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If you've got a flat battery, nothing gets your vehicle started more quickly, or more easily, than a good jump starter.

There are dozens of these indispensable tools to choose from. They'll have your car or truck back on the road in minutes, and many include valuable extras. The only challenge is picking the right one. That's where Infinity Light jumps in!

We will try to help you understand and choose the best one for you.

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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 is not 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.

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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. Which 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 down-side 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.

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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 Amp 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 amp hours as your car.

Unfortunately it doesn't work that way. Amps and amp hours aren't quite the same thing. 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 400 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 200 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.

You can have too few amps, but never too many!

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 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.

  • One model we reviewed included a 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.

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 make 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 an extremely painful shocks. Sparks could start a fire.

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 is 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.

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