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Discussion Starter · #1 ·
Hi all,
seen various threads regarding battery problems, but can't find an answer to what the "normal" current drain should be when the car is parked. I have a 2010 EOS 2L TDi, not a lot of fancy extra electronics. I fitted a new battery 6 months back the old one having been the original one that came with the car.
During Lockdown, the car has had little use, and on a couple of occasions. I've had to charge up the battery, a week later and there's not enough to start it. After fully charging, I put an ammeter in the battery circuit, and the drain is 600mA. There are no lights on , even took the bulb out of the boot, This is obviously way too high, Anybody have any ideas what the ambient current drain should be please? I've seen suggestions to remove fuses one at a time to see if the drain is reduced to narrow the problem down, so might try that, Will a computer diagnostic point out where the phantom drain might be?
( when connecting the ammeter, I used a prod from the meter to the battery post, so did not have to disconnect the computer when removing the main lead ) Incidentally, my son has an Audi A! which will sit for a month without use and start perfectly
Thanks very much..Pete
 

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2008 Volkswagen VR6 Eos
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When storing your car for long periods of time, installing a trickle charger to keep the battery fully charged is mandatory. The only way to stop any battery from going flat over time, is to completely disconnect it. Not really a viable option on the EOS.

FWIW, trunk light will turn off after 10 minutes or so, it stays on longer than all the other lights in the car, but will turn off automatically. No need to disconnect it.

If you replaced your radio with a aftermarket radio, this has been confirmed as a source of battery drain if you don't have the proper canbus adapter installed to address it.

A failing battery may not hold a charge for more than a few days. Also a good idea to have the battery checked.
 

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I did some tests on MY07. You can work out from the standby current draw how long in theory it takes for a battery to go flat. But it isn't an exact science because what matters is whether there's sufficient left in the battery to crank or not. I concluded that 3 months to 50% remaining charge was about the limit worst case in Winter. Now I always tender 24/7 when not driving the car. Battery life is best when they are kept fully charged. After leaving the electrical system 15 Minutes to go to sleep, I measured around 50-70mA. I had a faulty rear window module and was seeing 200mA, but current drain can be anywhere.

Not sure what solar panel chargers have to do with battery current drain unless what you are measuring is the panel charging current? Some of them don't have very good voltage regulators or non at all and can over charge batteries. They don't all have back flow diodes either and a battery can discharge into it when the panel is dark.
 

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Discussion Starter · #4 ·
Thanks for that, I realise that for long periods of time a trickle charge is needed, last summer in the lockdown I put a 30W solar panel in the window and all was fine. My car is discharging at 14Ah a day! there's a phantom discharge somewhere, the battery's only a few months old, and the "running voltage" is around 13.8 regardless of the load so the alternator's doing its job. I'm interested to know if anyones checked the current drain, and what it is please?
 

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Thanks for that, I realise that for long periods of time a trickle charge is needed, last summer in the lockdown I put a 30W solar panel in the window and all was fine. My car is discharging at 14Ah a day! there's a phantom discharge somewhere, the battery's only a few months old, and the "running voltage" is around 13.8 regardless of the load so the alternator's doing its job. I'm interested to know if anyones checked the current drain, and what it is please?
Did you replace the radio or not?
 

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Discussion Starter · #6 ·
Thank you both for your comments,
I used the solar panel all last summer during the lockdown which was fine. The solar panel has a blocking diode, and I was also at that time using a proper "intelligent" solar charge controller designed for a 12V battery system . Not a lot of point in using it now as the car is parked in a very shady spot this time of the year.

A current drain of 50-70mA sounds very reasonable, I'll have to try pulling fuses to see where the drain's occurring


I have not replaced the radio, it's the original as fitted in 2010.

I was doing some tests today with the battery disconnected, and was surprised when the alarm went off, I didn't realise that it had it's own power source, I presume it's a battery somewhere, I'd have thought it's way too old to have supercapacitors. I could not switch it off with the key fob, and had to re-connect the battery to do so, the indicators started to flash well when the battery was re-connected ( only the siren was sounding without the battery)

Love my EOS to bits, but think an ID4 is on the horizon
 

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It has a power source but not for long. I think it's a small re-chargeable NiMh ? 600mA is way too much, but you have to wait up to 10 minutes after inserting the mA meter inline. In fact you should hang around and watch it after making the connection. If it starts much higher then drops back to 600mA the CAN has sent a sleep command and what you are left with is either a fixed drain to find, or something isn't going to sleep when told to. If the drain stays high and nothing blips or changes, then either the drain is constant and far exceeeds the low drain in sleep mode or sleep isn't happening. 600mA is about 6 Watts, what I might expect from the trunk light, glove box or an interior light? The alarm is part of the standby current draw and I suppose something could be wrong with that? At least 600mA is big enough to chew on. It's drains of 100-150mA that are hard to find.
 

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Discussion Starter · #9 ·
Thankyou, that all makes good sense. I noticed this morning that initially there was a drain about 2.5A which slowly ramped down in stages to about 360mA, as things like the interior lights went off. (I tried removing the bulb in the boot in case it was staying on } Never seen a light in the glove compartment, p'raps the bulb has always been blown, I'll have to check. I'll possibly have to find a good Auto Electrician with understanding of the computer codes, meanwhile I'll look at the fuses and see if it can be isolated.
My local service garage who are excellent for normal "run of the mill jobs" don't seem too well versed in the diagnostic side of things, I Try and steer clear of the main dealer as they are super expensive, and reputedly re-map the engine management system without being asked, whenever a diesel goes in that hasn't been re-done since the emission scandal. ( I can get 65 mpg on a run and don't want that affected which I have seen reported may happen?)

Oh well, all part of the learning process, and so satisfying to try and fix things!
 

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It sounds like the CAN is sending out the shutdown commands. 2.5A to start will be the cabin lights before they fade. Yes, the stealer will re-map without asking, overwriting anything not V.W or give you the dieselgate downgrade. Diagnostics isn't really that good for diagnosing battery drains. A scan may tell you if a module is faulty, but not if it stays active and isn't going to sleep. With a service manual wiring schematic as reference, you have to meter each fuse line, reconnect the battery and check the drain after sleep which takes time. Removing fuses when the battery is still connected can give confusing answers because inbuilt diagnostics will start setting fault codes. Most fuses can have a few circuits on them so you have to dig further down.

The simplest thing to try first even though you may get a confusing answer is to photograph the fuse boxes, monitor the battery drain then remove one fuse at a time looking for the biggest drop in drain. Repeat for that fuse circuit with the meter replacing the fuse and reconnect the battery to confirm if that's where the drain is. Then dig into what's on that fuse. I got an old fuse, blew it on a battery and soldered wires to it connected to my meter. The killer drain fault nobody thinks of is the alternator electronics which are not fused, but you only investigate that if removing fuses makes no changes to the drain. There's also been a couple of cases where the main fuse box carrier has overheated and melted underneath causing voltage tracking to other circuits.

V.W have a fuse 'tree' hierarchy. The BIG fuses in the engine bay fusebox are generally feeders for fuse 'branches' in the cabin fusebox. If you start there and find removing a fuse reduces the drain, you would need the wiring schematic or owner manual to tell you what is coming off that fuse. If you start removing fuses with the battery connected, you will get some dash faults for ABS and steering which self clear after driving a few yards.
 

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Discussion Starter · #11 ·
Thanks again for that information, really useful, and I'll have to make a start. I fitted a new battery last week , and a few days after a 100 mile run it's down to 12.2V. I did as you suggested, and let the computer "go to sleep" for 20mins, and the drain current settled down at 70mA, better than I thought, but still I think, way too high? 1.68Ah per day

I fitted a digital meter to the accessory socket, and whilst running, the alternator seems to be supplying 14.2V
( should this be more like 14.4V?} which dropped down to 13.8 after about 80 miles which was when I assumed the battery was fully charged. I switched on the heated seats, de-mister, and headlights, and the voltage reading falls to about 13.9 from 14.2, I would have thought that the alternator would keep it up past 14v?
I understand that faulty diodes in the alternator can cause a reverse current, so maybe that's worth checking out too.
I'll start doing proper systematic tests, I've bought some battery terminal connectors so will make a proper jig for inserting the meter, On the 10A scale it reads down to 1mA which is useful.
Thanks for all the help...Pete
 

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The digital meters on the accessory socket are o.k for rough readings but not accurate readings of the battery voltage. They are also +- 1 digit after the DP. You will get a slightly different and sometimes variable result compared to what you could measure across the battery terminals. The accessory socket is connected by loom wiring, fuses and even could be a control module, with other circuits connected to a shared ground tap. When these circuits draw power they will cause a voltage drop or rise and your reading in the car will be different from that measured at the battery terminals.

Alternator diodes are always connected directly across the battery, maybe even its regulator? You will have to do more searching to get your drain below 70mA. The interior alarm with its ultrasonic sensors and immobiliser could take a chunk of that? The electrical system uses many semiconductor switches to turn off power consumers and one of those could be leaky. You will just have to dig deeper and not forget the alternator and anything else that might not be on a fused sub circuit you can easily access.

Your digging might produce a useful drain tree with your 70mA at the top and all contributing drains identified below. Obviously according to Kirchoff or somebody like that, what goes in must be the sum of what's coming out. If you start in the Engine bay fuses you should be able to more easily prove Kitchoff because if the drains there don't add up to 70mA it must be lost from an unfused direct connection to the battery - alternator, starter relay etc. Good Hunting.
 

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justcarkits
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Diagnosis is fairly straightforward.
Normal current drain when car locked and shut down will be in the 50mA to 70mA range (as stated by previous poster).
600mA drain will give you approx 100hrs before battery is flat and is way too high.

Alternator charging voltage in the range of 14.2 to 14.4 is normal.

Battery terminal voltage when not been charged will sit somewhere between 13.2 and 12V (when not discharged).

A quick scan with VCDS is a good starting point to see if any issues are present. Given the falt battery you will need to clear all codes and then read again. A very loe battery voltage will generate fault codes.

After that it is going to be quicker to isolate main power feeds and then trace current flows from there on.

Would also remove stereoffirst as have has these fail in high standby current mode.
 
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