Starter battery constantly draining

[Epic-Rob]

There seem to be a few threads on this but not one that covers my problem.

the back ground.
2021 T6.1 bi turbo 2wd with about 9000miles on, full camper conversion, have had an issue for a while now with battery going flat over maybe 3-4 days from fully charged to just a click when you turn key or not even enough power to open van.
Has been in to VW once before and cant find any fault.

i dont drive van daily so it can easily sit for a week, a few weeks back i had it checked for drain by an auto electrician, from just testing on the battery he couldnt really see any draw that was abnormal and would cause total battery discharge in a few days.

I have a BT battery monitor which i plotted it over 4 days - fully charged to flat, attached pics show 12.59v fully charged, to 12.32v, i think it was next day it wouldn't start.
my charger is a Victron Blue smart one so not a cheap charger.

i do have a dashcam which i am sure is on an ignition feed but for the sake of this test i disconnected it, i also have a feed to my DCDC charger but i also disconnected this too, so there is nothing conversion related connected to van battery (except which i noticed yesterday an earth from battery direct to DCDC)

OK so i have got this booked into VW but they tell me 3 weeks before they can see it! so i thought i would swop batteries with my 2017 T6 which doesnt have a problem just to eliminate a faulty battery. the T6 battery is a slightly larger Ah than the 6.1 one something like 80Ah V 95Ah
i will just refere to batteries as T6 (95Ah and T6.1 (80Ah)

I fully charged both batterys till the charger says full T6 was 13v and 6.1 was 12.9v (multi meter)
when i put them on van and tested with multi meter T6 was at 12.1v and T6.1 was 12.4v so i am not sure where this drop has come from! bere in mind i have swoped bigger battery into T6.1 now.
I started vans (T6 with the smaller battery in was a little sluggish to turn over) then took a multi meter reading
T6 was charging at 14.1v and the T6.1 charging at 12.45v (multimeter on batt terminals whilst running) so after about 15 mins turned off and checked again.
T6 12.7v T6.1 12.3v so the T6 gained a bit and the 6.1 lost a bit.

I took 6.1 for a drive thrashed it a bit - higher revs ets for about 30 mins when i got home and checked it it was at 12.2v - hope it starts this morn.....

I have also read recently that you have to have battery coded to van - will that make a diff if its not coded????
i have disconnected battery a number of times to charge it - could it be that it needed coding?

so i am a bit of a loss as to problem.

Any Theory's??

 

[Dellmassive]

Post pics of the 1 day. 7 day. 15day bm2 plots,

So we can see the drop over time.

 

[Dellmassive]

Disconnecting the battery will trigger a relearn.

You might notice that the stop start won't kick in for the next 10 or so drive cycles.

 

[Dellmassive]

Running the battery dead flat will seriously reduce Its capacity.

You need to test whether you dash can is connected direct to the battery.

Or via an ignition feed .

 

[Scottish Scrutineer]

When you swap batteries, you really should recode to make sure the van knows what capacity and type of battery is fitted.
When running the T6.1 to charge the larger battery, did you have any electrical loads on? If not, that may have been why it was not charging. If you can repeat with headlights, fans etc on to trigger the van charging, even better take it for a run and monitor the BM2 to check it charges. This may only be on over-run (if DSG, use Sport mode, or brake lightly to prevent coasting). When charging it alternator can kick up to 14+ volts.
I’d also disconnect the negative from the dc-dc from the starter battery, simply connect direct to the body earth. This effectively could be bypassing the OE ‘shunt’ which separates the starter battery negative from shell earth

 

[Dellmassive]

A few pics of the power install and batteries will help.

 

[Epic-Rob]

A few pics of the power install and batteries will help.

Epic-Rob’s Lithium Leisure Build Thread

No, look at my drawing in post #342, you missed the connection to the + on LB1 and the pos feed to the shunt.

www.t6forum.com

 

[Epic-Rob]

Disconnecting the battery will trigger a relearn.

You might notice that the stop start won't kick in for the next 10 or so drive cycles.

It did kick in when i drove 6.1 to wk this morn (15 min drive) i was quite pleased with that....

 

[Epic-Rob]

When you swap batteries, you really should recode to make sure the van knows what capacity and type of battery is fitted.
When running the T6.1 to charge the larger battery, did you have any electrical loads on? If not, that may have been why it was not charging. If you can repeat with headlights, fans etc on to trigger the van charging, even better take it for a run and monitor the BM2 to check it charges. This may only be on over-run (if DSG, use Sport mode, or brake lightly to prevent coasting). When charging it alternator can kick up to 14+ volts.
I’d also disconnect the negative from the dc-dc from the starter battery, simply connect direct to the body earth. This effectively could be bypassing the OE ‘shunt’ which separates the starter battery negative from shell earth

no i had turned lights off, but driving lights were on and maybe heater fan - i never checked that.
did disconect the DCDC earth from battery yesterday - but it has been connected during time i have been having problems BUT i had previously taken poss dcdc feed off the battery.

 

[Epic-Rob]

Running the battery dead flat will seriously reduce Its capacity.

You need to test whether you dash can is connected direct to the battery.

Or via an ignition feed .

pretty sure ignition feed - but i disconnected that a week or 2 back

 

[Epic-Rob]

Post pics of the 1 day. 7 day. 15day bm2 plots,

So we can see the drop over time.

Gradual drop is over last week whilst van sat, that dip is when i started it one day.
Last 2 high blips are from yesterday when i changed battery and went for a drive

 

[Dellmassive]

from your plot above. . . it doesnt drop below 12.0v?

is this on the starter battery?

as that should be able to start the van no problems.


my van sits at 12.2v most of the time - and its fine for about 3week.






+++++++++++++++++



see this guy who defo had a problem . . . . always below 12.0v untill the battery dies down to 9.0v





...++++++

here is a example of a good plot. . . . my van.

stays above 12.0v for the 7 - 15days. . .








......

 

[Paynewright]

Do you have any USB sockets connected permanently? They have a parasitic draw - perhaps not enough to drain the battery as quickly as you are experiencing.

 

[Sim60]

no i had turned lights off, but driving lights were on and maybe heater fan - i never checked that.
did disconect the DCDC earth from battery yesterday - but it has been connected during time i have been having problems BUT i had previously taken poss dcdc feed off the battery.

DCDC earth should not go direct to starter battery negative - it should go to the chassis - otherwise the van shunt will not measure the current taken by DCDC and will not replace this through the smart alternator- this will not be helping battery flattening problems

Simon

 

[Dellmassive]

Do you have any USB sockets connected permanently? They have a parasitic draw - perhaps not enough to drain the battery as quickly as you are experiencing.

very true.

 

[Dellmassive]

DCDC earth should not go direct to starter battery negative - it should go to the chassis - otherwise the van shunt will not measure the current taken by DCDC and will not replace this through the smart alternator- this will not be helping battery flattening problems

Simon

again very true, and something people should be aware of.

 

[Epic-Rob]

from your plot above. . . it doesnt drop below 12.0v?

is this on the starter battery?

as that should be able to start the van no problems.


my van sits at 12.2v most of the time - and its fine for about 3week.


View attachment 205867



+++++++++++++++++



see this guy who defo had a problem . . . . always below 12.0v untill the battery dies down to 9.0v


View attachment 205868


...++++++

here is a example of a good plot. . . . my van.

stays above 12.0v for the 7 - 15days. . .


View attachment 205869





......

if it gets to 12.1 -12.2v wont start.
for eg i had put the t6.1 battery into the t6, today it was at 12.15v wouldn't start, had to jump it.
The bigger t6 battery that i swopped into the t6.1 and seems to holding only dropping from 12.4 to 12.3 in 3 days so i am hoping the battery is my problem.
i havent tried to start 6.1 as i want to see what happens to the battery.

 

[Epic-Rob]

Do you have any USB sockets connected permanently? They have a parasitic draw - perhaps not enough to drain the battery as quickly as you are experiencing.

no they are all on leisure battery

 

[Dellmassive]

The starter battery must be bad then.

Work a poor state of health.

As 12.1v on a good battery will start a T6.

Unless you have an iffy starter. Unlikely though.

 

[Epic-Rob]

The starter battery must be bad then.

Work a poor state of health.

As 12.1v on a good battery will start a T6.

Unless you have an iffy starter. Unlikely though.

i recon it is starter batt the one i took out of the T6 seems to be settling at about 12.3v and started fine this morn.
the dodgy t6.1 one that is now in the T6 was low 1st thing this morn, but i put van outside yesterday and the solar charger in the Ctek250se bumped it back up to 13v by late morn. so it might be that if i put a ctek in the T6.1 as well that could solve the probs but i will also get the battery tested to see what its like.