Okay one quick question/concern I have relates to the post that I have copied and pasted below.
I specialize on Ford Thinks only, and there’s a major safety concern I have to address immediately. The 12 Volt nominal system is actually 13.0 Volts, and the negative lead from the DC-DC Sevcon converter is tied to the frame of the vehicle, hence it’s also a negative ground automobile.
The 72 Volt nominal battery pack is NOT connected to any ground, and particularly NOT the vehicle frame. The battery pack should be referenced as +72 (Positive), and 72 Volt (Negative, or RETURN), but not as ground. If you have ever notices the ‘Lightning Bolt’ icon on the cluster, that signifies an unsafe condition exists where the battery pack is sensing potentially dangerous condition where there’s a problem with the ‘isolation’.
You do not need a working DC/DC Converter for the car to charge and operate, although no ‘12 Volt’ accessories will work (lights, horn, wipers, brake lights, etc) and the Brake Icon will remain illuminated all the time. You MUST use an isolated DC-DC Converter for safety, and this will always be a 4 or more wiring connector (+72V in, 72V return, +12V out, 12 Return). You can buy cheap imported DC/DC Converters for $35, but don’t do it. It can kill you!
This is the link to the DC/DC converter that we are looking at from amazon. Think it is safe? The wiring diagram on the amazon ad shows the 12v negative return going to the battery but the post above say the 12v return is grounded to the frame. Also is a 5-wire setup and not 4.