Buying guide for Best jump-starters

A traditional jump-starter combines a pair of jumper cables and another car for the times when your vehicle’s battery dies. Compared to this old alternative, contemporary jump-starters are small and portable enough to keep out of the way until those unexpected emergencies, meaning they are a smart investment to stay safe and prepared.

The right jump-starter depends on the type of vehicle you drive and its engine. Since smaller vehicles will require less current for a jump-start, you can choose something with a lower power level and smaller footprint. SUVs and trucks, on the other hand, will require more power to get up and running. This will increase the size and price of the jump-starter depending on the battery type.

You shouldn't crank your motor for more than a few seconds with the jump-starter attached. You should also wait 15 to 30 seconds between attempts. Follow manufacturer's instructions precisely, or you could cause permanent damage.

What is a jump-starter?

There are three ways to get juice into a flat battery:

• A battery charger that you plug into the household electrical supply. Some can give a boost in half an hour or so that might get your car started. Generally, they provide a trickle charge over 12 to 24 hours. They work fine, but they're slow.

• Jumper cables consist of a bunch of wires wrapped in an insulating rubber or plastic sheath, with crocodile clips on each end. Cheap, simple, and can be very effective. The drawback is that you need another vehicle to piggyback off of. Even then, starting isn't guaranteed. If that vehicle is smaller or its battery isn't in top condition, it might not provide enough current.

• Jump-starters, for all their apparent complexity, are basically quite simple. A powerful battery wrapped in a case, with jumper cables attached. They provide instant current without the need for a donor vehicle. You can start your car or truck yourself in just a few minutes.

Our team looks for versatile jump starters when compiling a recommendation list. For example, jump starters with built-in air compressors tend to capture our attention.

A jump starter must provide an adequate charge to restart a flat car battery. We research jump starters to find those that provide the best charge.

Strong terminal clamps are advantageous on a jump starter because they maximize charging efficiency. We investigate the terminal clamps before recommending a jump starter.

We appreciate jump starters with long cables, as this enhances convenience in any space.

We look for jump starters that allow the user to easily check the charge status of the starter’s internal batteries.

Our team loves jump starters that are built for durability and portability. We search for these products so our readers get the most for their money.

It’s important for the clamp’s supporting springs to make a strong connection with the battery. As such, our team looks for jump starters with strong alligator teeth-style clamps.

A highly powerful jump starter can make all the difference in a roadside emergency. We look at portable jump starters and assess their power and potential helpfulness in such an emergency.

Because large vehicles and small vehicles have different powering needs, we note which jump starters are best for trucks and SUVs and which are best for compact cars and sedans.

We look for jump-starters with solid, secure cases that prevent internal battery leakage and can withstand everyday knocks and scratches.

Jump-starter considerations

So, we know what a jump-starter does, but why are there so many to choose from? In essence, there are two reasons:

• The smaller the vehicle, the less current the jump-starter has to supply. That leads to models with a wide variety of different power levels. This is fine because not everyone needs to start a V8 pickup.

• Manufacturers try to tempt you with a variety of extras. Control technology, built-in safety features, and a host of useful (and not so useful) options.

These elements impact performance and price, so let's look at each in turn.

Jump-starter power

In order to get your vehicle going, a jump-starter has to supply sufficient current (measured in amps) to get the starter motor cranking over. That, in turn, fires the engine. The jump-starter feeds current through the battery – temporarily taking its place. As soon as the vehicle is running, the jump-starter is disconnected and, if all is working properly, the vehicle begins charging its own battery.

Inside the jump-starter is one of two types of battery: lead-acid (the same kind as in your vehicle) or lithium (the kind you would usually associate with power tools).

Lead-acid versions have been around for decades. They are proven, effective, reliable, and durable. The downside is that they're bulky and heavy – anything from 15 to 30 pounds.

Lithium versions are much more compact; many would fit in a glove box. They weigh a couple of pounds or less. They also have smart microprocessor control, so they not only start your car, they can charge your phone, tablet, or laptop. The drawback with lithium models is lower performance. Though high-performance models are becoming more widely available, they tend to cost more.

How much current is enough?

With the exception of smaller models (used to start garden tractors and that kind of thing), the battery inside a jump-starter is the same voltage as your vehicle: 12 volts. However, what's more important is the current it supplies, in amps.

The motor in the average family compact needs far fewer amps to turn it over than the one in a sports car or big SUV. If you've ever bought batteries for different vehicles, you probably know that some need a higher ampere-hour (Ah) rating than others.

So, if you have a small car, you don't need a big, expensive jump-starter. On the other hand, if you've got a rumbling V8, then a cheap, low-output jump-starter isn't going to make it hiccup, let alone run.

So, the solution is easy, right? Choose a jump-starter with the same ampere-hours as your car.

Unfortunately, it doesn't work that way. Amps and ampere-hours aren't quite the same things. Also, jump-starter manufacturers usually report peak amps, which doesn't really mean a lot except as a comparison. What you really want are cranking amps (CA) or cold cranking amps (CCA).

No wonder choosing a jump-starter is confusing!

If you can find cranking amp figures, the following is a useful guide, albeit approximate:

For gas engines, you’ll need:

• 150 to 200 amps for a 4-cylinder.

• 200 to 250 amps for a 6-cylinder.

• 250 to 300 amps for an 8-cylinder.

For diesel engines, you’ll need:

• 250 to 400 amps for a 4-cylinder.

• 400 to 500 amps for a 6-cylinder.

• 500 to 700 amps for an 8-cylinder.

Peak amps may be the only figure you can compare across several manufacturers.

Look for 600 to 1,000 amps from a lithium-based jump-starter, and 1,000 amps or more from a lead-acid model.

Bottom line? If you can afford it – and certainly if you have multiple vehicles – go big. As our automotive expert says, you can have too few amps, but never too many!

Make sure your jump-starter is not going to fall into the engine bay or off the car when you attempt to start it. On the ground beside the vehicle is a place for it, but short cables can make this difficult.

Jump-starter features

Lead-acid jump-starters, being larger, have room for features that wouldn't fit in the compact case of lithium models.

• Compressors are popular, useful for inflating tires in an emergency.

• 12-volt DC outlets can power suitable accessories.

• A 120-volt inverter might be included, feeding power to ordinary household power outlets.

• A worklight is common, and sometimes detachable. Very useful if you're trying to start a car in the dark.

• A USB port is also common.

• Voltmeters and charge indicators are useful additions, so you can see when your jump-starter needs charging.

• Long cables make it easy to clamp to battery terminals while keeping the jump-starter on solid ground.

• Strong clips help make a good connection, biting through the corrosion that often forms on battery terminals.

• Cases are usually robust, built to take everyday knocks and scratches.

• Most have overload protection that prevents damage to your vehicle.

The compact size of lithium jump-starters doesn't allow for 120-volt outlets. Instead, they concentrate on providing power for your electronic devices.

• At least one, and often two USB ports (Smart technology adapts current to the device being attached.)

• 12 volt DC outlet

• LED worklight (may have multiple brightness settings or emergency strobe)

• LCD screen giving a variety of useful info

• Compass

• Microprocessor control (prevents overloads on vehicles and digital devices)

• Polarity sensors (warn if you've attached jumper cables to the wrong terminals)

• Cables are usually shorter, though the size of case makes it easy to position in the engine bay.

Regardless of type, always bear in mind that the more features you use, the faster you'll drain your jump-starter. Though most provide excellent performance and multiple vehicle starts between charges, it's basically a battery in a case, not a portable generator.

What does a good jump-starter cost?

There is a huge variety of jump-starters available, with something to fit any budget. Of course, you usually pay more for extra bells and whistles, so it's worth considering whether you'll actually use those enticing options very often.

There are some very cheap jump-starters around, but durability might not be what you hope. That said, a good, basic model, capable of starting the average compact, shouldn't cost more than about $50.

Something that will handle sedans, station wagons, and small trucks will be between $70 and $120. In this price range, you'll find everything from lead-acid jump-starters with lights and compressors to smart lithium models that will start your car and charge all your electronic gadgets.

Many of these models claim to start powerful gas and diesel engines. They'll certainly handle the vast majority of family vehicles. However, jump-starter performance depends on the time since it was last charged, the temperature, and the state of the engine being started. If you want something you can guarantee will start your muscle car, you'll need a high-end jump-starter. For one of those, you'll be paying around the $200 mark.
 

Tips

• If you have several vehicles of different sizes, you need a jump-starter for the most powerful. There's no need to worry about delivering too much current for smaller vehicles; the jump-starter will only provide what the motor draws from it.

• You might want to consider a small lithium jump-starter even if you've already got a big lead-acid one. Lithium models are great for charging your electrical gadgets, and one makes a very useful addition to your camping gear or RV.

• Many jump-starters have on-board storage for cables and safe areas for clips. Use them, or disconnect cables from your jump-starter after use – even when the machine is switched off. Accidental discharge can cause extremely painful shocks. Sparks could start a fire.

Smart jump-starters can charge phones, laptops, tablets, and more, but you may need to change voltage settings. Safety cut-outs are usually built in. The starter will shut down rather than produce too much power.

FAQ

Q. Are lithium jump-starters better than the traditional type?

A. It's not really a question of which is better; it's which is most suitable for you. Lithium jump-starters are small enough to keep in a glove box, but many lack the power to start big motors. Traditional jump-starters pack more punch, but are a lot larger and heavier. Our jump-starter report gives a complete picture. Reading through should help you decide which is right for you.

Q. Can I use my jump-starter straight out of the box?

A. It depends on the model. Some arrive fully charged, others need anywhere from 4 to 24 hours. It's not difficult – they just plug into an ordinary household outlet – but you must check the manufacturer's instructions.

Q. What’s the difference between peak amps, cranking amps, and cold cranking amps?

A. Peak amps are the maximum current available. Manufacturers love to quote it because it's the biggest number! Cranking amps is the current available at 32°F (0°C). It must be supplied for 30 seconds, at 7.2 volts minimum. Cold cranking amps is the current available at 0°F (-18°C). Again, it must be supplied for 30 seconds, at 7.2 volts minimum. The cold makes engines more difficult to start, so more current is needed.

There is no direct conversion, but a jump-starter with peak amps of 1,500 might only produce 400 cranking amps, which is roughly 320 cold cranking amps. If you can compare CCA ratings, that's when the jump-starter is working hardest, but often makers don't give figures. Peak amps is a reasonable alternative.