Good evening please can i get help...im a mother of 2...and i know nothing about inverters but it used to work as they showed me once...but now when there is no electricity and i switch on the inventer..it says battery low...im not sure when im charging if im doing something wrong ...i usually plug it in when there's electricity...i switch off the on button..then keep hybrid on,ups on and the charging moni thingy on.please advise where am i going wrong here??