Confusion: 12v Battery Connections Under the Hybrid Hood

[mhw21zap]

Exactly what happened to my truck. Came back from a short trip - less than 4 days - and my Maverick was going into deep sleep instantly after ignition off. (Related: wife's Bronco didn't do this. Both are '22 and I assume have similar Battery Monitoring Systems.) I checked the voltage numerous times over 3 days and was annoyed and frustrated, but then I reset the BMS which takes 10-15 seconds, and it's been fine for 3 weeks.

12.5V off is very strong. Somewhere around 12.0 - 11.8 is acceptable as a low range for a normal 12V battery when off.

Actually, both of those values seem a tad high. Maybe .2 to .3V higher than I'd expect. What did you use to measure?

Hey thank you for the insight. I'm just trying to gather as much data as possible on this. I used a voltage meter that I got recommended by a friend, it's in the truck at the moment, so I can't recall the name.

I have tried a few times now since this afternoon to reset the BMS. My understanding is

- turn the key ignition to on, and turn the little Maverick headlight knob on the left hand side clockwise down to the bottom "HI beam" setting five times (and then bring it back to standard auto)

- pump the brake three times immediately afterwards and wait about 10 to 15 seconds

I tried this multiple times and I didn't get any flashing lights or blinking battery icons. I'm going to try again in the morning.

Any tips or advice?

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[Darnon]

- turn the key ignition to on, and turn the little Maverick headlight knob on the left hand side clockwise down to the bottom "HI beam" setting five times (and then bring it back to standard auto)

You don't use the light switch (that's for your low beams), you use the stalk on the steering column.

 

[SLINGSHOT]

I would try a little dried bat blood and eye of newt also.
Talk about factory obfuscation. (Dictionary Definitions from Oxford Languages: obfuscation
the action of making something obscure, unclear, or unintelligible.)

 

[Dad]

I am trying to accurately answer this question as well. I've not yet seen a conclusive answer, have you sorted it out by chance? 2 dead batteries in the 1st month of ownership :/ I'm trying anything I can

Great post. I'm awaiting a definitive answer as well.

 

[Dad]

You don't use the light switch (that's for your low beams), you use the stalk on the steering column.

Exactly how it is supposed to be done.

 

[mhw21zap]

You don't use the light switch (that's for your low beams), you use the stalk on the steering column.

Okay thanks, I tried it with the knob to the left of the steering wheel to no success last night. I'll go give this a shot

 

[MakinDoForNow]

I will give that a shot after work. What might that help though given that I've got some form of parasitic drain? I just did a voltage meter reading and showed 12.53V off / 14.62V on. Could it be that the 2 most recent deep sleep notifications were caused / triggered by the Battery Monitor not functioning properly?

On voltage meter readings using dash cig lighter style power point
Key off and power point active reading will be 12v battery reading.
Key on in Accessory position power point IS ACTIVE and reading will be 12v battery reading
Key on in READY TO RUN position the dcdc convertor will be active and voltage will be set from 12.1v up to 15.2v (maybe more) depending to what items are being operated. The computer (BMS?) will increase voltage output (on the 12v bus) from the dcdc converter in order to provide the available amperage necessary to run the up to 60 amp fuzes (I believe the max sustained output of dcdc converter is 265 amps, verify...).
As far as BMS not working properly since it is highly dependent on readings on the negative battery post it is very sensitive to proper battery post connections and also to even a weak cell in the battery. If your battery was replaced the connections are most likely adequate as well as the cells within the battery. However if the BMS has NOT been reset it may be charging your new battery based on data saved from prior battery condition.

 

[MakinDoForNow]

On my hybrid maverick upon immediately turning truck off the 12v battery will be as high as 13.1 v this is with battery still hot due to charging which bms will know the approved limit. That's why to get proper sos reading of battery you have to wait maybe two hours for battery to settle. Also why battery is NOT in engine compartment and have to wait additional time before it can cool down. YOUR 12.53 volts if at settled state is pretty much fully charged.

 

[mhw21zap]

On my hybrid maverick upon immediately turning truck off the 12v battery will be as high as 13.1 v this is with battery still hot due to charging which bms will know the approved limit. That's why to get proper sos reading of battery you have to wait maybe two hours for battery to settle. Also why battery is NOT in engine compartment and have to wait additional time before it can cool down. YOUR 12.53 volts if at settled state is pretty much fully charged.

Update: April 24

I reset the BMS on Saturday. I bought a Faraday bag to keep my key inside JUST to make sure no signals in the middle of the night could be being sent. I turned off all system connections on my Maverick dash (location, fordpass, etc) and again made sure to turn off AC and music and dash screen before parking my truck yesterday at 4:00pm Sunday.

Monday morning at 6:30 am I went to test my voltage and I measured 11.49. The truck DID start, but neither screen/cabin lights came on. I'm going to call my dealer and re-schedule an appointment and see what we need to do next after just installing a brand new 12V battery 4 days ago.

WTF should I do next...

Here are a few ideas I've gleaned from the forums. Although, many are 6-12 months old and seeing as I have a 2023, I wonder if it could also be affecting the newer models too?

a. Connector C1457B not connected properly to the DCDC module / scan tool
b. Faulty solder on the wiring harness (needs to be crimped?)
c. Fuse box issue
d. parasitic draw from a kinked LVDS cable wire *(low voltage differentiation system)
e. Ideas??

I have another dealership appointment tomorrow. I plan on telling them to keep the truck as long as necessary to ensure something is done. Thankfully I still have my terrible POS old Ford Focus to put around in / a motorcycle for the time being...

 

[colinl]

Update: April 24

I reset the BMS on Saturday. I bought a Faraday bag to keep my key inside JUST to make sure no signals in the middle of the night could be being sent. I turned off all system connections on my Maverick dash (location, fordpass, etc) and again made sure to turn off AC and music and dash screen before parking my truck yesterday at 4:00pm Sunday.

Monday morning at 6:30 am I went to test my voltage and I measured 11.49. The truck DID start, but neither screen/cabin lights came on. I'm going to call my dealer and re-schedule an appointment and see what we need to do next after just installing a brand new 12V battery 4 days ago.

WTF should I do next. T

so, to be clear, did you have any Deep Sleep messages in Fordpass after resetting your battery monitoring system?

 

[mhw21zap]

so, to be clear, did you have any Deep Sleep messages in Fordpass after resetting your battery monitoring system?

Good morning,

Technically, no I didn't receive any additional Deep Sleeps since updating the BMS.

I got the new 12V battery on Thursday, got 2 deep sleeps on Friday, did the BMS reset on Saturday afternoon, drove it around on Sunday and parked it around 4:00pm.

I woke up this morning to no screen / lights and did the test - measured 11.49V. The truck did start up and I drove it to work. Planning on testing in a few more hours to see where I'm at.

 

[MakinDoForNow]

Update: April 24

I reset the BMS on Saturday. I bought a Faraday bag to keep my key inside JUST to make sure no signals in the middle of the night could be being sent. I turned off all system connections on my Maverick dash (location, fordpass, etc) and again made sure to turn off AC and music and dash screen before parking my truck yesterday at 4:00pm Sunday.

Monday morning at 6:30 am I went to test my voltage and I measured 11.49. The truck DID start, but neither screen/cabin lights came on. I'm going to call my dealer and re-schedule an appointment and see what we need to do next after just installing a brand new 12V battery 4 days ago.

WTF should I do next. T

Looks like you are locked in to a dealer must find the drain on battery warranty situation. Try to get them to furnish a ride and don't pressure them to get it back ASAP. They may need it several weeks if they need assistance from Ford tech. A thought are you putting drive selector in park and not setting the electric brake placing in park should turn off elec brake but something is using battery and maybe something like electric brake is staying on. Good luck.

 

[Dad]

Update: April 24

I reset the BMS on Saturday. I bought a Faraday bag to keep my key inside JUST to make sure no signals in the middle of the night could be being sent. I turned off all system connections on my Maverick dash (location, fordpass, etc) and again made sure to turn off AC and music and dash screen before parking my truck yesterday at 4:00pm Sunday.

Monday morning at 6:30 am I went to test my voltage and I measured 11.49. The truck DID start, but neither screen/cabin lights came on. I'm going to call my dealer and re-schedule an appointment and see what we need to do next after just installing a brand new 12V battery 4 days ago.

WTF should I do next. T

Have you tried wearing a Howard the Duck costume?

 

[mhw21zap]

Looks like you are locked in to a dealer must find the drain on battery warranty situation. Try to get them to furnish a ride and don't pressure them to get it back ASAP. They may need it several weeks if they need assistance from Ford tech. A thought are you putting drive selector in park and not setting the electric brake placing in park should turn off elec brake but something is using battery and maybe something like electric brake is staying on. Good luck.

I completely agree...

Here are a few ideas I've gleaned from the forums. Although, many are 6-12 months old and seeing as I have a 2023, I wonder if it could also be affecting the newer models too?

a. Connector C1457B not connected properly to the DCDC module / scan tool
b. Faulty solder on the wiring harness (needs to be crimped on / replaced)
c. Fuse box issue
d. parasitic draw from a kinked LVDS cable wire *(low voltage differentiation system)
e. Ideas?

I am going to bite the bullet and leave it with them as long as possible to hopefully allow them time. I wonder how it works with getting a Ford technician out? I've never had a new car before, so the whole corporate meets dealership world is new to me lol

 

[JimParker256]

Original question about where to mount an onboard battery tender I'm also interested in an answer to that. Do you connect directly to the battery under the rear seat and run your extension cord out the rear window to an electrical outlet or do you find a space in the engine compartment and connect to the red (+) post as listed above and to the neg (-) body bolt as indicated for jumper cables?

I'm pretty sure that Ford says to NOT connect ANYTHING directly to the battery, because there is a BMS (battery management system) slightly upstream from the battery which measures the "inputs" and "outputs" from the battery, and controls the charging of the 12V battery from the High Voltage Battery (via the DC-to-DC converter). If you have either a load or a charge "inside the fence" where the BMS doesn't see it, then the BMS cannot compensate for that, leading to either under- or (perhaps worse) over-charging of the 12V battery. Use the jump posts under the hood to connect your charger. That's where Ford intended you to provide external charging (or jump-start boosting).

And yeah, I realize that the starter actually runs off the HVB, and a 12V battery maintainer will not impact the HVG at all, but if there's no 12V battery charge, the computers (which tell the system HOW to use the HVB to start the car) won't operate... So it's still reasonably accurate to call it a "jump-start".

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