Editors' note: Portions of this review were copied from CNET's review of the Bolt Power D28 portable jump starter. The K3 Mini underwent similar testing.
Portable jump starters used to be a lead-acid car battery in a plastic casing, weighing up to 20 pounds. Now, improvements in lithium ion batteries enable a new breed of jump starter, one that can fit in your glove compartment and weighs about 10 ounces. Such is the BoltPower K3 Mini, a reasonably compact device that can rescue your car and also charge smartphones and other electronics.
At 6.75 inches long, 3 inches wide and well under a pound in weight, I could easily carry the K3 Mini around in one hand. It's a little big to fit in a pocket but would store in a car's glovebox or trunk easily enough. The K3 Mini comes in a zippered nylon case, holding its adapter and charging cables, which adds considerable size to the whole package. You might want to leave the case at home and just pack what's necessary in the car.
A black-and-gray plastic case gives the K3 Mini a modern look, and indentations along its body make it easy to hold securely. One long side holds two USB ports, a port for the jump-start battery clamp adapter, an LED charge level indicator and an electric input for charging the K3 Mini itself. A power button mounted on the top of the case turns on charging capability and also activates an integrated flashlight.
Cables included with the K3 Mini are the battery clamp adapter and a white multi-jack adapter with older and newer iOS plugs and plugs for Mini- and Micro-USB. In addition, BoltPower includes AC and 12-volt adapter cables to charge the K3 Mini.
To charge up my iPhone 5S, I had to plug in the white multi-adapter cable or my own iPhone cable, then press the power button. With the iPhone 5S plugged in and charging up, I attached another electronic device to the Mini-USB port on the same multi-adapter cable. Both charged simultaneously. Bolt Power marks one of the USB ports for 1 amp, and the other for 2.1 amps. The former will be suitable for most smartphones, while the latter is designed to charge tablets and larger electronic devices.
As the K3 Mini's battery is rated at 12,000mAh capacity, it could charge up my 1,900mAh iPhone 5S battery six times over. That amount of power is enough to charge a Nexus 7 tablet a couple of times, and can handle the latest iPad's 11,560mAh battery.