[DonRotolo]

I would shy away from connecting a battery charger to live electronics. A battery can handle momentary spikes, electronics not so much.

A 100A power supply is huge overkill, and brutally expensive.
A 20A power supply would be more than sufficient to maintain the battery and offer some oomph for the robot at times. Just adjust it so the output voltage (unloaded) is not more than 13.7 volts and you'll be fine.

Alternative is a larger marine (deep-cycle) battery, about the same cost as a power supply, might last all day like that.