Black & Decker Portable jump starter

A trunk companion with limits

I like the peace of mind that comes from keeping a jump starter in the trunk. Over several weeks with this jump starter, I found a mix of practicality and frustration: it’s compact enough to live in the car, has useful safety features and a built-in charger, but its performance and charge-status behavior make it hard to trust for anything more than light-duty use.

Design, size, and what’s included

At 11.5 x 10.0 x 5.5 inches and about 8.5 pounds, the unit is a classic briefcase-style pack that stores easily in a trunk cubby. The housing feels sturdy enough for automotive use, with molded carry handles and clamps that are adequate, if not heavy-duty. You don’t get an extension cord in the box, so plan to supply your own to use the integrated AC charger.

There’s a multi-LED battery level indicator, a power switch, the 12 V jump leads with a reverse-polarity alarm, and a single high-output USB port for topping up phones and tablets. It carries an ETL safety listing and a 1-year limited warranty.

Features and ease of use

• 700 peak amps / 300 instant starting amps (12 V)
• Reverse-polarity alarm that audibly warns if you clip the cables incorrectly
• Built-in AC charger; plug in with a standard household extension cord
• High-output USB port for portable device charging
• ETL listed

I appreciate the onboard charging—plug it in overnight and it tops itself off without an external brick. The safety alarm works; I intentionally misconnected a clamp during testing and the unit chirped immediately and blocked output. That’s the sort of safeguard I want in a glovebox emergency tool.

The USB port is handy in a pinch. It charged a phone and a small tablet without issue, and it’s a nice backup during power outages. Just keep expectations in check: this is primarily a jump starter, not a power bank.

Performance in real-world starts

The headline numbers promise enough current for most gasoline vehicles up to V6. In my use, that’s true under favorable conditions, but it falls apart at the edges.

• Four-cylinder sedan, mildly drained battery (interior light left on): Following the manual—positive to battery positive, negative to a solid, clean engine ground—the starter turned slowly on the first try and the car fired on the second attempt after waiting about 30 seconds. That’s acceptable performance from a compact pack with 300 instant amps.

• Four-cylinder hatchback on a chilly morning with a battery sitting at about 11.5 V: The pack struggled. The engine clicked and gave a brief crank, then nothing. After a minute of rest and a second try, it still didn’t start. Temperature and a lower state of charge make everything harder, and this unit doesn’t have much headroom for cold-weather cranking.

• V6 crossover with a weak, but not dead, battery: It produced a short crank but couldn’t sustain it. I could coax the car to life only after pairing the pack with a friend’s car via traditional jump leads—defeating the point of a standalone jump starter.

I also experimented with clamp placement. Many instructions recommend clamping the negative lead to a clean engine or chassis ground rather than directly to the battery’s negative post to reduce the risk of sparks around the battery. On one vehicle with a less-than-ideal ground point, the cranking performance improved slightly when I used the battery’s negative terminal instead. That’s a good reminder to find the best possible ground on your specific engine, but always follow the manufacturer’s safety guidance first.

Bottom line: it will help a small gas engine if the battery isn’t completely flat and the weather’s not working against you. It isn’t a miracle worker for dead batteries, larger engines, or freezing mornings.

Charging behavior and maintenance

This is where the experience gets bumpy. The indicator lights are vague. Plugged into AC, the meter often showed “full” after a while, but once I unplugged the unit and checked again, it sometimes dropped to a low reading. After cycling the power and letting it rest, the meter would occasionally climb back up. It’s not confidence-inspiring, and it makes it hard to know the true state of charge.

The manual’s recommendation to top off the pack every 30 days is wise for this kind of jump starter, and in my tests it did need frequent maintenance charging to stay ready. Leave it in the trunk for a couple of months without touching a charger and you may find it underwhelming when you need it most. If you’re diligent about a monthly top-up, it’s serviceable; if you’re not, its usefulness will taper off quickly.

The built-in charger itself is straightforward—just connect a household extension cord. I measured charge times in “overnight” terms rather than hours; figure on plugging it in at dinner and having it ready by morning. Faster would be nicer, but given the capacity and the convenience of an integrated charger, I can live with it.

Safety and usability touches

Credit where it’s due: the reverse-polarity protection works, and the audible alarm is loud enough to catch your attention under the hood. The clamps open wide and bite well enough on clean posts and brackets, though they’re not heavy, copper-jawed clamps you’d find on commercial boosters. Cable length is adequate for most small cars but a bit tight on some crossovers where the battery is tucked away.

The ETL listing is reassuring, as is the absence of gimmicks. This is a simple tool, and simple is usually better in an emergency.

The USB port: useful, not a selling point

As a portable power source, the USB port is a nice bonus. It kept a phone and a small Bluetooth speaker running for a weekend camping trip, and it’ll get you through a roadside delay. But I wouldn’t buy this unit for the USB capability alone; dedicated power banks are lighter, more efficient, and less fussy about monthly maintenance charging.

What I’d improve

• A more accurate, more granular state-of-charge indicator. A three-light meter that behaves inconsistently isn’t good enough.
• More cranking current or better cold-weather performance. Even an extra bit of sustained amp output would turn “almost” starts into starts.
• Clearer guidance on grounding with obvious labels near the clamps and in the quick-start summary on the case.

Who it suits—and who should look elsewhere

If you drive a small gas car in a moderate climate and you’re disciplined about monthly charging, this jump starter can be a reasonable emergency backup. It’s also a simple solution for keeping a USB-powered device running during a power outage.

If you drive a larger gas engine, frequently see freezing temperatures, or want something that can wake up a deeply discharged battery, you’ll be better served by a higher-output pack. There are compact lithium jump starters with higher starting amps and clearer displays that, while sometimes pricier, deliver more consistent results and hold a charge longer.

Pros and cons

Pros:
- Compact, trunk-friendly footprint
- Built-in AC charger; no external brick to lose
- Effective reverse-polarity protection with audible alarm
- Useful emergency USB port
- ETL listed, 1-year warranty

Cons:
- Inconsistent charge indicator; hard to trust at a glance
- Limited cranking performance in cold weather and on larger engines
- Requires frequent maintenance charging
- Clamps and cables are only average

Recommendation

I wouldn’t recommend this jump starter for most drivers. While it can start small gas engines under the right conditions and the safety features are solid, the combination of modest cranking power, a finicky charge indicator, and the need for frequent top-offs undermines its reliability as an emergency tool. If your needs are light and you’ll maintain it monthly, it can work. For everyone else, a higher-output unit with a clearer state-of-charge display will provide more confidence when you’re stranded on the shoulder and need a sure start.