I’m having what I think are battery issues with my first solar system setup that I did last Fall. It’s a small 12V system to power a TV (AC) and a portable Dish satellite receiver at our off-grid ranch in Northern Arizona. I tried to keep my costs down since this is only for entertainment and we’re not there full time so the batteries sit unattended in a hot building while we’re away. The system consists of a Morningstar TriStar controller (TS-MPPT-30), one Canadian Solar 305 watt panel and two Costco Interstate GC2 6V golf cart batteries. The TV and satellite gear only draw about 70W (based on Kill-A-Watt meter reading) so I started with a Samlex 150W inverter (PST-150-12) so I could get more hours from my batteries – wanted to draw the minimum I needed. All went well through this winter – could watch TV for hours. But now that it’s hotter, the inverter needed to run its fan more and the Samlex started setting off its alarm. Continuous alarm – presumably overload since it would stop if I shut off the TV screen while the satellite still ran. So I bought a Cotek 200W inverter (SE200-112) to just up the power a bit. Just started using it this week and quickly hit issues. With the Cotek, it starts throwing a low voltage alarm within about an hour of use. So I pulled out my little Ideal voltmeter to see what’s going on. Here’s the scenario:
Battery voltage prior to starting inverter (we're running the TV at night after a full day of charging): 13.1V
Battery voltage as inverter starts running: 11.6V
Inverter alerts start when battery voltage shows 11.1V; frequency of alerts increases as voltage drops
Battery voltage after about an hour of TV but once inverter has been shut off: 12.8V
So now I’m wondering if my decision to go on the cheap with the Costco batteries is my problem. I really don’t want to invest in expensive batteries that will be brutalized by our hot building when we’re away. I could switch to an RV DC TV, like a Jensen, since the TV portion of the system takes about 55W – but they’re expensive for the bigger screens – so I’d want to be sure this is the best path before doing that. We're here less than half time so I'd really like to stick with lower costs. Any insights into what’s likely going on here would be much appreciated. Thanks!