S90 batteries
 

Sorry, cannot find earlier relevant thread on S90 batteries.
Because of frequent recurrent Start/Stop error messages I bought a AGM charger for the front "support" battery. It does the trick but LockDown means long intervals of zero car use and in no time the support battery (which I guess is constantly working away at guard duty and similar) needs another energy dose!
The main battery is apparently located in the cargo area? Can't for the life of me quite see where. And what is the correct methodology for charging it? (Should the need arise, I mean.)
Thank you!

Always use the charger connection points in the engine bay to charge, don't try to connect directly to the batteries themselves. The Volvo mobile phone app shows you where to connect the charger leads.

Using the correct charging points charges both batteries; the support battery in the engine bay and the main battery in the boot (left hand side behind a panel in my XC90). Volvo recommends charging the batteries fortnightly if the car is standing for long periods, so I just use a smart charger.

Don't be tempted to connect the charger straight onto the battery terminals as it will confuse the battery monitoring system.

Hope this helps.

Totally helps.
I located the main battery in the rear compartment minutes after sending the above query.
But VERY glad to know using those points charges both batteries.
And that "fortnightly" is not ridiculous.
Thanks so much.