Siftah wrote:

Updates on the above saga...

I measure the current usage of the battery monitoring device and it was in the 20mA range and usually much less, so I've discounted it as being statistically significant and have left it connected.

I've swapped the battery for a new one, but I'm still seeing the same behaviour, if anything, on the first night I saw *more* voltage sag overnight than before!

I'm suspicious that the Naviplus I fitted is the source of the problem, in that it's potentially keeping the BCM awake - having emailed Naviplus they've suggested disconnecting the yellow (I think this is supposed to be an "accessory on" feed) and driving it direct from the fusebox on an ignition-on feed. I've not done this yet, I'm not convinced it's going to help tbh.

I'm still waiting for a clamp-type multimeter to arrive to I can non-invasively test the current draw around the alternator. Also still waiting for some new test leads to arrive for my multimeter, which have got destroyed

Lastly, I pulled the HVAC control board from the dash and took it apart to check for any signs of corrosion or possible reason for the fan staying on. It was immaculate inside, aside from a bit of dust where you'd imagine around the vent, but I see no reason to suspect it as being damaged by water or anything.

As an FYI, the way the temperature sensor and fan are mounted, there should be no issue in gently blowing dust out of that grille with an air duster, it vents to the back of the dash and I can't see how it'd do any harm to it.

So not much further, but I'll update the thread again when/if I find something more out!

Well, bizarrely it seems to have resolved itself - which I can't explain

I'd gotten into the habit of connecting up the charger when the car was due to be parked for a few days anyway, as it's easy to do with the towing socket electrics. Checking the logging app I could see there still times when the car would inexplicable start drawing more power and the battery voltage would dip.

It seemed to usually be around 4 to 6am for some reason.

However for the last month or so I've not connected the charger once - I've been using the car a little more, perhaps every 3 days on average with fairly short trips (around an hour). And I've not noticed the battery drop at all overnight.

All the big variations you see in these graphs are driving the car. You can see some small deviations when the car's parked up, but nothing like I used to see and nothing that's putting a dent in the charge level of the battery.

I have been investigating a similar problem on my 2006 TDV8. Initially it wasn’t going to sleep at all but I know the old Bluetooth module was defective, so unplugged it and looped the MOST out with a kit from eBay. So far the system goes to sleep now after 16 minutes. Losing about 0.02v a day from the battery so should last a week at least now. Seeing some difference between road height and access height when parked though. I know the system checks the vehicle height every few hours and tops up if needed. That may be your spike and could be a slight air leak somewhere. That’s the theory I’m checking anyway

I think that's probably a red herring to be honest. From what I've seen in the workshop manual the suspension is checked every 6 hours.

But it doesn't run the compressor and pump up the suspension (which would draw quite a bit), it just lowers the other corners to achieve a level. So this would only be a very small amount of current drawn (enough to open an air solenoid) and it'd only happen twice.

I don't think mine's losing any air as I've had it sat for a few weeks over the pandemic and it's never hit the bump stops or shown any signs of sagging corners etc.

Page 412 of this document explains it: http://duud.ee/LR-manualid/Range_Rover_Workshop_Manual_L322.pdf

You are most likely right then. I thought it topped up too, not just let down to balance. Do all the ECU’s all wake up again or just the ride height?

When a door's opened, keyfob used to unlock etc the BCU wakes up a bunch of stuff, boots the satnav, starts checking the temperature, wakes the suspension ECU etc.

BCU stays awake for 15 minutes; that's the ~16 minutes you observed.

When the BCU's told the suspension ECU to wake up, it'll raise or lower the suspension and it *will* run the compressor to keep enough air in the reservoir.

Once the 15 mins are over and the BCU is sleeping, the suspension ECU will wake periodically (every 6 hours or so) to level the suspension - but it won't run the compressor, nor will it use air in the reservoir to raise the suspension, it'll just open a solenoid to level the other three corners to the height of the lowest (so basically if you have a leak you'll eventually see all 4 corners sag to the bumpstops).

My wild guess is that there's lots of things that can wake the BCU up, for example if it thinks a doors been opened because of an iffy door switch, bonnet catch, etc. I'm not aware of anyway to find out the cause for the BCU waking up, which is a pain when you're trying to track down these kind of electrical gremlins.

I think my own battery drain was likely due to something like this, maybe one of my door switches is iffy and it's waking the BCU too regularly causing it to drain - I just wasn't able to pinpoint it

I read elsewhere that the Bluetooth module can be activated by other signals when in sleep mode which can wake it up. I have mine unplugged and don’t have a battery drain anymore so is that worth a try?

I don't know technically why it'd be necessary for a Bluetooth module to wake-up the BCU - but it also would not surprise me if it did

It's definitely the case that the BCU being awake is a cause of a reasonably large amount of battery drain, not least because it wakes the nav system, dash screen (on 2010+ cars) and loads of other systems that can draw significant current.

I'd guess it's more likely the bluetooth module was faulty and causing the BCU to never shut down, rather than it being an intended behaviour. I've heard people mention that things like the remote heater can be susceptible to interference and cause the BCU to be woken, there's likely lots of reasons!

As you've removed the Bluetooth module and it's made the situation better, I'd suggest that's positive progress, you may find that due to being repeatedly drained, your battery is now in need of replacement - hence you're still seeing it go flat after a week or so.

I'd highly recommend this device for monitoring the battery and helping to resolve issues and/or giving you peace of mind! https://www.aliexpress.com/item/32794632957.html

That looks perfect, thank you. Is that how you got the logs in the thread above? If it could send me a message once the battery drops below a value, that would be really useful

It is indeed, yeah, it can be set to give you a push notification when the battery falls below a certain threshold.

The only caveat emptor is that the phone has to occasionally go within Bluetooth range of the car in order for the message to be triggered - this is in the range of ~15 metres or so. Once in range you can download a few days worth of history so you can see at which points the battery started to drop, if at all.

I will get one ordered and see what’s really going on

Most of my dash is off, have decided to fix/replace damper motors whilst chasing the drain. With the Audio system offline there is no drain over night!! shock: next step would be to isolate carplay and check further. SOLD | Tuned MY 2011.5 Range Rover Autobiography 4.4 TDV8 Orkney Grey | e-diff | ACC

New Toy: Unimog U1550L/37
New : G350D

This may just jinx it but no more battery drain issues since isolating the Bluetooth unit. 🤞

ffrr14 wrote:

Most of my dash is off, have decided to fix/replace damper motors whilst chasing the drain. With the Audio system offline there is no drain over night!! shock: next step would be to isolate carplay and check further.

Interesting update! Would be curious how you get on!

RosieL322 wrote:

This may just jinx it but no more battery drain issues since isolating the Bluetooth unit. 🤞

Crossing my fingers for you too!