Diesel Batteries
Correct! It takes a lot more heat to get diesel fuel to ignite than it does for gasoline. Remember that diesel engines work on compression and they don't have spark plugs to ignite the fuel/air mixture in the combustion chamber.
Diesel engines also (typically) use heavier motor oil - 15w40 in the case of Ford and International - which is very, very thick on cold mornings. Heck, it gets to resemble Aunt Jemima syrup!
With smaller diesel engines, the batteries have to warm up the glow plugs first. After that expenditure of cold cranking amps, there still must be enough juice left to turn over the crankshaft to get the whole mess moving.
When I last owned a diesel truck, it had dual 925-amp batteries. A lot of over-the-road semis will have three or even four batteries! It will take some serious energy to turn over an 11- to 14-liter truck engine, you know.