If I use a battery charger for 1800cc on a 2000cc engine/battery will I die?

No.

No!

Your question doesn’t really make sense, sorry. Most chargers will be capable of charging many different battery capacities. Engine size doesn’t really come in to the equation.

Question might not make sense, but lots of battery chargers are sold based on engine size, doesn’t affect the answer though… It’ll be fine

The engine size thing is usualy used in refrence to starting the engine. Any charger should charge any battery but the boost start function will only be capable of providing so many amps.