Hello, i currently own a "POWER TREE S650BX". i need some information how to charge the UPS. I have been using it for 2 month with no problem whatsoever, but since two days the battery power is not kicking in after a power failure; the UPS only beeps 3 times, then there is total power off. How should i charge it? should the battery switch at the back be left ON while it's charging or should i turn it off? what about the blue button up front? should i turn it on or turn it off so as it can charge?