Ok,so been wfp 4 years now,all work is within about 3 miles,
do about three and a half thousand miles a year,
Started with 85 amp leisure battery,had to take in every couple weeks to charge because of short mileage.
Then had a big battery out of 3 litre jag,lasted over 6 months before I needed to take out van and charge.
Bought a numax 110 amp leisure battery about 6 or 8 months ago,its not charging,get 18 hours work out of it,may take a charge in the summer months but is too heavy for me to carry in to charge.
So got a 90 amp battery of gumtree,genuine bmw,unused the guy said,£55.
This battery is great,not had to take out and charge yet.
Think car batterys take a higher charge rate so more suited to short journey charging.
So the moral of the story is get a split relay,mines was about £20 4 years ago and fitted myself,easy,and dont buy a leisure battery if you do short miles get a car battery.
Split relays do work if you dont do many miles.