Vehicles with a two-battery system

Starter and system battery

A two-battery system has a starter battery circuit and a system battery circuit. An auxiliary control unit monitors both battery circuits. Depending on the situation, the battery circuits are connected to or isolated from the auxiliary control unit via an cut-off relay.

Two AGM batteries, whose design and properties are described in AGM BATTERIES , are used as a storage battery.

IMPORTANT: These batteries must not under any circumstances be charged with a voltage in excess of 14.8 V. Rapid programs must not be used either.

Receiving/giving starting assistance via external start terminal

The engine can be jump-started with an external voltage supply via the jump start terminal on the right side of the engine compartment.

NOTE: The starter battery is isolated from the alternators when the engine hood/bonnet is open.

Giving starting assistance via the jump start terminal is thus limited by the capacity of the starter battery when the engine hood/bonnet is open.

Charging starter and system batteries via jump start terminal point

The starter battery is charged as a matter of priority with a charger connected to the jump start terminal. The voltage at the starter battery is the decisive factor in determining whether the system battery is also included in the charging operation. The auxiliary control unit automatically detects a charging operation at a charging voltage at the starter battery of ≥ 13.5 V. The cut-off relay is closed and thus the system battery is connected in parallel. Both batteries are now charged.

Prerequisite:

Terminal 61 inactive
Terminal 15 inactive

If terminal 15 becomes "active" during the charging operation, the cut-off relay is opened immediately and again only the starter battery is charged.

NOTE: When the engine hood is open, the cut-off relay is also opened in normal operation when the engine is running.
A special mode can be set by means of diagnosis for workshop/garage operation. The cut-off relay is closed from terminal R in this operating mode. This mode is automatically reset once a distance of 5 km has been driven.

Trickle charging

The increased standby current consumption can be compensated for via the jump start terminal point with the aid of the "Acctiva easy" battery trickle charger.

IMPORTANT: The cigarette lighter is isolated from the electrical system after terminal R "OFF" on a timed basis (60 mins.), thereby interrupting charging of the system battery via the cigarette lighter. This is prevented if the battery switch (on the right side of the luggage compartment behind the panel) is turned on and off again twice within 2 seconds. (Cigarette lighter battery charging function).