Jump-Starter Buying Guide

Portable battery jump-starters are nothing new, but in the past they were sized like a hardcover dictionary and powered by heavy lead-acid batteries. While great for car dealers and auto recovery services, those traditional booster packs are too bulky to carry in a car emergency kit. Today’s mini jump-starters use compact lithium-ion batteries that can carry a lot of power in a small, lightweight package. Most weigh only 1 or 2 pounds and are roughly the size of a paperback novel. Many jump-starters can be found for under $200—and sometimes as low as $50. They can make an excellent gift because they’re often discounted for Black Friday and other seasonal sales. 

Jump-starters are also useful in a home emergency kit. Many include a built-in flashlight, which is just as useful in a home power outage as it is for finding your car’s battery connections in the dark. These units can also be used to recharge portable devices, such as mobile phones and tablets. USB ports are common features, and some jump-starters include connectors for charging certain laptop models. 

When Consumer Reports last tested jump-starters, we found that a higher price didn’t necessarily translate into higher performance. While the best-performing jumper pack was the most expensive, the weakest performer wasn’t the least expensive, and the second-priciest model came in second-to-last place in our ratings. Based on our testing and experience, here’s what you should consider instead when shopping for a jump-starter. 

Peak amps: The most advertised figure on most jump-starters is its peak amps (sometimes referred to as peak current). This refers to the maximum power the jump-starter will output over a burst of a few seconds long. The size of your vehicle’s engine can help you determine how many peak amps you need. Larger and higher-compression engines (such as diesels) require more power to get moving. 

According to Lectron, a manufacturer that sells electric vehicle chargers and jump-starters, small cars with 2.0-liter engines and smaller need at least 800 to 1,200 peak amps to start; sedans and SUVs with 2.0- to 3.0-liter engines need 1,200 to 2,000 peak amps; vehicles with engines larger than 3.0 liters need 2,000 to 3,000 peak amps (or potentially more for very large engines); and diesels need at least 3,000 amps. 

It’s a good idea to get a charger with higher peak amperage than you need because the car’s battery will only draw what it needs from the charger. Moreover, both a 12-volt car battery and a jump-starter’s lithium-ion battery are less efficient in colder temperatures, so buyers in cold climates need to account for a slight drop in performance on frigid days. 

Electric vehicle jump-starting needs: Even though they don’t run on gasoline, electric vehicles can still need a jump-start to get going because most use the same type of 12-volt battery as non-EVs to power key accessories and power up the car. Because there’s no engine compression to work against, EVs don’t need much amperage to get started. But EV owners should check the vehicle’s manual because it has specific precautions and directions for jump-starting these vehicles. The owner’s manual will also say whether an EV has something less conventional in place of a 12-volt battery, such as a small lithium-ion battery, and can tell you what to do if a vehicle with one of these systems doesn’t start. Never use a jump-starter on an EV, plug-in hybrid, or hybrid’s high-voltage drive battery. 

Cold cranking amps: Performance among the popular jump-starters we tested was nearly identical when charging a completely dead car battery at room temperature. Cold temperatures were where the real differences started to show. When both the car and jump-starter were cooled to 0° F, none of the units could jump-start weak car batteries, let alone the dead ones in our tests. But when the battery packs were at room temperature, most could successfully jump-start a frozen car battery. 

Cold cranking amps measure the longer-duration power required at colder temperatures, when battery performance degrades. A higher number of cold cranking amps means that a jump-starter is more reliable in frigid weather. A jump-starter should automatically discharge the appropriate amount of power for your battery. While it isn’t always listed in a jump-starter’s specifications, one with 400 to 500 CCA should be enough for passenger cars, SUVs, and pickup trucks. Heavy-duty, commercial, and diesel-powered vehicles may need more powerful units.

Jump-starter battery capacity: A jump-starter’s battery capacity indicates how long it can run before needing a recharge. This is usually measured in milliamp-hours (mAh) or amp-hours (Ah). The higher the number, the longer it will last. These capacities are typically shown as 1000 mAh, although it may be advertised as 1 Ah. Both examples in this case would be the same. 

This is especially relevant if you want to use your jump-starter as a power brick for other electronics. In our tests, we observed even greater variance when evaluating jump starters’ ability to charge devices such as tablets and laptops. One charger could keep a device powered for three times as long as the poorest performers in our tests. We consider this power source’s performance a notable factor because these units can keep vital devices, such as mobile phones, charged during a power outage and while road-tripping or camping.

Sturdiness: In addition to making sure the case doesn’t feel like it’s going to burst open if you drop it, look for sturdy battery clamps with thick, reasonably long cables. You need to keep the clamp securely on the battery (or your vehicle’s designated jump-starting points) for it to work, hence the need for stout, easy-to-open clamps. Look for enough cable length to set the charger somewhere secure while still being able to reach the (+) and (-) connections on your car. Thicker cables are typically higher-capacity and can transmit more power than thin ones, allowing the jump-starter to deliver more usable power to the car’s battery.

Safety features: Look for a jump-starter that offers protection against reverse-polarity charging, short-circuiting, and overcurrent or overtemperature conditions. Hooking up the positive lead to the negative terminal and the negative lead to the positive terminal can damage your vehicle’s electrical system. Fortunately, many jump-starters can detect when the leads are attached incorrectly, the vehicle’s battery is overheating while charging, or there’s another electrical fault, such as a short circuit, and they won’t work in those cases. Jump-starters should have clear warning lights for these problems and a display showing the starter’s current state of charge. 

Also look for well-insulated, spark-proof clamps. According to the jump-starter manufacturer Safemate, spark-proofing systems (as they include more than just the clamps themselves) prevent the jump-starter from sending current to the clamps until it detects a stable connection to a battery terminal. This protection also prevents it from shooting an electrical arc between the clamps and the battery terminals or other components in your engine bay. 

Some chargers also include an override button for these detection measures, which can also prevent the jump-starter from working on an extremely weak battery. Use these with extreme caution and double-check that everything is connected correctly and in decent enough condition to jump-start if you do. Consult your jump-starter’s manual for any unit-specific precautions with these modes. 

Extra useful features: We recommend looking for one with a built-in light as well as USB or other charging connections for laptops, tablets, and phones, but these aren’t the only things jump-starters can come with. Some can cover multiple vehicle emergencies at once with a built-in tire inflator. You may also want to consider the jump box’s size and weight, depending on where it’s stored and who uses it. 

Be sure to compare user reviews to make sure a jump-starter’s spec sheet reflects its real-world performance, especially when temperatures drop. Advertised battery capacities and amperages only mean something if they work in the real world.

The jump-starters we tested had a maximum recommended operating/storage temperature range of 120 to 185° F. While some manufacturers cautioned only against operating the units at high temperatures (with reduced performance as a consequence), others specifically warned against storing the units at high temperatures. 

That’s a major concern. According to the National Highway Traffic Safety Administration, the temperature inside a car parked in direct sunlight can reach between 131 and 172° F when the temperature outside is between 80 and 100° F. In hot desert areas, the inside temperature can rise even higher.

Unfortunately, the device manufacturers were guarded about the potential consequences of storing these units at high temperatures. Complicating matters is that most units list their temperature ranges (operating or storage) in their instructions but not on the product packaging.

The takeaway: Check the fine print before buying, and read the jump-starter’s instructions carefully before using. During the hot summer months, consider storing the unit in a cool location and taking it with you only on long trips. If you’re storing the unit in the car, choose a location out of direct sunlight, such as the glovebox or the trunk.

Parasitic loss is a concern for cars parked even for a week because they can lose enough energy from their batteries to no longer start. “Off” no longer means completely off in many new cars because the increase in electronic features causes many to perform functions and connect to wireless signals even when the vehicle isn’t in use. Some cars will experience a power draw if something is plugged into a charging port, a 12-volt power point, or a 120V outlet, such as a phone charger or a portable navigation device. This can pose a risk to those who drive a car only rarely or who may park the car for an extended period, such as when traveling. (The owner’s manual may indicate how long the car can be parked without losing significant starting power.)

When parking in a home garage, a battery charger—known as a trickle charger or a battery minder—can provide a slow, steady charge to preserve starting power.

For those who park outdoors, away from a power source, there are also solar-powered battery maintainers. These connect to the car battery, and some cars can be charged via the 12-volt power point inside. Because of their low amperage, solar units are used to offset any natural battery discharge rather than to recharge a weak battery. Most solar chargers come with a reverse-charge-blocking diode to prevent them from draining the car battery at night. Verify that the model you’re considering has this feature.

Learn more about how a car battery charger can keep your vehicle ready to go.