Advanced Diagnosis - SN00.30-P-0001-03S

Model all (CAR) 

12 V battery test with XENTRY Diagnosis - function and use 

The testing of the 12 V battery with XENTRY Diagnosis is a test of battery condition based on the battery's behavior in the vehicle.

On-board data is used for this purpose. This on-board data contains the last 100 stationary and driving cycles.

Different data is recorded for each cycle, including the battery's state of charge (SOC) as a percentage, the internal resistance of the battery and the release of ECO start/stop processes via the energy management system.

The testing of the 12 V battery using XENTRY Diagnosis requires at least 60 completed cycles for an evaluation.

These can be found in the cycle log. The cycle log is filled on a FIFO (first-time first-out) basis, i.e. the oldest data is always deleted and replaced by the most recent.

It is therefore only possible to view the period of the most recent cycles in the cycle log.

For this reason, it is important that the test is carried is carried using data that has come from customer use because test drives and workshop tests may influence the result.

As a result of insufficient support, the SOC is significantly worse in the workshop than with the customer.

The cycle log is always deleted when the control unit is flashing.

As the data is stored on the central control units (EIS in STAR3), the data can quickly be deleted by means of flash programming, the battery test should therefore always be performed prior to other tests and software updates.

If enough cycles are available, the algorithm takes 3 different criteria into account:

• SOC criterion:

  The battery's state of charge should ideally be at approximately 80 %, which is the value that is controlled by the energy management system.

  The criterion can be assessed with two grades:

  A slight problem with the SOC level and a serious problem with the SOC level.

  For this purpose, all available cycles (between 60 and 100 cycles) are assessed to determine whether the limit of a slight or serious problem with the SOC level has been exceeded.

  If the limit has been exceeded in a majority of the cycles, the criterion has been fulfilled, according to which of the two grade limits has been exceeded.

  This results in the following conclusions with respect to the overall evaluation:

  Short-term discharges, e.g. for 1 to 5 cycles, do not carry any weight when taking 100 cycles into account.

  As a result, a bus keepawake control unit or a long stationary phase is always assessed as OK.

  In both cases, it is still important to identify the cause and, if necessary, replace the battery according to the relevant damage code (damage code list). An single short discharge has no negative effect on the battery, but several such incidents may damage the battery.

  Permanent damage to the battery can best be evaluated by determining the internal resistance (RDI).

  If this is significantly increased due to a long idle period, it can be assumed that the battery is damaged. The RDI is always increased when the SOC is low, therefore please always consider this if the battery is charged.

  Damage can also be assumed for a battery that, despite being correctly connected to a charger or with a battery connected in parallel, can no longer be charged (some charging devices do not recognize a deeply discharged battery and therefore release no charging current).

• RDI criterion  : The RDI criterion evaluates the internal resistance of the battery.

  The internal resistance of a battery depends on several factors. This primarily includes the state of charge, the temperature of the battery and the battery size.

  For this reason, the RDI value of each cycle recorded in the 12 V battery test is compared with a corresponding characteristics map. Deviations from the ideal value are then evaluated across all cycles.

  If the internal resistance of the battery is increased during enough cycles (aging of the battery is indicated by increased internal resistance), in the same way as the SOC-criterion, this can be evaluated as either a slight or serious compliance with the criterion.

• ECO criterion  :

  The ECO criterion evaluates how many cycles of the ECO start/stop process were prohibited by the on-board electrical system.

  If this was prohibited in sufficient cycles, the criterion has been fulfilled. In this case, there is no grading of the criterion from slight to serious.

All three criteria are then finally combined to produce one result. These three results of the 12 V battery test with XENTRY Diagnosis are:

• "Battery is OK. Do not replace battery."
• "Battery is OK. Recharge the battery."
• "Battery is not OK. Replace battery."

The operation of the 12 V battery test with XENTRY Diagnosis takes place similarly to the description in the service information: 12 V battery test with XENTRY Diagnosis SI54.10-P-0074A.