Hands-On Review: Best Jump Starters for Emergency Starts and Portable Charging
We tested the best portable jump starters on the market so you don’t get caught unprepared.
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BY Mike Bumbeck / LAST UPDATED ON April 27, 2021
An engine-starting powerpack that fits into your glove box sounds like a revelation. If it works, it'll be a real game-changer. But if “12-hour” laptop batteries and “500-mile” range electric cars are any indication, sales-pitch promises don’t always live up to real-world results.
Portable jump starters promise to make unwieldy jumper cables a thing of the past. But here’s the hardest part: It’s easy to find out if your “all-day” smartphone battery really lasts all day, but unless you kill your car battery on purpose there’s no way to know if a portable jump starter will work when you need it most.
Do portable jump starter expectations meet up with dead-car battery reality? We wanted to know, too. Read on and find out if these jump starters stood up to two old cars, three dead batteries, and a simulated worst-case scenario torture test.
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Our reviews are driven by a combination of hands-on testing, expert input, “wisdom of the crowd” assessments from actual buyers, and our own expertise. We always aim to offer genuine, accurate guides to help you find the best picks.
How We Tested Portable Jump Starters
We put our jump starters through three different tests three different times — because the absolute worst time to discover a portable jump starter doesn’t work is the most likely time that you’ll need it.
First, we tested each jump starter on two old 4-cylinder vehicles with questionable but definitely dead batteries in below-freezing temperatures. Next, we hooked up a third marginal battery up to a carbon pile load tester and logged voltage and amperage. The load tester simulates a starter motor current draw and then some. We charged all the jump starters and let them rest overnight in the frigid garage before each test.
CHALLENGE ONE: STARION TURBO
The 1987 Mitsubishi Starion had a nearly 10-year-old battery that barely held 12 volts after a month in the frigid cold. It was dead. The battery failed a load test and couldn’t budge the cold, thick oil in the Starion’s turbocharged 2.6-liter 4-cylinder. Electronic fuel injection means the Starion's engine usually starts on a single starter crank, so by the numbers the jump starters should be fit to do the job. Battery voltage varied slightly through the jump start attempts, hovering in the 10-11 volt range.
CHALLENGE TWO: STARLET
The 1982 Toyota Starlet had a 5-year-old battery that passed the load test and held 10 volts for 15 seconds. We topped off the battery with a charger and let it sit overnight. The following day, we disconnected the ignition coil wire and killed the battery by cranking over the Starlet’s carbureted 1.3-liter 4-cylinder peanut grinder with the lights on. Battery voltage read about 11 volts by the time turning the ignition key brought nothing but the dreaded click. It was 24 degrees when we hooked the coil wire back up to the distributor and had at it.
FINAL FIGHT: LOAD TEST
We saved the carbon pile load test for last. A load tester simulates the amount of electricity a starter motor needs to crank over an engine. With our load tester connected to a discharged battery, we could test each jump starter in a controlled environment. We hauled out a third spare car battery, charged it, and let it sit overnight. The battery passed a load test in the morning, holding 10.5 volts at 200 CCA (Cold Cranking Amps) for 15 seconds, so we used that as our baseline.
Each jump starter was subjected to all three load tests three times, with a full charge in between tests. Test one simulated a jump start with a 100 CCA load; test two boosted things up to 200 CCA; test three maxed out the load.
None of the jump starters we tested melted or flamed out like a cheap hoverboard — but none hit its advertised peak output, either.
Benefits of Portable Jump Starters
- Reserve Starting Power. Stowed in a glove box or map pocket, rechargeable lithium batteries can (theoretically) retain a full capacity charge for up to three months for reserve engine starting power.
- Device Charging. The ability to charge a smartphone or device battery is a valuable benefit, especially for those whose jobs require a laptop and long hours behind the wheel.
NOCO has been in the automotive battery technology business since 1914. The Ohio-based company’s current in-house design, engineering, and testing teams create premium consumer battery chargers, jump starters, solar panels, and portable power devices. The NOCO GB40 took our best overall title with its consistent performance, and it’s only the second most powerful model in the NOCO jump starter lineup.
Tacklife offers a wide range of products for the home and automotive market with an eye on quality at a reasonable price. The product lineup includes everything from hand and power tools to specialized lawn and garden equipment, like a pool-cleaning robot or outdoor fire pits. We liked the T8 Jump Starter’s quality and performance and used their clamp multimeter to measure DC amperage in our load test.
Sears launched its DieHard automotive battery in 1967 with a thin-wall translucent case that made room inside for larger plates and a more powerful battery that fits into the same space as older thick wall designs. Sadly, Sears is gone, but DieHard lives on — in new TV commercials with Bruce Willis.
Portable Jump Starter Pricing
- Under $50: Expect smaller capacity batteries and some larger capacity units on sale in this range. Be wary of durability and safety, though, and don’t count on precocious claims.
- $50-$100: This is the sweet spot of portable jump-starting power for most 4-cylinder vehicles and some large-displacement V8 and diesel engines. All of the jump starters tested here came in under 100 bucks.
- $100 and up: Expect to spend more for portable jump starters with high-capacity batteries and heavy-duty cables for large displacement V8 and diesel-powered truck engines. More power is better than less.
Peak vs. Cranking Amperage
The single most important thing we learned in our test of these portable jump starters is to ignore peak amperage claims; we didn’t see one of these units hit their advertised peak amperage number. Battery capacity and cranking amperage are the critical numbers. Sustained cranking amperage helps a dead car battery turn over the starter motor and start the engine.
Charging Ports and Adapters
If charging up or powering multiple devices and accessories is required, look for a jump starter with lots of output ports and adapters. Some have various options, but many come with nothing but a standard micro USB charging cord and single output port. All of our test units quickly charged up a couple of phones, and 12V adapters can recharge the jump starter’s battery pack while you drive.
A flashlight is a vital part of any onboard vehicle tool kit, and all of the jump starters had one or more built-in LED lights. Since most of these units are flat and rectangular, the jump starters with lights on the ends or corners worked out better than the others. Just set the battery pack on a fender or nearby underhood spot and turn the light towards the battery terminals. Some of the jump starter lights featured built-in warning and SOS emergency modes.
- Engine Size. A 6.6-liter 8-cylinder diesel engine needs more jump-starting power than a puny 1-liter, 3-cylinder gasoline engine. An abundance of power is better than a shortage in both cases.
- Battery Condition. Portable jump starters only work if the car battery still has a little bit of life left, and some won’t work at all below a specific voltage. Only the NOCO GB40 could boost severely discharged batteries.
Best Portable Jump Starter Reviews & Recommendations 2021
Jump Starter Tips
- Safety first. Car batteries are full of corrosive acid and create flammable hydrogen gas while charging. Battery explosions are relatively rare, but they can and do happen. Inspect the battery case for swelling and leakage. Do not attempt to jump-start a damaged battery.
- Clean contact. Corroded or loose battery terminals might be why the battery died in the first place. Clean the battery terminals as much as possible and give each terminal a downward twist to make sure they’re tight on the battery posts before connecting the jump starter clamps.
- Practice and patience. Practice connecting the jumper cables before stowing the jump starter. During an actual emergency, give the jump starter a minute or two before turning the key.
- Take charge before you jump. Topping off your phone battery won’t draw too much juice — and you might need the phone to call a tow truck anyway.
Q: Can I Overcharge a Jump Starter?
Unless the unit is damaged or defective, no. Built-in circuitry should turn off charging automatically once the battery is fully charged. We discharged, recharged, severely discharged, and recharged our test jump starter lineup several times without a problem.
Q: Which Battery Cable Clamp Goes Where?
The red clamp goes on the positive battery terminal (+) first (positive battery posts often have a red plastic cover), and the black clamp goes on the negative battery terminal (-) next. Remove the cables in reverse order and don’t let the cable clamps contact any metal parts — or each other.
Q: How Many Times Will a Jump Starter Recharge my Phone?
Depends on the battery capacity. But always check your phone or device’s battery before using the jump starter; you may need to call for help if the engine doesn’t start.
Q: Will a Jump Starter Charge My Car Battery?
Probably not. Portable jump starters work by teaming up with a depleted but not completely dead car battery. Their combined power starts the engine.
Q: Why Does the Jump Starter Keep Clicking?
It means that the jump starter is trying to charge the car battery back up. The clicking is a power cycling safety measure that prevents the car battery from drawing too much current too quickly and sending the lithium battery into thermal runaway. (If you’ve watched flaming hoverboard videos, you’ve seen thermal runaway. Not good.)
Q: What Size Jump Starter Do I Need for My Engine?
The jump starter with the largest capacity battery and highest cranking amp rating that you can afford. Most 4-cylinder engines can get by with lower capacity and amp jump starters, but larger displacement engines with more cylinders demand more power.
Compact rechargeable lithium battery jump starters can be an outstanding modern alternative to jumper cables, but power management and quality are crucial factors. Our best overall NOCO Boost Plus GB40 packed heavy-gauge battery cables and foolproof power management that delivered consistent and repeatable results.
When shopping for a portable jump starter, ignore peak amperage claims. Use battery capacity and cranking amperage as your guide. Remember, a larger engine requires a more powerful jump starter.
[NOTE: We tested several other portable jump starters that either didn’t pass our tests or didn’t work at all. We’ve reached out to the various manufacturers for comment and will update this story when we get a response.—Ed.]