Ideally no battery should be run flat. It can permanently damage it.
What pump are you using on the trolley?
I use a Pure Freedom trolley. However, about 3-4 years back I replaced the Sureflo pump for one these from eBay
![](http://www.cleanitup.co.uk/smf/1593293394_conversion_03.jpg)
It will run all day on a 10ah Yuasa SLA
![](http://www.cleanitup.co.uk/smf/1593293755_conversion_04.jpg)
The battery pictured is a 7ah which will be good for all day if you are using a 4lpm 60-70psi pump. I'm using a 5lpm 70 psi pump so the battery I'm using is the 10ah version which is 13mm taller. It lasts me 9am-3pm and is still going strong. My round is very compact so it's in use a lot of the time.
It is charged every night.