Is jump-starting a lawnmower a wise idea? Find out.

Dear Car Talk

Dear Car Talk | Aug 01, 2010

Dear Tom and Ray:

This question isn't about a specific car, but is a general equipment question. Of course, during the winter, my riding lawn mower has gotten no driving time, and thus the battery has died. I was wondering if it is safe to jump-start the lawn mower with my car, and if you have any tips on how to do it. Thanks!

-- Cameron

RAY: Carefully.

TOM: Right. Every year we hear about some moron who doesn't know what he's doing and blinds himself in a battery explosion. So if you're planning to be that moron this year, Cameron, stop reading right now.

RAY: Seriously, if you don't know what you're doing, ask someone who does to help you.

TOM: But if you're technically adept, this is a perfectly good solution. Your car battery is 12 volts. Most riding mowers have 12-volt batteries, too. Of course, you need to check to be sure.

RAY: If your mower uses a 12-volt battery, use the jumper cables as you would when starting another car. Hook the positive cable to the positive terminal of the car battery. Then connect the other end of that cable to the positive terminal of the mower battery.

TOM: Then connect the negative cable to the car battery's negative terminal, and the other end to the frame of the mower. They come off in exactly the opposite order.

RAY: Because the battery on a riding mower often is buried down deep underneath the seat, be especially careful not to allow any part of the positive clamp or the exposed cable to touch the frame. Otherwise, you may end up with a hairdo like my brother's.

TOM: Or a hairline like my brother's.

RAY: Finally, make sure the car's engine is turned off. The alternator in your car produces way too many amps for the lawn mower, so you don't want your automobile engine to charge the lawn mower's battery. You want it to provide the mower's battery with just enough juice to start the mower's engine. Once the engine is started, the mower's own generator will charge the battery.

TOM: Jump-starting a riding mower from a car or truck is a trick that landscapers use all the time. But there are several even better solutions for homeowners, Cameron.

RAY: One option is a "jump pack." That costs 50 or 60 bucks. It's essentially a plastic-encased 12-volt battery with jumper cables already attached to it. You plug it into a wall socket once in a while to keep it charged, and when you need to jump-start a car or a mower, you tote it out and clamp the built-in cables to the dead battery.

TOM: Another great option is a trickle charger. You can get a cheap one for about 40 bucks. You can use it on your car or mower batteries. But in this particular case, you could hook it up to the mower the day before the first big spring cut. Then go to sleep, and you'll be ready to hack down your wife's prized tulips first thing the next morning.

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