HDC system fault

Would appreciate if anyone can help me on this one.My 2006 RR Sport is throwing up an error only on startup first thing in the morning.Its coming up on the screen that there is an HDC system fault and special programmes cannot be used.This does not appear at any other time.It was in at my dealer for this and they said it was battery voltage drainage and recharged and checked the battery.It was ok for a while but has started to appear again.I have lost faith in them as my car hasd been damaged on both occasions i have used them and if its an easy fix i would rather do it myself.

Maybe a duff battery or the alternator not charging properly. Check the voltage at the battery terminals with a DVM, should be arround 12.5 volts, start the engine and check again should read 14 volts or more.

You may just have a dodgy cell in the battery which is causing the voltage to drop when starting, these cars are very sensitive to battery voltage.

Could also be corroded connections at the battery terminals.