Yeah if you disconnect the pole and don’t plug in to recirculate within a short time it can turn off then you have to go through the start up cycle again,as you know Spruce on start up cycles the batteries are under a heavy load if it drops down to 11.2 volts at some point during that time it’ll turn off I had this countless times due to a badly charged battery. If you use pumps only you’d get away with wiring straight to the van battery they draw very little,I know quiet a few that do just this but with a heater well charged batteries are a must as well as a decent split charge system the £30-40 quid types are useless.
In my experience even an expensive battery 2 battery charger won't full recharge a battery (leisure or starter) doing short runs.
Batteries only accept a limited recharge rate even although, in the case of a starter battery, can discharge a high current rate.
If I take 4 amps from my leisure battery, my van's alternator through a Sterling b2b charger will only charge my leisure battery back up at around 2 amps. In theory, if the figures remained the same, it would take my alternator 2 hours to fully recharge my battery. But as the battery accepts a lower and lower charge the closer it gets to fully charged, it will take longer than 2 hours.
We have tried to run a single pump off the van's starter battery a number of times over the years; Peugeot Partner, Ford Transit Connect and now my son's Citroen Berlingo. Starter batteries were flat between 4 and 7 days. We just don't do enough mileage or travelling time to recharge the batteries. Yet, there was a windie down South who only ran his pump from the starter battery on his Berlingo and replacement van without issue.
In today's world, I believe Lithium-ion batteries would work better in our industry as they will accept a faster recharge rate. But they need a b2b charger programmed for lithium. The cost of £600 for a 100 amph battery also puts me off TBH. Freezing temps are another issue with them. You can discharge a frozen lithium-ion battery, but can't recharge it.
Splash and Dash has stated that his Marine expert friend that has done all his WFP installations in his vans has commented that there is another battery 'in the wings' that is better than Lithium-ion.