Portable jump starters used to be a basic 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 D28, the company's most powerful jump starter, which is also designed to charge your smartphone and myriad other electronic devices.
At 6.5 inches long, 3 inches wide and well under a pound in weight, I could easily carry the D28 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 D28 comes in a zippered nylon case, holding its various adapter cables, which adds considerable size to the whole package. You might want to leave all that at home and just pack what's necessary along in the car.
The brick that is the D28 fits a power switch, USB port, charging port, universal output, jump-starter output and on/off switch down one long side. There is also an LED showing its charge level, a handy feature, and a button that turns on the integrated flashlight. Along with the basic unit, Bolt Power includes a battery clamp adapter, a white multijack adapter with older and newer iOS plugs and plugs for Mini- and Micro-USB, and a universal cable with eight different plugs for different type electronic device charging ports. In addition, there are AC and 12-volt adapter cables to charge the D28.
To charge up my iPhone 5S, I had to plug in the white multi-adapter cable (or I could have used my own iPhone cable), then turn on the power switch. To further test the capabilities of the D28, I plugged in another device to the Mini-USB plug at the same time my iPhone was connected, and both charged simultaneously.
As the D28's battery is rated at 13,600mAh capacity, it could charge up my 1,900mAh iPhone 5S battery seven times over. Likewise, that amount of power is enough to fully charge any other smartphone on the market, not to mention most tablets. The USB port outputs power at 2.1 amps, the maximum for USB 2.0 charging.
Using the universal output cable is a little trickier. This adapter will work with almost any electronic device that has a round port for charging. It includes eight different-size plugs to fit the variety of different charging ports on devices. Further, you have to know the charging voltage of your device. The D28 lets you change the output voltage of its universal port between 12, 16 and 19 volts.
I found the right plug among the eight available for a portable audio recorder, and noted that the recorder's DC input was labeled for 13 volts. Plugging in the cable, I was pleased to find that the D28 was smart enough to choose its 12-volt setting and did not let me switch to a higher voltage. These round plugs will also fit many Windows laptops on the market, making the D28 an all-around portable backup battery.