It seems to me camper electrics are whoefully inadequate and that the domestic battery only get charged at the very low charge rate when the main car battery is charged. I have driven 350 miles in 4.5 hours and the domestic battery only had 10.25V on it at the end of it - What alternative charging systems are there - On boats the are using a Pathfinder system with a battery monitoring device - What is available for campers?
First you need to check what your leisure battery is recieving via the split charger from your vehicle alternator with the engine running on fast tickover, if its charging at around 13-14 volts, then you would probably need a new leisure.battery. Do you know how old that battery is ? Would also be worth checking out if you have any discharge from it when not in use. This cold weather sorts out batteries that are on their last legs. Good luck.
I agree with previous poster that you seem to have a fault somewhere. How long have you had the van and how old is it ? Has it always shown this problem ?
On a long run there should be plenty of opportunity for the leisure battery to be fully charged together with the starter batt. if all is working as it should. I have 3 batteries on mine, 2 x starter and 1 x leisure and within a few miles they are all fully charged but then my batts are only 4 yeras old and in good condition. Your alternator is working OK if the starter battery is getting fully charged so the options are your leisure battery has expired or there is a problem in the electrics and the charge is not getting through to it. Do you have a large drain on the leisure battery somewhere which is stealing the current ? Hope you haven't left the fridge on !
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As your leisure battery is so very flat, it will try to take a massive charge and it's possible that the surge of current has blown the fuse between your battery and split charging unit. Many of these only have a 30A fuse which blows when it gets the full power from the alternator. Check the fuses and charge your battery up, with a battery charger, before starting the engine again.
Could you possibly enlighten me(or maybe all of us on this forum) re. the kind of speed you were doing to do 350 miles in 4.5 hours please, i go down south ie. Crowthorne in Berk,s and its exactly 216 miles from my house here in Liverpool, BUT THERE IS NO WAY i can get there in less than 5 hours if all the motorways are clear. By the way i know this is nothing to do with your posted topic.
It sounds like you have a problem with your charger, after that distance you should be fully charged. The alternator will supply max power until the battery is charged