Hi, I have a 600VA UPS for my computer, I have it as an UPS but as soon as the power goes UPS also goes. No back up at all. I can Change the battery but I hope I can get only about 10-15 mins of backup. So what I am planning is to get a 100AH battery and use it with the UPS I have. I will remove the battery inside the UPS and connect the 100AH one. I know that the charging current from the UPS will not sufficient to charge the 100AH. So I am planning to buy a seperate charger and connect that charger to 100AH battery and same time I am going to connect the battery terminals to the UPS. Will it workout?? attached a diagram.