u/Interesting-Track830

I connected my trailer light 7 pin connector to a single 12v lithium ion battery (my car has an issue of providing power to 7 pin connector that is why)

black battery cable connected to Pin 3 (ground)

red cable connected to Pin 5 (rear front light)

Issue: only one of my light can light up at the time.
I tried to test touching with red cable on all pins exept ground, it can light up left & right side but not at the same time.

I tried a red cable split, to connect two pins identified previously as left & right but didn't work either.

I also try to disconnect ground & touch the metal frame of the trailer with it but that doesn't work at all (no light)

Would you know how to have both light lighting up (left & right?)

Do I need a second battery ?