.

In other words, you can certainly build something that will work well. It will be larger than you expect if you want it to work well.


Not the answer you're looking for? Browse other questions tagged or ask your own question.