12v battery charging issues…. Ongoing

BillPitman

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I have been having issues since 5/2/22, warning: “12 v battery fault, service soon”(several times)
and anon-display info: “System off to save battery” ( twice)

What follows is running commentary on today’s issue/ comments…..

5-6-22, noontime, car has not been plugged in since midnight 5/1, HVB SOC is 59%

Entering car, display shows “System off to save battery”

car on , collecting OBD info, 12v SOC 37%, charging at 14.6v

12:06 pm, car off, 12v SOC 50%, 12.5v

12:08 pm, car on, 12v SOC 50%, 14.5v

** Is if possible 12v battery cannot hold a charge & is bad?! Or more likely…

** It appears DCDC converter is not being commanded on, to charge the 12v battery

12:13pm, will pull codes once 12v SOC reaches 75%

12:16pm, LvBA showing 36 amps…… is this amps being drawn from or going to the 12v battery….
looking at OBD data, it is amps being put back into the 12v battery!
@ 76% SOC, amps are 26, going down as 12v SOC goes up

12:21pm, car off, 12v SOC 78%, LvBA now settling at -7 amps!
There appears to be a 7 amp draw on the 12v battery when the car is off !?

12:26pm, car off, 12v SOC 76%, 12.7v, LvBA= -7 amps

12:27pm, car on, 12v SOC 77% charging @14.5v, LvBA= 24 amps

12:28pm, car on, DTC‘s PULLED-

Car Scanner ELM OBD2
DTC report
Selected brand: Ford
VIN: 3FMTK3SU1MMA56293
============1==============
B1533(08)

Raw code: 953308
ECU: BCM[Archive (inactive)]
Status: Confirmed
Ford: Memory 1 Switch Circuit Short To Battery

============2==============
B115E(97)
Raw code: 915E97
ECU: CMR[Archive (inactive)]
Status: Confirmed
============3==============
B15E1(97)
Raw code: 95E197
ECU: CMR[Archive (inactive)]
Status: Confirmed

============4==============

B15E2(97)
Raw code: 95E297
ECU: CMR[Archive (inactive)]
Status: Confirmed


I continued to monitor charging of 12v battery until 1:04pm- 12v SOC 92%, maintaining 13.3v, 0 amps going in

1:05pm, car off, 12v SOC 91%, 12.7v, LvBA showing -7 amps
7 amp draw = about 84 watts….. what is the draw of my OBDLINK dongle? Can’t be anywhere near that much

I will continue to gather information….. thanks for reading….. Bill Pitman
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louibluey

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Bill, A number of us have been looking at 12V LVB charging / discharging behavior since last year. There are number of known charge/discharge cycles, some from Ford docs, some from our own various studies. In some circumstances, it is completely normal for a MME battery to cycle from 40% soc to 80% - 100% soc. We can debate the merits of that range, but that is just how it works in some situations.

A few notes that might help your study. The LVB BMS computer is mounted on the negative terminal of the LVB, the small box that is part of the negative terminal. The BMS sends at least LVB voltage and LVB soc to the BCM by LIN bus (the two wires on the small connector, one is +12V, the other LIN data). You need a LIN monitor to read that LVB BMS data directly, and hardwire connection tap to the two wires. It is not clear to me yet where the LVB voltage that is reported by OBDII comes from, but the LVB soc undoubtedly begins with the LVB BMS value.

The BMS (LVB BMS) reports many times a second when on, and every 15 minutes when MME is at rest.

One problem is that many scanners and OBDII apps are only reporting the last reported value before MME goes to rest, so that is something else to look for.

Another general guidance is that any value 13.4V to 15.1V means the DC/DC converter is running. The DC/DC converter output #2 cable is directly wired to the 12V LVB plus terminal, then on to the main distribution bus behind the battery junction box (BJB) next to the frunk under a side panel. Anytime the DC/DC converter is running, the voltage you are measuring is the output voltage of the DC/DC converter, which forces the battery terminals to follow that driven voltage. In that case, think of the LVB like a big capacitor hanging on the 12V bus.

If you look back through old threads a few of us have posted a number of graphs of LVB soc over time. We have noted that under some circumstance, can be as low as 35% to 40% soc, at the moment the DC/DC converter comes on, a 12V service message is generated. In most cases, the LVB is still fine, and nothing is wrong.

There are some more serious cases, more than a few, but less then tens (we think) where there is some kind of failure in the hv junction box / block. HVBJB There are at least two different hv power scenarios for the DC/DC converter. For example, when plugged into L2, the high voltage power supply of the hvb charger in the car, also provides the hv to power the DC/DC converter. However, when unplugged, including driving, of course the DC/DC converter is powered directly by the hvb. There are a number of different contactors, four or five, that make this system work, it's in the past threads. In some failures, one or more of these hv contactors does not work correctly, and almost always, eventually the LVB is completely discharged. So it will be obvious if you have this problem.

If you get the service message every day, it may mean that you have a constant load, either some fault, or something you added. Or, the headlights might be staying on after shut down MME, just cycle the normal headlight rotary switch to off.

Keep taking data, the more we have the better! Keep in mind that some OBDII or other scan data may be very old and stale data, even though it might seem to be current.

It cannot hurt to charge you 12V LVB using the jump terminals if you are worried about it. Also, read about @Mach-Lee 's method of conditioning LVB's. How to Recondition/Service Your 12V Battery That too cannot hurt, and if it works, your LVB is still fine!

Try to scan through some of the many old threads on LVB problems and solutions. One of the more informative Ford pdfs was a police version maintenance note from last winter, shouldn't be too difficult to find.

Also, ask in the FDRS thread for a list of SW Updates your MME if you have not done that yet.
Post here if you have an active FDRS account and are willing to look up info for others

Then ask your dealer to do the scheduled SW Updates, possibly including one of those early SSMs or TSBs which addressed a 12V charging problem (if it applies to your VIN).

Here is another quick example of a 12V service warning which just corresponds to the DC/DC converter charging the LVB.

It is not always easy to find the most relevant posts, but LVB problems are some of the most common discussions. There are literally hundreds of posts now on LVB observations, problems, and solutions.
 
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Logal727

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I ended up turning off the welcome lights because they kept turning on while car was in garage because it can sense my phone through the walls, and also the sync screen backlight would also come on, so I figured that was the source of my battery drain. Turning off welcome lighting while it’s in the garage seems to have fixed this issue.
 
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BillPitman

BillPitman

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Bill, A number of us have been looking at 12V LVB charging / discharging behavior since last year. There are number of known charge/discharge cycles, some from Ford docs, some from our own various studies. In some circumstances, it is completely normal for a MME battery to cycle from 40% soc to 80% - 100% soc. We can debate the merits of that range, but that is just how it works in some situations.

A few notes that might help your study. The LVB BMS computer is mounted on the negative terminal of the LVB, the small box that is part of the negative terminal. The BMS sends at least LVB voltage and LVB soc to the BCM by LIN bus (the two wires on the small connector, one is +12V, the other LIN data). You need a LIN monitor to read that LVB BMS data directly, and hardwire connection tap to the two wires. It is not clear to me yet where the LVB voltage that is reported by OBDII comes from, but the LVB soc undoubtedly begins with the LVB BMS value.

The BMS (LVB BMS) reports many times a second when on, and every 15 minutes when MME is at rest.

One problem is that many scanners and OBDII apps are only reporting the last reported value before MME goes to rest, so that is something else to look for.

Another general guidance is that any value 13.4V to 15.1V means the DC/DC converter is running. The DC/DC converter output #2 cable is directly wired to the 12V LVB plus terminal, then on to the main distribution bus behind the battery junction box (BJB) next to the frunk under a side panel. Anytime the DC/DC converter is running, the voltage you are measuring is the output voltage of the DC/DC converter, which forces the battery terminals to follow that driven voltage. In that case, think of the LVB like a big capacitor hanging on the 12V bus.

If you look back through old threads a few of us have posted a number of graphs of LVB soc over time. We have noted that under some circumstance, can be as low as 35% to 40% soc, at the moment the DC/DC converter comes on, a 12V service message is generated. In most cases, the LVB is still fine, and nothing is wrong.

There are some more serious cases, more than a few, but less then tens (we think) where there is some kind of failure in the hv junction box / block. HVBJB There are at least two different hv power scenarios for the DC/DC converter. For example, when plugged into L2, the high voltage power supply of the hvb charger in the car, also provides the hv to power the DC/DC converter. However, when unplugged, including driving, of course the DC/DC converter is powered directly by the hvb. There are a number of different contactors, four or five, that make this system work, it's in the past threads. In some failures, one or more of these hv contactors does not work correctly, and almost always, eventually the LVB is completely discharged. So it will be obvious if you have this problem.

If you get the service message every day, it may mean that you have a constant load, either some fault, or something you added. Or, the headlights might be staying on after shut down MME, just cycle the normal headlight rotary switch to off.

Keep taking data, the more we have the better! Keep in mind that some OBDII or other scan data may be very old and stale data, even though it might seem to be current.

It cannot hurt to charge you 12V LVB using the jump terminals if you are worried about it. Also, read about @Mach-Lee 's method of conditioning LVB's. How to Recondition/Service Your 12V Battery That too cannot hurt, and if it works, your LVB is still fine!

Try to scan through some of the many old threads on LVB problems and solutions. One of the more informative Ford pdfs was a police version maintenance note from last winter, shouldn't be too difficult to find.

Also, ask in the FDRS thread for a list of SW Updates your MME if you have not done that yet.
Post here if you have an active FDRS account and are willing to look up info for others

Then ask your dealer to do the scheduled SW Updates, possibly including one of those early SSMs or TSBs which addressed a 12V charging problem (if it applies to your VIN).

Here is another quick example of a 12V service warning which just corresponds to the DC/DC converter charging the LVB.

It is not always easy to find the most relevant posts, but LVB problems are some of the most common discussions. There are literally hundreds of posts now on LVB observations, problems, and solutions.
Bill, A number of us have been looking at 12V LVB charging / discharging behavior since last year. There are number of known charge/discharge cycles, some from Ford docs, some from our own various studies. In some circumstances, it is completely normal for a MME battery to cycle from 40% soc to 80% - 100% soc. We can debate the merits of that range, but that is just how it works in some situations.

A few notes that might help your study. The LVB BMS computer is mounted on the negative terminal of the LVB, the small box that is part of the negative terminal. The BMS sends at least LVB voltage and LVB soc to the BCM by LIN bus (the two wires on the small connector, one is +12V, the other LIN data). You need a LIN monitor to read that LVB BMS data directly, and hardwire connection tap to the two wires. It is not clear to me yet where the LVB voltage that is reported by OBDII comes from, but the LVB soc undoubtedly begins with the LVB BMS value.

The BMS (LVB BMS) reports many times a second when on, and every 15 minutes when MME is at rest.

One problem is that many scanners and OBDII apps are only reporting the last reported value before MME goes to rest, so that is something else to look for.

Another general guidance is that any value 13.4V to 15.1V means the DC/DC converter is running. The DC/DC converter output #2 cable is directly wired to the 12V LVB plus terminal, then on to the main distribution bus behind the battery junction box (BJB) next to the frunk under a side panel. Anytime the DC/DC converter is running, the voltage you are measuring is the output voltage of the DC/DC converter, which forces the battery terminals to follow that driven voltage. In that case, think of the LVB like a big capacitor hanging on the 12V bus.

If you look back through old threads a few of us have posted a number of graphs of LVB soc over time. We have noted that under some circumstance, can be as low as 35% to 40% soc, at the moment the DC/DC converter comes on, a 12V service message is generated. In most cases, the LVB is still fine, and nothing is wrong.

There are some more serious cases, more than a few, but less then tens (we think) where there is some kind of failure in the hv junction box / block. HVBJB There are at least two different hv power scenarios for the DC/DC converter. For example, when plugged into L2, the high voltage power supply of the hvb charger in the car, also provides the hv to power the DC/DC converter. However, when unplugged, including driving, of course the DC/DC converter is powered directly by the hvb. There are a number of different contactors, four or five, that make this system work, it's in the past threads. In some failures, one or more of these hv contactors does not work correctly, and almost always, eventually the LVB is completely discharged. So it will be obvious if you have this problem.

If you get the service message every day, it may mean that you have a constant load, either some fault, or something you added. Or, the headlights might be staying on after shut down MME, just cycle the normal headlight rotary switch to off.

Keep taking data, the more we have the better! Keep in mind that some OBDII or other scan data may be very old and stale data, even though it might seem to be current.

It cannot hurt to charge you 12V LVB using the jump terminals if you are worried about it. Also, read about @Mach-Lee 's method of conditioning LVB's. How to Recondition/Service Your 12V Battery That too cannot hurt, and if it works, your LVB is still fine!

Try to scan through some of the many old threads on LVB problems and solutions. One of the more informative Ford pdfs was a police version maintenance note from last winter, shouldn't be too difficult to find.

Also, ask in the FDRS thread for a list of SW Updates your MME if you have not done that yet.
Post here if you have an active FDRS account and are willing to look up info for others

Then ask your dealer to do the scheduled SW Updates, possibly including one of those early SSMs or TSBs which addressed a 12V charging problem (if it applies to your VIN).

Here is another quick example of a 12V service warning which just corresponds to the DC/DC converter charging the LVB.

It is not always easy to find the most relevant posts, but LVB problems are some of the most common discussions. There are literally hundreds of posts now on LVB observations, problems, and solutions.
Thanks for the reply…… our Mach-e is a job 2 car, built 10/17/21, delivered 1/11/22
It just seems odd that this problem has only started within the last week or so.
I have only had the “ System shutdown to Save battery” come up twice within the past 3 days, and never before. No accessories have been added….
light switch shutoff is something I will try over the next week….. Regards, Bill
 

louibluey

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System shutdown to Save battery is also very common, and has happened, as you report, weeks or months into driving a MME.

The BMS soc value, possibly including some algorithm which follows in the BCM module are undoubtedly cumulative values on which those LVB actions, alerts, and/or warnings are based. We got some confirmation recently in the new updated 21G01 update procedure, which charges the LVB to full, then resets BCM battery, followed by a BMS reset. You need some kind of scanner program like FDRS to do those resets. Not sure if ForScan can do both. They may also eventually reset or "catch up" with good LVB conditions by themselves.

There are literally tens of reports of these events on the forum from last year, maybe more over the cold winter temperatures. Here was another recent report attributed to a day of running the car for the Earth day show in different modes, which likely confused BMS/BCM into thinking there was a 12V problem. Maybe you did something different in recent days, or weeks? Anyway, these events are very common and generally not a problem. If your 12V LVB goes dead (cannot start without a jump), that might be an entirely different matter.
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