ANOTHER Battery question - Sorry!

[SOLOMAN]

Hi All,

2004, MKVI T280 here.

I'll try give a summary of history of this, then ask some particular questions:

1. About two years ago van starts cutting out randomly while driving
2. Increasingly, I've had to jump start it, after shorter periods of inactivity
3. Two weeks ago, came to start it, it was COMPLETELY dead, no lights nothing on the dash, central locking not working etc.
4. It has two batteries, the one nearest the bulkhead, I'm informed is the starter battery.
5. Tried to jump start it, no joy, just clicks not turning the engine over.
6. Thought to myself "you know what i think this is the original battery, I'll get a new one"
7. Put new battery in, worked first time.
8. Had to take the stereo out to get the unlock code - While in there I noticed what appeared to be a small multicore cable that's clearly just been cut and stuffed back in. (Van used to be a National Grid van, so I wonder if there were some dashboard attachments etc that may have been removed prior to selling it). Thought nothing of if - taped the cable up as a whole and put it back in.
9. After three days of no use, I tried starting it last night with brand new battery - COMPLETELY DEAD again.
10. Something is clearly draining the battery.
11. Tried starting with the recently re-charged older battery no joy -(A multimeter across the terminals gave a 12.5 volt reading, is this high enough? )

So my questions:

1. It's been suggested to me that the leisure battery might be draining the starter battery and to disconnect it - I can't really think what purpose the leisure battery is serving for me, so assume it's OK to do this? (They appear to be wired in parallel, with some sort of 'thing' in between them - Apologies, I know nothing of car electronics!)
2. Do you think the small severed 'multicore' cable behind the stereo might be 'shorting out' some how and draining the battery? (Tonight, while it's dead I'm going to strip the cable and separate each individual core and tape them up, so they cannot make any sort of connection anywhere or with each other just in case, but i have no idea what this cable is. (You'll see I'm guessing at this here!!)
3. Of course doing these two things at the same time might not help me figure out which one is causing the problem, but I need to use the van tomorrow!!

So tonight I'm going to try re-charging the new battery and topping up the old one again, then I'll try again tomorrow! If that works I will try recharge the leisure battery too, just in case.

Of course, I'll need (Or get somebody else) to figure out what's draining the battery..... Mucho FUN!

Cheers All!!

SOLOman!

[dumper]

You really need to change both batteries at the same time if this is the standard van set up the front battery powers things l on the van that are not needed to start the van but if it is dud when the relay connects them together for starting it will drag the starter battery down it’s also no good checking a battery with a volt meater you need a heavy duty battery tester .but you may still something drawing the battery down

[Brains_transit]

After I had battery drain on a 2002 I removed the dash loom and engine loom to test and it was the indicator relay under the rad expansion tank on the inner wheel was full of water

[SOLOMAN]

You really need to change both batteries at the same time if this is the standard van set up the front battery powers things l on the van that are not needed to start the van but if it is dud when the relay connects them together for starting it will drag the starter battery down it’s also no good checking a battery with a volt meater you need a heavy duty battery tester .but you may still something drawing the battery down

Cheers for that! I'll give the second battery a charge too. Re testing the battery, I read in a number of places that using a multimeter would give a good indication of the charge status of a battery, and it does produce a measurement which matches with the advice I have read online.

Cheers!

[SOLOMAN]

After I had battery drain on a 2002 I removed the dash loom and engine loom to test and it was the indicator relay under the rad expansion tank on the inner wheel was full of water

I'll keep that in mind! But I won't removing wiring looms, I wouldn't know where to start!!!!!!!

[Brains_transit]

After I had battery drain on a 2002 I removed the dash loom and engine loom to test and it was the indicator relay under the rad expansion tank on the inner wheel was full of water

I'll keep that in mind! But I won't removing wiring looms, I wouldn't know where to start!!!!!!!

Just check if the relay is there and see if it's wet and rusty.

[amlav]

Best is to change both batteries in the same time . The one you did not change is draining the other battery (the new one ).
Now.....the bad news is that if your new battery was drained down by the older battery (to bellow 11 volts ) than the new battery will be cactus too .
Most likely it will show 12..13 Volts after recharge but that would be only surface charge (so to speak ) but it won't be able to deliver at heavy load .
After being charged batteries need to be load tested to get a conclusive good-no good verdict .
Average live span of a battery is between 3 to 5 years . Some can go to 8 years but verry rare .

[Altransit]

As above, by amlav, you might have already killed the new battery, since on the Mk6, the batteries are connected together at all times, (unless it's aftermarket with a charge relay) unlike the Mk7 where the rear one is isolated for starting.
It's therefore important with this Mk6 setup that both batteries are equal in age, type and size/capacity.