This page is dedicated to helping you boost start your vehicle quickly and safely. Here you’ll find a short video outlining the jumpstart process, from battery terminal identification to connecting sequence, starting the vehicle, and finally removing the boost cables.
Mechanics Jumpstart Tips
Jumpstarting is a simple process, but as you know, connecting the jumpers correctly is really important. Getting this wrong can cause damage to a modern vehicle’s sensitive control modules and sensors. That said, I’ve added a couple of tools below that remove the possibility of an incorrect battery hookup.
Here are a few tips to help you nail the jumpstart process like a pro:
- Check both vehicle battery locations before maneuvering the vehicles.
- Identify the battery polarity of both cars – check out this post, “Unmarked battery terminals” or check out this video.
- Check battery terminals clamps are clean and tight – loose terminals are a common cause of no-starts.
- Use top-quality jumpers cables – poor-quality jumpers cause resistance which makes the job a ton more difficult.
- Turn all consumers off – a/c, radio, heater, etc. of both vehicles before jumpstarting.
- After connecting the jumpers to both vehicles and before jumpstarting, allow the donor vehicle’s engine to idle for five or ten minutes. This helps send some charge to the flat vehicle’s battery prior to jumpstarting.
- After starting the flat vehicle, drive for at least fifteen minutes (30 min best) at highway speeds with consumers off. This helps charge the battery.
- Ideally, after a thirty-minute drive, the battery voltage should be checked, and if fully charged (12.65 v) the battery should be load tested. I’ve listed an inexpensive and easy-to-use battery test tool below.
Boost – Try boost starting from another vehicle. This will eliminate or confirm a flat faulty battery issue.
Add jumpers in sequences 1,2,3, and 4. Start flat vehicle, and while running, remove jumpers in reverse order 4,3,2 and 1. Check out the jumpstarting video here.
Flat Battery Causes
Batteries don’t go flat by themselves, and so you already know unless there’s a solid reason for the flat, i.e., (light left on, etc.), we’ll be revisiting this problem real soon, like tomorrow morning soon.
If your battery is a little weak, the end of summer is usually when you get the warning. As the temperature drops, the battery struggles to hold a charge. That said, batteries don’t like really warm ambient temperatures either and so extreme heat will also cause the battery failure rate to rise.
Having to jump-start your vehicle usually means you have an underlying, weak, and soon-to-fail battery is the most likely cause. If you have a battery tester, check the battery under load. If you don’t have a tester, bring your vehicle to a local parts shop. Most good shops are happy to load test the battery for free.
Anyhow, here are a few of the most common causes for a flat battery:
- Failing battery – batteries typically last between 3-5 years.
- Faulty alternator – alternator may not be charging the battery and or maybe draining battery power.
- Slipping alternator drive belt – drive belt or belt tensioner may require attention.
- Ignition switch left in position two (ignition on) – modern vehicles will drain the battery quickly if the ignition is left on.
- Consumer left switched on – leaving a door or trunk lid ajar overnight may be enough to drain the battery.
- Loose battery terminal connector – a loose battery terminal will prevent the battery voltage from reaching the starter motor but also prevent full alternator voltage from reaching the battery.
- Corrosion on battery terminal connector – corrosion on the terminals is common and just like loose battery terminals, it will prevent voltage flow both ways.
- Wiring circuit short – a short circuit commonly occurs when the power side of an electrical circuit is grounded. In real life, a small wire inside a wiring loom rubs through and makes contact with the chassis. This condition usually causes a fuse to blow, but not always.
- Extended crank – a mechanical issue causing an extended crank time will kill a battery over time.
- A faulty electrical component – a faulty component is a common cause of a battery drain. It is usually a poorly fitted accessory or piggyback wiring on the OBD port.
Battery corrosion – corrosion will cause resistance.
Warning – The corrosion is acid, so wear gloves and glasses. Dilute baking soda in water and pour over the corrosion to neutralize.
Below you’ll find some tools that make the whole jumpstart process easy.
This is a safe set of jumpers for those that are unsure of the jumpstart polarity. The smart jumpers employ an integrated light to indicate incorrect jumper location. In addition, the light panel lets you know the battery state of charge and how well the alternator is performing. Pic links out to Amazon.com.
The NOCO jump starter pack is a serious tool, don’t let its size fool you. This little guy fights way above its weight. Capable of starting a diesel truck engine and yet small enough to fit in your glove box. Pic links out to Amazon.com.
The NOCO genius battery charger is what’s known as a smart charger, also known as a battery maintainer or trickle charger. They are smart because they detect the battery state of charge and automatically turn it off and on as needed. Pic links out to Amazon.com.
The Topdon is an inexpensive, reliable battery tester, running alternator and battery crank tests. Pic links out to Amazon.com.
Schumacher OBD-L Memory Saver or KAM tool. Important to fit the memory tool before disconnecting the battery. Modern cars don’t like being without power. The Schumacher is easy to use with its 3 steps guided procedure. Pic links out to Amazon.com.
Battery post and terminal cleaner. Dirty terminals are a root cause of a ton of electrical issues. Stainless steel cone wire brush side for terminal cleaning and internal brush for the battery posts. Suits top and side post batteries. Pic links out to Amazon.com.
About the Author
John Cunningham is a Red Seal Qualified automotive technician with over twenty-five years of experience in the field. When he’s not writing about car repair, you’ll find him in his happy place – restoring classic cars.
May find the following links helpful:
- Beginner car maintenance page
- Car repair and troubleshooting index
- OBD fault code list
- Tools and parts page
- About the Author
- Latest Posts
John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.