Friday, February 4, 2011

Solar iPad Charger Test Results

I get asked more and more about how to operate, charge, or otherwise power an iPad when away from civilization. Seems that the iPad is becoming a popular device for documenting expeditions. The iPad or the iPhone 4, but that is a topic for another post.

So, knowing the basics before actually getting my hands on an iPad, I knew that it uses a somewhat new twist on the USB standard... the iPad charger uses a 10 Watt USB port. The spec is 2.1 Amps at 5V. Not something that you find everywhere. Doing a little internet research quickly revealed work-arounds for PC's whose USB ports were not able to provide enough power to sync an iPad. Based on further research, I got the impression that any portable power system would need to be able to deliver the full 10 Watts in order for the iPad to be able to use the power at all. But, I was pleasantly surprised once I had an iPad & did some testing...

As it turns out, an iPad will draw power from any USB port that is Apple-friendly. This "Apple-friendly" description is the topic of yet another future blog post, but it essentially boils down to this: the USB port must be able to mimic a computer port with active data lines. Some USB chargers cut corners and are not designed to do this. So, consider that if a USB charger states that it is made for iPod or iPhone or is Apple-friendly, it will work with all USB devices. The iPad was happy to draw power from any of these USB ports, as long as they were capable of at least 500mA. The iPad would only "charge" from ports that were capable of getting close to the 2.1A spec.

With solar gadgets, it is often a matter of trial & error, especially when the manufacturer does not specifically state that their solar charger is Apple-friendly. So, I tested a variety of solar chargers that specifically state that they work with Apple devices, and tried them with the iPad.
Here are the results...

Performance: Power & Charge the iPad
PowerFilm USB+AA (using built-in USB port)
Brunton Sustain Battery (using 12V socket & Griffin PowerJolt USB adaptor)
Brunton Impel Battery (using 12V socket & Griffin PowerJolt USB adaptor)
Tekkeon 3450 Battery (using 12V socket & Griffin PowerJolt USB adaptor, or 2.1A USB port option)
Novuscell 50 Battery (using 12V socket & Griffin PowerJolt USB adaptor)
Novuscell 24 Battery (using 12V socket & Griffin PowerJolt USB adaptor)

NOTES: Any of the batteries listed above can be charged from standard 12V portable solar panels. A 5watt panel would be able to offset up to 10 hours of iPad use per day (summer month averages)

Performance: Power the iPad (but not able to charge)
Brunton Restore (via built-in USB port)
Brunton Freedom (via built-in USB port)
Brunton Inspire battery (via built-in USB port)
Brunton Sustain battery (via built-in USB port)
Brunton Impel battery (via built-in USB port)
Tekkeon 3450 battery (via built-in USB port)
Voltaic Amp (via built-in USB port)
Voltaic Fuse (via built-in USB port)
Voltaic V11 battery (via built-in USB port)
Solio Classic A (via built-in USB port)
Solio Mono A (via built-in USB port)

This is OK in my books because essentially you can easily create a solar-rechargeable external battery for the iPad. Presumably the iPad could be powered for a couple of hours a day from these devices without affecting the status of the iPad's own internal battery. This would be useful on trips of perhaps as long as 2 weeks. As long as iPod use is not excessive.

A note about solar-direct...
I did not attempt to plug the iPad directly into a solar panel, partly due to the fact that I do not like these "mercy-of-the-sun" type of configurations, partly because it was the middle of winter when I did these tests, and lastly because I am skeptical that anything less than a 5W panel in full sun would be able to 'power' the iPad, let along 'charge' it. But, I will certainly return to this topic this summer to see exactly how an iPad performs in this configuration.

I hope this note has been helpful. Please feel free to send any questions or comments.