Let me say at the outset, this review/assessment does not speak to longevity or durability, two of the solar units are new, the third is a little used one I've kept but seldom made use of. Also, because of the time involved, I did not check for charging times of specific devices.
For the first round of testing, a Drok mulitmeter was used to test output charging into a Anker Astro battery pack with a 1 amp charge rate.
The panel sets tested were an older Thunderbolt Solar 5 watt set (from Harbor Freight) I've had for several years, a SunKingdom 19.5 watt set recently purchased on Amazon, and an Aukey 20 watt unit, also bought on Amazon. The SunKingdom rig cost under $40, the Aukey was under $50.
|Top: Thunderbolt 5w. Middle: SunKingdom 19.5w|
Lower: Aukey 20w
Here are the results:
The older and under-powered Thunderbolt delivered 4.57 volts and .44 amps while charging the Anker pack:
The SunKingdom delivered 5 volts at .89 amps:
And the Aukey gave 5.18 volts at .89 amps:
Testing conditions were sunny, breezy and an outdoor temp of 60F on this early spring day. Time was around 1:00 pm EDT. The Aukey and SunKingdom sets come with advertised outputs of better than 2 amps, but the uptake capacity on the battery pack appears to have been a limiting issue.
Curious, I moved on to try two of the panels with a LingsFire charger loaded with one old Kodak NiHm battery. The 5 watt Thunderbolt was relatively competitive with the 20 watt Aukey in this test, with peaks around 4.84 volts, .42 amps with Thunderbolt, 5.21 volts; .48 amps off the Aukey. I didn't test the SunKingdom with the LingsFire. The LingsFire charger appears tobe a pulsing type, so there' bursts to the peak intermittent with drops in amperage.
|w/ Thunderbolt 5w|
|w/ Aukey 20w|
The LingsFire, when plugged into an AC wall outlet USB also drew only .48 amps, the Anker battery pack only drew .92, this is consistent with the draws from the solar panels.
Unfortunately, I don't have any USB powered devices that utilize higher amperage to see if more capacity could have been drawn out of the solar panel sets under today's conditions.
I like the idea of being able recharge using solar on the go. Great for hiking, travel, power outages, or to stash a panel in a bugout/get-home bag to keep your phone, AA/AAAs and other batteries topped off.
Because the LingsFire charger works so well with the bare bones 5 watt charger, a low wattage unit may be the way to go when using this kind of charger. Five or seven watt solar chargers can be had for around 20 bucks today, the LingsFire charger itself was around 10.
I presently have two of the Lingsfire chargers, and the Aukey and Sunfire, with double USB outputs, appear to have the power to handle two chargers at once. If a couple more additional tests go well, I may get more so I have a AA/AAA charger for each of my five USB portable solar outputs.
If anyone has good experiences with a AA/AAA USB charger with a higher amp intake, I'd like to hear from you. More amps mean faster charging. If anyone's using specific 5 or seven watt solar chargers with good results, I'd appreciate like to know. I'm thinking bare bones charger combos make for excellent birthday or holiday gifting.
One more thing worth noting, the SunKingdom and Aukey charger canvas (or canvas-like) cases have loops to allow hanging at various angles to maximize sun exposure. Online reviewers have also suggested hanging them over a backpack to allow some degree of charging while on the go. For someone planning to be on the move while charging, the Aukey controller and USB ports are mounted inside a zippered mesh bag, allowing batteries or other devices being charged to securely travel in the pouch attached to the charger. The SunKingdom charger has a pouch near its USB ports, but it's a snug fit for my iPhone5.
Update 4/4/2016: My iPhone battery was nearly depleted late this morning, so I put the SunKingdom charger up on my deck rail and plugged the phone in.
Charging as normal, no error warning that typically accompanies alternative power recharging an iPhone. The charge rate also appears to be on par with Apple wall cube. Note that I've used an extra long charging cable to allow the phone to be stashed in a shady spot while charging, and the cable's wrapped around the deck rail so that the phone won't follow if the charger is blown over the side by breeze.