There will be two occasions in the near future that I might need to disconnect the battery. First one is to work with the connectors of the Haldex controller and the other is when/If I will leave the car parked for 4-6 weeks. For the first case disconnecting is not 100% necessary but rather for eliminating any possibility of fault codes showing up. For the long-term parking I was thinking of it as a way to preserve the battery life as I am 2yrs into ownership already.

My question really with this heavily loaded with electrics car is can I just go ahead and disconnect it as usual? or I will have to deal with resetting systems, fault codes and other gremlins upon re-connection? 

I disconnected mine when trying to install the power feed for my subwoofer as I’d read there was an access grommet behind the battery.

turns out yes it’s there but nigh on impossible to get a cable through and fish it down behind the glove box (so I went through the unused clutch grommet with heat protective sleeving).

after reconnecting the dash lit up like a Christmas tree with a ton of errors.

I only had Carista at the time (now have full VCDS) and it took several attempts to clear some of the faults as they would reappear straight away.

the front assist being unavailable was the scariest but thankfully it all sorted itself out after turning the steering full lock side to side and a short drive.

still gave me serious worry for a while so I won’t be doing this again unless I have to.... 

@newbie69 If you have a look to may tutorial for Haldex oil replacement, you'll see that I disconnected the Haldex Control Unit indeed. Nut I did not disconnect the battery for that. I had no error message. Thus... I would say it's useless.

 

I would do the same for the 4-6 week parking (not battery disconnect). Just be careful to "prime" the fuel system with switching contact ON, wait 10s, switch OFF, wait 15s and repeat agina 2-3 times before really starting the engine... It should help the engine idling quickly and will prevent you from "cristmas tree" and DTC... 

My opinion... May be not the best... 

Thanks for sharing (both).

I went ahead and disconnected the Haldex without disconnecting the battery but only after the ingition had been off for a good 15min already. I based that on the JB4 installation instructions which stated  either disconnect the battery OR leave the ignition OFF for 10-15min before disconnceting sensors to allow all car's systems to be fully switched off.

No errors after re-connecting everything so all good.