Closed Circuit Current

Closed-circuit current measurement using the of the intelligent battery sensor

Description
In the event of problems with increased closed-circuit current, it is frequently the case that this must be determined during Service. With the conventional procedure, a shunt resistor must be fitted at the ground strap of the vehicle.

Evaluating of the closed-circuit current monitoring:
On vehicles with an IBS (Intelligent Battery Sensor), the DME/DDE monitors the closed-circuit current when in the idle state.

The IBS is only fitted with certain equipment options (e.g. M-ASK or CCC). The test module for evaluating of the closed-circuit current monitoring first of all tests whether an IBS is fitted at all.

In this model series, the results of the last 32 cycles of closed-circuit current monitoring are stored in the DME/DDE. A new cycle of closed-circuit current monitoring is stored under the following conditions:
- Terminal R is off for at least 70 minutes.
- The vehicle is in the idle state for at least another 120 minutes without being wakened.

If these conditions are met, the result of the closed-circuit current monitoring is stored in a new cycle. The oldest cycle of the 32 cycles is overwritten by the new cycle.

If the vehicle is wakened after saving a cycle, a new cycle can then begin if the conditions are met.

The result of a cycle of closed-circuit current monitoring has two categories:
1. In the first category, whether or not an auxiliary consumer unit was logged in during the idle state (at least 120 minutes) is stored. An auxiliary consumer unit is a consumer unit that can also be activated in the idle state of the vehicle. In the case of closed-circuit current monitoring, a distinction can be made with regard to logged in auxiliary consumer units:
- No auxiliary consumer unit was logged in
- A statutory auxiliary consumer unit was logged in (e.g. light or hazard warning lights)
- The independent heating was logged in
- Another auxiliary consumer unit was logged in

2. In the second category, the range of the closed-circuit current during the idle state (at least 120 minutes) is stored. In the case of closed-circuit current monitoring, a distinction can be made with regard to closed-circuit current:
- 0-80 mA (normal closed-circuit current in the idle state without auxiliary consumer units)
- 80-200 mA
- 200-1000 mA
- Over 1000 mA

Increased closed-circuit current in a cycle can be seen above all when no auxiliary consumer unit was logged in, but the closed-circuit current was above 80 mA.

Bear in mind that in the event of problems with the idle state of the vehicle no new cycles for closed-circuit current monitoring are stored. If the vehicle does not 'go to sleep', e.g. due to a 'sleep preventer', no new cycle of closed-circuit current monitoring is stored. Saving a new cycle of closed-circuit current monitoring is also prevented if the vehicle is permanently wakened by a control module or a user.