[pilleya]

So if your power usage is 6a/h per day ( at 12V) and you are wanting minimum battery changes/maintenance surely larger batteries would be better.

Is there anything which makes large lead-acid batteries unsuitable for this purpose?

A large sealed lead acid battery/marine battery ( let’s say 60a/h) should be able to power the bench for more than a week before needing a battery change.

Because of the relatively high weight of the battery (probably 20kg) you could have a high-amperage battery charger already attached to the battery and simply need to run a power cord to the bench to plug in and charge with when possible or when the gallery is closed etc. You could even use two batteries in parallel if you have the space. Although the battery(s) would be bulky and heavy this has benefits, if you attach it to the bench securely enough (in a nice looking weather-proof enclosure) the 20-40kg of battery weight, is going to make someone seriously reconsider trying to steal or move the bench.

If you have battery charger permanently attached to the battery the people at the gallery would simply have to run an AC power cable to it occasionally, and potentially click a switch to change it from operation to charging.