Does anyone know what the battery charge level is when the BMS sends the System shut down message?

 

You need to know not what the charge level is, but what the State of Charge voltage is with the engine off, before cranking.
This level determines the running charge voltage after starting.
The charging voltage also is determined by the battery age and temperature and SOC before cranking, at that time.
The relationship is a bit more complex and is why BMS control is used to determine the conditions of battery level and charge level needed to restore it.
Putting the Dash Screen into Engineering Mode before cranking will tell you his information before and after starting when stepped to the battery data reading.
Knowing this takes all the guessing out of the situation.
For example, at very cold temperatures, the BMS will not allow full charging voltage of an AGM until the Battery has warmed up. Not knowing this can lead to misinterpretation of the charging level as too low, at that time due to temperature.
These specs are listed in Ford Doc General Bulletin on Battery Maintenance.

Good luck.

 

With the engine off, the System Off to Save battery message is displayed when the state of charge is less than 50%. Note this same message may occur based on a timer alone, such as 45 minutes have elapsed without engine running.

 

Bluegrass, I have a 2019 F150 XLT. Once I have "engineering mode" on the screen which button do I press to step to the battery data? The ok button or one of the arrow buttons? Thanks.

 

Once in engineering mode, you use the up and down arrow buttons to change the different displayed data.

However, you asked what battery level generates the system shut down message. That is when the BCM detects battery state of charge is below 50% with the key on, engine off, or 45 minutes have elapsed.

None of this really helps understand what the issue is. If the truck sits for long periods of time, eventually, even a battery that was fully charged will be drained due to some current flow to keep the modules available while the truck is off. Lack of use, battery aging, charging system concerns, and abnormal battery drains all have a role in this.

 

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Either the up or down. All they do is change the stepping direction.
Expect to step about 40 positions +/-.
A good SOC range would be 12.2 to12.6 volts.
Cranking should not fall below about 10.
Running voltage, at about 15 seconds after starting would show about 14.2 to 14.6 depending on battery condition, drain and temperature after cranking.
The variable values are all dependent on battery age, state of charge and temperature so the evaluation has the be judged on that basis and load testing. With any excess drain taken into consideration while at rest, over time.
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As a note; trickle charging can take the SOC to the max is also sensed by the BMS.
It may take several drive cycles for the BMS to reflect full system parameters because it does not normally run at the levels the Trickle Charging has forced the battery to.
For example, 6 cells at 2.17 volts per cell = 13.02 volts. Any level seen above this is called a space charge and needs to be drained off to the actual working voltage. Usually, the head lights On for a couple minutes will take care of space charge.

Good luck.

 

Adding to what Bluegrass said there is about 60 pages in all and I recall having to page down 42 times to get battery voltage. Paging up instead, it's about 1/3rd less. 5 clicks up from battery voltage gives you trans temperature. Once you start the engine you'll see the voltage rise to whatever the BMS decides to apply. Note your voltages for report. Also, engineering mode stays on the display fulltime until you key off. You can drive around and observe the charging.

I always suggest investing in a good smart charger like a NOCO or CTEK to top off your battery's SOC, something I do periodically then let the system sleep for 8 hours to recalibrate the SOC for the BMS. It can keep an aged battery at peak health, extending its life before needing to be replaced. Mine is close to 4 years old now and continues to start my truck with no perception of weakness or massages. It is a preventative maintenance measure like topping off fluids.

Checking your SOC while the truck is in SLEEP MODE is something I will do as well by unlatching the hood and waiting 0ne hour before taking a measurement at the battery. It takes about an hour to enter sleep mode. You can't just open the door to unlatch the hood and take a reading right away because much of the system will come alive so you must waite first. I like to see at least 12.65 volts. Last check I made after a week from using my CTEK was 12.72 volts.

 

Thanks guys, I really appreciate the information.