Thursday, April 22, 2010

The Three Mowers; or An Open Letter to Black & Decker: Part 1

With my history of planes, tractors, and automobiles, there can be no doubt that I am a regular user of internal combustion engines. That said, I am currently stationed in southern California; and when in Rome . . . So, shortly after getting the house last year, I acquired a Black & Decker cordless lawnmower.

Black & Decker CMM1200 24-volt rechargeable mower.
Shown here with its rear bag, although I use it in mulching mode.

What I like about it is that it is relatively quiet, and is no effort to start. Although it has almost enough battery capacity to do the entire yard if I mow really quickly and don't go more than a week between cuttings, my gripes are primarily centered around the connection point for the charger and, to a lesser extent, the operator switch.

The charger plugs into a jack in the control box on the mower's handle. This same jack is also used for the mower's key, as seen here:

The orange key plugged in: The mower is ready to go. Remove the key, and it won't run.
In the manual, B & D specifically suggests that you shouldn't do what I've done here, namely attach the key to the mower. Having misplaced any number of keys and drill chuck wrenches, I don't see not doing something like this. In a household with children, however, this would be a very bad idea.

Here's the business end of the key. As far as I can tell, it encloses a jumper wire that connects the two contacts, thus closing the power circuit.

And here's the empty jack. The key plugs into the two separate light grey connectors, left and right, thereby covering the charger's triple-wire plug in the center. So you can mow or charge, but you can't do both at once. The key is ambidextrous: it can be plugged in either way.

The charger, however, is not. It has to be inserted the correct way, or else no charging will take place. This is a head-on look at the charger plug. If you look very closely, you can see that the prong on the right has the upper corners cut off, as compared to the square prongs, left and center. This is intended to make it only plug-in the correct way. It doesn't work. Even when it is plugged in correctly, it's not a secure fit; it's easily jostled loose.

This close up of the jack shows how the charger connector is shaped to only accept the plug in the correct orientation. It's hard to see, even in this close up, which was shot from below. It's almost impossible to see from any normal position.

Another shot of the charger plug, this time with it flipped over: the odd-shaped prong is now on the left. This shot also shows how I marked the plug with yellow paint so I can easily tell which way to hold it for insertion into the jack, like so:

The charger, plugged in correctly. Even with the yellow paint, it's rather fiddly to get connected. Thanks to this, I expect that this will probably become a failure-prone part of the mower/charger system.

The switch to make the mower operate incorporates a "dead man" safety: When the operator lets go, the mower stops almost instantly. All lawnmowers are required to have this feature nowadays, regardless of power source. I wish my brother's bulldozer had had one a few years ago. The switch is operated by an orange lever attached to the control box on the mower's handle:

The orange switch lever in the Off position. It's spring-loaded to return to this position if the operator lets go of it. To use the mower, you first have to unplug the charger, then insert the key, as described earlier. The operator then extracts the orange lever from it's resting position, and holds it against the handle while using the mower:

Thanks to the shape of the housing, getting access to the lever requires a funny finger dance.
One finger pushes the lever out of its slot . . .

And another finger snags it . . .

And then the lever is held against the handle by the right hand while mowing. The finger dance is sort of tricky to figure out at first, but becomes smoother with practice.
Not a serious deficit, compared to the hassle of some other mowers I've had, but this issue will reappear in the next part.

With all the photos, this has gotten longer than I expected, so I'll break here. In Part 2, I'll describe the 'new and improved' version.


  1. does the middle prong have an electrical sleeve inside - just like the two on the sides? I think my son yanked on the mower when it was plugged in and now it won't charge. I noticed that the middle prong does not have a metal sleeve inside, but I can't tell if that is how it is supposed to be.

    1. If you mean the flat plug from the charger (seen in photos 5, 7, 8), the answer is yes -- each prong has a metal ring or sleeve inside; the cord that runs between the charger and the mower has three wires in it. I'm sorry to hear that you're having trouble with yours. Your comment has just made me realize that I've had this mower for four years now!