Technical Battery imobiliser

[MGRobbie]

It is my intention to install a switch at the negative pole side to interrupt all amperage, so isolate the battery.
On the picture you see the smart controller of the (smart) dynamo. Dynamo manufactuers state that this switch should not be isolated however no reason is indicated.
Also it does not consume lots of power(Amps) it is my prefference to isolate it.
Can somebody explain me why or why not to isolate the switch and how this works??

 

[the green vanper]

Hello,

You want it for anti-theft purpose, or just to cut out the starting battery?

I assume you are aware that the nowadays cars are computers on wheels, with multiple electronic modules that might not like longer periods without power?

 

[the green vanper]

If you want to use it as an anti-theft device, I'll do it using a hidden switch on the ignition itself.

 

[Communicator]

Judging from the fact that it has only two small wires connecting to, the device is a simple shunt, used by the smart alternator controller to measure battery current. I cannot see any reason why the device should not be isolated when the vehicle is not being used. However do consult your handbook for procedure to be followed when disconnecting the battery, which will also apply to operating a battery isolator.

 

[the green vanper]

Judging from the fact that it has only two small wires connecting to, the device is a simple shunt, used by the smart alternator controller to measure battery current. I cannot see any reason why the device should not be isolated when the vehicle is not being used. However do consult your handbook for procedure to be followed when disconnecting the battery, which will also apply to operating a battery isolator.

The owners handbook for the newer models request a dealer visit to replace fuses...
So I doubt the OP's will find such an information there.

I also understood that the OP wants to isolate the whole negative pole of the battery.

 

[Reg 65]

As has already been stated computers don't like being disconnected before they have shut themselves down
And if you disconnect the battery from inside the cab how are you going to lock and unlock the doors?
If you are doing this as an anti theft measure would suggest a secret switch interrupting something else
like the antenna coil around the ignition switch that communicates with the chip in the key

 

[Communicator]

As has already been stated computers don't like being disconnected before they have shut themselves down
And if you disconnect the battery from inside the cab how are you going to lock and unlock the doors?
If you are doing this as an anti theft measure would suggest a secret switch interrupting something else
like the antenna coil around the ignition switch that communicates with the chip in the key

In view of the very low voltage output from the antenna, a switch with electronic style gold plated contacts should be used.

 

[RS3100]

Judging from the fact that it has only two small wires connecting to, the device is a simple shunt, used by the smart alternator controller to measure battery current. I cannot see any reason why the device should not be isolated when the vehicle is not being used. However do consult your handbook for procedure to be followed when disconnecting the battery, which will also apply to operating a battery isolator.

I assume that it is like the system on my Volvo. The shunt is fitted to vehicles with smart alternator and/or start/stop systems. The perceived state of the battery is transmitted constantly to the Battery Monitoring System which controls various functions on the car according to demand and battery state.

If the shunt is interrupted, or the battery charged by bypassing the shunt (charger earth lead directly connected to the battery earth terminal) the BMS detects an anomaly since the expected state of the battery and it's actual state appear to differ. This takes 6-8 hours of being parked with all doors locked to rectify, unless reset with diagnostic equipment. During that time, start/stop is unavailable (not a bad thing, and mine is permanently disabled anyway) and other functions on the car may operate in a different mode, such as air conditioning working in a low power mode.

The Ducato system may not of course be exactly the same, but I would anticipate that the system behaviour must be similar, or their would be no reason for the shunt.