While prevailing misconceptions might have you thinking otherwise, it's entirely possible to jump start a dead motorcycle using a car's battery, provided they are of the same voltage rating. Since most car and motorcycle batteries are of the 12V lead-acid variety, it's perfectly fine to hook them up for a quick boost, according to RevZilla's latest YouTube upload, and the procedure isn't any different from what you're used to. The misconception that the car's larger battery might cook the motorcycle's smaller battery for whatever reason is nothing more than, well, a misconception.
Start by locating the battery (you'd usually find it under the seat or behind the motorcycle's side panels) and inspecting it for any kind of damage. As is always the case with jump-starting, before you begin, it's important that you connect the jumper cables in the right order — you really don't want to mess that up. Park the car with the donor battery close to the motorcycle. You may choose to keep the car running or not, but if you suspect the donor battery isn't quite as healthy as you'd have thought, RevZilla recommends you let the car idle.
Connect the red clamp to the dead battery's positive terminal (+) and then clamp its other end on the positive terminal of the donor. Next, take one end of the black cable and connect it to the donor's negative terminal (-), after which secure the other end to any unpainted metal surface on the motorcycle to complete the circuit. Let it sit for 30 to 60 seconds, and then crank the engine. If it starts right away, great. But if it doesn't, don't keep pushing the starter button for too long. Not only will that damage your bike, but it may also compromise the donor's electrical system.
What should you do next?
Once everything is up and running, disconnect the cables in the reverse order. So, the black clamp from the frame/grounding point first, followed by the donor's negative terminal, then the donor's positive, and finally the red clamp from the motorcycle's positive terminal. Of course, you can still use a portable jumper pack if you don't want to do things old-school.
The next question is: How long should you keep the engine running after a jump start? RevZilla recommends riding the motorcycle for at least 20 minutes to let the battery recover some of its lost charge. Later, leave it on a Battery Tender so that it can fully recharge. Before that, however, you might want to check its resting voltage to see whether the lead-acid battery is ready for a replacement or not. After the short 20-minute ride, let the battery sit for an hour or so. If the multimeter reading shows between 12.4 and 12.6V, the battery is likely fine and simply needs a recharge. If the reading is between 12 and 12.3V, the battery is noticeably discharged, and if it's 11.9 or below, it might be time for a new battery, especially if you notice its cranking voltage is below 9.6V.
But what if you have a lithium-ion battery in your motorcycle? Is the jump-starting sequence different for lithium-ion chemistry? Generally, unless the battery has a built-in BMS (battery management system) and it's not in a "sleep mode" (with a resting voltage above 10V), the procedure is no different. However, RevZilla recommends that you read the OEM's instruction manual, as lithium-based designs can vary across the board.
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