12V Parasitic Drain - could it really be this easy? Service managers say "Lock your truck"

[colinl]

Unless I am missing something with the hybrids it shouldn't be possible to discharge a 12v battery to the point you can't start the truck. They like the Ecoboosts have an BMS (Battery Management System/Sensor) that will cut off all electrical inputs into the batttery when the battery voltage drops to a certain level. Unless you wire around it or there is some defect in the BMS itself a parasitic drain or any outlet in use with the key off can not take down the battery. If the 12V battery is losing charge to the point you can't start the truck it is most likely the battery itself.

it's unfortunately very possible. one way is to not drive it a long time, same as a gas-only / non-hybrid vehicle.

the other 2 ways are issues with the charging system. there was a cable issue TSB last year and by this point, all trucks should be fixed if they were affected. and then there's a second TSB just issued last month (or maybe April) where the 300A fuse which controls the connection between the high voltage battery and the 12V battery can look fine on visual inspection but actually test open (failed). when it's open the HV system can't charge the 12V battery.

if anyone gets deep sleep, either ecoboost or hybrid maverick, the first thing to do is the battery monitoring system reset. it's in the manual and several youtube videos exist. it takes 30 seconds or less and for my truck, it fixed deep sleep.

Sponsored

 

[jsus]

Unless I am missing something with the hybrids it shouldn't be possible to discharge a 12v battery to the point you can't start the truck. They like the Ecoboosts have an BMS (Battery Management System/Sensor) that will cut off all electrical inputs into the batttery when the battery voltage drops to a certain level. Unless you wire around it or there is some defect in the BMS itself a parasitic drain or any outlet in use with the key off can not take down the battery. If the 12V battery is losing charge to the point you can't start the truck it is most likely the battery itself.

And yet the BMS is not exactly infallible. I've had two different Fords equipped with BMS, built a decade apart, have their 12V batteries discharge below the point where they could start the vehicle, within 6 months or so of purchase, as the original buyer. Oddly, the one from a decade ago lasted 7 or so years and only really died because the dash cam was draining via the 12V outlet when the vehicle was off.

Doesn't help these hybrids that the batteries Ford uses are tiny, or that the vehicle constantly wakes up to drain more power. Opened a door to grab something? Now everything is powered up, draining the battery that the BMS was struggling to keep alive.

 

[27DTunes]

it's unfortunately very possible. one way is to not drive it a long time, same as a gas-only / non-hybrid vehicle.

the other 2 ways are issues with the charging system. there was a cable issue TSB last year and by this point, all trucks should be fixed if they were affected. and then there's a second TSB just issued last month (or maybe April) where the 300A fuse which controls the connection between the high voltage battery and the 12V battery can look fine on visual inspection but actually test open (failed). when it's open the HV system can't charge the 12V battery.

if anyone gets deep sleep, either ecoboost or hybrid maverick, the first thing to do is the battery monitoring system reset. it's in the manual and several youtube videos exist. it takes 30 seconds or less and for my truck, it fixed deep sleep.

Thank you for sharing this information as I haven’t fully navigated the forum or the manual just yet. Life is crazy! I will be sure to do the battery monitoring system reset once my vehicle has had its repairs completed so I will know what steps I may or may not have to take next. Hopefully that will do the trick!

 

[jewc75]

Hybrid or EB?

EB

 

[Maverick2022XL]

And yet the BMS is not exactly infallible. I've had two different Fords equipped with BMS, built a decade apart, have their 12V batteries discharge below the point where they could start the vehicle, within 6 months or so of purchase, as the original buyer. Oddly, the one from a decade ago lasted 7 or so years and only really died because the dash cam was draining via the 12V outlet when the vehicle was off.

Doesn't help these hybrids that the batteries Ford uses are tiny, or that the vehicle constantly wakes up to drain more power. Opened a door to grab something? Now everything is powered up, draining the battery that the BMS was struggling to keep alive.

A faulty BMS certainly could be an issue. So can any part of the system if it is not working as designed. They do short if moisture, dirt or battery acid gets inside of them when the shell is not sealed correctly or it cracks from time and wear. You also can have corrosion problems. I don't have the service manual in front of me but there is a way to test the sensor when a visual inspection doesn't show anything obvious.

I do have to correct myself on something, It is actually the BCM module not the BMS that makes the voltage adjustments and shuts off electrical outllets and such based upon the BMS readings. The BMS primarily measures current to and from the battery. Depending the BMS it may also measure battery voltage, state of charge and aging, battery temp.

 

[GPSMan]

This is such B.S.

Deep sleep should only occur if you park it and don't drive it for several weeks. Or you have a defective or poorly made battery from the start.

Guess hundreds (thousands?) have bad batteries from the start.

 

[Red Ryder]

29.5 mile commute each way, 22,000 miles the first year. Always locked.

So, no sitting, not driven or unlocked. Yet I often go out in the morning to no interior lights (deep sleep) and periodic no-power, requires jump start.

I still think I have a harness issue, but two Ford service departments said "they checked that".

 

[MakinDoForNow]

12 volt socket stays on for 90 minutes after turning off. At least my hybrid does.

By memory of other posts. The front 12v cig style socket stays on if something is plugged in and pulling current. It will stay on for a time specified in BCM (90 minutes is default unless it has been changed) OR until the 12v soc drops to (I believe someone said) 12.1 volts. I think the overhead light ceases to turn on below 11.8v. I think some things act differently maybe XL XLT than XLT LUX LARIAT. Someone posted they had 12v soc of 6 or 7 volts.

Sponsored