Pros / You can disconnect the battery from the panel and use it as an external battery pack.

Cons / The Amp’s case isn’t large enough to keep your device inside while it charges.

 Verdict / The Voltaic Amp is a perfect mix of form and function. The dual-voltage-capable panels expand its use beyond charging simple small devices, making it great for rechargeable DSLR cameras too.

Editor’s Note: This product has been removed from our side-by-side comparison because it has been discontinued. You can still read our original review below, but Top Ten Reviews is no longer updating this product’s information.

The great thing about the Voltaic Amp is its detachable battery. The company makes great solar panels for this portable phone charger, but the rechargeable 5-volt Lithium Polymer batteries are very nice. The batteries are smaller than most smartphones and not permanently attached to the solar panel. They’re also stylish enough that you won’t be embarrassed to be seen using one out in public. One of these batteries can be charged in under 5 hours when plugged into a USB, and barely longer than that when plugged into the solar panels.

The panels themselves really are impressive. The Amp comes with two 2.2-watt monocrystalline silicon panels that measure 4 inches by 4.75 inches. Voltaic publishes that they are capable of delivering 6 volts with an option to deliver 12 at the flick of a switch. We suspect this was the voltage measured at Voltaic’s Brooklyn, New York, offices as the Amp tested much better at the higher elevation of 4,215 feet in our Ogden, Utah, office.

The battery is a rechargeable 4,000 mAh, making it big enough to charge most smartphones at least 1.5 times before going completely dead. However, it charges passively when left connected to the solar panels inside its handy carrying pouch that can be easily carried or left in most any bag. The only downside is that the pouch is not large enough to keep your device inside while it charges.

The Voltaic battery pack is designed to work with any 5-volt electronic that’s powered by regular and micro-USB. This includes smartphones and handheld games. It has a clear charging indicator near the USB port that displays the charging status for quick reference with the push of a button. It even has a mode that allows you leave the display in an always on state, although this mode does consume power.

The battery is stable enough that it allows for pass-through charging, which is charging your device at the same time the battery is being charged, although we did find a small issue when testing this. The battery displayed no voltage when we plugged it into the solar panel with the digital multimeter already connected. The battery pack had to be plugged into the solar panel before we could connect our tester. This does make some sense as a safety feature related to built-in components that regulate the battery’s charging cycle. Normally these stop your battery from overcharging, but it may also keep that sudden rush of current from frying that expensive smartphone.

We taunted Voltaic over Twitter when the Amp came in for testing. The simple response was, “Go ahead and bang on the panels.” We took them at their word and after doing more damage to a desk than we did to these solar panels, we were surprised to find that the scratches buffed right out. The urethane coating did less well against the concrete curb outside, but still mostly managed to buff out.

The strength of these panels is in their protective coating. Voltaic’s panels are thick with a generous urethane coating. This is important not just for the finish quality, but it also makes them incredibly easy to clean and keep free of debris, which helps them keep their efficiency. Voltaic reports a 5-volt output each, though we tested them slightly above 7 volts in normal outdoor lighting at a 4,200-foot elevation.

An interesting additional feature of the Voltaic Amp is a switch near the battery that turns the panel's output voltage from 6 to 12 volts. This extra output comes in handy for certain rechargeable devices like DSLR cameras.

The higher voltage setting appears to change the connection between the panels from series to parallel. The relationship between the two connections is inversely proportional, meaning the output amperage at the higher setting will be half that at the lower setting. This means it will take longer to charge a device using the 12-volt setting.

The switch for changing between the two voltages is small and recessed so it won’t get accidentally moved, but it might also be easy for you to forget about. You should never charge the Voltaic battery with the 12-volt setting. The higher input voltage will damage the battery and the output amperage cut in half will never be able to give it a full charge. A panel output voltage indicator or feature that automatically reset the output to 6-volts would go a long way towards preventing such accidents from happening, but so would looking at the switch.

At first glance, the device may seem bulky and inconvenient as a unit, which makes the fact that the battery is not permanently attached to the panels a real perk. On its own, the battery is smaller than the average smartphone, which gives it great portability. Overall the Amp is one of the more versatile devices we’ve seen in our review of solar phone chargers. It comes with a microUSB connector, but connecters for other phones are available on Voltaic's website.

The Voltaic Amp ranked well in portability. We based this value on a combination of factors, including weight, dimension and the materials from which it’s made. The entire setup is housed in a recycled polyethylene terephthalate (rPET) shell that’s barely larger than a pocket dictionary. Polyethylene terephthalate is the same material that makes up plastic water and soda bottles. Approximately 4-billion pounds of PET end up our landfills each year, so it makes us happy to see a company that recycles this discarded resource.

What makes polyethylene terephthalate a good choice for a solar phone battery charger is that it helps protect the electronics inside. The case is lightweight and resistant to water and ultra-violet light. This of course does not mean the Amp is waterproof. The zippered enclosure leaves more than enough room for water to get in. It is safe enough to get a little rain on it, but we do not recommend leaving it exposed to the elements for any extended period of time.

Voltaic warranties its equipment separate from the batteries. The case and panels are guaranteed to be free of defects for two years. The battery, however, is warrantied for one, which is the common period for the non-Voltaic solar phone charger batteries we reviewed.

This is a great company with a lot of great resources for its customers. The website’s Support section features a collection of online and offline materials to answer practically any question you may have. There is even a Post a Public Question button where your question may be added to the online Support Center.

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The Voltaic Amp was the easy favorite in the solar phone chargers we reviewed. It travels well as a complete charging unit, and the battery can be separated from the panel for better portability. The panel also doubles as a 12-volt charger, meaning you can use it to charge your DSLR camera, too. However, there is no automatic feature to reset the voltage back to 6 when you’re done.

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