Hi guys! I've just joined your forum.
To cut the long story I'm an electronics engineer (it's my profession for the last 46 years ☺️) and half a year ago I purchased Karoq. After three months I found that the start-stop system doesn't work as it did before: sometimes - it worked, sometimes -not. After search in the internet I started to suspect that my battery supplies too low voltage. I measured it with my Fluke directly on the battery terminals immediately after I stopped the engine. It was 12.5V and during 20 seconds decreased to something about 12.1V. I started the engine again, asked my wife to keep the revolutions about 2000/min and the voltage increased to 14.1V. In my opinion the alternator worked as it should. Next morning before starting the engine I raised the bonnet and measured the battery voltage - it was 12.0V.
I connected to the cigarette lighter my mobile phone charger equipped with DC voltmeter. It showed 11.8V (I'm an old bore - I tested this toy in my laboratory - in the range 10 - 20V the measurements accuracy was excellent!).
Also I found that the measurement difference between direct battery terminals test and the phone adapter is always the same ~200mV. I suppose the reason is the voltage drop on wires and fuses.
I think there are only two reasons for such battery voltage drop: or there is any device with significant current consumption when the ignition is OFF, or my battery is defective. So during afternoon break I raised the bonnet and measured the current in the wire connecting the "negative" terminal of the battery to the chassis with DC Clamp Meter while the ignition was OFF and the car was locked. The test lasted 3 minutes. In the beginning there was 6.5 Amps current but after ~35 seconds the clamp didn't see any current at all (@ the full scale 10 Amp)!!! Now I was sure there is no load draining my battery at night!
I've came to the Skoda service with all the meters needed, explained the problem and required battery replacement. It was rather hard battle but I won and came home with a new battery. Their electrician made new battery adaptation routine also.
Do you think that the battery problems were behind?! NO!!! The next morning on the way to my job (about 25 miles on highway) I asked my engineer to monitor the voltage with the mentioned above phone adapter. He reported the voltage 14.2V. But after 10 miles he exclaimed "Wow! It's only 13.1V now!" The speed was ~70 m/h and the tachometer showed ~2000/min! I was so astonished that took my foot from the gas pedal. "Wow - he shouted again - the voltage jumped to 14.3V!" I made this trick five times with the same result: gas depressed - 13.1V, no gas - 14.2V! And all this bull**** happens at the same speed with no change of the engine revolutions! Fairy tale! I think the only change is the info the gas pedal sensor reports to the car computer...
Can anybody explain this? All ideas will be appreciated.
P.S.
I wanted to make sure the new battery is OK so I found and purchased electronic battery tester:
The test results: SOC (state of charge) - 80%, SOH (state of health) - 100%
Michael