1. Make sure the other vehicle's battery is 12V and approximately the same capacity (in ampere-hours), just like your battery.
2. Do not disconnect a discharged battery from the on-board network!
3. To avoid a short circuit, the bodies of both cars should not touch each other.
4. First connect the positive (+) battery terminals. BMW 535i, 524td: connect to an external battery the positive lead from your battery, located in the engine compartment under the cap with the symbol "+" (the protective cap must be removed by pulling the tab - see figure). Then connect one end of the auxiliary cable to the negative (-) external battery terminal, and the other to the race "masses" on the body or engine of your vehicle.
5. If the battery from which you start the car is weakly charged, then you must first start and do not turn off the engine of this car. When you start your car, don't turn it off either. After starting the engine, before disconnecting the auxiliary cables, turn on the lights, heated rear window and heater fan at maximum power. This is necessary to avoid a voltage surge in the vehicle's on-board network when the cables are disconnected. After that, disconnect the auxiliary cables in the reverse order than when connecting, turn off the electrical consumers and leave the engine running to charge the battery.
Attention: Touching the conductive elements of the ignition system while the engine is running is life-threatening!
To avoid injury or damage to both vehicles, strictly follow the above procedure.
BMW 520i, 525i
These vehicles use a digital electronic engine management system that uses data from the mass air flow sensor to start the engine. Do not use starter aerosols as this will damage the sensor!