How To Revive a “Dead” Cordless Mower

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by Tim Fulton on August 1, 2011

This entry is part 1 of 2 in the series Reviving a dead cordless mower

One of our forum members, MetroMPG, recently picked up a Black & Decker battery powered cordless electric push mower. He found the mower during a town wide “Community Treasure Hunt” day where people put unwanted things to the curb to see if anyone else wants them. His mower came with a big “DOES NOT WORK” sign attached to it. Thankfully, MetroMPG knows a thing or two about electric dodads being an owner of a home built electric car. So, he decided to pick it up and see if it couldn’t be salvaged.

Knowing that these mowers are relatively simple electric devices, MetroMPG knew the problem was likely one of four things:

  • A dead battery
  • Bad wiring or a dead switch
  • A dead charger
  • Worst case a dead motor

mower

The first thing he tested once getting it home was the charger. To do this, he checked the voltage output with a multimeter. Everything seemed in check with the charger. It showed a 15.5V output just like the label says it should.

mower

The next thing on the list to check was the battery. He put the multimeter on it and it showed 11.0V. A fully charged battery should show about 12.7V. So he either had a very discharged battery, or a dead one. To attempt an easy fix he first tried charging it up. Once it was done charging, he put it in the mower and threw the power switch. The voltage of the battery immediately dropped to 4V. That is a perfect indication of a dead battery. He then tried hooking up a car battery to the mower to verify the problem. The mower spun to life just like it should have with a good battery.

If the problem would have been a bad switch or wiring, you could check that by connecting power directly to the motor leads. If it spun up, you know you have a short along the way somewhere. At the same time, you would know if the motor was bad because it would make nasty noise or wouldn’t spin at all.

If you have some other problem, feel free to post on our forum We would be happy to help you figure out what is wrong.

Next week, we’ll go over how MetroMPG fixed up the mower to usable condition. To get the full scoop now check out MetroMPG’s forum thread.

{ 1 comment }

1 wogga June 7, 2012 at 9:20 am

I have that mower or a similar one. For anyone considering a rechargeable mower, remember to keep the mower charged all the time (if it’s lead-acid battery, not Li-Ion) including winter. Most of these units have smart chargers (even this one) and drop the charge rate down to a trickle when the battery is full. Or, you can use a solar panel on it in the winter with some units, like this one. My battery is now about 6 years old, a pretty good age and is getting tired. I’m experimenting with a ‘desulfating trickle charger’ to see if I can get a bit more life out of it, but replacing at/after 5 years for about $100 is expected.

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