Jump Starter Advice

Does Battery Size Matter When Jumping a Car?

Have you ever wondered if battery size matters when jump starting a car? It’s a pretty important thing to be familiar with, so let’s talk about this issue right now.

Jump Starting a Car With Another Car

You might be wondering if you can use a little Mini Cooper to jump start your massive Cadillac Escalade SUV.

You might also be wondering if this is possible to do the other way around, or in other words, using the much larger car and battery to jump start the smaller vehicle.

What it really comes down to is the car which is doing the jumping, more so than the car that is receiving the charge. If the batteries are not of the equal size or power rating, serious damage can occur to the vehicles, especially the batteries.


Jumping Starting a Larger Battery With a Smaller One

Now, using a smaller car battery to jump start a larger one is definitely possible, although it is going to take a while. For instance, if you have a 300 amp battery in your small car, and you are looking to jump start an SUV that requires 600 amps to start, you are going to have to wait a while. You can make all of the connections with the cables as you normally would, but you cannot start the larger car right away.

This is because the smaller battery needs to run for a while, with the smaller car’s engine running. This way, the larger battery, the one being jumped, can take some time to build up a charge. Once this charge has been built up, the larger car battery may then start. The bigger the difference is between the two, the longer the larger battery will take to build up a charge large enough to turn over the engine. However, this does run the risk of draining the smaller battery, in which case you will then need to jump that next time.

Jumping a Smaller Battery With a Larger One

This is where things can get a bit tricky because here the battery size does matter. If you are trying to use a 1,000 amp pickup truck battery to jump start a much smaller 300 amp battery, you are going to have some problems. Of course the larger battery technically has more than enough power running through it to jump start the much smaller battery. However, the difference in volts and amps matters here.

Simply put, if the battery doing the jumping is too large compared to the battery being jumped, you could overload the smaller battery. The result is going to be a lot of sparks, a battery that might explode, and a car that could very well be set on fire.

Simply put, it is possible to jump start a big battery with a small one, and with relative safety, but going the other way is not recommended, as you might overload the smaller battery to the point of damage, and possibly even a fire.

Jump Starting a Car With a Portable Jump Starter

It is of course also possible to jump start a car using a portable jump starter, and in fact, this is what portable jump starters are intended for. These are very useful tools to have around if you are worried about your car battery not having enough juice to cause the engine to turn over. They are simply little tools which feature a battery that you can connect to your car battery for charging and jumping. It is more or less the same as using another car battery to do it, but instead of needing a whole other car, you can just use one little portable device.

When it comes to battery size, you will notice that portable car battery jumpers will be rated for a specific battery size, and this can have some leeway. For instance, you could get a small portable jump starter that only puts out 300 amps, which is a onetime thing. In other words, with a 300 amp portable jump starter, you will not be able to start a 600 amp battery.

Now, the beauty here is that many newer models allow you to adjust the amount of power being provided to the car battery. So, if you have a portable jumper rated for up to 1,000 amps, you should be able to turn it down to a level low enough to jump a 300 amp battery without blowing it up.


So, when all is said and done, when jump starting a car, the battery size does matter.

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