It seems that AS/NZS standards require all live (unearthed) conductors to be protected in overload/overcurrent devices. Why exactly does Victron not support anything other than a direct negative connection to Multiplus II in parallel?
asked
Exactly why is switching in the Multiplus II negative not allowed in parallel configurations?
I am not sure about now with newer tech but it was for galvanic reasons before.
Negative is common in mosts circuits
The VE.Bus connection between parallel units also makes a connection between the battery negatives of the units. Breaking one negative lead would force negative DC current to flow through the CAT 5 cable and there would be damage.
Victron cautions that all DC negative connections must be made prior to interconnecting the VE.Bus connections.
Thanks Kevin. When you say "there would be damage" do you mean the VE.Bus line drivers would be damaged? Or something worse? If it is just the RS-485 line drivers at risk is there anything I can do to protect them? Maybe series current-limiting resistors?(Could be a problem with RS-485.) Some sort of RS-485 line protection device? Or is it impossible to solve this problem with external equipment?
I really need to solve this because I must comply with local NZ regulations and I absolutely need a parallel configuration.
You would burn up the CAT 5 cable and possibly traces on the circuit board. And, you could blow up the drivers when 12-48 volt battery voltage is applied to a driver expecting 5 volts max.
No there's nothing you can do to prevent this damage. There are capacitors at the input of the DC inputs that would remain charged and carry enough energy to damage the interconnect cables and small circuit board traces even of the units are powered off first.
JUST DON'T DO IT !!!!!
