Spruce may come along and give you all the maths, but unless you do a fair amount of driving split charges aint that great.
I drive 30 miles a day and that JUST about charges my battery.
looking at hours worth of driving = around 5 - 10 amps of power put back into battery!
i find this quite odd as i do between 15 and 30 miles and have never had to charge my battery , i use a car battery rather than a leisure battery though and as i understand it a car battery can take a higher charge rate .
In our experience with leisure batteries, it isn't the distance you drive that matters, but rather the time it takes to drive that distance. 10miles at 60MPH will take you 10 minutes. 10 miles in stop start traffic may take more than 30 minutes. The alternator will deliver the same amperage of charge to your battery whether your engine is idling or travelling down the motorway. So logically, you battery will get a better charge if it takes you longer to get there.
I would expect that if a voltage was taken of the state of your battery's charge you may find that it isn't fully charged. A battery at 3/4 charge will accept a faster charge than one that is 85 or 90% charged. The last little bit will take a long time.
What I find interesting is that Webasto, who make fuel burning parking heaters to heat the engine and interior of your car in the winter say that if you run the parking heater for 30 minutes to warm your engine up, then you must drive the equivalent amount of time to ensure your battery stays fully charged. That's for a starter battery. A parking heater will draw around as much continous current as a Shurflo pump with a contoller.
Many cleaners manage quite well with their pump connected up to their van battery. It never worked for us on 2 different vans. The most we got was 4 days and then the battery was flat and wouldn't start the van.
Can James run 2 pumps from his van battery? I will stand up and say no, definitely not in our experience. If each pump draws 4 amps an hour and you run your pumps for 4 hours, then thats 32 amps used that day. That's a lot of charge to put back. A big commercial job will probably use more battery power as there will be less stopping. He might get away with it the first day, perhaps even the second day, but I couldn't see him getting through a third day TBH.
A car starter battery is designed to give out a large dose of power for a brief few moments to start the engine. A leisure battery is designed to release it's power much more slowly. We have found that after starting the van, it takes about 20 seconds before you hear the split charge relay kicking in. If the starter motor draws 100 amps, for 2 or 3 seconds, the battery has only lost a tenth of an amp. That's nothing.
When my leisure battery is powering 2 pumps during the day, that charger is on for most of the evening to replace that. If I didn't charge it until the next evening, then I would have to leave the charger on all night as the battery wouldn't be fully charged before I went to bed. My battery is a 110 amph leisure battery.
