If the charger has a flashing red LED, it’s typically bad news. The battery won’t charge, which indicates it’s probly dead and in need of an immediate resurrection.
My Hikoki 18V battery did this to me lately, and initially, I had no idea why. I thought it was hosed for good. But it wasn’t; it just needed a jump start.
Alternative Power Supply Method
The most common fix involve another battery pack. Because the dead cell is still too low a voltage, you want one that’s already charged up; either a Hikoki or any other 18‑20 V will do. The charger can’t see the pack when it’s like that. Plugging power right to the terminals fools it into believing everything is OK and I’ve had great luck doing it that way.
First, you want to make sure that you have the right terminals connected. Connect negative to negative and positive to positive. This prevents any immediate issues. It also keeps your short circuit from ruining anything in the process. It’s dangerous and it will mess up your gear. So be careful here, take your time and line the contact up properly before moving on. It is worth taking extra time here.
To share voltage between packs, I laid my old pack down next to a good pack and bridged it with some basic wires. Make sure you keep it all tight. That’s important for safety and for keeping everything stable while you make the connection. Red to red and black to black. Don’t allow your wires to contact each other but maintain the connection.
Wait about 15 seconds, and I did. No smoke, no foul, and the battery perked right back up. No bad odor, no melted wires. You will notice a slow increase in voltage. Be careful not to let it get too hot. If it does emit smoke, then you has got some problems and it’s time to unplug.
A third-party 18-20 V pack should also work for this trick if you don’t have an extra Hikoki pack laying around. Heck, I even tried a DeWalt 20V battery and it worked like a champ for this very reason. Brand loyalty goes out the window when compatibility with your tool is the only thing on the line; just pay attention to the voltage range. Whatever you’ve got in that range will help revive the poor dead guy.
As always, mark the B- and B+ terminals on your donor pack and hook it up accordingly. Use alligator clips or something else suitable; whatever you use, make sure that positive connects to positive and negative connects to negative. Why? Because if the connections aren’t tight, there will be a voltage drop which wastes precious time while reviving. Make sure everything is secure.
Wait about fifteen seconds before disconnecting the donor battery and watch carefully during that time. If something heats up, disconnect it, but mine took the charge just fine on the test battery. After that the LED stopped behaving as it was no longer in need of preparation and was ready to be charged properley. A simple trick but it made all the difference.
And finally, there’s also the DC power supply route, but this requires some equipment. For my example, I’m using a WANPTEK. To use it, I adjusted its voltage output to 18 volts. Keep the current limited to an amp or less; anything higher will risk damaging lithium cells. That said, with this you have a controlled way to reset the battery.
Connect one end of the negative wire to the negative battery terminal and the other end of the positive wire to the positive battery terminal. Make sure you check for proper polarity; it’s an easy mistake to make and a very expensive one. While I was working on it my power supply read steadily with no spikes or excessive current draw.
Leave it connected long enough for the internal management chip to reboot (maybe 15 seconds). While you wait, you’ll notice that the voltage has settled in and is stable. At least, that’s what happened with my battery, which immediately reacted to the power being fed to it.
Success! Just like it was supposed of.
Once you have tried one of the above tests then hook the revived pack back on to your charging base and see if it starts. If you get a steady red light, the charger is working correctly and will work with both Hitachi and Hikoki chargers. I can confirm that for me and it totally removed the flashing error.
All in all this was a quick fix and saved me from having to purchase some new batterys for my revive experiment. If you still have old packs lying around, don’t throw them away just yet. Give these three simple resets a try. You’ll be happy with how well they may bring your tools back to life. It is definitely worth trying before you toss them.
