This LRO reader emailed LRO.firstname.lastname@example.org seeking a solution for a battery draining issue on his Range Rover Sport.
The battery of my 2010 Range Rover Sport 3.0-litre TDV6 HSE discharges within a week if the vehicle’s not used regularly - even though I’ve replaced the battery.
The diagnosis, not covered by the extended warranty, has a fairly hefty labour charge associated with it. The main dealer technicians found that there’s a 118 micro-amp drain in its sleep mode but they couldn’t find the source after the two days of experimentation.
What checks can I carry out to identify the problem area?
John Lee, Welwyn Garden City, Herts
You need to measure the amount of battery drain - easy to do.
Check you have the radio code. Open the driver’s window, disable the bonnet light and disconnect the battery negative. Put an ammeter on the 10A scale, from the battery terminal to the lead disconnected. This may initially give a reading of 5A because the ECU is still awake.
Wait for the ECU to go to sleep - maybe 20 minutes - and then read the current, which should be below 0.1A. If it’s a higher figure then for every 0.5A think 6 watts.
What could be on that draws the power indicated? Occasionally, the ECU is awoken by spurious signals from mobile masts etc., so you may need to watch the meter to see if it ‘wakes up’. Do you have a split-charge system for a caravan on the vehicle? If you do, disconnect it.
This workshop advice appeared in the December 2014 issue of LRO. Back issues are available to download on digital devices here.