Outlined here
https://lockdownsecurity.forumbee.com/t/m2gvh9/ford-trucks-bms-battery-monitoring-systems
Note on adding accessories directly connected to the negative battery post
https://www.noln.net/articles/2122-battery-management-the-challenges-of-a-smart-system (https://www.noln.net/articles/2122-battery-management-the-challenges-of-a-smart-system)
QuoteTo preserve the battery, the system monitors the condition of the battery and may disable certain electrical systems when an excessive electrical drain is detected. Systems that could be disabled may include heated and cooled seats, heated steering wheel, rear defrost, AC/heater fan, audio system or navigation. If the system disables these accessories, a message usually appears to reflect that this action has been taken to protect the battery. It does not indicate a problem with the mentioned accessories or recommend a battery replacement.
Accessory devices added to the vehicle should not be attached to the negative post of the battery, as it can cause an inaccurate measurement of the state of charge of the battery. Also, when charging the battery, attach the negative cable of the charger to a good engine ground instead of the negative post of the battery. This allows the BMS sensor to accurately measure the battery state of charge.
I wholeheartedly agree to not mess with the Negative side on the Battery!
I have the Meth Alky kit connected to the (Positive side) of the Battery terminal and used the inside fender for Ground refererence source as pictured below. Z :)