Does my batteries discharge eachother?

We often get the question of whether a charged battery is discharged by being connected in parallel with a discharged battery. In the movie below we show how the current moves around between pareallel connected batteries. Unfortunatley it is on swedish with no text yet.

In the movie Lars get a question about if an almost empty consumer bank can empty the starter battery when the connect via a separating relay. So Lars went to a store and purchased a relay and two batteries. He loaded one of the batteries to max and emptied the other to 12 V (25% of its capacity). When connecting the batteries with eachother and faking a start it went 30 Amps at the first seconds and thne it sank to 10 Amps. Lets say that the engine is slow started and need to glow for 10 seconds and the power rush is 30 Amps, it emptied the starter battery with 0.08 Ah. (30 Amps x 10 sec / 3,600 sec = 0.08 Ah). At the end of the movie he also measured the voltage on the battery bank when it was connected and it was 12.5 V, which is enough to start the most engines with.

So the answer to the question is: Not much!