E26,
Going back and checking your battery, I now see it is a lawnmower battery. It does not have a lot of amp-hour capacity. I would guesstimate 10AH. This means it is only going to give you one hour of runtime before damage starts to happen. I would set it up to run around 9AM and have it turn off around 3PM max after you are sure it can produce enough power for this timeframe. This may be too much for the battery if it is cloudy.
I would expect you could get as little as 10 watts per "100 watt" panel if it is cloudy during the day. This means you really need to pay attention to your voltage to see how the battery is doing periodically.
So here is my recommendation:
Get your second 100W "panel"
Run for three hours a day and see how the battery does
Up the run time as your setup allows
Get a better charge controller
Get better batteries
Run your system as long as possible for the power you are producing less 15%
Reassess
