If you're holding the brakes hard, as long as the engine is warm it won't run the engine as long as the battery is in its preferred range (even the low end). I've not run the battery below the preferred range since getting the miniscanner, so I can't say for certain how long it takes. But if the engine is running at idle and the battery is being charged, it usually rises 1/2 % SOC about every 5 seconds. So one might rashly extrapolate that it would take 100 seconds to recharge from 20% (barely willing to try starting the engine) to 40% (bottom of the preferred range). Of course the 2004 could be completely different also.
The engine will run just long enough to get the charge-level back to the into the preferred zone (the blue bars).
In other words, only a minute or two.
Last year, while trapped in absolutely awful winter congestion, my charge-level dropped into pink (2 bars). Even with the camera right next to me, I barely had enough time to snap 2 photos before it was already back into the blue and the engine shut off. And that's in the winter.
In the summer without the A/C running, the engine might not startup at all. The system will just wait until the next time the wheels move before doing any recharging.
On my '04, I had it parked for about half an hour with no A/C or heat, just fan and radio going. It *DID* discharge into the pink/purple zone, and the engine only ran for about two minutes (long enough to get to the blue zone.) I then started driving again before it dropped into the pink/purple again.
A few days ago, I started the car and it was at only three bars, and turned on the A/C. Because of various delays, it ended up being a few minutes before we got to driving, and with the A/C going, it dropped the battery to two bars before we started driving. Again, the ICE only came on for somewhere around two minutes. (Again, I started driving before the battery dropped down to two bars again.)