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Battery problem


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Fab saloon - 13 years old - FSH (Main Dealer) - oversize battery - once a week use.

 

On the last three occasions I've gone to use the car the battery has been completely discharged i.e. not even power to run the cabin light or instrument binnacle clock.

 

On the first occasion this happened the car had been standing, unused, for about 4 weeks, so its to be expected that it would drain down because of the alarm. In the past, when its done this there is usually some charge left for the cabin lights and the instrument readings.

 

Since the first time it discharged the battery, I've been using the car once a week and it still seems to be completely discharging between uses.

 

When its has been fully discharged in this way, applying  a stand alone battery booster/starter to  the engine starts it   first time and keeps it running. There are no engine or electrical error symbols coming up on the instruments in the  binnacle.ry

 

To restore battery function, I usaullly run it up the motorway on a 40 mile return journey to re-charge it, stopping half way and re-starting the engine from its own battery. No problems !

 

The battery is only two years old, starts the car OK, and is slightly oversized  for the car (63 amp-hours - in order to deal with extended periods between use), so I am assuming that its unlikely to have gone as its got a 5 year warranty.

 

 I take it that there must be a massive drain on the battery when the car is not in use.

 

Any ideas ?

 

Two that come to mind are the alternator and the high amp battery fuse.

 

Any others ?

 

Nick

Edited by Clunkclick
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This just needs a boring step by step approach, first measure the drain after the BCM has closed down any unwanted supplies - after you have a known figure for that it will be down to isolating the, I think, two main power distribution points (fuse boxes) and taking it from there. The usual glovebox/boot lights need checking, or removing.

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Varta. Previously had same make, but lesser capacity, and it was good for six years.

 

It was from an on-line provider, so fast turnover of stock.  - however,  it may have been on the shelf a bit longer as it was oversize (62ah).

 

And there's  two and a half years left on the warranty.

 

N.

Edited by Clunkclick
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I've got a C-Tek and various other profile chargers so we'll see what's what tomorrow.

 

Similarly an LED voltmeter for the cigarette lighter and 10 amp Fluke, so I'm alright as far as instrumentation.

 

If necessary I can do a VCDS.

 

On Fabias, you do hear  horror stories about alternator regulators going wonkey only when they get warm, alternatot earth  leads coming adrift (Diesels only) and steering angle sensors in fault mode getting the steering pump to demand 60amp when its not needed. Let's hope its not one of those. A broken battery link fuse would be nice.

 

In fact, all the VCDS reports I've done over about 9 years show  faulty relay in the electrics, but the main dealer hasn't actioned that.Maybe its now permanently stuck on.

 

Thinking about it, this only started happening after I pressure washed the car about 3 weeks ago . . lets hope the ECU case  is not full of wasser.

 

Nick

Edited by Clunkclick
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Ah, the Fluke, built like a brick toilet - especially when it has its yellow protector on!  My preferred method of checking natural drain is to use a crock clip on to the car battery earth and a pointy test probe down on the top of the battery earth pillar and then slacken off the clamp and ease it up over the pointy test probe. Obviously this needs done after the BCM is meant to have closed things down.

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Yes, the battery light comes on when the ignition switch is turned-on and goes out when the engine starts.

 

I took it out again today.  6 mile round trip, with one stop. No problems. Started from its own resources.

 

  On returning PM, I noticed that the cabin overhead light switch was at the full right position  but  thtthe light had been on the whole time I'd been moving.  There's obviously something going on there as the light should only come on with the doors open in that position. But that's not necessarily indicative of a dodgy circuit or door switches, as I've had the same effect before when the battery has been depleted and it takes, centralising the switch (Off, at all times) and a few drive cycles before it resumes normal operation.

 

So, pro temp, I've put the switch in the always off position. 

 

Its been sitting in the car park now for 6 hours and the battery voltage measured at cigarette lighter socket was 12.1 v  (50%  battery charge ?).

 

On start, voltage went up to 14.0 volts.

 

I think what's happened is that the battery got thoroughly discharged , through disuse over 3 weeks and only light use prior to that.

 

The  Battery is showing 50% charge at the moment. Clearly, running it around yesterday and today hasn't raised the charge level sufficiently, despite the engine operating at 3,500 -4,000 RPM on the motorway section. Bit of sulphation there perhaps/acid stratification ?  I'll remove the battery tomorrow and recharge it on the C-Tek.

 

 

Nick

Edited by Clunkclick
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Today, clamp multimeter says that the drain current (Ignition off, all others off, doors closed) at the battery negative terminal is 0.35 amp max - it was jumping about a bit between .15 and .35.

Resting voltage 11.7 volts (0% charge !). Down from 50% charge last night - oh dear, doesn't look good.

VCDS, of course, has catalogued a shed load of electrical error codes, most of which have never occurred before and most of which are probably spurious, consequent on the low state of the battery and the jump starts viz anything from the throttle body, through the powertrain, to the driver's door module (Hence the courtesy light malfunction ?):-

VIN: Mileage: 99300km-61702miles

-------------------------------------------------------------------------------

Address 01: Engine Labels: 036-906-034-APE.lbl

Part No: 036 906 034 DF

Component: MARELLI 4MV 5020

Coding: 00071

Shop #: WSC 25021

VCID: 59B3E0EDC338878A87-4B00

3 Faults Found:

16786 - EGR System

P0402 - 35-10 - Excessive Flow - Intermittent

18043 - Powertrain Data Bus

P1635 - 35-00 - Missing Message from A/C Controller

17972 - Throttle Actuator (J338)

P1564 - 35-10 - Under-Voltage during Basic Setting - Intermittent

Address 09: Cent. Elect. Labels: 6Qx-937-049-C.lbl

Part No: 6Q1 937 049 C

Component: 00 BN-SG. 1S33

Coding: 17418

Shop #: WSC 25040

VCID: 3B7F5A652944559AB5-5120

4 Faults Found:

01598 - Drive Battery Voltage

07-10 - Signal too Low - Intermittent

00906 - Horn (H1)

28-10 - Short to Plus - Intermittent

00975 - Heated Rear Window (Z1)

28-10 - Short to Plus - Intermittent

01054 - Power Supply Relay; Terminal 30 (J317)

28-10 - Short to Plus - Intermittent

Address 46: Central Conv. Labels: 6Q0-959-433.lbl

Part No: 6Q0 959 433 E

Component: 31 Komfortgerát 0001

Coding: 00067

Shop #: WSC 13765

VCID: 3D7B547D37505BAA8B-4AE6

Subsystem 1 - Part No: 6Q2959802

Component: 31 Tõrsteuer.FS TFK 0002

Subsystem 2 - Part No: 6Q2959801

Component: 31 Tõrsteuer.BF TFK 0002

2 Faults Found:

01331 - Door Control Module; Driver Side (J386)

53-10 - Supply Voltage Too Low - Intermittent

01332 - Door Control Module; Passenger Side (J387)

53-10 - Supply Voltage Too Low - Intermittent

Clearly, some components are more susceptible to low voltage than others.

Anyway, battery out now and re-charging on C-Tek - light no 3. No error light, so by tomorrow morning it might be fully charged. Although that loss of charge overnight doesn't look good.

Once I've replaced the battery, I can zero all error codes with VCDS, give it a run and scan it again on return to check for errors. Hopefully, it will just be the old recurring faithfuls that come up.

01598 - Drive Battery Voltage

01054 - Power Supply Relay; Terminal 30 (J317)

Nick

Edited by Clunkclick
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That discharge current is too high, should be more like  35>55 milli amps after 20 minutes or so. I would not use a clamp meter for that small current measurement it is not what one that is big enough to clamp over these big cables is made for, that is why I mentioned just carrying out an in-circuit current check on a low range after the BCM has shut things down.  I must admit to trying to get away with using my HEME clamp on its low range, but I could not get consistent believable values so did the right thing and used the Fluke to measure in-circuit.

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Charging for two hours now. The C-Tek is still on light No 3 and getting a bit toasty. Voltage across the terminals is 14 volts. Am I correct in thinking that anything between 13.2 -14.4 indicate that its accepting a charge ?

 

If there is a drain going on how do you do an in-line multimeter reading without breaking the circuit ?

 

If it is kaput, I should get 50% back on it with a 5 year warranty.

 

Wouldn't it be nice if modern cars had electronics and alternators that could do all this ****e for you i.e. in situ, while parked-up, sense that the car is being under-used and send you a message to the instrument binnacle, which you could act on. Or better still start-up automoniously and go through a simulated drive cycle, tranny disengaged. ? The all electric drive's have that level of vehicle management, why not the hydro carbon fuelled stuff ?

 

Your right on the DC range  of the MM 40-400A - I'll have to use the probes on the 70's vintage  Low-range Fluke.  Correction, the ranges are 0-40 and 0-400A, so I should be able to do it with the probes on the clamp meter. ​

 

Postscript

 

2.25 hours on charge - just gone up to light no 4 (Not fully charged, but ready for normal use according the C-Tek manual). C-Tek classify the ready for use level to be 80% charged. So its gone from  completely discharged to 80% in 2 hours. Nah ! Even C-tek state that the charger will take 12 hours to get to this state from flat. What's the betting its gets stuck on light 5, short of full charge.

 

I think its had it. But I will persist overnight to see what happens.

 

Big contrast to the old days when you could take a hydrometer test and immediately see if there was a duff cell. Bloody "Maintenance- free" crap !

 

 

 

Nick

Edited by Clunkclick
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I've stuck mine through te CTEK recondition mode, but Skoda manual and CTEK manual both advise doing it with battery disconnected from the car due to the higher 15v+ voltages.

 

I used it on a smaller battery on a different car after it had been sat and drained entirely and it did seem to do the trick.

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Good luck getting any kind of meaningful number using a clamp to measure DC current!

 

Eh, have you not heard of DC current clamps, I've had my HEME for about 15 years now, what I was questioning was trying to measure 20>80 milli amps on a meter with a rated 40 amp FS or more.

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Clunkclick, if you do what I suggested, you can insert an in-line current meter without breaking the circuit, which must be left connected to avoid the BCM wakening back up.

 

Set the Fluke on DC current as low a range as possible as you should be looking for less than 500 milli amps (in reality a passible drain will be 35>55 milli amps), fit a crock clip lead to the negative side of the meter and connect that to the car body where the battery earth lead connects, fit a pointy probe lead to the positive side of the meter and press it down on to the negative post of the battery, while holding that down firmly with one hand, slacken off the earth leads clamping bolt and ease the earth lead up off the post and up over the pointy test lead, the meter should now read the drain current. After that reconnect the earth lead and then remove the pointy test lead from the earth post.

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Eh, have you not heard of DC current clamps, I've had my HEME for about 15 years now, what I was questioning was trying to measure 20>80 milli amps on a meter with a rated 40 amp FS or more.

 

Dude, please, they work ok with big currents but not milliamps. They might tell you if there's a current moving in the conductor but that's about it.

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Dude, please, they work ok with big currents but not milliamps. They might tell you if there's a current moving in the conductor but that's about it.

 

Well the way you wrote that posting did say "using a clamp meter to measure DC current " did make it sound like it was the "DC" that was the problem not the value of the current!

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Well the way you wrote that posting did say "using a clamp meter to measure DC current " did make it sound like it was the "DC" that was the problem not the value of the current!

 

No, I said "good luck getting any meaningful numbers", to be fair you went off half-cocked. I wasn't looking for an argument.

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