What happens after a battery boost (car jump start)?

Sparky Express Roadside Assistance

There are two types of battery boosts

When asking someone for a boost (jump start) for your vehicle, it's because the battery is dead. Vehicle batteries "die" for two main reasons:

  1. You have accidentally discharged the battery by leaving the lights or something else running inside your vehicle.
  2. Your car battery must be replaced.

Scenario "1" above is pretty straight forward: you'll get a battery boost, the engine will start and the alternator will re-charge your battery. However, if your car battery must be replaced, it usually "dies" for no reason. You drive the car to your parking spot, everything is off, but next morning (or few hours later) the car won't start. How can you tell?

As a battery boost roadside assistance provider, we see this every day. We jump start someone's car, we make a recommendation of how long the engine should run for so the battery can charge, but we always measure the voltage of the battery before we boost it. We also test the battery with the engine running after the car has been jump started, an that will show us if the alternator is charging and also the condition of the battery. But the battery health status is not always accurate when you test a battery with the engine running. So there are two ways to tell if your car battery is still ok:

  1. If you leave the car running for the period of time recommended by us after the boost, turn off the vehicle and see if the car starts again, If it does, your battery might still be good.
  2. If it doesn't start it clear as daylight that the battery is done and you need a new one.

When we give you a boost, we just assist you to start the car. As a rule of thumb, the car batteries must be tested when charged, but this is not possible when we assist you with a battery boost, because we won't be there 1hr or even more later, to test the battery. The accuracy of a battery test with the engine running is about 60% accurate reading.

We always recommend that our customers turn off the vehicle in a location where they can leave the car for a while if the car doesn't start again (when battery needs to be replaced). Recently, after the pandemic, our customers haven't been driving their vehicles a lot due to lockdowns, and in at least 75% of the cases, the batteries had to be replaced. If you didn't drive the car for a long time, your vehicle might not start again after a battery boost, so you will need a new car battery installed.

We can jump start any vehicle (provide a battery boost), we will test your battery and alternator and provide advice. But we cannot guarantee that your vehicle will start that after the battery charging period has elapsed.