Hi I’m looking at fitting towing electrics to a 2019 v60 D3 momentum pro and am just after advice on disconnecting the batteries

 

I do not know what towing electrics is , is it the plug for a tow bar , if so just disconnect the battery do the wiring and reconnect all the codes will be fine for al least a few days on a new car like yours , you may have to reset the steering by turning lock to lock if yours has electric steering
Just realized from your post how many Batteries do you have? is yours a Hybrid?

 

Yes it’s the plug for towing lights and no cars not a hybrid but it has two batteries the main starter battery in the trunk and it has a small battery for the stop start system under the hood

 

Ok did not realize that stop start needed 2 batteries , on my Alfa it has only one but must say its a bit problematic as a result so 2 is probably a good idea,
Anyway I am not sure if you need to disconnect both as the smaller one may be used for other functions besides stop start as stop start requires a lot of power so probably uses both