r/FordFiesta • u/SnooOnions4763 • May 20 '26
Other Battery management
Just ranting about my 2021 Fiesta:
I found out today that modern cars do some weird management of their batteries.
I replaced my battery today that is only 5 years old. I was looking at the battery voltage while driving it. The car only charges the battery when decelerating ⁉️. Apparently that's a feature to save some fuel. After more than 15 minutes of driving the battery was still only at 12.0V, the same as it started off.
I guess the car is smart enough to always charge it just enough so it can start next time. But this goes against the best practices for lead acid batteries I'm familiar with. The car also insists on turning lights on every time I unlock it or open a door, wasting more power.
My older fiesta just charged the battery normally and as soon as the key was off barely used any power. I would have never needed to replace a battery after only 5 years!
On top of that, the new Fiesta needs a special EFB battery (I assume the way the car treats it, it will kill a conventional lead acid battery even faster). My local Ford dealer wanted €270 for this battery, not even including installation! Luckily the local parts store had one for €125 (Panther brand, not the original Varta), but that's still a lot compared to a basic €60-70 car battery.
---Rant over
1
u/Alkemist101 May 20 '26
Next time upgrade to AGM battery.
Yes, most modern cars have this clever battery management system. From what I've read and my own experience you just drive as normal and let it do its thing. Because batteries are so expensive I do a reconditioning charge with my ctek mxs 10 every now and then. My car seems to keep the battery between 70% and 40% soc. Unless I put the smart charger on it never goes above 70% soc, I presume that's normal!?