I need to upgrade my system to Lithium. What battery should I buy? I just had 6 lead acid sealed Marine batteries die after one year of use/never performed correctly (which is another topic). I believe investing in a Big Battery LIFEPO4 battery will give me peace of mind (10 years of warranty). Also it makes sense money-wise: 8 Marine batteries @$120 each for two years (in theory) vs one Big Battery 5.8KWH @ $2300 for ten years. The cost of the Big Battery is about $230 per year over 10 years. I live in PR where our electric system was just privatized to a ill-prepared LUMA Energy. In the two weeks since they took over we have had several outages. I have a hybrid system where my inverter can charge the batteries from the grid BUT ... with no reliable grid. My array is four 315w polycrystalline panels. I have an AIMS MPPT 100 amp controlar and an AIMS 2000w Inverter. I live alone and my usage is about 3.5 KWH per day or less (I tested and my refrigerator uses exactly 1K per day). I use lights, fans, TV and computer. The Big Battery website says that the 5.8KWH battery is out of stock. I hope not for long. My other option is the 24V HAWK MAX - LIFEPO4 5.2KWH (instead of the 5.8kwh MAX 2). I am told that I should have 3 times my daily usage in the battery power to account for cloudy days. Math: 3 x 3.5kwh = 10.5 KWH. But I live in sunny PR, so how about 2 X 3.5 KWH per day= 7.0 kwh. What size battery do I need? Thanks in advance for any help. Kathy