In order to get the fullest potential out of rechargeable NiMH batteries, you will need a good smart charger and a solar battery charger. This will allow you to keep your electronic gear “up” in deep remote areas and after a long duration power failure. The ability to charge batteries should be considered a vital part of ones personal equipment. Flashlights, GPS receivers and vital communication equipment are useless without batteries to power them. Don’t overlook the importance of keeping these items powered up.
Modern NiMH batteries need to be charged in a specific manner in order to retain their usefulness and achieve full potential. A computerized “smart Charger” is needed so that the battery is charged at the proper rate, then when it has reached its capacity, stops receiving a charge and changes over to trickle charging.
To put together a solar battery charging system for NiMH batteries, you will need a smart charger (for NiMH) that comes with an adapter for its power source, and a solar panel assembly that will output through the mating adapter port. This is often a 12v car (cigarette lighter) power port. Connect the two together and you have a working solar NiMH battery charger system.
One highly recommended solar charger is the Guide 10 by a company called Goal Zero. When tethered to its companion solar panel (such as a “Nomad 7”) it will charge 4 NiMH batteries. It also has USB and Micro USB outputs that allow the charging of things like Cell phones and digital camera batteries right off the power pack. The guide 10 is also a flashlight.
The solar panel is the heart of the power supply system. It is also the most expensive piece of the power kit. The solar panel you choose needs to be capable of mating to your smart charger, it must be lightweight, small enough to fit in (or clip onto) a backpack, durable enough to be reliable in the field, and put out enough power to charge batteries in a reasonable time.
Goal Zero offers a 7 watt monocrystalline panel that offers all of these features; it is the Nomad 7. It has a USB output (5V) a 12V output and an output to charge the Guide 10 smart charger. The panel is the size of a paperback book, weighs about 1 pound, and can charge 4 AA batteries in approximately 2 hours.
Another, more powerful, portable, and foldable backpack solar panel is the PowerFilm F15-600. Powerfilm makes solar panels for the US military and that quality is reflected in their commercial panels as well. The PowerFilm F15-600 comes with a female 12V car adapter so the appropriate smart charger needs to be acquired for it. Any “smart charger” that supportts 12v car adapters will work.