If there are ants inside, there might be some MICE too !!!
Let's hope not. They chew wires.
It really is a good idea to pickup a cheap multi-meter, like from Harbor Freight for $10 and at least learn how to measure 110 VAC and 12 VDC.
Like for instance: if the voltage at the battery measures 13.4 when the AC power is on, either from the shore or the gen BUT then immediately drops below 12 V when the charging is stopped.....then it's time to shop for new batteries; assuming the connections are clean and tight.
I have a 12 V meter and a 110 V meter plugged in all the time. They are about $10 each and have come in very handy several times.