This problem comes up every couple of months. I have a 2018 Ford Focus Platinum with 97k miles. I bought a new battery last year and also replaced the terminal end, but this issue keeps happening.
Have you tested the battery with a multimeter? Even though the battery was replaced, it could still be faulty.
I had a similar issue with my MK3 RS when the battery was failing a few months ago. The issue stopped once I replaced the battery.
Also, do you have a dash cam or something else that could be drawing power from the battery constantly?
Did you reset the BMS after the new battery was installed?
Leith said:
Did you reset the BMS after the new battery was installed?
I didn’t reset it after replacing the battery.
Leith said:
Did you reset the BMS after the new battery was installed?
I didn’t reset it after replacing the battery.
That might be the issue. The Focus Mk3 has a BMS (Battery Management System) that keeps the battery at about 80% charge. Over time, the battery degrades, so the BMS adjusts itself to the battery’s condition.
The problem is that after installing a new battery, the BMS adapts based on the old battery’s settings. This can cause issues after a year.
You basically have two options: reset the BMS so it adapts to the new battery, or disconnect it (there should be a plug on the negative side of the battery). Once you do that, the car will handle the battery like usual, keeping 12V when off and 14.4V while driving.
@Leith
I reset the BMS. I have a car scanner with live data, so I’ll check the voltages. Before I reset it, the voltages were between 14.9V and 15.6V.
Wynter said:
@Leith
I reset the BMS. I have a car scanner with live data, so I’ll check the voltages. Before I reset it, the voltages were between 14.9V and 15.6V.
The Focus has a diagnostic tool built into the gauges. You can check the battery voltage there too.
Here’s a video that shows how: https://www.youtube.com/watch?v=zG0KA2bNb1k.
Yeah, those voltages sound normal for the BMS to be charging the battery. For cars without this system, the voltage is usually stable around 14.4V to 14.5V.
I get that message too on my ‘12 SE, but only when the car is on but not running (ACC power) for about 10-15 minutes. I think it’s because of the power draw from my subwoofer, but I haven’t noticed any real problems.
Maybe check if you have any electronics draining the battery?