Progress?

Joined
Jun 8, 2016
Messages
1,962
Location
Texas, USA
I know we've all encountered features on new cars that seem like excessive over-engineering, and items that solve problems that never existed. As a Mustang owner, this one made me shake my head until I was dizzy.
If you replace the battery in a Mustang, the computer takes hours of uninterrupted 'thinking' to register the new charge state of the battery. If your battery dies, and you replace it with a fully-charged battery, crank it up and go for a drive, the system will actually overcharge the battery until it learns the new voltage level. Additionally, if you hook a charger / maintainer to the positive and negative terminal of the battery, instead of using the ground connected to the strut tower, the computer won't recognize the new charge state of the battery, and will charge the battery at next startup as if the battery were still at a low-voltage state. If it's already fully charged, it will overcharge it. Connecting the charger / maintainer to the positive terminal, and the strut tower ground is alleged to give the computer the information it needs, as it apparently makes a note of incoming charge through that ground cable.

I guess this is what carmakers are calling" progress". A 'smart' charging system that is too dumb to recognize the real-time charge state of the battery, and therefore, overcharges it. This isn't isolated to Ford....apparently GM employs a similar system. So, when my Mustang sits in the garage untouched for a month, I've been charging the battery using the negative and positive terminals. Sometimes I take it for a drive, sometimes I close the hood and don't touch it again for a month. It's good to know that during the times it was taken for a drive, the alternator was charging a fully-charged battery. Head ---->Brick wall.

From The 2020 Mustang Service Manual

Battery Charging

When charging the vehicle battery by connecting the charger to engine or chassis ground, the negative charger clamp must be connected to an unpainted chassis surface or a solid engine component such as a generator mount or engine lifting eye. In this instance, after charging, the BMS Reset is not required. Through this method of charging the BCM updates the battery state of charge during the charging process.

When charging the vehicle battery by connecting the charger to the negative battery terminal is necessary, such as when using a combination battery charger and battery tester/analyzer, like the GR 1 190 V3.0 Intelligent Diagnostic Charger, the BCM does not immediately update the battery state of charge. In this instance, the BMS Reset must be carried out using a diagnostic scan tool. This reset is needed for proper engine off load shedding and to prevent invoking of engine off load shedding earlier than normal.

If the reset is not carried out, when the battery is charged by connecting the charger to the negative battery terminal, it takes approximately 8 hours for the BCM to learn the new battery state of charge.

During this 8 hour period, the vehicle must be undisturbed, with no doors opened or keyless entry button presses. If the vehicle is used before the BCM is allowed to learn the new battery state of charge, engine off load shedding can still occur and a message may be displayed.
 
Joined
Dec 13, 2004
Messages
3,248
Location
Chicago Area
I don't know if this would qualify but the OnStar on the Cobalt stopped working a couple of years ago. The system was getting no power. Since I get a break from the insurance company by letting OnStar tattle on my use of the car (and it is worth the savings for me), I took the car in for service. It all came down to a blown fuse (how that happened I don't know) but the dealer needed to keep the car almost the entire day for the OnStar system to reinitialize/reset once the fuse was fixed.
 
Joined
Aug 30, 2004
Messages
24,933
Location
CA
Thinking about adding an Autel BT608 to my arsenal - it has a guided function for resetting the BMS and initializing various functions after a battery replacement:

 
Joined
Jan 1, 2003
Messages
1,247
Location
Daytona Beach
BMW's do the same thing. I think they require a scan tool to reset the computer in order to "register" the change in battery. Prob, Mercedes as well.
 
Joined
Apr 29, 2007
Messages
925
Location
Connecticut, USA
Seems like many "newer" vehicles have this feature regardless of brand... On BMW and MB, it depends on year and model. Granted the european manufactures seem to have started implementation earlier.

For example: 2011 MB E350 has a smart charging system with AGM battery, where it never fully charges the battery (target is 80%). This increases MPG, but battery life is shorter on this chassis compared to older E classes without smart charging system. Part of the system is battery monitoring, but it doesn't get reset (nor can it be) if the battery is replaced or charged.

The smart charging system is across the entire* (may be an exception or two) W212 line-up from 2010-2016. The BMS is not resettable from 2010-2013. 2013+ its a bit uncertain if it needs to be with battery replacement.
 
Joined
May 18, 2012
Messages
6,333
Location
Baltimore, Maryland, USA
Use Forscan and a cheap OBD dongle and you can just reset the BMS so it knows a new battery is installed...
I did just this. Took me about an hour, and most of that was figuring out how to use ForScan on Ubuntu 20 Linux since I had never even tried to run a windows program in Linux.
 
Joined
Nov 9, 2008
Messages
18,648
Location
NH
So it's not so bad... if you have the tool to tell the ECU exactly what to do?

I'm still in the camp of "it's not progress" though. I thought car batteries were lasting long enough before smart charging? Not sure what was "fixed" here.
 
Joined
Sep 17, 2002
Messages
4,974
Location
Lakeville, MN
I have the tools anyways for diagnostics (being invested in Ford Products makes it easier to justify) and reality is these items are inexpensive.

I've used Forscan for diagnostics and to switch some settings (like when I installed the plug n play subwoofer - just had to tell the truck it was there to turn it on). Others have gone much deeper and there is a robust community on the F150 world at least. If I heard it right, the 2021's F150 may use a different setup...
 
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