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"Quiescent current" is current drawn from the battery by vehicle components that require power when the key is in the "off" position. The draw may include the radio, clock, security system and ECU memory. It will also vary depending on the "sleep" status of various ECUs.
Some electronics, including plips from other vehicles in the vicinity, can "awaken" an ECU. When testing avoid the use of plips in the vicinity. If consistently and repeatedly "awakened" over an extended time, the ECU quiescent draw can drain a battery.
A battery will self discharge at a rate between 0.1 - 1% at 20°C (68°F) depending on the age and condition of the battery. The self discharge rate will INCREASE 1% for every 10°C (19°F) increase in temperature
Dirt and moisture on the top surface of the battery will also increase the discharge rate.
A quiescent current draw that exceeds specification can cause excessive battery drain while the engine is off. This may result in a dead battery or inability of the battery to maintain a charge.
Here is your test.
MEASURE QUIESCENT CURRENT LEVEL
1. Verify that the battery is fully charged.
2. Remove key from ignition lock.
3. Open hood.
4. Disconnect bonnet switch.
5. Close all doors.
6. Verify that all interior lights have extinguished.
7. Lock vehicle with remote.
NOTE: Ensure that the vehicle electrical system remains powered throughout the following steps.
8. Connect a suitable ammeter between the battery and vehicle electrical system.
9. Wait 30 minutes for all on-board systems to power down. In some cases a Discovery Series II may take up to 60 minutes to completely power down.
NOTE: Any accessories fitted to the vehicle with a permanent battery connection, will adversely affect quiescent current. They should be disconnected before testing the vehicle
10. Measure the current level between the battery and vehicle electrical system.
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