An interesting thread and one which caught my eye as I’ve had my battery drain a couple of times due to lack of use. Thing is though, after recharging the battery and reconnecting, I’ve never had any issue with the idle speed or had any indication that anything was resetting itself. The car has behaved perfectly normally. Maybe I’m just lucky (or have now jinxed myself)…
I read somewhere that it is a good idea to touch both battery terminals together after removing the battery.
This drains any residual power from the ECU and ensures that the old memory is completely removed.
When battery is reconnected run the car on idle for at least 10 minutes without touching anything.