Johngerard

My nearly 7 year old original (Polo) 59AH EFB battery on a VCDS scan last month shows a battery at rest voltage of 12.4V which is nominally 70% SOC, it shows a usable battery charge of 23AH which might indicate that the 100% SOC or maybe state of health? is now, 23/0.7, 32.9AH or the battery capacity is now, 32.9/59, only 55.8% of its original 59AH capacity. The stop/start (used selectively) has never failed to operate even down to 65/68% SOC and the BMS does return the battery to its normal indicated max of 85% SOC but it can take days, you can see that even with a alternator charging voltage of 14.6V that the charging current is still only 3A and goes as low as 1.5/2A when the charging voltage falls to 13.3/13.6V while driving normally, it never maintains a high charging voltage continuously up to 85% SOC. IDE01829 Generator exciter current 2.125 A IDE01834 Battery voltage 14.598 V IDE01836 Battery current 3.024 A IDE01837 Temperature of battery sensor 26 °C IDE01839 Battery charge level 70 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 23 Ah IDE01843 Battery voltage at rest 12.4 V

I might try that fix as suggested by @MaxvdP on my Polo, every VW I've ever owned had to have the mirror heating switched on in order to work, a pain to remember to switch off, some say the heating elements burn out if left permanently on, I had a Bora driven by myself for 10 years and I used to switch them off regularly but my daughter drove that car for another 12 years with, I would think, the mirror heating permanentl on but the drivers side was definitely demisting on the day I drove the car to the VW dealer to get the scrappage offer.

Have you got or able to borrow a multimeter?, if so, while watching the M.meter set to 20VDC or nearest and with the probes on the battery + and - terminals, get someone to start the car, the terminal volts will/should rise to almost 15V even if only for less than 20 seconds or so, at least this will show you that the alternator is not at fault, of course it still could be the BMS. You could pop in to Halfords or the like and buy a DVM (digital volt meter) for a few quid and plug it in to your auxiliary power point and observe the charging pattern (carefully, while driving), the voltage should always rise to almost 15V (14.6/14.9) on the overrun and may hover around 13.2/13.5V while driving, mine seems to do this (original almost 7 year old 59AH EFB battery) even with a 68% SOC and can take days to recover to its normal max of 85% SOC, stop/start has never failed though even at this low SOC. If you can'r source a DVM, you can make one up with a 12V plug, a bit of wire and a connector block and stick the M.meter probes into it if you only want to trouble shoot the (if) problem.

Unlikely but possibly the thermostat is failed/stuck partially opened, all VAG cars display a constant 90C between ~ 75C and 107C, in traffic, the temperature will tend to rise but on the move might be down to around 75C ish even though still reading 90C which might affect the heatinhg system.

My daughters 8 year old Tiguan I think the query has been properly addressed by Stonemason below. My daughters ~ 8 year old Tiguan brings on the cars accessiories (spelling?) if you press the start button only but gives no immediate or later alarm, but when you get out and lock the car you get a audible alarm which is easy to miss....battery goes dead after a few hours so she has to remember to press the start button again to switch off the accessiories before exiting the car.

The OP's car displays this alarm almost immediately on entering the car and in reply to your query last Sunday said that the Stop/Start does work but he doesn't know how consistently as he disables it on entering the car so don't know what you mean by "the car can’t restart if it’s not been started first." Its over a month now since the car was purchased so its about time it was sorted out under warranty.

Surely there must be a number of conditions met to flag this alarm, once the ignition is on, the very lowest battery load is almost 5A and will obviously be higher depending on what is switched on, I have never sen this alarm even with a 70% SOC, the stop/start operates fine at this level, the engine will restart if the battery load exceeds something like 15A if the fan speed is switched to its max setting of 4, it will occasionally restart at speed 3 but never at my normal setting of speed 2.

Your entire energy input compared with mine, pro rata, might seem high but I dont have AC so once the engine is running and even at idling with HRS + dipped beam + fan on speed2 will not drawdown anything from the battery, the Alternator will supply all + ~ 2.A charging current. Polo has 23,573 miles up, all short runs, say 30MPH average gives engine running time of 786 hours add 25% for stopped in traffic gives a total of 983 say 1000hrs, my recharge is 3478AH which gives a average charge level of, 3478/1000, 3.48A which probably isn't too far off the mark? You can do a similar calc based on your mileage, might tell something. I have a 59AH EFB. The first set of readings I took after 2.5 years, below, still showed a fairly high resistance. Sept 2021 IDE01834 Battery voltage 13.487 V IDE01836 Battery current 2.639 A IDE01837 Temperature of battery sensor 32 °C IDE01838 Battery temperature 27 °C IDE01839 Battery charge level 85 % IDE01841 Battery internal resistance 6.6 mOhm IDE01842 Usable battery charge 38 Ah

Its under warranty? but would be interesting if you have a multimeter and see what the battery terminal voltage is while idling.

HRS....all the way, yes.

The Stop/Start logic is a bit illogical IMO, mine (2019 Polo) has never failed to operate even with a nearly 7 year old battery at 70% SOC, like just now, only indication I get of a low SOC is that the battery charges at well over 14V constantly, not sure what SOC when reverts to "normal" charging, ie, only 14.6/14.8V on the overrun. Set of VCDS readings taken just now. Mileage: 37935kMs = 23,573 miles 12:34:12 20102025 IDE01829 Generator exciter current 2.125 A IDE01834 Battery voltage 14.598 V (Engine Idling) IDE01836 Battery current 3.024 A IDE01837 Temperature of battery sensor 26 °C IDE01839 Battery charge level 70 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 23 Ah IDE01843 Battery voltage at rest 12.4 V IDE01948 Battery internal resistance not normed 8.2 mOhm IDE07681-MAS06086 Battery total charging throughput-Total re-charge 3478.6 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 3669.3 Ah

All the VWs I've had since 2000 don't require the HRS on to enable the mirror heating, it would be much better IMO if they just came on/off with the HRS or switch off automaticall after 20 minutes or so like the HRS, I also saw something in VCDS about the temperature setting of the HRC, maybe 34C? which I think is settable so wonder can this also switch off the HRS before the time out period.

Probably, the DVM is excellent for showing the charging pattern but does read 0.2V ish lower than what VCDS or the actual measured terminal volts show, I've certainly seen DVM readings of 14.8V so would think that occasionally the charging votage goes as high as 15V. I will log a few VCDS readings on the run soon.

What is fake recuperation and how is it switched off ?

Even with a "fully" (85%) charged battery, these BMS systems will always charge at 14.6/14.8V immediately after starting but normally only for 20/30 seconds or less and will then charge at 13.3/13.6V, but on overrun will always charge at this higer voltage. I have a DVM (digital volt meter) permanently plugged into the auxiliary power socket so quite easy to see the charging behaviour, they only cost less than a fiver. I would monitor the battery terminal voltage with a multimeter while someone starts the engine, you should then see the voltage rising to ~ 14.8V for a brief time. Even so, that Low 12V battery alarm should not be up at anything above say 12.4V. Borrow your friend's VCDS and take a set of readings as below, will give some idea of what's what, these are mine for a 6.8 year old Polo with its original 59AH EFB battery, these were taken with ignition switch only on hence the negative battery current, due to the daylight running lights etc., but readings can also be taken with engine running. IDE01834 Battery voltage 12.313 V IDE01836 Battery current -4.420 A ID01837 Temperature of battery sensor 21 °C IDE01839 Battery charge level 82 % IDE01841 Battery internal resistance 7.4 mOhm IDE01842 Usable battery charge 33 Ah IDE01843 Battery voltage at rest 12.5 V IDE01948 Battery internal resistance not normed 5.8 mOhm

Don't most VAG engines now have two stats?, mine (a 2019 petrol Polo) has, with opening temperatures something like in the attached, if so, should both be tested in the event of a overheating problem?. See (VW SSP 820333 pdf) Two Stat Photos.docx

My original 6.8 year old battery never charges at less than 13.5V/1.0 to 2.0A, even with a SOC of 83% and 14.7/14.9V on the overrun, its possible that your OBDelevan is reading ~ 0.5V low, in which case the battery charging looks about correct but again I can only suggest getting the battery coded properly to remove all doubt.

Does the DVM show charging characteristics like mine, (DVM), normally only 14.8V on the overrun? and have you taken any VCDS readings recently?

Battery, believe it or not, back up to 82% SOC after another 2 hr round trip, on the 1 hr outward trip. its normal 14.8V on overrun only, otherwise its normal 13.5V but on the return trip charged at a constant 14.4V continuously for 35 minutes and then back to its old ways. I won't post again until either the battery or I die!! 18:57:34 20092025 IDE01834 Battery voltage 12.313 V IDE01836 Battery current -4.420 A ID01837 Temperature of battery sensor 21 °C IDE01839 Battery charge level 82 % IDE01841 Battery internal resistance 7.4 mOhm IDE01842 Usable battery charge 33 Ah IDE01843 Battery voltage at rest 12.5 V IDE01948 Battery internal resistance not normed 5.8 mOhm IDE07681-MAS06086 Battery total charging throughput-Total re-charge 3441.7 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 3630.8 Ah

Yes, 14.6/14.9V is quite normal after every start, it might tell the OP something about the state of his Alternator even if it does drop back to 12.5V which IMO will not charge any battery, might give a trickle charge of 0.5/1.0 amp, as you are probably well aware all the older type VAGs charged at a constant 14.2/14.4V to give, in my case, a minimum of 10years battery life and even then I used only change them as a precautionery measure as the car was handed down the line. It mightn't be bad advise if the OP got the battery coded and also invest a fiver or so in a DVM, (digital volt meter) and he can keep an eye on the charging patterns. "When your Car have every time min 13,X Volt, your Batterie ist EOL" what is EOL? and ""Fake" rekuperation?", as stated, I've never seen the DVM displayed voltage fall below 13.3/13.5V under any circumstances.

Are you saying it never went to 14.8V on overrun? My 6.8 year old battery has a 70% SOC but allways goes to 14.8ish on overrun and never below 13.5 when driving normally, I can't see any battery lasting very long if charging for any extended time at 12.5V. If you monitor the battery terminals with your M.meter and get someone to start the car, then after start up,the voltage will/should rise to almost 15V but only for ~ 15/20 secs.

Even without coding I would be very surprised if the charging voltage ever went below 13.5V or so, the BMS will allways charge at 14.8V/15.0V on the overrun but nearly allways 13.5ish while driving normally, if you turn on all the auxiliaries does the M.meter still show 12.5V while idling or increasing the revs a little, if it does then possibly the lack of coding, if not, possibly a Alternator problem.

I've replaced several throttle bodies for people with used ones and they have never required re adapting, the engine takes a few minutes to return to normal idling speeds.

Re the throttle body, if its like my Polos, then if you press the accelerator with just the ignition on, the throttle valve should open fully. You should also be able to move off by just releasing the clutch pedal without leg on the accelerator and also go up a fairly steep incline in first gear without any accelerator.

Generally speaking, I find that if the (a) car is driven even for 2 or 3 miles daily then one should get a reasonable battery life, my Jan 2019 Polo has no problem with the stop/start on the rare occasions that I enable it and will do so after driving the mandatory 500 meters even if parked up in the airport for 8/10 days. It wouldn't do any harm to invest less than a fiver on a DVM (digital volt meter) and leave it permanently plugged in to the cabin power socket, you should find that the battery charges at 14.8/15.0V allways on the overrun and ~ 13.6V while driving or idling. The batteryhas never indicated more than 85% SOC, even when new, one might think that at its present alleged 71% SOC that it would charge at well over 14.0V to get the SOC back up to 85% but it doesn't, on a 2 hour trip a few weeks ago it just did its usual 14.8V on overrun and 13.5V ish, while driving normally but I will be happy enough if I can knock around 8 years out of this battery, car has only 23,000 miles up but as stated above, driven daily. If I check the battery current (VCDS) sitting in the car with the doors locked and ignition key out, it reads ~ 2.5A for a few minutes and then falls to zero, presumably means little or no parasitic loss, all my previous cars had a parasitic loss of ~ 40mA when measured with a multimeter in series with the battery, but one, a 2005 Polo, still in the family had/has a parasitic loss of 85mA from new and even with a 10 year old battery would start up after being parked up for a week or more, after a draw down of presumably ~ 16AH from a 44AH rated battery, of course these cars charged properly at a constant 14.4V. (VCDS readings taken with engine idling) Original, 59AH, EFB Battery, 6.7 years old. IDE01834 Battery voltage 13.499 V IDE01836 Battery current 2.828 A IDE01837 Temperature of battery sensor 34 °C IDE01839 Battery charge level 71 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 26 Ah IDE01843 Battery voltage at rest 12.4 V