For the making of their Kickstarter video, and because destructive testing is always fun, Zendure founder Bryan Liu rolled over the external battery's A4 model a dozen times as it charged an iPhone 4S. Presumably with a car, not a big wheel. And Zendure the Strong & Durable, he remained unperturbed. I don't think the batteries come with a money-back guarantee for buyers who try to replicate the experiment without similar success, but it's probably safe to say that the Zendure A-Series maintains its integrity and dependability when tossed in backpacks and luggage, or inadvertently dropped and impacted during futile efforts to charge while intoxicated.
The A-Series shell is fashioned from a composite material, and reinforced by support ridges to resist warping. Zendure designers have also inserted a shock-resistant rubber belt between the front and back covers to help protect the battery during falls (and tire encounters).
In addition to resilience, Zendure says their batteries' internal system has a total energy conversion rate 10% higher, and circuitry efficiency 5% higher than similar products. Individual units are conditioned to complete over 500 full charge/discharge cycles over their usable life. They can juice up 2 devices simultaneously, as well as output their charge while they themselves are plugged in for a refill.
With A3 (9,000 mAH), A4 (12,000 mAh), and A5 (15,000 mAh) versions available, Zendure the Strong & Durable can charge most USB-powered devices. In terms of single-charge capacity, as a point of reference, the A5 can re-up an iPhone 4, 4S, or 5 about 8.5 times, or a Samsung Galaxy Note 4.8 times before needing its own recharge.
The Zendure A-Series campaigns for crowdfunding on Kickstarter through October 9, 2013.
June 2014 Update: Zendure batteries exceeded their crowdfunding goal and are now available for direct purchase through Amazon--follow the link below.