The PowerFilm USB + AA charger is probably the best product and design I have seen in terms of AA solar chargers, especially for backpackers. Stores like REI and EMS need to carry this charger. Basically, this is 2 devices in 1. It is a solar charger for NiMH batteries (2 NiMH Sanyo 2000mAh batteries come with the product). It is also a voltage transformer that takes the 2.4v of the NiMH batteries and ramps it up to 5v allowing you to charge a USB device (like a cell phone or iPod) using the charged batteries, even when it is NOT in the sun. This means that you can lash the unit onto your backpack or car dash without having to tether your phone to it all day, and then draw from the stored energy in the batteries at night. I charged two batteries in the sun with no problem and then charged an iPod Nano 2G while the solar panel was folded up, and it work perfectly.
In terms of backpacking, I can't imagine that there is a better option. It is light weight (I weighed it myself and it's 4.95oz without the batteries, 6.80oz with batteries) and has a large enough solar panel to get the job done. It also has a number of grommets for lashing the unit to the hood of a backpack, and the solar panels themselves are just about the width of a hood on most backpacks (not daypacks for school, but full-on internal frame Gregory, Dana, Osprey, REI backpacks). Most AA solar chargers have a ridiculously small solar panel that would require a week in the sun to charge a AA battery. This unit can charge two dead 2000mAh NiMH batteries in 5 hours of full sun. Given that you might have a cloudy day, that is exactly the type of power you need.
In regard to the reviewer who gave this a 1/5, you have to install the batteries into the unit and charge them some before it will produce sufficient USB power. If you had a lot of sun and dead batteries, then charge them for 2-3 hours first and then plug in your USB device. The instructions clearly state this as follows:
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ATTACHING A USB DEVICE FOR CHARGING
Plug the USB cable that came with your device into the USB socket on the side of the battery compartment. Connect your device to the other end of the USB cable. Check your USB device to determine if the device is charging. Note that the AA batteries are required to be installed for USB charging, and that the AA batteries must have some level of charge. Charge AA batteries from the sun before charging USB devices for best performance.
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The only "con" to this things is that the manufacturer really has not taken the time to explain how versatile and useful the thing is. Prior to making my purchase, I really had to search through a lot of web pages to figure out that it can charge a USB device from the batteries when it is not in the sun. That is a big positive feature that they have not mentioned.
Overall, I can't think of a better charger that is this small, lightweight, durable and is versatile enough to charge AA batteries for something like a Garmin GPS for hiking (eTrex, 60CSx, Oregon, etc), and it works on USB devices as well. In addition to an iPod Nano 2G, I charged a Nokia cell phone with no trouble. It is definitely the best of the best in terms of solar AA/USB chargers.
I know solar chargers aren't that powerful and can be fragile, but I decided to gamble on this one because I really like the concept. I could not be more pleased! Very very versatile. Rugged design, super light, folds up small enough to fit in your pocket, charges AA's AND USB devices (using AA power). I hang it in my window before I go to bed and by the time I'm leaving for work, the batteries are fully charged. I've been experimenting with it to see how good it is --I mainly bought it for camping and when I travel for work (all too often I find myself sitting in airports for hours).
Here's some random info that I would have found useful in a review:
1) Folds up to about the size of a large men's wallet.
2) This thing works waayy better than those Radio Shack solar chargers (which you have to buy charging tips for, I might add).
3) I was planning on making a MintyBoost, but now I've got no need as this is essentially a MintyBoost that charges itself!
4) The extra flap next to the battery compartment can be wrapped around something (like a pole) and it fastens to itself with velcro. In other words, there is usually no need to use bungees or string to tie it up to something if you're outdoors on a camping trip or whatever.
5) The solar panels themselves are flexible, really flexible, like you could fold them in half (though I wouldn't recommend doing that).
6) Battery compartment is NOT waterproof, but it is on the underside (from the solar panels), so a light drizzle isn't going to harm it.
7) Charges 2 AA's at a time (I wasn't 100% certain of this when I bought it).
8) I charged my Android phone from it and got about 50% extra battery power from it before it stopped --note, it did not drain my phone afterwards (I think that only is an issue with iPods). This is pretty impressive considering the amount of power a smartphone uses.
For those interested in it for "alternative power":
You could use this to take your phone off the grid, BUT not easily. Either charge the batteries before you leave in the morning (I don't leave at the crack of dawn) or if you have a long commute, you could at least partially charge them by putting it on your dash or whatever. Then charge the phone partway. Hang the solar panel in a window or something (facing the sun!) until it charges them fully again, then charge your phone again in the evening. Turn your phone off at night so it keeps at least some reserve power. Tadaa! (This really only works if you're sedentary like me.)
For people who have no experience with solar panels:
Don't expect too much out of solar. This is NOT more efficient than plugging your phone/pmp/etc. into a wall outlet. You need full sun and hours of patience.
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Having read the reviews I was very excited to receive this unit! As has been noted, it is well constructed, of good materials, is very lightweight, and comes supplied with high quality Sanyo Eneloop batteries. I was very excited to try it out, and anticipated using it on long distance cycling tours. Unfortunately, my experience varied significantly from other reviews. Perhaps I received a defective unit, or perhaps it had defective batteries that did not achieve/maintain a proper charge. Or perhaps, it is just the Northern climate in which I live. But nonetheless, here was my objective experience, in southern Minnesota, in mid to late May (in terms of intensity of sun). All testing was done outside on clear days, without any trees or other sunlight obstruction. After properly installing the batteries, and placing the device in direct sun, the appropriate charging lights illuminated and the device achieved a full charge in 5 to 7 hours, depending on how close it was to mid-day. I thought this was reasonable for a relatively northern latitude, for a unit of this surface area, and I was excited to proceed with using it.
Unfortunately, my enthusiasm quickly waned. Upon attaching an iPhone 3GS (after fully charging the solar unit and with the light indicating a full charge) and running a golf GPS app, the battery drained from 100% to approximately 40%, over the course of a 4 hour round of golf, on a clear day in mid-May. This is incrementally better than the usual draining from 100% to 20% charge over a typical round without any charging device. So, it did slow the loss of charge, but it was nowhere near able to maintain a full charge. In defense of this unit, the golf gps app does obviously require a lot of power (as indicated by its ability to nearly completely drain an iPhone battery in 4 hours), and the solar charger did delay the power drain somewhat. However, I was hoping that on a clear day, with the unit affixed to my golf bag on a cart, that it would have been able to maintain a much better charge. In fact, the golf bag push cart to which it was attached is angled and I intentionally rolled the cart with the device facing the sun to give the solar device the best opportunity to perform, and the angle of the cart is such that it would facilitate a perpendicular angle of the charging surface relative to the sun.
The next test was the use of the device away from the sun. After fully charging the device in direct sun on a clear day, with the light sequence appropriately indicating a full charge, I brought the device indoors and immediately attached my iPhone 3GS, that was at a mid-charge level. The wireless and bluetooth were turned off, and I put it in locked/standby mode to minimize power usage. I did not want active phone/wireless/bluetooth use to be a confounding variable. After three hours, the iPhone had only gone from 48% charge to 51% charge. While I realize that the solar charger technically "charged" the phone somewhat, it was not doing so at a practical rate, and I terminated the test at this point to use the phone.
As a third test, I inserted two Sony AA 2500mAh batteries that were fully charged by a wall charger, into the solar unit battery chamber, and attached a completely dead iPhone to the unit. It charged the phone from 0% to 51% charge with this set-up. So, clearly, the electrical connections, and USB port worked fine. Unfortunately time constraints and cloudy weather precluded me from testing the device with solar charging with the Sony batteries, to attempt to differentiate betwen bad batteries versus insufficient unit charging capacity as the etiology of the suboptimal performance. I also did not test the supplied Sanyo Eneloop batteries in a home charger, in terms of their ability to accept a charge.
So, there's my experience. You can decide for yourself.
As my experience was an outlier, I encourage others to post their experience. Specifically:
1) Time for solar batteries to achieve full charge
2) Whether they are then capable of charging a device while the unit is away from the sun
3) Ability of the solar device to achieve maintain a charge on your electronic device when in direct sun
If you choose to post, please indicate degree of cloud cover, your location and time of day (as latitude and time of day affects sun angle/intensity) for your experiences.
Who knows? If the overwhelming response is that these units did much better than my experience, maybe I'll reorder one, and try it again, to ensure that it wasn't just a defective unit or defective batteries that I received.
Read Best Reviews of PowerFilm USB+AA Solar Charger Here
I bought this so I can always have good battery in my GPS (uses two AA) and cell phone (uses a 3.7V 850 mAh ) for doing weeklong bicycle trips such as GOBA. It turns out to be small enough that I just keep it in my emergency repair kit all the time. I leave the batteries out of the device because the USB charger draws ½ mA with no load. This would discharge the batteries in about six months.
Before you buy one, you should probably do a little math. The product description lacks the detailed specs (the reason for only four stars) so here is what you need to know:
The USB charger is rated at 5V with a 1 amp maximum load. If your application requires more than this it's not going to work. The solar cell charger is rated 3.6 V at 400 mA in full sunlight which is optimized to charge the batteries that come with the device. To determine if the USB device will recharge your battery, look at the current and voltage on the battery to calculate Vah (Volt/Amp hour). For example; my cell phone battery is 3.7 V at 850 mAh = 3.145Vah. It will take at least 20% more than this to charge the battery due to losses. So in my case, I estimate it takes 4 Vah to charge this battery. The AA batteries that come with the unit are rated 2.5 V (for the pair) at 2000 mAh = 5 Vah. This turns out just about right because after fully charging my cell phone battery, there is still enough in the AA batteries to power the GPS for about two hours.
To help speed things up, place the solar collectors on something cool with all cells exposed to sunlight. Charge the USB battery with fully charged AA batteries and the solar collector exposed to sunlight.
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I've tried about a half dozen or so small AA-type solar chargers, and all of them have been disappointing to some degree or another. Either they are flimsy and break all too easily or they take two days to charge a few AAs... They all seem to have the same weaknesses, with the occasional tradeoff for a strength or two.
This one is the exception. Not only is it far more ruggedly built than the competition, it seems to have much better charging capacity. Most of the ways you could think of breaking your typical AA charger will not work on this thing. It's flexible and long drops will have no effect. It doesn't seem you'd be able to crack or shatter the panels. The wiring is buried safely. I can't imagine how I'd break this unless I actually set my mind on it.
Charge time seems to be much shorter than competition, too. I haven't done anything empirical, but it does seem to charge my Eneloops much faster than the other chargers I've got and have had in the past. As a bonus, it seems to charge more USB devices than some of the other chargers I've got. You do need to have the batteries in to do this, it should be noted.
I like this one so much I ordered it's strictly-AA cousin (the 4xAA charger) to increase my charging capacity. I have finally found a charger that I can trust.
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