It does "recover" instantly, ie if I relock the doors the voltage rises immediately from 12.33 to 12.46V & if I unlock he doors, the voltage goes from 12.46 to 12.33, these numbers may change if I wait 15/20 minutes each time??. Even from new I have never seen the standing charge (VCDS indicated) higher than 12.5V)

Can you see what the instantaneous changes are, doing the same tests and if these value(s) change again after this time period?.

Edited 14 March, 20224 yr by Johngerard

The wait is required only when seeking the highest (closest to no-load) voltage reading. If you choose to keep monitoring the voltmeter display, you may see the voltage reach a stable maximum sooner than that.

 

There could be some difference in systems response due to the fact that to access the bonnet release lever I open the driver's door.

 

Anyway, my point was that the voltage read after the driver enters the car is too far from the no-load voltage to be used to determine the battery SOC.

 

Edited 14 March, 20224 yr by agedbriar

I take your point obviously but you can monitor it though through the window of the drivers door?, I can't do that as having a voltmeter/m.meter permanently plugged into the cabin power socket is no good for monitoring the above as the socket is dead until the ignition is on  but I am reasonably happy that VCDS does give a  true reflection of the battery at rest battery voltage which still is not a true indication of the SOC as it should be done with a open circuited battery, but is IMO good enough for most purposes.

I only want this battery to last 10+ years like all my other ones!!.

I have the internal voltmeter connected to the cigarette lighter socket, which on my Karoq is permanently live. That's why I say that I'm contributing to battery drain with the constant 8 mA that the LED V-meter draws.

My goal is to keep the battery healthy by connecting it to the external charger before its no-load voltage drops to  12.4 V, where sulfation starts.

 

Edited 14 March, 20224 yr by agedbriar

An update.

 

The car is a 2018 1.5 SEL bought in Jan 2019 pre registered with 10 miles on the clock  . The car was manufactured September 2018 so sat idle at the dealers for about 4 months, it has covered 22,500 miles.

Today I drove 70 miles to the East Coast and monitored the voltmeter plugged into the aux socket.

 

Before start Voltage =                          11.3 volts

For 2 minutes after start the drive volts = 14.4 

It then increased  to                            14.7 

After 38 minutes it dropped to          13.3 on drive reverting to 14.7 on over-run

At 50 minutes auto stop actuated    Battery read 12.3 volts this fell to 12.1 after 2 minutes waiting

On drive volts then  =                         13.7     on over run= 14.7

After 1 hour 35 minutes at jouneys end engine off and battery = 12.3 volts

 

Return journey  6 hours later, before start battery volts=12.0 volts

Drive volts =                                         12.4 

After 3 minutes Drive volts =            12.7

After 30 minutes Drive volts varied from 12.7 - 13.0 Overrun alway 14.7

Journeys end after 1 hour 35 minutes ( 70 miles) Engine off battery volts = 12.1

 

On the over run or braking the volts always measured 14.7 with occasional peaks at 14.8 and 14.9

 

 

 

That charging pattern looks very similar to mine, however, a bit concerning that the voltage falls from 12.1 (50% SOC) to 11.3 which is less than 10% capacity.

Sounds similar to mine. Tdi but registered new after 4 -5 months in storage. Aug 2020 and good deal after lockdown and dealer needing to clear stock before registration change
Car would not start next day. AA turned up and gave it a boost to get going. I blamed it on having the ignition on for some time with engine off learning and sorting settings.

Did several reasonable trips over next few days, but noticed on a 40 mile trip for work that items were not working such as cruise control and stop start.

Following day would not start on drive again despite 80 miles day before in August so no use of heated seats etc.

AA again checked battery and it was virtually dead. New battery fitted at dealers and has been fine since.

Every car that I've/family owned (all VWs) were purchased new and all I would think were in one form of storage or other for up to 6 months, all (apart from present Polo) were/are just lead acid types and all apart from one (my first car, a 6V 1963 Beetle, whose battery failed after 5 years) lasted > 10 years, not one failed and I only replaced them as the car(s) were handed on.

The present Polo has a Botswana  build label which shows 19/4/2018, I registered this car on 03/01/2019 so lying around somewhere for 8 months or so.

So batteries must have either been topped up regularly as the parasitic loss would flatten then in ~ 5 weeks or so, or they were stored with battery disconnected of they were simply left flat for months on end?.

Edited 18 March, 20224 yr by Johngerard

The ECU's are set to transit mode which I believe reduces all parasitic losses, the vehicle has to be opened using the key and only when the ignition is switched on will current be drawn.

 

Thats my understanding from reading the VCDS description of the function.

 

When I buy a new battery it may have been standing for 6 months, they never have a full charge as delivered.

I've seen transport mode in the VCDS so it makes sense, I think you can't then reactivate it after the car has travelled a a 100 miles or so as the it will have been delivered by then.

It's speculation on my part that there is zero standby consumption, no systems like central locking reciever, burglar alarm etc running when ignition key removed but it does make sense.

 

VCDS does say that the alarm is disabled

Good morning - this is a really interesting thread to me. I went out to the car on Thursday morning and click - nothing - dashboard lit up like a Christmas tree and then warning message after warning message saying that all the systems were unavailable. Message appeared - battery low please recharge or take a drive. So I had to call the AA through Skoda (great service by the way) and he turned up and my battery was reading 11.3. It had been static for a few days but last week I did a number of 30 mile trips although interestingly I noticed that stop / start was reducing the number of times it kicked in. Also, as a result of a speeding ticket / bad boy driving course, I have been driving far more 'economically' than before. Saying that, Mr AA said driving style made little difference. Anyway, a quick jolt from his starting pack and off it went. The car is only 14 months old and just over 6k miles so I'm thinking I may have a dodgy battery. I'm keeping an eye on the charge is 11.3 and sure enough, trying to start the motor na-dah, nothing.

11.3 volts is < 10% capacity, if it rises to 12.3/12.5V after engine switch off after a 15/30 min run then more than likely that the charging system is OK and the battery either on the way out or you have a very large parasitic loss. If the battery is OK then it would need to be charged with a external charger as you will be wasting a lot of fuel trying to trickle charge it from the alternator controlled by the energy saving BMS system.

 

With what & where are are you measuring the battery voltage.

Edited 19 March, 20224 yr by Johngerard

Hi - thanks for the reply - just using a digital multimeter on the battery terminals. I'll speak to Skoda on Monday. I already had it booked in for a couple of other glitches - intermittendly not being able to turn on cruise control being one of them. I've had more issues with 14 months of ownership of this Skoda than 20 years of Audi before it. Frustrating.

With engine running but all auxiliaries off check voltage, then with heated rear screen, dipped beams and fresh air fan on speed 2 or equivalent check voltage again.

If only I could start the car - I'm waiting on AA to arrive so that they can give it a kick and then I'll try what you say

On 08/03/2022 at 22:56, agedbriar said:

All these electronics that shut down only to a standby level seem to drain quite a lot. KESSY, especially, is a relatively high load and that's why the passenger door handle shuts down by design after about three days of inactivity.

 

Another problem is the fact that the alternator won't charge the battery to full unless it can do that last part without causing extra fuel consumption, i.e. on deceleration or while going downhill.

 

I have a voltmeter connected permanently so that I can read the display through the closed driver's window. Turns out that after about five days of rest the voltage drops to 12.4, where sulfation starts to deteriorate the battery, so at that point I connect it to my external charger.

Just discovered a few days ago that VCDS (on this car anyway) maintains communication after switching off the ignition and removing the key and locking the car so I observed the battery voltage/current, on locking the doors the indicated voltage/current is 12.65V/2.6A, the amperage falls to 1.16A after around 30 secs or so and to a indicated 0.0 A after 90 secs or so with a indicated voltage of 12.85V so definitely while 0.0 A parasitic loss is highly improbable, it may be practically 0A for periods and then wakes up and do a few checks? before going back to sleep, same indications if I unlock the door and then just open/shut it to prevent it auto locking after 30 secs, it indicates 0A after 90 secs with doors remaining unlocked.

I will try that on the 17 year old Polo 9N which always seemed  to have a parasitic loss of 95ma when measured with a M.meter connected between the disconnected earth strap and the battery negative terminal 

On 08/03/2022 at 22:56, agedbriar said:

 

 

0.0 A is the correctly rounded notation of any current of up to 50 mA.

 

Edited 21 March, 20224 yr by agedbriar

58 minutes ago, agedbriar said:

0.0 A is the correctly rounded notation of any current of up to 50 mA.

 

 

Just wonder how accurate is the battery charge/discharge (amps) measurement device on the negative terminal is, at very low inputs, I presume it has to be calibrated to measure up to 400/500A to cater for the cranking current, but must still be accurate for very small battery charging rates for the BMS. Assume a range of 0 to 500A, 5A = 1%of range, 500ma = 0.1%  & 50ma = 0.01% so no wonder it shows 0ma.

This car is on its second replacement cabin fan resistor pack, it third in all and I monitored the current draw at the different fan speeds, both with engine off and engine running. The fan loads on speeds 1&2 don't make any sense with engine running, so wonder why this is, I am subtracting the (charging current+the current usage with engine off) from the Alternator output so either my calculations are wrong or something(s) arn't being measured accurately? 

The battery volts with engine off are 12.35 to 12.7V.

 

20/03/2022	Engine OFF		20/03/2022	Engine ON
	Battery			Battery	Alternator	Battery
Engine Off	Amps		Engine On	Amps	Amps	Volts
speed 0	-4		speed 0	4	5.5	13.50
speed 1	-8.6		speed 1	5.3	7.4	13.46
speed2	-10.9		speed2	4.9	9.2	13.45
speed 3	-15.5		speed 3	4.5	17.5	13.44
speed 4	-21.7		speed 4	4	26.5	13.40
	Fan Amps (calc)			Fan Amps (calc)
speed 0	0		speed 0	-2.5
speed 1	4.6		speed 1	-1.9
speed2	6.9		speed2	0.3
speed 3	11.5		speed 3	9.0
speed 4	17.7		speed 4	18.5

1 hour ago, Johngerard said:

Just wonder how accurate is the battery charge/discharge (amps) measurement device on the negative terminal is, at very low inputs, I presume it has to be calibrated to measure up to 400/500A to cater for the cranking current, but must still be accurate for very small battery charging rates for the BMS. Assume a range of 0 to 500A, 5A = 1%of range, 500ma = 0.1%  & 50ma = 0.01% so no wonder it shows 0ma.

 

No experience with VCDS, but this makes sense to me.

 

17 year old Polo N doesn't give up its secrets to VCDS like the mk10 but got readings with ammeter connected between disconnected earth strap and negative battery terminal. The original resistor pack is in this car. I installed two pollen filters in the 17 years.

 

Fan powers very similar in both models.

 

23/03/2022	Engine OFF
	Battery
Engine Off	Amps
speed 0	-1.85
speed 1	-5.5
speed2	-8.1
speed 3	-12
speed 4	-18
	Fan Amps (calc)
speed 0	0
speed 1	3.65
speed2	6.25
speed 3	10.15
speed 4	16.15

Edited 23 March, 20224 yr by Johngerard