Did you know that diesel engines do not need batteries to run? Diesel engines do not have spark plugs like gasoline engines. Gasoline engines have Spark Combustion while Diesel Engines have Compression Combustion to run. Gasoline engines compress the fuel and air mixture of around 10:1. So if that volume of 10 fuel/air mixture is compressed to 1, it will need the spark from the spark plug to have combustion. The diesel engine meanwhile, has a bigger compression ratio of around 24:1. So, when a volume of 24 pure air is compressed to 1, diesel is injected, combustion occurs! In place of spark plugs, diesel engines have diesel injection to do the job. It was my former mechanic who taught me about this first.
Note that gasoline engines compress the fuel/air mixture. Diesel compresses only the air first and when it is about to be compressed to 1, diesel fuel is injected. So, if your diesel-engined vehicle has a dead battery, you can still start the engine start the engine by pushing the car and crank starting it! Beware though, if your transmission is automatic, this might not allow crank starting!