Battery was doing fine on the fan but the lights deadly

First, you can't judge anything by a battery indicator light panel. You have proven that by using the draw of 6 light bulbs. If you would let the battery rest between short sessions of just using those lights, the battery indicator will show fuller than when the lights are on. Use a hand held multimeter across the battery terminals.

FWIW, a single grp 24 battery doesn't hold a lot of amp hours. A battery addition or upgrade is a good modification to keep the 12V bogeyman away.