Johngerard

It will be interesting to see how long my 53AH, EFB, +7 year old battery lasts, battery SOC always between 72% to 83% ish vis all my other 100% charged ones, (at a constant 14.2/14.4V), where I never had a failure and used to renew them purely precautionary after 9/11 years before passing the cars down the line.

Battery chemistry has always been a mystery to me, my battery has a apparent internal resistance of 8 mohms, 0.008 ohms ( a new battery might be as low as ~ 2 mohms?) and a standstill voltage of 12.5V, yet when charging at say 13.5V only takes few amps, the net difference in charging volts is 13.5-12.5, 1.0V, at least at the commencement of charging but the current flow simplistically should be a massive, (I=V/R), 1.0/0.008, 125A??, so what prevents this, do the two voltages more or less equalize instantly and the tiny remainder do the chemistry??.

While its idling switch on the dipped or main beams, then check battery volts, if OKish switch on heated rear screen and check again, then finally, put fan speed to 2 and check voltage again.

If the Alternator "test" is OK, then looks like a failed battery to me but hopefully not.

5 miles each way should be more than adequate to keep the battery charged IMO, we have a > 7 year old Polo (stop/start) and average ~ 6/7miles per day, the key is the daily driving, all modern alternators can (for years now) supply all reasonable electrical loads even while idling and still charge the battery, my normal test for years is to have the dipped beams, heated rear screen and fan on position 2, on, and the voltage was/is around 13.6V.

When you do get it started, check the battery voltage (engine running) should be ~ 14V, certainly > than say 13.5V while idling.

IAN: 383685_2100S./N:278007 It also has Manufactured: 2022/35 above the IAN details. It's a ULGD 5.0 C1

Thats the one, Nigel. Should also maybe have mentioned that some time ago, I put this charger on a 11 year old 44AH Varta lead acid battery installed in another (22 year old) family Polo and the charger worked exactly the same, this battery of course would have been Alternator constantly charged at 14.4V throughout its long lasting life.

Just for interest I used a Ultimate Speed ULGD 5A charger on my battery for over 8 hrs. Before charge the Battery at rest Voltage was 12.5V, Battery Charge level (SOC) 76% and Usable Battery charge 24AH. Afer 3 hrs, where the charger ouput was 4.0A at 13.4V for ~ 8 minutes, then ~ 5 minutes at 1.1A, it then reached 14.4V and cut out until voltage fell to ~ 13.1V, then commenced recharging at 1.1A for another few minutes and then stayed trickle charging at 0.25A at 13.4V for those almost 3 hours, battery readings then, at rest voltage 12.5V, SOC 76%, Usable Battery Charge 25AH (increase of 1AH), left on charge for another 5 hrs with no change in above readings, just trickle charged at 0.25A at 13.4V. The ULGD allegedy trickle charges at 0.1A at 14.4V but mine certainly didn't, as soon as it hits 14.4V it shuts down until the voltage falls to 13.1V. One way or the other don't think this does anything for this battery in its present state of 76% SOC. The Alternator does get it up to 80/85% eventually, but I did notice that its lowest charging rate is ~ 1.0A at 13.5/13.6V.

Possibly/probably cranking speed too low, if too low, heat of compression especially on a cold start is lost through the cylinder walls. I remember well, in the 60s, the Standard Ford Major Tractor had a decompression lever, there were two levers, in cold weather/first start in the morning, you used one lever to decompress by keeping the either (can't remember which) the inlet or exhaust valves open, you then used the other lever to crank the engine, after a few seconds, you released the decompression lever, and away you went. With a hot engine you didn't use the decompression lever but after many many thousands engine hours and wear it was difficult to start when hot even with a new battery but once you increased the cranking speed by using the decompression lever then no problems.

I would definitely get it coded, may cost you nothing if you buy in the right shop. Re battery charging, Lidl sell a Ultimate Speed ULGD 5A charger with a inbuilt voltmeter, very useful, for around £15, only drawback is that it will not charge a "flattened" battery, if voltage < than something like 8/9 I think. Also check that your Alternator is OK.

AI says: Detailed Meaning of Light No. 6 (Recond Mode) Active Reconditioning: The charger is adding a special step (Step 6) to the normal 8-step charging process. What it does: It applies a higher voltage—around 15.8V—to create controlled gassing in the battery, which breaks up acid stratification. Duration: Recond mode adds between 30 minutes to 4 hours of extra charging time on top of the normal charge cycle. Indication: When this light is on, the charger is actively working to restore the battery's capacity, not just charging it. CTEK +3 Key Considerations Battery Type: Only use this mode on Flooded/Wet or Calcium/Ca batteries. Warning: Do not use Recond mode on AGM, GEL, or Lithium batteries, as the high voltage can damage them.

The only way I can monitor the charging current from the alternator is by using VCDS, after starting, it charges at a fairly good lick, can't quite remember now, but ~ 16/20A?, but only for a few minutes...... even if the battery is well below its 85% SOC, it then just trickle charges at around, again I think, 1 to 2A or so at a terminal voltage of 13.5/13.6V, I presume this is in the interest of fuel savings since the BMS can and does use variable voltage charging right up to almost 15V which would certainly force more amps into the battery to get its SOC up relatively quickly. Modern Alternators give fantastic output though, even at idling revs, at idling, with headlights on full beam, HRS on, and fan speed on 3 (normally 2) the alternator will still charge the battery, in effect, this means, that the battery will never discharge while the engine is running, even if only idling.

@nta16 , yes, the DVM is one of those cheap and cheerful mushroom voltmeters and also showes the car interior temperature for a mere £3 or £4, its accurate to within 0.1C of my M.meter plugged in to the same auxiliary socket but the readings here are ~ 0.2C lower than that taken off the battery terminals, I think this has been noted/noticed elsewhere. @hubrad, I will code in the new battery when installing it, easy to say as I've got VCDS which was presented to me for services rendered to many people over dozens of years, don't think I'd have bought one myself, my diagnostic equipment is a M.meter and a small darning needle stuck into a cork for piercing wiring harnesses. If I didn't have VCDS I would initially monitor the new battery charging pattern for a few days, if somewhat similar to the past, probably would't get it coded, I remember all my older VWs charged at a constant 14.4 ish Volts and (the batteries) lasted "for ever". Still, it's worth finding some battery shop that does the coding "for nothing", Halfords maybe??. No, pretty sure the VCDS doesn't show the battery installation date.

Mine has often been charged to 80/85% and I've never seen the DVM reading any lower than 13.5V and its allways read 14.8V ish any time I've glanced at it while on the overrun. Seems a bit daft then if the battery is only allowed to charge to 85% which, presumably, is to allow a bit of room to avail of "free" charging on the overrun at 14.8V, yet seemingly doesn't allow this, may as well charge to 100% if thats the case.

If you have a multimeter you should also just check that the alternator is charging the battery, with engine idling, 13.5V to 14.8V. A DVM (digital volt meter) is also a good investment for a few bob, you can either leave it plugged in permanently or just use it to check periodically that the battery is charging at ~ 13.5V while driving (sometimes, 14.8V) and allways at 14.8V on overrun. My original 59AH EFB battery is now 3 months into its eight year, stop/start operates even if SOC down to 70% but have noticed recently that it charges at a constant 14.8V if the ambient is less than 6C, once the temperature rises a degree or so the charging then returns to its 13.5V/14.8V.

I'd like to know how VCDS can conjure up a battery at rest voltage, 12.4V, if true is ~ 71% SOC, VCDS shows 73%, not a whole lot different. Below is the first set of (partial) data that I took after 2years and 8 months and todays one again, below that. Two things that strike me is, one, the usable battery charge, 21AH now vs 38AH then but I suppose there is a lot of starts left in that battery at ~ 0.25AH/start, assuming a 3 sec crank at 300A, and two, which will/may eventually cause real starting problems due to voltage drop, internal battery resistance, 8.2mOhms now vs 6.6mOhms then. IDE01834 Battery voltage 13.487 V IDE01836 Battery current 2.639 A Engine ON, idling. 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 IDE01834 Battery voltage 12.081 V IDE01836 Battery current -4.997 A Engine OFF. IDE01837 Temperature of battery sensor 16 °C IDE01839 Battery charge level 73 % IDE01841 Battery internal resistance 8.2 mOhm IDE01842 Usable battery charge 21 Ah IDE01843 Battery voltage at rest 12.4 V IDE01948 Battery internal resistance not normed 7.6 mOhm 12V Battery Voltage State of Charge 12.70 100% 12.50 90% 12.42 80% 12.32 70% 12.20 60% 12.06 50% 11.90 40% 11.79 30% 11.58 20% 11.31 10% 10.50 0%

Jan 2019 Polo 40,062kms, 24,893miles. original 59AH EFB Battery. VCDS Battery Scan 11:52:26 07032026 Engine OFF. IDE01834 Battery voltage 12.081 V IDE01836 Battery current -4.997 A IDE01837 Temperature of battery sensor 16 °C IDE01839 Battery charge level 73 % IDE01841 Battery internal resistance 8.2 mOhm IDE01842 Usable battery charge 21 Ah IDE01843 Battery voltage at rest 12.4 V IDE01948 Battery internal resistance not normed 7.6 mOhm IDE07681-MAS06086 Battery total charging throughput-Total re-charge 3706.5 Ah IDE07681-MAS06087 Battery total charging throughput-Entire energy throughput 3908.8 Ah

Coolant temperature plays no part in my stop/start, if the ambient temperature is greater than -2C, the stop/start operates as soon as you drive the mandatory 0.5kms even when the car has been parked overnight for 8 or 10 hrs which means the coolant temp is the same temp as the ambient temp on start up and (via VCDS) only risen to 20/25C after 0.5kms.

My (Polo) battery is now 3 months into its 8th year (original). I noticed in the last few coldish days that if the ambient is < ~ 5C that the stop/start is inhibited and also, as per my DVM, charges continuously at 14.6/14.8V, once the temp rises above say 6C, then the charging returns to its normal 13.5ish, except on overrun where it (as normal), rises to 14.8V, and the stop/start returns to normal. I will be taking a set of VCDS battery condition readings very shortly and will post same.

On a number of VWs I've owned, if the bonnet wasn't closed properly, the wipers just didn't operate.

Yes, wipers resume constant operation once I move off.

Another nice touch, if the wipers are on, either intermittently, or constantly, and you reverse into a parking spot or where ever, the rear wiper then operates automatically while the car is in reverse gear.

A new innovation from Skoda.... Its the Stop/Start Wiper!.

(Polo) If my wipers are on constant speed, they will go to intermittent once I've stopped and will then resume constant operation when I move off but don't know if I must reach a minimum speed for this to happen. (Will check tomorrow)