Car Jump Starter Use and Safety

How to Safely Use a Car Jump Starter

car jump starter safety
Car jump starters are totally safe to use, but you have to follow the same rules as normal jump starting. Paul Viant / Caiaimage / Getty

Question: How do you use a car jump starter, and is it safe?

“I’ve heard that it isn’t safe to jump start my car, but I’m really afraid of getting stuck somewhere at night with a dead battery and having to sit around waiting for a tow. Is it really dangerous to jump start some cars? And what about those jump starters you can buy? Do you think it's safe to use a car jump starter?”

Answer:

Although there is a certain level of risk involved in jump starting a car, you can minimize it to almost nothing if you follow the correct procedures. Of course, there are a few instances where jump starting really is a bad idea. For instance, many hybrid vehicles have a 12 volt “auxiliary” battery that can be jump started if it goes dead, but attempting to provide a jump start from it may drain it to the point where the vehicle won’t start. If you drive a hybrid, that may be why you were told that it’s not “safe” to jump start your car.

There is another potential jump starting issue that’s associated with vehicles that have batteries that are difficult to access. Some of these vehicles have a remote positive charge/jump start terminal, and others require you to do some work to access the battery. In cases where a remote terminal isn’t available, it’s typically a bad idea (and potentially even unsafe) to jump the vehicle by using the positive terminal on the fuse box, or any other connection that isn’t actually the battery.

As far as portable car jump starters are concerned, they’re perfectly safe with the one caveat that you still have to follow all of the correct procedures. You still need to hook a car jump starter up in the right order and in the right places, and you can only use one to jump start a traditional car battery or the auxiliary 12V battery in a hybrid, but not the high voltage batteries in a hybrid. Of course, using a jump box presents a unique danger in that you have to be careful about where you set the device while it's hooked up.

Safely Using a Portable Car Jump Starter

There are two main dangers that are commonly associated with jump starting a car: damaging delicate components in the electrical system, and blowing up the battery. Both of these situations can result from crossing the positive and negative cables or shorting them out if you’re jumping one car’s dead battery with the good battery from another car. Of course, if you’re using a portable car jump starter, the latter isn’t going to be an issue.

It is still possible for your battery to blow up if you’re using a car jump starter, which is why it’s so important to hook the cables up right. If your battery is accessible, then you’ll want to hook up the positive jump starter cable to the positive battery terminal first. Then you’ll want to locate a clean, unpainted part of the car’s body, frame, or engine, which isn’t in close proximity to:

  1. moving parts like the fan or accessory belts
  2. the battery itself.

The main reason that you don’t want to hook up your car jump starter directly to the negative battery terminal is that doing so typically creates sparks. If your battery isn’t working due to having been overcharged, or due to an internal fault, it may be full of flammable vapors, which can seep out even if the battery is sealed. Sparks can ignite these vapors, which can cause the battery to explode, which will then shower you with acid. Although this isn’t incredibly common, it can cause serious injuries, and according to The Straight Dope, it may happen to somewhere between 6,000 and 10,000 motorists each year.

When Is It Unsafe to Use a Car Jump Starter?

If you drive a hybrid, then it’s typically safe to use a car jump starter (or a regular jump start) on the auxiliary battery. These auxiliary batteries are nominally 12V, just like regular car batteries, but they’re typically much smaller. That means the main danger associated with hybrids and jump starting is that if you try to use the auxiliary battery in your hybrid to jump someone else’s car, you may end up depleting it to the point where your own vehicle won’t start. It also means that it’s perfectly safe to use a jump starter or portable power pack on that type of battery.

The other type of battery contained in most hybrids uses a different, much higher voltage than the 12V used by conventional cars and trucks. That means you can’t jump start the main batteries in your hybrid with a car jump starter or jumper cables and another car.

If your car has a battery that’s difficult to access, then it may or may not be safe to use a car jump starter. It’s perfectly safe to use one if your vehicle has a remote positive terminal that’s designed for charging and jump starting, but you should never hook up the positive clamp of your portable jump starter to the fuse box or anything else that isn’t actually meant for that purpose. In some cases, the only safe way to use a portable jump starter is to gain access to the battery and connect directly to the positive terminal.

Of course, depending on where the battery is located, it may then be impossible to make connections to both the positive battery terminal and a clean, unpainted section of the body or frame. This can make it difficult to use a jump box if the included cables are too short. In this type of situation, you may have to use actual jumper cables or a jump starter that has longer cables.