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Why will State of Charge not reach 100% ... So Annoying!

Started by SHOdded, December 20, 2019, 08:03:12 AM

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SHOdded

This is a question I have seen cropping up from time to time.

And the best answer I have seen yet is here on the F150 forum
https://www.f150forum.com/f38/battery-management-system-reset-109656/

Basically, if you use a charger to get the battery up to 100% state of charge (SoC), you MUST connect the negative charge lead to a ground post rather than directly to the negative battery terminal.

Full post is quoted below:
QuoteYou are on the right track. As you can see, this is a new function and not many people are aware of the battery management system. I just reviewed the workshop manaul and there is no procedure listed for the BMS reset using the scan tool. However, in our testing we perform the following:

Perfroming a BMS reset will reset the battery SOC to a default of 85%- regardless of its true state of charge and reset the SOC drain timers. This should get you out of load shed. The following is the procedure using the Diagnostic Engineering tool.

BMS reset procedure with Ford "Diagnostic Engineering Tool":
Go to Gen Diagnostics and select Module ID to 726 (BCM)
Select Service 0X10 and extendedDiagnosticSession, and press "Send Message" button
Select Service 0X31
Check "User Defined" box, and type in "201A"
Press "Send Message" button

For all future reference, do not connect the negative charge lead to the negative battery post. Connect it to another ground attachment point on the truck. That way, the re-charge will be measured by the BMS hall sensor (very near the negative battery post) and will correctly re-adjust the battery SOC.

If the dealer plays dumb, here is the section in the workshop manual:

When charging the vehicle battery by connecting the charger to the negative battery terminal is necessary, such as when using a combination battery charger and battery tester/analyzer, like the GR 1 190 V3.0 Intelligent Diagnostic Charger, the BCM will not immediately update the battery state of charge. In this instance, after charging, you must carry out the Battery Monitoring System (BMS) Reset using the scan tool. This reset is needed for proper engine off load shedding and to prevent invoking of engine off load shedding earlier than normal.

NOTE: If the reset is not carried out, when the battery is charged by connecting the charger to the negative battery terminal, it takes approximately 8 hours for the BCM to learn the new battery state of charge. During this 8 hour period, the vehicle must be undisturbed, with no doors opened or keyless entry button presses. If the vehicle is used before the BCM is allowed to learn the new battery state of charge, engine off load shedding can still occur and a message may be displayed.

When charging the vehicle battery by connecting the charger to engine or chassis ground, the negative charger clamp must be connected to an unpainted chassis surface or a solid engine component such as a generator mount or engine lifting eye. In this instance, after charging, the BMS Reset is not required. Through this method of charging the BCM will update the battery state of charge during the charging process.
2007 Ford Edge SEL, Powerstop F/R Brake Kit, TXT LED 6000K Lo & Hi Beams, W16W LED Reverse Bulbs, 3BSpec 2.5w Map Lights, 5W Cree rear dome lights, 5W Cree cargo light, DTBL LED Taillights

If tuned:  Take note of the strategy code as you return to stock (including 3 bar MAP to 2 bar MAP) -> take car in & get it serviced -> check strategy code when you get car back -> have tuner update your tune if the strategy code has changed -> reload tune -> ENJOY!