Product Details

• LED flashlight
• 15V/10A DC output
• 5V 1A USB-A output
• 5V 2.4A USB-A output
• 5V/9V USB-C input

Portable Car Battery Jump Starter

Portable Car Battery Jump Starter

To test starting performance, all jump starter packs were used on a 1.6-litre petrol engine, and we expected the motor to turn over five times for five seconds each time, with a two-minute break between.

Each was fully charged before starting the test and the battery state logged when we finished. We also rated each starter for practical features such as cable length and clamp size, tech spec and weight. Instructions were also rated, as were safety and options, including sockets. As ever, price from a range of online sources was the final factor.

The JSM300 is Clarke’s mid-range Jump Start device, offering a neat balance of capability and price. Despite weighing just 627g, the Clarke has 12Ah, which was easily enough for all of our tests; we also measured a max 109 amps while the engine turned over. Like many rivals, it flashed LEDs to show it was connecting, which then went to solid green to show it was ready.

While many larger-amperage products offer multiple voltages, it’s quite unusual to find 5V, 12V and 19V (for laptops) with adaptors at this price. The JSM300 also comes with a four-into-one multi-plug connector with an Apple 30-pin (a little outdated), Lightning plus mini and micro USB. The zip-up case is strong and large enough to handle the battery and the various accessories, which are secured by elasticated straps. It also includes both mains and car chargers. The jump-start socket is covered, but the two (4A combined) USB outputs aren’t.