Stop in for a cup of coffee

So I forget who was asking about solar systems a while back. I’ve got a very small one and decided to do an experiment. Friday, I took my deep cycle battery and connected it to a pair of Kc 350,000 candlelight off road lights, left them all all day. Drained the battery until they shut off. Checked with the multimeter, 0.0 volts showing. Completely dead. Hooked it to my solar panels, it will not register on a charge controller. Which confirms the reports ive read from online, solar panels won’t charge a battery at 0 volts. Needs a minimum of 1-2 volts depending on the charge controller