Charging Batteries
Only applies to vehicles equipped with automatic transmission and start/stop. Charge point for the secondary battery is in the fuse box in engine compartment 15/31.
Charging battery (main battery)
When the external auxiliary battery or battery charger is temporarily connected, the battery's negative pole must never be used for connection, only the vehicle's chassis must be used as an grounding point. When connected correctly, the battery monitoring sensor awakes from its sleep mode as the current through the sensor (in to the battery (main battery)) exceeds 250 mA. The sensor the registers how much current the battery (main battery) is charged with and can then calculate the battery's (main battery) correct charge status/capacity. When the current through the sensor is less than 250 mA the sensor continues in sleep mode.
If the battery's (main battery) negative pole is used when charging, the battery monitoring sensor does not register the current that the battery (main battery) is charged with. When the ignition is switched on, the battery monitoring sensor registers that the voltage across the (main battery) poles has changed since the last registration. The battery monitoring sensor can interpret this as the calculation of the battery's (main battery) SoC currently does not correspond (not reliable) and sends the message about this to Central electronic module (CEM). Central electronic module (CEM) forwards the signal to the Engine control module (ECM) which prevents the function automatic start/stop of the engine from being active.
If the sensor's calculation is reliable or cannot be read off in VIDA. See: VIDA - DIAGNOSTICS/VEHICLE COMMUNICATION/CEM.
For the battery monitoring sensor to calculate the battery's (main battery) correct state of charge the vehicle must be in sleep mode for 4 hours. Sometimes, 6 hours in sleep mode may be required. This is on the condition that the ignition key has been removed, doors and hatches closed and the car is locked. If the SoC is still low, the automatic start/stop of the engine function will not be permitted. The battery (main battery) needs to be charged.
For descriptions in where and how the cable clamps are to be positioned, see the Owner's Manual.
Charging the secondary battery
The secondary battery is normally charged via the vehicle's charging system while driving. When using the battery charger to charge, the battery charger must only be connected directly to the secondary battery's poles or temporarily via the terminal pins for the secondary battery's battery relay (relay disconnected).
It is of the utmost importance that:
- The charger is correctly connected as connecting to the wrong pins can damage other components.
- Charging occurs at low current so that the secondary battery is not overcharged. Quick charger or booster charging must not be used.
- Measure the voltage after charging at the charge point to ensure that the fuse is intact.
During key start for vehicles with automatic transmission and the start/stop, the start sequence is the same as at autostart. For more information, see "Automatic start/stop of engine - Description" VCC-421709. If the secondary battery is discharged or in the event of certain component faults, the start only occurs by means of the main battery which then supplies the entire electrical system and starter motor. On the cars that use a secondary battery even during key start, the secondary battery can be charged from the fuse box in engine compartment 15/31. The fuse box has a flat pin (male), at position F34 (terminal F46 on the V40 and V40 Cross Country), which is directly connected to the positive terminal of the secondary battery. The battery charger's positive supply can be connected on the flat pin via a cable lug. The charger's negative cable must be connected to the car's chassis.