Anyone who uses an iPhone knows that under normal usage the battery rarely lasts a full day. When I'm at home relaxing, the battery life issue is not really that big a deal since I can simply plug my phone into the USB charger half-way through the day and top the battery up to full, usually in an hour or so. But unfortunately when I'm traveling (which is quite often as most people know), plugging my phone into an outlet isn't always an option . Sometimes when I'm working from coffee shops it simply isn't possible to find a plug. Occasionally an airplane will have a USB port in the chair ahead ...

I found this useful deep-cycle battery FAQ that included a rough voltage level chart which helps you determine how full your deep-cycle battery is: State of Charge 12 Volt battery Volts per Cell 100% 12.7 2.12 90% 12.5 2.08 80% 12.42 2.07 70% 12.32 2.05 60% 12.20 2.03 50% 12.06 2.01 40% 11.9 1.98 30% 11.75 1.96 20% 11.58 1.93 10% 11.31 1.89 0 10.5 1.75 While I haven't blogged about it, I have a small solar panel setup on my patio which provides enough power to run a few lights in my living room each night for a few hours. This information lets me know how charged ...