Charge Controller Question
Hello I had some questions about how charge controllers operate. I have installed grid tied systems before but this will be my first system with a battery backup. I am installing a system for someone who will be grid tied and only wants to use the batteries when the grid goes down (I tried to talk her into just using a generator but this is what she wants). Her system is small compared to her load - 2kW that will supply maybe 10% of her daily needs. I would size the battery bank to run critical loads for about 3 days(15kWhrs or so). My question is, is there a charge controller that would charge the batteries when applicable and then not draw from the batteries unless the grid was down. This way she could have adequate battery back up on a relatively small system. From what I understand they are not usually designed to operate this way. I would most likely be using sealed batteries that are designed for long life with a low number of discharge cycles. Thanks in advance.