Oh, and my own personal testimony here... This just happened last Sunday morning, when the temp was -15ish up here. I had to start my old Ford truck to get to work. I cranked SOLID for about 2 minutes on my 8 year old Duralast black top (now they have red tops). I never ran the battery down, I just quit cranking... It wouldn't start. I plugged my block heater in about 6 hours and it fired right up still substantially below zero temps.
2012 FJ Cruiser, 76 FJ40, 85 mini almost redone.
Misc Cruiser parts and mini parts available.