Johngerard

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!!.

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?.

Couldn't do your test as I don't have a permanently installed voltmeter but (with bonnet opened) terminal voltage just now 12.46V, car locked, and 12.33V car unlocked (no DRLs in both cases), if I then relock the doors battery voltage returns to 12.46V, this gives a load of 16.7A, (0.13/7.8*1000), really can't account for this as obviously can't be continuous.

My battery's Vd of 0.334V, (12.50-12.166), gives a likewise unlikely load of 43A?. from the VCDS but only a Vd of 0.08V, (12.18-12.1) from the M.meter readings giving a more realistic loading of 10.26A. I will carry out your tests above later on today.

The SOC voltage should ideally be checked with the battery terminal(s) disconnected, VCDS apparently measures the battery at rest voltage but the only way it can is if the at rest voltage is stored in the BMS system because the ignition must be switched on for VCDs logging which means the load is at least 4.4A from the DRLs which with a battery internal resistance of 7.8 mohms will account for ~ 0.04Vd apart from any other parasitic loss or loads. Your readings above indicate a 0.4Vd, indicative of a unlikely load of ~ 50A at a battery resistance of 7.8mohms.

It might but the killer IMO is the battery internal resistance, if you use the 3 year old battery (59 AH) resistance above of 7.8 mohm as typical then assuming a petrol engine with a 1kw starter motor will require 200amps at a nominal 10V & 50% starter efficiency, voltage drop while cranking, 200*7.8/1000, almost 1.6V, so your cranking voltage was ~ 9.8V?. Batteries even when almost completely knackered can start a car once (only) each time after a recharge or stopping after a run. My neighbours 2011 diesel Opel Omega failed to start a few weeks ago (original 95 AH? battery), the terminal volts were 11.8 so I connected in my 3.8A smart charger, after 32 minutes the battery/charger were up to 14.3V and the charger then went into trickle mode, 15 minutes after disconnecting the charger the terminal volts were 12.5 and the car started immediately and was constantly charging at 14.3V so alternator OK, next morning same story, no start, so new battery (after 10 years). Its amazing that my charger had only put 2AH into this battery in 32 minutes and it was then capable of starting the car even if only once, I can only explain it by the fact that while a cranking current of say 400A (this was a 2 litre diesel) is required the energy (AH) required is quite small, a 3 sec crank at 400A only requires 0.33 AH.

Would have to agree with that, I can go for months, 5/6, between top ups, present car, a polo, pressures fell ~ 0.15/0.2 bar before I topped up after exactly 3 years., don't know what the ambient temperature was on charging, new, but it was ~ 5C when I topped up, so if one assumes air as a perfect gas and the charging temperature was 15C and the pressure at 2.0 bar then without any leakage whatsoever the pressure at 5C will be (3*278/288)-1, almost 1.9bar, so my pressures probably only fell by 0.1bar or 1.5 psi in 3 years??, not a lot.

From the "Get Nitrogen Institute" Nitrogen provides better maintenance of tire pressure. Because of its larger molecular size, nitrogen migrates through a tire three to four times slower than oxygen. A tire filled with �plain old air� will lose 1.5 PSI in less than a month; with nitrogen, this could take three months or longer.

And its 20% oxygen which is where the permeability comes in.

I think air is permeable to any fabric and pure nitrogen presumably is not, so tyres hold their pressures longer. Don't know all the new cars I have bought come nitrogen filled but they certainly do not need re pressurizing for 18 months or even longer, of course this may just be down to everything being shiny and new. Years ago, service stations used to have a big pressure gauge mounted permanently so less likely to cause inaccuracies due to getting knocked about like the ones attached to the filling hose, have never used service station ones but pump my own with a Argos mini compressor whose gauge reads the same as my 40 year old pop up type (Dunlop) pressure gauge so it must be accurate!!.

Mine, just now, after standing overnight, is 12.18V at the battery terminals (DRLs off) and 12.1V both at the auxiliary socket and the battery terminals with ignition on (and DRLs on) so ~ 55% SOC, yours has ~ 43% SOC, strictly speaking, the battery voltage should be taken open circuit, the last VCDS reading (24th Jan) shows a alleged 79% SOC.The DRLs woul be on when taking the VCDS log as the ignition must be on, I don't know how it calculates the "at rest" voltage which presumably is a calculated open circuit voltage. 4:58:57 24/01/2022 14,154kms Engine OFF IDE01834 Battery voltage 12.166 V IDE01836 Battery current -4.386 A IDE01837 Temperature of battery sensor 12 °C IDE01839 Battery charge level 79 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 28 Ah IDE01843 Battery voltage at rest 12.5 V IDE07681-MAS06086 Battery total charging throughput-Total re-charge 1354.8 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 1478.3 Ah At Rest (Open Circuit) Battery Voltage Volts Capacity % volts/cell 11.51 10 1.918 11.66 20 1.943 11.81 30 1.968 11.96 40 1.993 12.10 50 2.017 12.24 60 2.040 12.37 70 2.062 12.50 80 2.083 12.62 90 2.103 12.73 100 2.122

Yes, very very hard to see how any savings accrue when stop/start operates with a stone cold engine, "less than a mile" on mine is exactly 0.5kms despite the manual clearly stating that the car must reach a minimum temperature before S/S is enabled. Despite all this I use it as I see fit and it doesn't annoy me in the slightest, Perhaps, like cruise control, adaptive stop/start will soon be ours?, why not, especially if one does the same run to work or whatever, every day, where traffic congestion etc will be simillar, the learning curve is easy.

My (wife's) 3 year old Polo which only does very short runs (< 15,00kms in 3 years) generally shows ~ 79 to 82% SOC (VCDS), she never enables stop/start (disables it at ignition on) I only replaced her last Polo's (a 2005 9N) battery after 12 years, purely as a precautionary measure as daughter was/ is still driving it, of course all the pre smart BMS/alternator charged at a constant 14.1/14.3 volts so will be interesting to see how this variable energy saving/regenerative charging pans out. Re parasitic losses: Can't comment on modern car demands but on at least 6 different family (VW) cars that I checked for the parasitic loss with a multimeter connected between the disconnected earth strap and battery negative terminal, all, apart from the 9N Polo, drew 40 to 60 ma, the 9N, from new, drew, and still does, almost exactly 95ma but right up to the time of the battery change was regularly left at the airport for 10 days or so which means the consumed AH were ~ 23AH, a fair whack by any standards, but car still started no problem. You say that your car battery voltage falls to 12.4V after 5 days which is around 72% SOC, assuming that the external charger gets the SOC to 100% (12.7V?). You are losing 28% SOC so (if) a 70AH battery will have lost 19.6AH so parasitic loss is 160ma?. Quite possible but I would be mildly surprised if todays cars have a parasitic loss of > 100ma. Unfortunately, because present car has DRLs which draw 4.4A, I can't measure the parasitic loss with VCDS.

Can't remember off hand what the S/S inhibit battery voltage is set to, but its fairly low. S/S even though a lot of drivers arn't great fans of it and I use it selectively isn't quite the demon its painted at times. a 1/1.5 litre small petrol engine with a 1kw starting motor @ 50% efficiency will require 200A, or consume 0.17AH for a 3 sec crank at 10.0 battery voltage and a diesel (2 kw starter) approx twice that at 400A and 0.34AH, the DRLs require a continuous 4.4A so theoretically at least 26 starts/hr for a petrol engine and 13 starts/hr for a diesel would only consume the same energy as the DRLs in a hour at 4.4AH, the cranking voltage drops would be 1.6/3.1for petrol/diesel at a battery internal resistance of the above 7.8 mOhm so again, theoretically at least, even a 30/40% SOC should start both engines. The at rest voltage above is 12.5V (wonder how that is derived) 79% SOC. At Rest (Open Circuit) Battery Voltage Volts Capacity % volts/cell 11.51 10 1.918 11.66 20 1.943 11.81 30 1.968 11.96 40 1.993 12.10 50 2.017 12.24 60 2.040 12.37 70 2.062 12.50 80 2.083 12.62 90 2.103 12.73 100 2.122

Of course it could be any one of the above, but don't think this car was laid up?, if the dealer didn't carry out proper battery maintenance pre sale then they are responsible for a failing battery which is covered under the 3 year warranty, they said the dashcam was the problem but after the car was returned with stop/start working the dashcam was not used but problem returned a day or so later, if I am interpreting the posts correctly. There are high power usage warnings flagged up as well. As I stated previously they have dedicated diagnostics that can give a excellent view of the battery condition, high power usage etc, alternator charging voltages which change constantly from anything between 12.8V when driving normally to 15.0v on the overrun, parasitic losses etc, it will be at least as revealing as the VCDS log below of my 3 year old Polo. This car was parked up at the airport very recently for 14 days and the Stop/start operated perfectly after the mandatory 0.5km required to enable the stop/start. At the end of the day, the dealer should provide a loaner car and sort out this problem one way or the other. Polo Jan 2019 4:58:57 24/01/2022 14,154kms. Engine OFF. IDE01834 Battery voltage 12.166 V IDE01836 Battery current -4.386 A IDE01837 Temperature of battery sensor 12 °C IDE01839 Battery charge level 79 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 28 Ah IDE01843 Battery voltage at rest 12.5 V IDE07681-MAS06086 Battery total charging throughput-Total re-charge 1354.8 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 1478.3 Ah

Can you add me to the list please. Cork. T23DE6P HEX-V2 Dual-K & Can USB Interface for VCDS

Your dealer certainly isn't sorting this out, they will definitely have access to diagnostic equipment which will give at least the same info as VCDS which should reveal something, I would ask them for a print out of this, so suggest you do a little probing yourself. If you have or get a simple multimeter you can get a attachment to plug into the power socket, and go for a dive with the multimeter set on 0 to 20V DC scale, with a fully charged battery if the accelerator is pressed then the (charging) voltage will be in the 12.5 to ~ 13V range, if coasting with accelerator not depressed then the (charging) voltage will rise to 14.8 to 15V, its called regenerative charging. If yon havn't the power attachment just check the voltage at the battery terminals with car idling and see what the reading is. Have a browse through thread "Battery not charging problems" and you will see the kind of info that your dealer will have without doubt.

Where is the "add reply button" please ??. John

I wouldn't recode if the old battery is re installed, a new EFb battery, yes. I have VCDS and you might find below interesting, (from a Jan 2019 Polo) To recode, just change the last (generic) serial number to a 2 and your done. Apparently when IDE07681-MAS060876 becomes > IDE07681-MAS06087 then the BMS system will start inhibiting non essential items like stop/start, etc. VAG use 50 X battery capacity as a benchmark for useful battery life, in real terms don't really know how this pans out, battery below at 59AH "life" is 50X59, 2950AH so apparently 1478/2950, 50% life used so 50% remaining or another 3 years for this car, 6 years in all?. This is reflected in the usable battery charge at 28AH below even though a battery charge level of 79% might indicate a actual battery charge of 47AH. If you are down around my neck of the woods (Cork) then no problem in having a look at your car values. From Can Gateway, advanced values. 4:58:57 24/01/2022 14,154kms IDE01834 Battery voltage 12.166 V IDE01836 Battery current -4.386 A IDE01837 Temperature of battery sensor 12 °C IDE01839 Battery charge level 79 % IDE01841 Battery internal resistance 7.8 mOhm IDE01842 Usable battery charge 28 Ah IDE01843 Battery voltage at rest 12.5 V IDE01848 Energy balance of last driving cycle 0.0 Ah IDE01849 Previous journey duration 0.0 H IDE07681-MAS06086 Battery total charging throughput-Total re-charge 1354.8 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 1478.3 Ah Adaptations from can Gateway IDE03256-MAS06105 Battery adaptation-Rated battery capacity 59 Ah IDE03256-MAS06106 Battery adaptation-Battery technology EFB IDE03256-MAS06107 Battery adaptation-Battery manufacturer JCB IDE03256-MAS06108 Battery adaptation-Battery Serial Number 1111111111

Is the above resistor located in the fan air flow for cooling purposes?. I have a Jan 2019 polo that is on its second replacement (under warranty) resistor, it is apparently located with the "resistors" in the fan air intake but it doesn't have a heat sink like the one above, it appears to be enclosed (see attachment), The pollen filter was replaced after the first replacement, fan apparently is rotating freely. I have ordered a spare replacement so can measure the (3) resistors resistances and as I have checked the fan loads I can then calculate what power the resistors are absorbing, that's assuming that this resistor pack isn't a electronic controller of some sort?. I got the following amperage readings with VCDS (after subtracting the DRLs ~ 5 amps). The car does not have AC. Fan speed 1 3.9A Fan speed 2 6.2A Fan speed 3 10.8A Fan speed 4 17.0A If some one has measured these at any time from a Fabia or likewise they might please comment or post the readings for comparison purposes.