I still have my doubts as I still contend (as discussed on previous different threads) that, once the car is in READY with no errors, the dc-dc converter keeps the 12v battery voltage within acceptable limits even if the 12v battery is extremely weak. kiev, in the above example, sure, the 12v battery sags a bit and is may be a bit weak depending on what accessories are running if the measurement was made right at the battery, but once in READY there is no reason for any subsequent voltage drop - thus negating this as a cause of the errors appearing while driving.
kiev wrote:...This much sag indicates the battery is weak or worn out. It's at least 5 years old so i think it has given good service....
Um, maybe not...I just ran out to the garage and here are my 12v battery readings right at the battery (I have a fused Anderson connector on each car's battery), and I didn't bother with the READY voltage - these are all original batteries in early 2012 cars:Mitti
OFF ==> 12.96v (about an hour since it was last run)
ON ==> 12.25v (radio, GPS, dashcam, low fan ON)Moto
OFF ==> 12.69v (about 1/2-hour since it was last run)
ON ==> 12.02v (radio, GPS, low fan ON)Mitsi
OFF ==> 12.76v (about 20 hours since it was last run)
ON ==> 12.20v (radio, GPS, low fan ON)