Wednesday, 18 April 2018

Can You Jump Start a Car with a Motor Bike?

Can You Jump Start a Car with a Motor Bike? 


This is a common question on the web, with lots of dissipated information between you tube, forums and product reviews. So I have tried to summarise here.

In short this will work if you have a large bike and a small car. You will not be able to jump start a pick up truck with a scooter.

Its all about amps (CCA). A motor bike battery of any size will likely provide a maximum of 300 amps, but more often will be 200 amps.

A car will need 200 amps as a minimum, so the larger your bike, hopefully the larger its battery, and the better luck you will have.

Damage to Either System

The main thing to watch here is voltage. Both system should be 12v otherwise you will damage teh lower voltage one. Bear in mind that most 12V system runs at 14 - 15V (which is confusing).

The only problem I can foresee is that if after you jump start the car, the jump leads are left attached for too long, causing the car's alternator to charge the bikes battery too quickly.

Case Study 1 - Jump Start a Large Pick Up with a 250cc Bike

PROBABLY NOT - This doesn't doesn't work. A large diesel engine will require 500 - 600 amps plus current to start, and a small motor cycle battery will not provide enough current.

Case Study 2 - Jump Start a Small Petrol Car (1.5l) with a Power Bike (900cc)

PROBABLY YES - This would likely work OK, as the two systems are more closely matched in terms of their current requirements at start up. 

A Note on Battery Chemistry

The above applies for all types of Lead Acid battery which are the norm in most bikes and cars. However some upgrade batteries for Motor Bikes use lithium technology. The graph below shows that  lithium batteries but out more amps for their size than lead acid equivalent. 


The (red) line above shows lithium performance, vs lead acid performance (blue). So we can see that whilst a small lead acid battery will not get above 300 amps, a lithium battery can supply up to 1000 amps. Which would be plenty for even a moderate diesel engine start up.

Illustrator Devon

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