Does Revving Your Engine Really Jump A Car Battery Faster?

Many drivers will have experienced the hassle of a flat battery and had to jump-start it to get themselves back on the road. Friends or relatives helping jump-start said battery might have also been keen to dispense their advice on how best to get it started as quickly as possible, with one common piece of advice being to rev the engine of the car that's doing the jump-starting to increase the charge that's being delivered.

Like many pieces of passed-down car advice, the answer to whether this is useful isn't a definite yes or no. However, Popular Mechanics tested the theory for themselves and found that revving their donor car higher only resulted in a voltage increase of a few hundredths of a volt. In most cases, such a small increase won't make much of a difference when jumping another car. As such, while you could attempt it as a last-ditch effort if the conventional jump-starting method hasn't been successful, it isn't likely to be the deciding factor on whether you'll be able to jump a car.

If you still can't start the car after trying to jump-start it, then it's time to buy a replacement battery. You can potentially replace the battery yourself, since it only requires basic tools, but if you're not confident, then it's easiest to let someone fit it for you. There are multiple types of car batteries, each varying slightly in their design and use, so you'll need to make sure you pick the correct type for your car. Some modern cars will need an AGM battery instead of a standard one, while others will happily take a cheaper traditional battery.

If you manage to start the car by jumping it, then it's a good idea to drive it for at least half an hour to charge up the battery. Otherwise, you may need to jump-start it again next time. This isn't a definitive figure, and different types of cars might take more or less time to recharge their batteries, but it should be enough for most cars. If you take the car for a longer drive and the battery is flat again the next time you try to start it, the battery likely needs replacing anyway. You should also be on the lookout for other telltale signs that the battery is on its way out, such as dimming headlights or a rotten egg smell, which indicates that the battery is leaking.