Leisure battery help for a newbie please

[kevinpke]

We are proud new owners of a 1987 T25 Caravelle, with a shocking lack of practical knowledge or ability.  Our leisure battery seems to have stopped working completely - so what do we do now?  I have tried looking on here but the remarkable amount of advice looks a bit technical for a beginner. Can anyone recommend a real idiot's  guide, ie this is how you charge it/tell if it has run out of charge/which fuse connects to what diagnostic guide?    Thanks in advance!
 

[Mocki]

Good evening , I will move this post to technical electrics , so more will see it and help 

first thing I would advise is taking the battery out of the van and charging it on a mains charger 
( or disconnect the neg ( -12vdc) connection and charge it on the van if you can .) 

then look for the split charger , it will be one of two types of relay next to the main battery , and will ( hopefully) have a fuse on it, or nearby , which will be blown ( hopefully ) 

what be generally happens is people throw a second battery in and connect a split charger ( or sorts ) but more often than not they fail to use a big enough capacity relay , thick enough wiring And too small a fuse , so when the leisure battery gets too flat and you start the engine the battery tries to take 50 or More  amps from a 20amp circuit and ( hopefully) the fuse blows .... 

a few picture will help folk help you 

[aknapper]

I just had to diagnose why my leisure battery wasn't charging and it was a blown 20amp fuse on the positive (red) split charging cable, located in the main battery box (under the driver's seat).
There may be another fuse on the line (like mine) near to where the leisure battery is.

[kevinpke]

Thanks for the advice - steep learning curve!  A friend recommended we get a portable battery charger, any recommendations on which one to go for?

[maxstu]

Thanks for the advice - steep learning curve!  A friend recommended we get a portable battery charger, any recommendations on which one to go for?

Welcome to the club...
Go back a few steps before splashing on a charger. Your camper may already have one built in to the circuit. Have you a fuseboard in habitation area
As stated before a few pictures may hold a few clues. Or at least conversion name if possible.
Firstly with engine off. And then running are you able to check voltage on leisure battery?
Do the interior habitation lights work?