Unable to get positive charge on jetson nano

Hi guys,

Currently facing a charging issue when my jetson nano, which is connected via a suptronics t208 UPS board with 4 x 18650mah batteries). The power source is coming from a forklift (using DC 36v lead-acid batteries).

I have no charging issues when i connect my jetson setup directly to an AC source.

Problem only arises when my setup is powered via the forklift batteries (DC).

What could be the possible reasons that may cause the batteries in UPS not to charge?

Forklift batteries (DC source) → UPS Board (with 18650mah batteries) → Jetson Nano

Thank you!

Regards,
Ian

Anyone can help with this?