Parasitic battery drain Rover 75

[Synchromesh]

When it has gone to sleep my 2L V6 petrol draws 16mA with higher pulses of current corresponding to the red flashing alarm LED. I connected the ammeter using some long test leads so I could close all the doors, the boot and the bonnet to ensure it was fully asleep. I didn't observe the ammeter as the various systems went to sleep so I don't know how long it took to drop to 16mA. I think I returned to it after an hour.

[SD1too]

Originally Posted by Synchromesh

... with higher pulses of current corresponding to the red flashing alarm LED.

That's interesting Steve. How many mA were the higher pulses please?

Simon

[Synchromesh]

Originally Posted by SD1too

That's interesting Steve. How many mA were the higher pulses please?

Simon

The LED is pulsed for such a short period of time the meter reading starts to rise but the LED has extinguished before the meter catches up. An oscilloscope would be required to measure the LED pulse but I haven't got one.

[edwardmk]

My 2.5 V6 petrol starts well after being left for a full calendar month. The V8 though will only last 3 weeks from a full battery. I haven't had time to trace the last bit of parasitic drain on the V8. I leave it hooked up to a CTEK MXS 5 when not in use which has fixed the issue for me ( from advice in this forum). My Transit has marginally worse battery drain than the V8. For that I installed a battery isolator switch which works a treat. Downside is I lose radio settings and clock and can't auto lock the truck. I see you can now purchase remote operated battery isolator switches but they are around £40 and I don't fancy the problems if the remote failed with a locked van. (I guess I could use the key manually to unlock it). One fine day I'll find the time to track the cause of the parasitic drain in both vehicles, but those two solutions have saved me considerable frustration. Our 2005 Astra turbo cabriolet( petrol) will sit for three months and start first time. My daughter's 2002 2.2L petrol cabriolet runs down in a week, but I know that's a power sounder issue. It's also on a CTEK when parked up, and no more issues with it not starting. One fine day I'll rip out the power sounder. I did that for my 2005 Astra which fixed all parasitic drain issues with that car.

[Synchromesh]

Originally Posted by edwardmk

My 2.5 V6 petrol starts well after being left for a full calendar month. The V8 though will only last 3 weeks from a full battery. I haven't had time to trace the last bit of parasitic drain on the V8. I leave it hooked up to a CTEK MXS 5 when not in use which has fixed the issue for me ( from advice in this forum). My Transit has marginally worse battery drain than the V8. For that I installed a battery isolator switch which works a treat. Downside is I lose radio settings and clock and can't auto lock the truck. I see you can now purchase remote operated battery isolator switches but they are around £40 and I don't fancy the problems if the remote failed with a locked van. (I guess I could use the key manually to unlock it). One fine day I'll find the time to track the cause of the parasitic drain in both vehicles, but those two solutions have saved me considerable frustration. Our 2005 Astra turbo cabriolet( petrol) will sit for three months and start first time. My daughter's 2002 2.2L petrol cabriolet runs down in a week, but I know that's a power sounder issue. It's also on a CTEK when parked up, and no more issues with it not starting. One fine day I'll rip out the power sounder. I did that for my 2005 Astra which fixed all parasitic drain issues with that car.

Although some cars will start when left for several weeks with no maintenance charger connected it is not good for the battery. The 'starter' type batteries used on cars deteriorate if the charge level is allowed to go below 90%. If 16mA is typical for a 75 and that was the only thing that is reducing battery charge level then that will take a battery from 100% to 90% in about 3 weeks but chemical degradation will also run down the charge. There is a lot of interesting information if you search Battery University lead acid battery.

[MSS]

Originally Posted by Synchromesh

Although some cars will start when left for several weeks with no maintenance charger connected it is not good for the battery. The 'starter' type batteries used on cars deteriorate if the charge level is allowed to go below 90%. If 16mA is typical for a 75 and that was the only thing that is reducing battery charge level then that will take a battery from 100% to 90% in about 3 weeks but chemical degradation will also run down the charge. There is a lot of interesting information if you search Battery University lead acid battery.

Absolutely spot on.

With a number of cars and each one only getting limited use, I give each car a few hours with a 5A CTEK each week in order to keep all the batteries at near 100% state of charge.

[Savestones]

Originally Posted by SD1too

No Tony. The output of FL3 is on a single wire which en route splits into four wires, each connected to a separate pin on the passenger compartment fusebox connector.

No again! If it was, that would cause FL3 to blow which isn't the case. What you have isn't a short circuit or an open circuit, it's a malfunction of the multiplex wiring system causing a circuit to draw current when it should be "asleep". The difficulty we are having is identifying that circuit.

Simon

How would one generally go about this? Or is this to difficult to explain through forum posts