I gave up on alternators twice. I can't keep the belt on at 10k. I now run a single D1600 no alternator, drive up to the lanes and back to the pits, and I can go 2-3 runs with no issues. Probably more but I haven't tried it. I tend to charge it every run just to maximize the life of the battery. The bulk of the charging is done in 10-15 minutes. A big part of this is the mechanical fuel pump. The only significant draw on the battery is the starter and the radiator fan. With a big electric fuel pump that draws a ton of power, two batteries would be the way to go, and should still last longer than my one battery does. Charge time will be longer. I did run a single battery even with an electric fuel pump several years ago, and it worked, but it took a lot longer to recharge and I don' think it would make it for more than 1 run on a charge.
I actually ran a single 12v battery with no alternator all of last year and that worked ok. I used a boost a pump to boost the voltage to my ECU, engine harness, and MSD box to 13.5v. Not the most stable setup but it worked.

I like the 16v battery better for obvious reasons.