That is still possible with our classics. With modern cars, the use of a start booster can lead to great electronic misery, so consult your instruction manual for your modern car, or rely on your mobility guarantee. But a car from 1984 can also have a 'computer' on board…
Immediately after starting, the dynamo supplies a maximum charging current to replenish the charge of the battery as quickly as possible. Now a starting aid is usually provided when the battery is discharged. An annoying feature of a discharged battery is the high internal resistance. As a result, this battery cannot absorb a large charging current. If the discharged battery does not absorb the charging current after starting, the majority of the charging current goes to the starting aid battery.
So far there is no problem. But when the starting aid is then released, the misery starts. The current supplied by the dynamo falls (for example) back from 80 to 20 ampere. This large current change in the windings of the dynamo causes an enormous change of the magnetic field in the dynamo. This again produces a strong peak voltage in the same coils. Due to the size of these coils there is a lot of energy in this peak voltage. This peak voltage can reach values of 70 Volt and more.
It is this peak voltage that can destroy the power supply circuits in many computers.
This voltage peak can be controlled with an overvoltage protection, but the 'ANWB Roadside Assistance' also offers relief. Engage as many users as possible before the start aid is released. All charging current is thus used by the car so that there cannot be a major current change when the starting aid is released.