@icic , unfortunate that you are having these issues with your van. I know, it can leave a bad taste about dealers and VW. I would personally gather more information, before even approaching a dealer. There are a few things that you can do.
I would deal with the two batteries separately. However, before that, a few questions -
a) how old is your van? I am assuming less than 2 years old. (your Join date is Aug 2019). Information on the Year of the van will help.
b) Also, did you have it from new? I am assuming yes. Do correct me if otherwise.
c) Information on the number of miles it has done since it date of registration will also help.
You will know that all electrics ahead of the B-Pillar is on the starter battery and everything behind it is on the two leisure batteries.
Dealing with one battery at a time.
1. Engine Starter Battery.
- In your other thread on heater smoke, you mentioned that you were able to start the van without any issues. Since then, has the van been not driven for > 1 week?
- the reason I ask - with a healthy battery, people on here have left their vans not started for extended periods (>4 weeks) and have been able to start the van perfectly. It could mean a weak battery.
Get the starter battery checked (Halfords do that), and see what they report back on the health of the battery.
Also, while at that, do see if Halfords can check that your alternator is producing sufficient juice to keep the battery charged.
- As Qnapper has said, to maintain a healthy battery, recommended to plug it in for 24 hrs every month (not required if you drive it regularly). In the last month, my van was plugged in for a week continuously as my son was using the van as his study room.
- Either which way on whatever Halfords report, is there anything else that is plugged into the van such as USB phone chargers, especially the ones with a small light on them, which are technically always ON and have the ability to drain a weak battery fairly easily.
_ do you have any additional accessories running off the starter battery - trackers, cameras, or any other devices?
Do check all these, and if the answer to the last 2 questions is a no, then it points to a weak battery and you may need to get it changed.
If you've been driving regularly, (and long distances - you mentioned 200 mls on your other post) and still this has happened, it will surely be a warranty job as the dealer could have given you a van with a weak battery, as it may have been standing in their forecourt for extended duration without any charge.
Another thing - if plugging in the van and it does not have any impact on the starter battery, check the split charge relay fuse. I am forgetting which fuse it is, but do search on here and you will be able to find information on it. (example - see this -
https://vwcaliforniaclub.com/threads/leisure-battery-not-charging-when-driven.16396/ )
2. Leisure Batteries
From your earlier post on the smoke from the diesel heater and it switching off, it seems that all points to a failing leisure battery. The kitchen lighting will have a negative impact on it ... and if it is randomly coming off and on, then yes, that can drain the battery.
If you have been using the van regularly, and plugging it in as advised, then, I would
a) get the batteries checked independently
b) get the dealer to fix the kitchen lights
c) at the same time report that you have been doing everything right on the battery charge front and that points to you being given a van with a possible failing battery which has to be replaced under warranty. If they say that the battery is alright, then show them the other battery test report, if it is reporting a weak battery.
All the best and do let us know in case of any other queries.