Hi all Some weeks ago i forgot to put in the battery charger. So i got a low battery, car turned 2 rounds when i tried to start, then it stopped. After charging the battery over the night to full level, car runs well again. Now i saw, that the voltmeter display swings between 12V and 14,xV when driving. There is no cycle or logic, it swings within seconds up and down. Is this normal ? I don't remember this before, but to be honest, i never looked on this. Can someone check this at his 812 ? Many thanks for helping me. Daniel
It can be normal, but can you elaborate on "swinging"? Do you just see it changes as you drive, or is it bouncing all over the place each second? The cars, like many modern cars, use a smart charging system which means the charging output voltage from the alternator is digitally controlled based on multiple conditions like battery state of charge, battery size, engine speed, battery load, etc. So the voltages will change as the parameters change. If however a battery starts to fail, or in the case of lithium batteries with internal protections that can internally disconnect them, the smart charging system can start to behave erratically, but you'll typically see some associated warning lights also.
I think it’s fairly normal. If you are going to leave the car for more than a day, put it on the tender. If you don’t drive it for about 45 minutes at a clip, then put it on a tender. [Editorial] Welcome to the world of the smart alternator because it’s mandated by the EU. Basically it only charges the battery when it thinks it should. You are literally getting 0.1% better fuel economy for this nonsense. Sent from my iPad using FerrariChat
Well, it's going up and down, sometimes it stays a few seconds, then go up, then go down, .... So if the current alternators are "smart", it should be normal. ignition on with engine off - 12 Volt Perhaps i order a new battery for the next spring. This season ends in 2 weeks, so next year in March/April Many thanks for your input. @Caeruleus11 Oh yes, many things, the EU parlament decides, is crap. And often i think Germany is in front of all, we save the climate. Uneducated people are in positions which is not good for many many people. Daniel
Or like Mark Twain said Never argue with an idiot, they will drag you down to their level and beat you with experience. Daniel
I think perhaps both. If you have stock battery and it completely discharged then its likely toast. However, my voltage swings from 12.x to 14 when acceleration to deceleration. Only charges on deceleration. So I think both.
Thanks for the input. Battery wasn't completely discharged, but it is is stock, 2019 car with now 2300 Km on the clock, so 4 years old. March 2024 i will order a new one from Varta or Bosch. Daniel
New battery is best idea. I had a 3 hour wait at a fuel station recently, 2 miles from home. Battery just went dead. Got it back home, on the tender, returned to normal….except I knew it wasn’t. Battery is just out of warranty so I got the dealer to fit an alternative one that is recommended.
