Hi,
Just to add that the battery problem exists here in the US as well in a warm & sunny climate. I have an RX400h (2008) and my brother has the (mechanically identical) Toyota Highlander. Unattended battery life is 3 weeks maxiumum - leave the key in the ignition and its one hour, leave a door cracked open and overnight a dead battery. Part of the problem is that many electrical components are "live" and actually functioning when the vehicle is switched off ) only a battery disconnect solves it and then you have to reprogra, everything: It's a royal pain.
However looks like you guys may have come up with a couple of partial solutions (70ah deep cycle and/or portable jump start)which is an option when I ,ove to France
Cheers
David