12V LVB MME start, MME Accessory Mode

OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
Using a Volt Meter that is plugged into the cigarette lighter socket can I tell if the LVB is being charged or not?
While the car is on, and for some time after the car is off. The voltage is much higher than 12V when charging from the DC-DC converter.

I hope to get back to this project, left off with measuring 12V at OBD (does not turn off) during L2 charging. Plan was to see some graphs showing 12V LVB charging (car off, L2 connected) before and after the software fix. My dealer appointment got delayed some weeks for tech training, so at least that part of the project is on hold.
Ford Mustang Mach-E 12V LVB MME start, MME Accessory Mode DMM-1 Run 2 2021-04-07T20.08.14
Sponsored

 
Last edited:

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
While the car is on, and for some time after the car is off. The voltage is much higher than 12V when charging from the DC-DC converter.

I hope to get back to this project, left off with measuring 12V at OBD (does not turn off) during L2 charging. Plan was to see some graphs showing 12V LVB charging (car off, L2 connected) before and after the software fix. My dealer appointment got delayed some weeks for tech training, so at least that part of the project is on hold.
Thanks for the work you’ve done thus far. I appreciate it!
 

bryan_m

Member
First Name
Bryan
Joined
Apr 21, 2021
Threads
2
Messages
16
Reaction score
60
Location
Texas
Vehicles
2021 Mach-E Select RWD
Country flag
I recently got a dashcam that records motion events in parking mode so I'm watching this thread to learn more about how the 12v battery is maintained when the vehicle is off.

I'll sleep much better knowing that, if my Mach-E senses the 12v battery is getting a bit low if I haven't driven the vehicle for a few days the DC-DC converter will open up and give some charge to the 12v battery from the car's battery.
 

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
I recently got a dashcam that records motion events in parking mode so I'm watching this thread to learn more about how the 12v battery is maintained when the vehicle is off.

I'll sleep much better knowing that, if my Mach-E senses the 12v battery is getting a bit low if I haven't driven the vehicle for a few days the DC-DC converter will open up and give some charge to the 12v battery from the car's battery.

I installed a 12V Battery Monitor in my Mach-E to monitor my voltage.

https://www.amazon.com/gp/product/B07WCW49YM/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Ford Mustang Mach-E 12V LVB MME start, MME Accessory Mode E54730E0-AF3F-42DE-B993-A92EACE35363


With the graphs it produces, hopefully I will be able to see when the 12V battery is getting a charge.
 
OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
It will be good to get some comparisons for many MME.

For dashcam parking modes, some dashcams (Thinkware) have a built in low voltage dropout. My first BlackVue dashcam, several EVs ago, needed an extra little module with the settable low voltage dropout.

I too am hopeful that after the TSB software update (still waiting) MME might monitor and wake the DC-DC converter while parked and either connected L2, or without a charge cord connected.

I have not verified, but my few odd measurements so far indicate that without the TSB update, probably the 12V LVB would go flat. That may or may not apply to MME after the TSB cutoff date.
 
Last edited:


OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
One thing I've been meaning to try, possibly this weekend, is to see if I can get a more wide range bipolar 12V LVB current measurement. The clamp on direct current current transducers (DCCT) are really convenient, and make a relatively large signal for data logging. Of the two I use, one is very fast (high bandwidth) but only goes to full scale 50A in one direction, and has limited range (12A) in the other direction. The other is less sensitive and does not indicate polarity (charge or discharge).

I want to try to use the ground wire (cable) including that Ford LVB sensor part in the power circuit, to see if I can use that short wire and sensor combined as a current shunt (so no limits on full scale current, and with polarity information). So, maybe the signal lead on the 10mm nut on the battery, and the ground lead on the chassis nut. The signal will be small, but might be useable with a laboratory preamp with built in filters, for any science electronics geeks out there, I'm going to try a (now somewhat ancient, like me) battery operated PAR model 113 PRE-AMP.
 

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
I installed the Thinkware U1000 but instead of using the Low Voltage Setting to disable Parking Mode recording I installed the Cellink Neo to power during Parking Mode. I found that my Dashcam would record almost continuously in Parking Mode even when parked in the garage. I’ve also installed a switch to disable the Dashcam when parked in the garage to conserve the Cellink Neo charge.

Cellink claims that using the car battery for Parking Mode would shorten the life of the car battery.??
 

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
While the car is on, and for some time after the car is off. The voltage is much higher than 12V when charging from the DC-DC converter.

I hope to get back to this project, left off with measuring 12V at OBD (does not turn off) during L2 charging. Plan was to see some graphs showing 12V LVB charging (car off, L2 connected) before and after the software fix. My dealer appointment got delayed some weeks for tech training, so at least that part of the project is on hold.
Ford Mustang Mach-E 12V LVB MME start, MME Accessory Mode E54730E0-AF3F-42DE-B993-A92EACE35363
I assume that the spike during 9h is the charging of the LVB by the DC-DC converter?
 
OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
I installed the Thinkware U1000 but instead of using the Low Voltage Setting to disable Parking Mode recording I installed the Cellink Neo to power during Parking Mode. I found that my Dashcam would record almost continuously in Parking Mode even when parked in the garage. I’ve also installed a switch to disable the Dashcam when parked in the garage to conserve the Cellink Neo charge.

Cellink claims that using the car battery for Parking Mode would shorten the life of the car battery.??
I've definitely thought about one of those Li packs over the years. First, they were too expensive, then I opted away from more clutter. Nothing wrong with that solution for parking. IDK about the LVB battery life thing, might be a bit of marketing.

For all my interest in 12V systems, I have never had a no start situation from a dead 12V battery. Also never needed to change the LVB in the last decade (several EVs PHEVs). That's with un heated garage, and we can get several winter mornings of -25 F every year. I would expect the typical 4-6+ years 12V battery replacement, dashcam or not.
 
Last edited:
OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
I assume that the spike during 9h is the charging of the LVB by the DC-DC converter?
yes, just an example where, while plugged in to a L2 charge station, the DC-DC converter did come on to charge the 12V LVB. Unclear if it was a MME pre-programmed LVB check, and then take action, or some kind of poke, a network communication, Ford telematics (network or cell), maybe seeing my iPhone or FOB that woke it up to check?
 

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
yes, just an example where, while plugged in to a L2 charge station, the DC-DC converter did come on to charge the 12V LVB. Unclear if it was a MME pre-programmed LVB check, and then take action, or some kind of poke, a network communication, Ford telematics (network or cell), maybe seeing my iPhone or FOB that woke it up to check?
How fast is the LVB charge rate? Do you think that it’s would take longer to charge the LVB battery than the graph indicates?
 
OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
I keep meaning to make some careful studies, but so far just have snap shots. I've seen momentary charge current of over 10A, but then just 2A or 3A over tens of minutes. MME is just topping off the LVB, so depends on how much energy it takes to get to the stop point, usually just some preset voltage (I do not know for sure how MME decides when to stop LVB charge, when the car is OFF).

If the 12V LVB was actually "dead", but still chargeable, probably hours at 10A or less (36Ah nameplate).

Ideally, MME is just always topping the LVB off as needed. During actual run conditions when the car is ON, the DC-DC converter is actually powering the 12V power bus, and the LVB is just kind of "hanging" there in parallel like an electronic capacitor, following whatever the bus voltage is (so, I guess "charging" by definition, because the DC-DC converter voltage is above 12V).
 

MTNestr

Well-Known Member
First Name
Paul
Joined
Feb 27, 2021
Threads
8
Messages
193
Reaction score
98
Location
NW Ohio
Vehicles
2021 Grabber Blue FE MME
Occupation
Retired
Country flag
Thanks for answering my questions
 
OP
OP

louibluey

Well-Known Member
First Name
Joe
Joined
Dec 21, 2020
Threads
60
Messages
888
Reaction score
1,097
Location
NY
Vehicles
FE "Louibluey" GB
Occupation
retired
Country flag
In post #4, there is a graph for 12V LVB battery current over time for "full accessory mode". MME start button without stepping on the brake (no charge cord attached here).

So, I tried another way to measure the negative terminal battery current, by logging the voltage drop from the heavy ground jump start terminal to the Ford battery monitor "shunt", at the negative battery terminal. Because this is a tiny voltage (hundreds of millionths of volt), there is a pre-amp (Princeton PAR 113) and filter (set to 30 Hz) before the data logger meter (Keithley DMM6500). Data taken about every second where the preamp gain is set to give about 0.1V per amp (so, 1V =10A battery current). I used the preamp variable gain knob (x100 x unknown variable gain, [check later, about 182]) and a FLUKE 376 clamp on current meter for the rough cal, so later I need to check the actual preamp gain (to comment on the total resistance of that short leg plus the Ford shunt [about 550 micro ohms including the Ford sensor shunt]).

Anyway, this graph by voltage drop across the LVB ground cable, looks very much like the one in post #4, taken with a clamp on DCCT sensor which had a limited range of -12A to +50A:
Ford Mustang Mach-E 12V LVB MME start, MME Accessory Mode Screen Shot 2021-05-02 at 2.12.17 PM

I ran the headlights for some tens of minutes to run down the 12V LVB with MME off before the test. Anything in the top half is battery discharge, the lower half 12V LVB battery charging by the MME DC-DC converter.

On turning on MME full accessory mode, after a very short 30A battery supplied spike to start the car, MME turned on the DC-DC converted and charged aggressively at 48A for a very short time, then ramped down to about 5A in minutes and charged the LV at 5A for about 15+ minutes. Then, as in the post #4 test, MME turns off the DC-DC converter, and runs the car on the 12V battery for some time (20+ minutes here), then goes into some lower current state (probably headlights and climate control off) for some 10 minutes, then just turns off.

The 30A battery draw for more than 20 minutes is significant considering the battery is rated for 36 Ah, so that's about a third of its capacity drained down.

I may let this one run for some time (MME OFF) to see if the unplugged MME every comes back on to check/charge the 12V LVB. Note, that I do not yet have the 12V LVB TSB update yet for this earlyish FE MME.

At least in these two full accessory test runs, the DC-DC converter comes on right away to charge the 12V LVB, but at least on the order of an hour to hour and a half, the DC-DC converter did not come on again (well, except for that odd spike around 4:30 for about 1 second.)

Why this new way - The DCCT could only measure -12A to +50A. This way -50A to +50A or more is doable.

Somewhat surprisingly, the red 12V battery warning on the driver's display is lit always in accessory mode, whether the DC-DC converter is on or not. So, as far as I can tell, it is just a warning that the car is in accessory mode, and not an indication of 12V LVB voltage or SOC (too bad).

Last note/update - The preamp has an intermittent (it's old), or the connections were not good, and there were a couple of false periods of high current. With the longer term test canceled (for preamp maintenance), I plugged in MME. Confirmed with the Fluke DC clamp on meter, when plugged in L2, I see 12V LVB charge currents as high as 90A, ramping down through 65A, 39A as I close this note, over about 15 minutes. So, the LVB charge current can be relatively high.
 
Last edited:

Illinibird

Well-Known Member
First Name
Mike
Joined
Oct 13, 2020
Threads
40
Messages
1,563
Reaction score
1,445
Location
Frankfort Illinois
Vehicles
2015 Acura MDX Adv; 2016 Titanium Fusion Hybrid
Occupation
retired Endodontist (root canal specialist) and Clinical Assistant Professor
Country flag
Somewhat surprisingly, the red 12V battery warning on the driver's display is lit always in accessory mode, whether the DC-DC converter is on or not. So, as far as I can tell, it is just a warning that the car is in accessory mode, and not an indication of 12V LVB voltage or SOC (too bad).
I've read through this entire thread and it's out of my pay grade trying to understand everything but you're doing a great job. My question to you is more mundane in that the red 12V battery warning light comes on in accessory mode and stays lit as you have said but sometimes there is also an orange plug that goes to the red battery warning light. Does that mean that the LV battery is being charged at that particular time?
Sponsored

 
 




Top