Firstly, I apologise but I have just posted this in the MkIII Section in error!   

Hi, I was wondering what voltage to expect across the battery terminals on idle please?   Last week my rear sensors advised that they needed cleaning and that manoeuvre braking no longer worked.  All sensors were clean.  Reading some comments on this forum I decided to charge the battery overnight.  Upon selecting Reverse for the first time following engine start everything worked as expected.  Subsequent selections of Reverse lead to the 'Clean Sensors' etc. warning.

 

I have measured 13.0v across the battery terminals whilst idling - Is this normal?  I was expecting closer to 14v.  Could there be a cell failing - The battery is the original from 2020.

Any thoughts please?  

Kind regards

Alan

Is this a hybrid or straight ICE?

I have seen other postings where the Mk IV hybrid 12volt battery was not being charged correctly.

If vehicle is straight ICE, the smart alternator control can often show a lower charging voltage - relying on energy recuperation to fully charge. 

A search on the forum may give you some information on charging rate.  A load test will confirm battery condition.

Edited 4 February, 20251 yr by Warrior193
repetition

Hi Warrior193, thanks for your reply.  The car is a straightforward 1.5TSI ICE.  It  is due to be looked at by Mitchells of Chester next week, (All in Service Warranty) I will point them in the direction of battery capacity! (Understanding that a battery is not a warranty item)

Warranty on battery can depend on reason for failure - I had battery and alternator replaced under warranty in the first year of ownership of my Octavia - but yours, if it is failing, would probably be considered normal wear and tear.

There was also an issue with a faulty batch of Moll EFBs a few years back, but I think that was before 2020.

Have you tried running down the battery voltage a little, then rechecking the alternator voltage output at the battery terminals?

1 hour ago, Warrior193 said:

If vehicle is straight ICE, the smart alternator control can often show a lower charging voltage - relying on energy recuperation to fully charge. 

On the ICE versions there is a form of micro hybrid using the battery/alternator to only charge the 12V battery to around 80% capacity most of the time.

 

Battery voltage of around 14.5V only occurs just after starting and when coasting/braking at all other times the battery voltage can be as low as 12.5V - so I would say that 13V when idling is NOt an indication of a failing battery.

Edited 4 February, 20251 yr by PetrolDave

Hi PetrolDave, thanks for the information, very interesting.  I am of the age that I can still remember DC generators on cars, some with 6v electrics!   I have just had the battery tested by a local garage, result was the battery had <80% capacity with a 'Resting' voltage of <12.2 V.  I am assuming that one or more cells may be failing.

 

I was quoted £200 for a new EFB, but will see what Skoda say!   I am tempted to save the Dealership diagnostics charge to investigate the Rear sensor issue and just replace the almost five year old battery anyway and see what happens to the sensors!   Bearing in mind that they work immediately after the battery has been fully charged but not after driving around for a few miles.

 

  

17 hours ago, AlanOsborne said:

Hi PetrolDave, thanks for the information, very interesting.  I am of the age that I can still remember DC generators on cars, some with 6v electrics!   I have just had the battery tested by a local garage, result was the battery had <80% capacity with a 'Resting' voltage of <12.2 V.  I am assuming that one or more cells may be failing.

 

I was quoted £200 for a new EFB, but will see what Skoda say!   I am tempted to save the Dealership diagnostics charge to investigate the Rear sensor issue and just replace the almost five year old battery anyway and see what happens to the sensors!   Bearing in mind that they work immediately after the battery has been fully charged but not after driving around for a few miles.

 

  

Unless the battery was fully charged before the test, <80% capacity can be considered completely normal given the way the alternator smart charge controller operates - particularly if the vehicle often does short trips. 

A resting figure of 12.2 volts on a EFB equates to approx. 65% charged - again, normal, taking into account the smart charging system. Unlikely that one cell is failing at that reported resting voltage. Suggest a full charge, then a good load test to check battery condition.

i plugged simple obd2 tool and with Torque app monitored some stuff.

also, charging voltage ov battery goes up and down, even to 13V to 14.5V.

as lond as none error displays on dashboard its ok.

smart battery managment - smart batteries - EFB, AGM, new technolgies.

their reason is again ecological, an unnecessarily loaded alternator puts a strain on the engine, which then consumes more fuel and increases emissions.