B7 TDi Dead battery after 10 days away!

[booba]

the car will still have an alternator wouldn't it?

I note that VW make a big deal of the battery being charged when braking.
"Energy recovery"
So how does this occur?
New V7 Golf now has this feature, and in addition, freewheels down hills!
Once again, how to ensure battery is charged to capacity?
For example, trip from Sydney to Melbourne. Cruse control on. Night time, raining. demisters on!
If dependent on brake input may not be able to cope!! ???
Bit of a worry, as about to give Golf to Son, and purchase 125TDI Passat

[Cossor]

the car will still have an alternator wouldn't it?

One would certinly hope so.

But how is energy recovered during the brake cycle?

If free wheeling down hill, then engine RPM minimum
Ditto during braking, assuming Bluemotion DSG disengages motor

So how does it work? I can only envisage standard alternator with very smart decision algorithim.
OR external alternator perhaps on the rear wheels, used in conjunction with engine alternator.

BTW, Driving Commodor in rain, stop start traffic, night, AND with rear demister on. Battery failed at que near lights.
Dead lucky, was NRMA vehicle one car behind me. Got jump start and limped home. Battery tested OK, Car in use every day.

[MJW]

My understanding is that the car monitors voltage & makes a determination if the energy re-generated from the braking is sufficient to maintain minimum safe voltage & if not then the alternator will kick in as per normal.

I believe the energy generated from braking is more than the alternator for the same period of time. Also note that the less the alternator works, the more usable power you have & saving on fuel.