Just read the PC mag article about these. Looks like valid technology, however, their intended use is to extend the life of throw away batteries. They do this by boosting the voltage and draining the batteries more fully. The life of rechargeable batteries can be significantly reduced by discharging them too far. The article mentioned that the product can
boost the voltage of rechargeable AA batteries, but they don't provide information about how this affects battery life.
The voltage boosting technology has been around for a while, what makes this product novel is its size.
My take: cool product. Rechargeable batteries are still more environmentally friendly. Voltage boosting technology makes sense with renewable
energy as long as the allowed discharge is coordinated with what the batteries can regularly handle.