I received this as a bday present and thought it was a very thoughtful gift for someone that is an evironmental scientist. However, after charging it in the sun for multiple days the battery only will charge my cell phone or i-pod for about 15 minutes before dying and needing 8 hrs of sun again. This is great if you only listen to your ipod or talk on your phone for about 10 minutes a day. I'd save your money though.
Before the actual review of the V-Dimension Helius backpack, the support by V-Dimension requires a special mention. The first backpack that I received also had problems to maintain a charge. Shortly after contacting V-Dimension I received a new backpack with an updated design that resolved that problem. Overall I am impressed by the quick and satisfactory response and I would urge anyone with problems to contact their support.
Now to the actual backpack. Backpack: The backpack itself is solidly made, comparable to other notebook backpacks I have owned. However, only time will tell how well it will withstand regular use. So far, no complaints regarding the choice of materials. The biggest issue, however, is the size. A 15.6 " notebook will fit in, however you have to essentially fold the top over the edge of the notebook. It is a very tight fit and leaves no space e.g. for a sleeve. The compartment itself is slightly cushioned, roughly the same as most low- to mid-range notebook backpacks that do not rely on especially heavy padding. For convenience I mostly just shove the laptop into the main compartment, if I am not carrying too much gear around. In addition there is another zipped front compartment, where the battery is normally located. Overall, this is a decent backpack if you do not need to carry too much gear around . I would have preferred a larger size, though. On the plus side it is fairly light, comfortable to carry and sufficient for most office or school uses
Battery/Solar: The main distinguishing factor of this bag is obviously the included solar charger. I received an updated version in which the battery is removable, so that it can be used outside of the bag (either in order to charge it via wall socket or to charge devices outside of the bag), which is much more convenient than the initial design. According to the manufacturer 8 hours of sunlight will fully charge the battery, which is roughly the same time I got after testing. With the new backpack I also had no problems of it holding its charge for at least a week. During smaller hikes I found that it nicely extends the lifetime of phones and MP3 players (assuming that the sun shines, of course).
Overall I am quite satisfied with this backpack. Having the additional charge is quite useful to me since I tend to lug quite a bit of electronics around. One cannot expect to be able to charge the devices fully just using sunlight, but squeezing just a few additional calls (or more if you have the battery fully charged) can be very useful .