Revive a Ryobi Battery

I’ve been able to revive a dead power tool battery before, but Ryobi has some extra protection so you can’t trickle charge them from the contact points on the outside of their batteries. I was able to use a method I found on YouTube to trickle charge from the inside and the battery is working again.

When I say “dead battery” I mean the charger status shows the battery is defective. It can do this if the battery completely loses all of its power or the cells become imbalanced. The charger has built-in safety measures that prevent it from charging batteries in this state.

Be aware that opening the battery like this will void the warranty. Due to the special screws (T10 with a hole) I bought a security bit set from Menards for $5.

Update: A second battery went dead the day this was published. This method resurrected that one as well.

Battery Leak in TV Remote

Not long ago I pulled out the original TV remote to change some settings. When it wasn’t working, I found a bunch of battery acid had leaked. Good reminder to remove the batteries from items you’re not using.

Resurrect a “Dead” Power Tool Battery

Ever had a “dead” power tool battery that wouldn’t charge? It may not have been dead-dead. Some chargers have a safety feature that prevents trying to charge a battery completely out of juice. I was able to bring a Craftsman power tool battery back from the dead using a trick I found in the comments on a YouTube video. Sometimes it pays to read the comments.

This battery was part of a used Craftsman cordless tool set I practically stole. The set was a battery charger, small circular saw, reciprocating saw, nice case for those 3, drill/driver, nailer/stapler, and 2 batteries. Everything is in excellent condition and I only paid $30! The original sticker price on the box for the nailer alone was $80.

Negative Voltage

The girls were having some problems with the LEDs in a couple of stuffed bears. Mom thought there might be a short in the wiring because they’d work for 10-15 seconds and then the LED sequence would freeze up or turn off. Before tearing into the bears I got out my multimeter (has become quite the handy dandy tool for me) and tested the batteries, which had been straight out of a package when they were used in the bears.


Two of the AA batteries were reading right around the expected 1.5v, but the other was -0.3v, as shown above. I’ve never seen that before, so I did some Googling.

Any type of battery can and will begin to charge a dead cell in reverse if you keep trying to draw current out of it. Remember, a battery is a series connection of cells, so in any pack regardless of chemistry, a dead cell once depleted is going to be subjected to voltage reversal.
– Source

It looks like something happened to reverse the polarity during manufacturing or the battery was DOA and got charged in reverse from the other two AAs.

After replacing the batteries all of the bears work again. It’s a good reminder to check your power source when things don’t work.

Wire Loop Game

Kennedy and I made a wire loop game, using some basic cheap electronics.

  • 9v Battery
  • Buzzer
  • Old light switch
  • LED
  • Various wires
  • Nuts and bolts
  • Electrical tape
  • Wire screw caps
  • Cardboard box

The initial wiring and cutting of the box took more time than I figured and she started to lose interest until we got around to the top. We did this all on-the-fly, but there are plenty of tutorials (like one on Instructables) you can follow.

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Test LEDs with a Coin Cell Battery

The battery (CR2450) in my garage door sensor was getting low, so I replaced it. I’ll keep the old one in my electronics kit for LED testing, as shown in this video. Touch the longer leg (anode) of the LED to + and the shorter leg (cathode) to . Usually + is the top of the battery where the words are. Don’t worry, you won’t hurt the LED if you connect it the wrong way.