Hi,
forgive me if there is the same topic somewhere, but I have not found it.
I'm just curious on why certain type of modern lead-acid car batteries dies "instantly". I heard stories by many people, in the recent years, so I guess is a pitfall of the modern batteries, and the other day happened to me as well.
Interestingly, I bought an OBD Bluetooth monitor for my car just few days ago, and I used it on my mother's car to see the parameters ecc. The battery, with no engine running but ignition turned on, was well above 12V and all electronics of course was working (ok, I could have used the multimeter for that). The next day I used the car for about 200km (a travel of 100km x2), and on the way back the electric system, while cranking the engine, failed by dropping the voltage, so I tried again, and all went ok. It seemed like a "bad contact", because there were no loss of power on the next crank.
The day later: car is dead. Battery measures 12.5V ish with all shut down, but when I turn on the small interior light or even worse turn on the ignition (NOT cranking, it just does nothing if I crank), drops to 4.5/5V. Seem that the internal impedance grew enormously in the last 2 days.
After additional 20 hours of the car staying parked, when all is off, I measured with my multimeter and battery is now 3V. I jump started with emergency cables, drove for 30 minutes at high rpm, battery settled at 9V. Drop again to 3-ish V when attching a load, like ignition.
Reading about it on batteryuniversity and other sources on line, the chemistry should not be that sharp in dropping power, regardless the conditions. I will change the battery, but this still puzzle me. Is true that the car was used for short distances, and is not the best use case, but how could it fail so quickly, and why?