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Home >> Volvo >> 2012 >> C30 R Design L5-2.5L Turbo VIN 67 B5254T7 >> Repair and Diagnosis >> Starting and Charging >> Charging System >> Description and Operation >> Function

Function






Function

Control alternator
The alternator and charging of the battery is controlled by the Engine control module (ECM) using signals from the battery monitoring sensor about the status of the battery.
The Engine control module (ECM) calculates the engine's efficiency (need of torque for power transfer) and controls the alternator so that battery charging is maximized when "it is free" and reduces the charge when the engine's efficiency is low. i.e. when the engine's torque is needed to propel the vehicle.
Depending on the engine's efficiency, power consumption in the vehicle and the battery's status, the alternator is controlled as follows:
- Conventional charging
- Reconditioning battery
- Brake energy regeneration. Regeneration can occur in the following ways:
- slowly
- quickly
- slowly without discharging

Conventional charging




For optimum battery charging, the output voltage from the alternator is calculated from the battery's calculated temperature. The temperature is obtained from the battery monitoring sensor.
Depending on the demand from the Engine control module (ECM), the Alternator control module (ACM) (charge regulator) regulates the output voltage according to the image above. With traditional conventional charging, the battery is always charged to a SoC level of 100%.
For the brake energy regeneration function, battery charging occurs in the conventional way until the battery has reached a SoC level of 80 %.

Reconditioning battery
Performed at least 3 times per year (at least every 120 days) with the purpose of preventing the battery from sulfating permanently. On this occasion, the battery is fully charged in a few hours. Charging can occur during several operating cycles.

Brake energy regeneration
Depending on which type of power consumers are active, control of the alternator occurs in different ways.

Brake energy regeneration, slow
Voltage sensitive consumers are activated. This refers to consumers that are sensitive to voltage differences where voltage changes can be noticed by the driver. The voltage changes slowly as brake energy regeneration is activated so that the change is not noticeable. Applies to consumers such as headlamps, fog lamps, fan motor and windscreen wipers.

Brake energy regeneration, quick
No voltage or power sensitive consumers are activated. The voltage changes quickly or immediately during brake energy regeneration.

Brake energy regeneration, slowly without discharging
Voltage sensitive consumers are activated. This refers to consumers that are sensitive to voltage and power differences. Applies to consumers such as engine cooling fan motor, preheating elements, connected trailer and blower fan. When voltage and power sensitive consumers are activated, the voltage changes slowly and the alternator voltage is not permitted to be less than 13.2V. This is to prevent the available output from being too low.

Description of an operating cycle




1. Conventional battery charging. The battery's SoC is below 77 % (poorly charged battery) and the system strives to charge the battery up to 80 %. Brake energy regeneration is not permitted. The charge voltage increases (level depending on the battery temperature) so that the battery charges. When the correct SoC is reached, brake energy regeneration is permitted.
2. Battery not charging. The engine's efficiency is low (the engine's torque is needed to propel the vehicle) and the battery is not charged. The alternator is controlled so that only the vehicle's power consumers are supplied with the necessary current.
3. Engine braking (brake energy regeneration). The alternator charges the battery with a voltage up to 15.0 V (charges with energy).
4. The battery produces energy. The engine's efficiency is low (the engine's torque is needed to propel the vehicle). Regeneration of previously stored energy with a fast current output from the battery down to a voltage of 12.4V.
5. The battery produces energy. The engine's efficiency is low (the engine's torque is needed to propel the vehicle). Regeneration of previously stored energy with a slow current output from the battery down to a voltage of 12.5 V

Note! When driving in the dark, the lowest permitted charge voltage is limited with the purpose of providing maximum output for lighting for example.

The dotted graph illustrates when quick brake energy regeneration is activated, i.e. when the function permits a greater voltage level during brake energy regeneration and more energy can thereby be regenerated (charged in the battery). The solid graph illustrates when slow regeneration is activated.

Battery charging




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) exceeds 250 mA. The sensor the registers how much current the battery is charged with and can then calculate the battery's correct charge status and capacity. When the current through the sensor is less than 250 mA the sensor continues in sleep mode.
If the battery's negative pole is used when charging, the battery monitoring sensor does not register the current that the battery is charged with. When the ignition is switched on, the battery monitoring sensor registers that the voltage across the poles has changed since the last registration. The battery monitoring sensor can interpret this as the calculation of the battery's SoC currently does not correspond (not reliable) and sends the message about this to the Engine control module (ECM). On these occasions the sensor's calculation of the battery status is not reliable and the function is therefore not permitted.
For vehicles with the automatic start/stop of the engine function, the function is not permitted temporarily.
The status of the sensor's calculation can be read off in VIDA. See: VIDA - DIAGNOSTICS/VEHICLE COMMUNICATION/ECM.

Note! For the battery monitoring sensor to calculate the battery's 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 brake energy regeneration function will not be permitted. The battery needs to be charged.

For descriptions in where and how the cable clamps are to be positioned, see the Manual.

Miscellaneous

Blocking the brake energy regeneration function
The battery monitoring sensor can be diagnosed by the Engine control module (ECM). If the DTCs for the battery monitoring sensor are detected and the fault is active, the brake regeneration function is not permitted.

Note! For vehicles with the automatic start/stop of the engine function, the function is not permitted temporarily.

Other situations where the battery monitoring sensor does not permit the brake regeneration function:
- Charging the battery via the battery poles. See: Battery, charging.
- The standby current consumption is more than 250 mA for 7 days. This means that the sensor never has the opportunity to measure the battery's standby current and therefore cannot calculate the battery's charge status.
On these occasions the sensor's calculation of the battery status is not reliable and the function is therefore not permitted.
The status of the sensor's calculation can be read off in VIDA. See: VIDA - DIAGNOSTICS/VEHICLE COMMUNICATION/ECM.

Replacement of the battery / battery monitoring sensor
For replacing the battery or battery monitoring sensor, battery information must be reset.
See: VIDA - DIAGNOSTICS/VEHICLE COMMUNICATION/ECM/Advanced

The vehicle's battery is completely discharged or the battery monitoring sensor has been disconnected from the battery pole.
If the battery has been completely discharged so that the vehicle does not react to the ignition key (in principle, is completely dead) and the vehicle is then started using an external auxiliary battery or battery charger, the battery monitoring sensor can interpret this as it being disconnected from the battery (main battery). The battery monitoring sensor then reads off the battery voltage and assumes a SoC that is proportional to the voltage. If the SoC is low, the automatic start/stop of the engine function is not permitted.

Note! For the battery monitoring sensor to calculate the battery's 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 then needs to be charged.

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