question

You'll have to use an 'allow to charge' connection from the BMS to engage the alternator.

I'm not familiar with the BYD batteries, but usually the BMS sends the battery current to the Venus device, so the Venus can calculate how much the other components can put in / pull out of the batteries (use 'has DC system' setting)

What you are looking at doing is adding the alternator to a complete working system (with CCGX or Venus) or have the system with no CAN communication at all?

The reason why the warranty requires you to run with a Venus or CCGX is because the ´allow to charge´ and ´allow to discharge´ relays will only avert overchage or overdischage risks. However, the Venus and CCGX are capable of understanding all other alarms plus adjust the system currents based on the exact status of each battery cell.

hi, this will be part of an inverter system with a Mulitplus / CCGX and batteries. One of the sources of charge will be from the Alternator.

I would sugest turning the alternators Field off and on and not using a BP at all otherwise you may blow the alternators diodes up in you open circuit the alternator.

If the alternator is not dedicated to the byd but also has the start battery I cannot see this happening as it would not go open circuit? Unless I am misunderstanding?

The alternator is used for purely supplementing the charge.

Matt