I bought a solar charger - similar price. It's difficult to know whether this helped or not. I left the car for abour 4-5 weeks and it was ok. Then I left it for 6 weeks and, even with the solar charger, the battery went flat. That's why I am trying the battery disconnection alternative.

In any event, I tried something else to get around the alarm beeping.

I opened the car with the key buttons - so that, I guess, the alarm was disabled. Then I locked all doors except for the driver's by pressing down the buttons on the inside of the doors. Next I disconnected the battery - negative terminal only. Then I locked the trunk with the key and finally I locked the driver's door using the key. The alarm didn't beep.

So my only remaining concern is whether, by leaving the +ve terminal still connected, I may still experience