X2 on the battery. The Parallax 7155 I think requires a good battery presence to operate an RELAY inside the converter before it will work. Some of the older converters require the battery to be in the circuit to enhance their internal poor designed regulation circuits.
You might be able to just jumper the battery with a car battery and get thins to start working.
However once you have depleted the deep cycle below 50% charge state it is not going to be very good if you get it to charge back up.
You really should replace the battery first. This would be a good time to replace the battery with two 6VDC gulf cart battery wired in series and that will give you a big 220AHs of capacity which is what you need if you ever are going to do any OFF THE POWER grid camping.
I would also start thinking about replacing the 7155 Converter with a Progressive Dynamics PD-9260C Converter which supports the smart mode charging technology. This will automatically take care of your connected batteries...
Roy Ken
