Can A Motorcycle Battery Jump Start A Car?

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If your car battery has low voltage and you need a quick jump start to get back on the road so you can get to the parts store or back to your house, you may wonder if you can you use a motorcycle battery to start your car.  I have been asked this question many times, and I got so curious after a while that I tried it!

So, can a motorcycle battery jump start a car? A motorcycle battery can jump start a car if the motorcycle is running.  Connect the positive and negative leads of the jumper cables to both batteries.  Have one person rev the motorcycle to around 4000 rpm’s and have the second person try to start the car.

There are a few other things that will aid in starting the car with the motorcycle battery like the size of the car engine, how many cold cranking amps the motorcycle battery has, the temperature of the car engine, and trying to start the car in short bursts instead of long ones.

If you’re trying to start a car with a battery that has been removed from a motorcycle then it will probably work under certain circumstances, such as if the engine is warm.  The smaller the car engine the better chance it has starting with the motorcycle battery.

How To Jumpstart A Car Using A Motorcycle Battery

When you try to start the car with the motorcycle battery, make sure the motorcycle is running to have the best possible chance of starting the car. There is much more available current to flow to the car battery if the motorcycle is running.

It will also help to have someone assist you during this process.  The first person should rev the motorcycle to around 4,000 rpm’s while the motorcycle is in neutral and sustain it to that rpm.  Have the second person try and crank the car; with good timing and a little bit of luck, you should be able to get the car started.

There are many people out there who say that revving the motorcycle won’t help, but they’re misled. It will make actually make a big difference because you’ll be creating a higher amount of current, and with the jumper cables hooked up correctly, that excess current will be transferred to the car battery and help start the car.

Some people don’t understand that a motorcycle battery is less powerful than a car battery which is why revving the motorcycle to get the higher current to the car battery is important.

If you happen to be stuck with just a motorcycle battery but no motorcycle, you’re in luck because it’s still possible to jump start a car battery from an isolated motorcycle battery if it is warm outside. If it’s too cold then you might only be able to start a small engine.

If it is fully charged, a motorcycle battery will have around 12.6 volts when the motorcycle is shut off (or not connected to the motorcycle at all) which could be enough to jump start the car battery.  

But you’ll have better luck with a motorcycle battery that’s connected to a motorcycle; while it’s running, the motorcycle battery and charging system will have between 13.5-15 volts, which makes a huge difference when trying to start a second vehicle from it.

Cold Cranking Amps Required To Jump Start A Car From A Motorcycle Battery

Every automotive battery that has the intended purpose of powering a vehicle has a specification called the Cold Cranking Amps or CCA.  Cold cranking amps is a measurement of the power output of that battery at 0°F for 30 seconds.  Car batteries are usually rated with higher CCA’s because their engines are bigger and they need more amps to turn the crankshaft.

Every car has a specification in its owners manual of how many CCA’s the battery should have in order to start the car, but that’s for regular year-round use.  It is possible that for a one-time use you can get away with having less CCA’s than what is listed.

The average car battery is going to have between 200-700 cold cranking amps depending on engine size.  But be sure that when you buy a replacement battery you get one that has equal or greater CCA’s than the manufacturer recommends, or you might have another dead battery sooner than you would like.

Smaller car batteries generally take between 200-400 CCA while V8’s with larger batteries are closer to the 700 CCA range.  Buying a battery with much higher CCA than your original battery had is just fine, just make sure it doesn’t have less CCA’s than the original battery.

The average motorcycle has between 200 – 400 CCA as well which is why it is completely possible to jump start a car using a motorcycle battery. This is also why you’ll have better luck with jump starting smaller cars compared to bigger cars, though jump starting bigger cars is completely possible using a motorcycle battery.

Number Of Cylinders On The Car Vs. A Motorcycle

The number of cylinders of the car that you’re trying to start makes a huge difference on whether you’ll be able to crank it over using the battery from a motorcycle.  A big V8 is going to take about twice as much force to turn over as a small 4 cylinder is.

If there are only 4 pistons that you have to push up and down along the cylinder walls then you have a pretty good chance of starting the car.  The less friction from the pistons the better if trying to use a motorcycle battery.

The number of cylinders of your motorcycle has will have no bearing on whether it can start the car.  The only part of the motorcycle that makes any difference in whether or not it can start the car is the stator.

The motorcycle stator outputs a certain voltage and current to recharge its own battery, so that’s the current that the car will see when you put the jumper cables on. The bigger your stator, the better chance you have at starting the car. Click here to learn more from an article I wrote that discusses in more detail what a stator does

From my experience, I have never seen a motorcycle battery successfully start a V8 engine.  I have seen it work on a 4 cylinder though. A motorcycle battery would have to have pretty high cold cranking amps in order to produce enough current to push 8 pistons up and down.

The Temperature Of The Car Engine

It should come as no surprise that a warmer car engine will start easier than a cold engine.  The warmer engine will start easier because of friction. Colder engines have more friction and take a higher amount of current to the starter in order to turn over.

If the car engine is warm then the fuel in the lines will be somewhat preheated and will combust easier.  This will assist in starting the car with as little current from the motorcycle battery as possible.

The only way I could see a motorcycle battery starting a large engine is if it was on a really hot day.  Otherwise, I think you would only be able to start smaller car engines if it’s cold outside.

Don’t Make This A Regular Habit

Motorcycle batteries were intended to start motorcycles, not cars.  There are a lot less plates inside a motorcycle battery because they don’t have to push out as much current in order to start a motorcycle engine.  

Trying to start a car engine with a motorcycle battery isn’t good for the motorcycle battery because it draws a much larger amount of current than it was intended to.  That quick discharge of a high volume of current isn’t healthy for a small battery, especially because motorcycle batteries aren’t intended for deep cycling.

This is only something that should be done in an emergency.  Afterwards you need to go to the auto parts store and get the correct battery for your car.  Using this method won’t really create any safety risks, it’s just not advised for the long-term health of the motorcycle battery.

Turn The Car Engine Over In Small Bursts

One key point to remember when you’re trying to start your car with a motorcycle battery is to try and start the car in short bursts. While trying to start the car, don’t hold the key and crank for a long time, you’ll discharge all the current very quickly.

Turn the key in short bursts and if it doesn’t start right up like it normally does then let it sit for a few more minutes while revving the motorcycle engine and try again.  I’ve done it and seen it work firsthand.

Related Questions

Can a car battery jump start a motorcycle?  A running car can absolutely jump start a motorcycle.  I have done this dozens of times myself and it works great.  Because the motorcycle battery usually is tucked up by the frame be sure you don’t touch the positive terminal to the motorcycle frame or you’ll get quite a shock and some sparks.

How long can a motorcycle sit before the battery dies?  The average motorcycle battery will die after 2-4 months without running.  Newer batteries can last longer with an average of 3-5 months. For more information on this topic see our article about batteries here.

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