Ask MO Anything: Jumpstarting A Motorcycle From A Car

Dear MOby,

With my state softening the restrictions of the Coronavirus lockdown, I decided to get my bike ready for a weekend spin. But all I got when I turned on my bike and pressed the starter was a click-click. Yeah, I know I should have a smart charger, but I’m cheap. Is it safe to jumpstart my motorcycle from my car?

Powerless in Piedmont,

Sparky


Dear Sparky,

You’re right that you should have a battery charger. They really aren’t that expensive when you consider how much longer you can make your battery last when using one regularly. You’ve got a spare $20, don’t you? Here’s our handy Battery Charger Buyer’s Guide. It should have what you need for future motorcycle storage. 

If you use a smart battery charger, your motorcycle’s battery will last longer, and you’ll never hear the dreaded click-click, like our friend Sparky.

For years, we were told that you should never jump a motorcycle battery from a car battery because they are bigger and pack a high amperage wallop that could damage the delicate moto-battery. Well, in recent years, I began to feel that this was…what’s the technical term…hooey. 

The advent and popularity of the compact lithium battery boosters made me suspect as much. After all, we’d have heard by now if these high-amperage batteries were blowing up motorcycles during jumpstarts. Still, I decided to poke around and ask some industry friends about this. 

Take an extra 30 seconds to connect your battery to a charger after you ride. The life you save could be your battery’s.

Yuasa, which is the biggest motorcycle battery manufacturer we know of, says on its website: “Motorcycle batteries can be jump started from another motorcycle, car battery, or portable battery jump starter.” Well, that’s good for the heavy, old lead-acid batteries. What about those racy lithium batteries? According to Jason Levitt, Owner of Full Spectrum Power, in my Lithium Motorcycle Batteries: Myths VS Realities article:

Can you safely jump start a lithium battery? That depends on whether the battery has a BMS [Battery Monitoring System]. Don’t hook it up to a running vehicle. Instead, hook it to another battery. Race teams do this by using a booster battery system to start the bike, which allows them to use an extremely small battery on the bike for when the engine is running. When jump-starting a lithium battery, be sure to connect the booster battery in parallel [as described below]. Connecting them in series will make it 24 volts, and the BMS will trigger its protection. Also, in cold weather, you should follow the same startup process before you hit the button on the jump starter. Connect the booster battery for a few minutes to wake up the lithium battery on the motorcycle.

Every motorcycle garage should have a set of jumper cables, just in case.

So, the biggest problem with jumpstarting a motorcycle from a car battery will likely be having the right sized jumper cables. As bikes get packaged ever more tightly, there’s less room to fit those big honkin’ automotive battery clips into the confined space. You may want to invest in a set of motorcycle jumper cables.

For maximum safety, you want to follow the directions for hooking up jumper cables below while making sure not to touch the connectors to each other and creating a spark. One of the byproducts of charging a lead-acid battery is explosive hydrogen gas. Now, with firm resolve, press ahead!

If you’re unsure of where to connect the negative lead on the dead bike, look for a place on the engine where other cables are bolted down, like this starter motor.

The proper steps for jumpstarting a motorcycle are:

  1. Make sure the ignitions of both vehicles are off.
  2. Connect the red lead to the good battery’s positive terminal.
  3. Connect the other red lead to the dead battery’s positive terminal.
  4. Connect the black lead to the good battery’s negative terminal.
  5. Connect the other black lead to a grounded, unpainted metal piece on the dead motorcycle’s engine or frame.
  6. There is no need to start the engine of the vehicle with the good battery.
  7. Start the motorcycle with the dead battery and let it run, while you carefully disconnect the cable connectors in the reverse order.
  8. Now, take your motorcycle for an hour-long ride.

And you really should buy a battery charger.

Battery Charger Buyer’s Guide


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Direct your motorcycle-related questions to AskMoAnything@motorcycle.com, though some say we’re better at non-motorcycle-related ones…

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