Start-Stop not working

[Ed4573]

Hi all, have seen how helpful this forum is to other people, so was hoping someone would be able to help me with a problem I’m having!!

The start stop on my car hasn’t worked for about a year and a half now. A error for start stop system showed a couple of times about a year ago and went away, however this was during winter so thought it was a fluke and it didn’t come back so left it.

Fast forward to this spring and no start stop at all, even after driving over 2 hours to London on a motorway. Car was in for a service in April and so I bought it up with the dealer and asked that they looked into it.

They came back and said the battery required an acceptance charge?, which they did and it worked flawlessly for about 2 journeys then went back to not being functional! I’ve tried charging with a ctek to 100% but that hasn’t made a difference.

Is there a chance that the EFB battery is shot, as I don’t commute to work and the car only does short journeys to and from the shops maybe about 30 miles a week? The past few months there were lots of low battery warnings and often I would get into the car without any lights on as the charge had dropped to low!


Sorry for the long post, but any insight would be greatly appreciated. Thanks!

[SRGTD]

Welcome to the forum @Ed4573.

There are a number of conditions that need to be met for stop start to work - I think these are outlined in the owner’s manual (sorry, I can’t check as I no longer have a Polo or any other VW). From memory, the conditions are;

- the driver’s door must be closed
- the driver’s seatbelt must be fastened
- the bonnet needs to be fully closed
- the steering wheel needs to be in the straight ahead position
- manual gearbox; the car should be in neutral and the driver’s foot off the clutch pedal
- DSG transmission; car must be stopped and the brake pedal depressed

If one or more of the following conditions are present, stop start won’t work (there may be others conditions I can’t remember);

• Engine hasn’t reached normal operating temperature

• battery state of charge is too low

• the car’s petrol particulate filter (OPF) is going through an active / forced regeneration process to neutralise accumulated particulate matter in the filter

• there is heavy demand on the car’s electrical systems - e.g. heavy power sapping functions being used such as the rear screen heater, heated seats (if fitted)

• climate control is working hard in extreme temperatures

As you’ve been getting low battery warning messages, I suspect it is your battery that’s the primary reason for stop start not working. From what I’ve read on other VW forums it’s not that unusual for the 12v battery to need replacing at around four years old. When you do get it changed, ensure you get the new battery coded to the car so the car’s battery management system recognises the new battery and adjusts the charging rate accordingly.

Hopefully the new battery will restore your car’s stop start functionality.

[Ed4573]

Thanks for such an in depth reply!

Unfortunately just what I suspected, the car is on its original battery and it was treated pretty badly for a while (constantly on low charge).

I have got in contact with the dealer again but I suspect like you say they will replace the battery as the next step.

I knew there was all of the conditions for the start stop to work but I had met all of those so there isn’t anything else I can think of that could be wrong.

I may ask if they can fit an AGM instead.

Thanks

[Johntheo1]

I have a Jan 2019 and a April 2026 Polo, the stop/start will be enabled after 500 meters as long as the ambient is > -2.5C, engine coolant temperature doesn't come into the equation, then, no matter what distance you've travelled, no matter how far, the stop/start will not be re enabled until the ambient rises to -2.0C, thats it.
Stop/Start still worked with the lowest battery SOC that I've seen, at 64%, also increasing the fan speed to max (4) will disable it but "normal" running with headlights, HRS and fan on speed 2 will not.

[CarbonChaos]

Firstly I would get your current battery checked on a decent tester , one which can check the batteries SOC (state of charge) and SOH (state of health) .
You may have charged the battery to 100% SOC but if the battery is in poor condition as you stated the SOH may be down ie no reserve capacity to restart the engine so the car will disable the stop-start system.

[Ed4573]

Have just checked with a battery tester and the SOH is at 45%, V:12.32 R:6.35. Not sure if these numbers are normal or not?

I'm also having to guess with a picture of the battery from eBay with the part number what the specs are as the positive terminal covers them!