When you turn the hand crank, you're creating kinetic energy that is stored in the internal battery as reserved power. As soon as you connect your smartphone to the BoostTurbine, your phone will transfer that stored energy into its own battery. Eton says that 1 minute of cranking will give you 4 minutes of talk time. You need to rotate it about one or two revolutions per second to generate enough energy to charge the battery.
Though the BoostTurbine has four LEDs that lit up to show the battery's level when I turned the crank, it was hard to tell exactly how much power I was creating. For instance, if the battery is at 50 percent, two LEDs will light up solid and a third will blink, indicating that you're charging the battery. I never got the next light to come on, as my hands got tired after a few minutes of continuous cranking.
Eton notes that it takes 4.5 hours to get the BoostTurbine to a full charge while plugged into a power source. In my testing, it took just around 40 minutes for the device to go from two lights to three while plugged into my computer via USB, so that's a plausible time frame.
Charging your gadgets
The device gets its name from its internal 4,000mAh lithium ion battery. While that power capacity is lower than competing portable chargers', the BoostTurbine still provides enough power to charge nearly any smartphone once or twice on a single charge.
I tested the BoostTurbine's charging capabilities on a completely dead. After connecting it to the phone, it took around 5 minutes for the charger to give the phone enough power to turn on. I was then able to use the Lumia 925 to make phone calls and check e-mails while it continued to charge.
Two hours later, the phone had 50 percent battery charge and the BoostTurbine had gone down to only 75 percent.
Though the portable charger doesn't have enough juice to fully charge a fourth-generation iPad, which has an 11,666mAh battery, I was able to get some power. My iPad went from 80 percent to 90 percent charge in around 20 minutes, but the BoostTurbine was nearly dead afterward.
The BoostTurbine performs best when charging gadgets with 4,000mAh-or-lower batteries, which includes the, the , the , and the .
Rechargeable batteries, like the one in the BoostTurbine, have a tendency to lose the ability to hold a charge over the years. While I didn't notice any issues in my testing, it's worth remembering that batteries like this don't last forever.
Given that the BoostTurbine 4000 is heavy and clunky, it's not the most portable gadget charger on the market. And even though it has a hand crank for when the power goes out, it's not the most ideal emergency device either because it's missing a flashlight and radio. Still, with 4,000mAh of power, the BoostTurbine will save your phone when it runs out of battery life.
At $80, the BoostTurbine is pricey compared with most other portable chargers out there, even ones that have more power capacity. For your everyday power needs, you're better off looking at the cheaper, which has a bigger battery as well. If you need something to keep you up and running during a power outage, camping trip, or disaster, the BoostTurbine 4000 is a decent choice, if you don't mind turning the crank for a while.