Hi Dazmond
What charger are you using, you have said an intelligent battery charger but does it stipulate what size battery it will charge or is it an intelligent charger from say a trolly system. What size is the battery you have, how many Amp hours?
I would recommend spending some money on a good charger like a CTEK, in the long run a good charger will prolong the life of the battery. I'd also recommend getting an AGM battery, however seeing as you only run one pump this is less of an issue, but an AGM battery as opposed to a standard Lead Acid will last a lot longer.
If your work is compact then I would advise against wiring to the van battery as you will drain you battery and not be able to start back up. I do think the option of getting batteries from a scrap yard is a good idea certainly cost effective even if the battery only last 3 months or so.
There is a difference between starter batteries and leisure, a starter is made do give out a lot of amps in one go but not to discharge to near empty levels, where as a leisure is the other way around, discharges to near empty ok but can'y give out a lot of amps in one hit.
Simon.
