So I trundled out this morning, remote didn't work. I went off to get the spare one, but that didn't work either. I opened the car with the blade, no alarm, no ignition - just dead as a doornail.

There was no indication of anything battery related afoot. No warnings, messages or bad starting. It's been A1 apart from a driver's side electric step that can't decide if it wants to be in, out or halfway.

I had to cadge a lift off wifey to work, and will bung it on charge when I get home. But for something to have drained the battery overnight, is there anything that is a known issue here? Nothing jumped out when I had a search.

Any thoughts or known L405 foibles in this area? 2017 4.4 SDV8 Autobiography in black
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Last edited by Stuart- on 3rd Jul 2023 6:58pm. Edited 2 times in total

So here's the update. When the battery is dead, you cant get in the boot to access the battery to charge it.

However, I found on a US forum via Google this advice:

Quote:

Open the hood, attach a jumper box or car with jumper cables to the positive terminal on the right hand side under a plastic box that has a big Plus symbol…the Negative to the post right next to it. That may give you enough electrical power so you can then open the rear gate with the switch. Might take a few minutes to get enough juice to the car…but should work.

So the box with the big + on is actually on the left (looking from the front), and you can hook up a battery charger.

Click image to enlarge

And as soon as you do, the horn starts blaring and the alarm goes off.

The key fob (both) seems to have no effect, the boot won't open as yet, but the back and interior lights are on. Eventually, the alarm shut up, not sure yet if it responded to the fob or shut up on its own. I'll try and get some charge into it and see. 2017 4.4 SDV8 Autobiography in black
2018 D300 SE Velar in champagne
Spiffing wheel centre caps available

Unusual to be completely drained overnight - have you found the source ?

The only time it happened to me it was a bad alternator - but you could smell it when opening the bonnet.

Not yet. My inclination at the moment is to leave it overnight charging from the front posts. I found an earlier topic here that suggests that this method is OK.

If it starts in the morning, I'll see if it happens again. It's due a service anyway so no doubt something relevant will be stored on the computer pointing towards the likely cause they can do at the same time.

I've got a Sytner warranty I've never used since I bought it last year, so if it doesn't go tomorrow, or conks out again, I might end up getting my money's worth from that.

Edit: a bit of charge in it now and the fob unlocked the rest of it. Will leave overnight. 2017 4.4 SDV8 Autobiography in black
2018 D300 SE Velar in champagne
Spiffing wheel centre caps available

Last edited by Stuart- on 3rd Jul 2023 8:32pm. Edited 1 time in total

I watched a utube video only the other day. They had power to a degree but a whole lot of warnings on the dash. It was an earth point under the driver wheel arch. Don’t know if this may be related  2016 4.4 diesel

Interesting video, thanks. Someone might want to put that more accessible here, maybe in the Wiki. That will be of great use to many.

I just found an older topic here discussing the main battery and the stop-start. I am not a big fan of the stop-start and would prefer not to have it, but mine seems to have a mind of its own. In traffic queues, it turns off sometimes, but usually not. It might not work for days on end, then half a dozen times on my way to work. I never give it too much thought as I've not had that system before so I am not sure how they tend to work and how predictable they are.

If it starts in the morning, I'll bung a voltmeter on it at work, and if charging OK from the alternator, have the battery tested.

That said, I'm not convinced that with so few symptoms, even a failing battery would go randomly dead overnight without a bunch of gremlins heralding its demise. But others here may know better.

For the benefit of others who may find this topic in the future with battery-related issues, here is a link that shows many historical battery related topics via Google on this forum. 2017 4.4 SDV8 Autobiography in black
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https://www.fullfatrr.com/forum/topic62384.html

Topic here about the earth points in both wheel arches. overfinch modified

I charged it overnight, it started fine this morning. No warning lights. I just put the voltmeter on it at work and it's showing its charging at 14.67v which seems fine.

I am going to call in at the indy on the way home and have them plug it in and see if that sheds any light on it. If not, its a battery test I guess. 2017 4.4 SDV8 Autobiography in black
2018 D300 SE Velar in champagne
Spiffing wheel centre caps available

It could be a failing second battery, using those charge points under the bonnet does not charge the second battery, both batteries charge separately but back each other up when power is needed...

You have a smart alternator which should vary the voltage from the batteries resting charge to around 14.7volts, if it stays at 14.7 all the time then that is another indication of a failing battery...

Worth getting both batteries checked, you have to remove the drivers side (RHD) boot side panel to access the second battery....  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Popped along to the indy this afternoon, battery tested fine (he said the secondary one wouldn't cause this as it's only an auxiliary one). Plugged the computer in and it showed no faults.

All I can do is wait and see if it does it again. 2017 4.4 SDV8 Autobiography in black
2018 D300 SE Velar in champagne
Spiffing wheel centre caps available

It connects to the main battery when needed and if it's flat it will drag down the main battery...... It costs noting to check the voltage on it....! Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

the aux battery [or capacitor if fitted] is mainly used to supplement the main battery in the stop/start situation..

if its flat or disconnected then the stop/start will not function..

some earlier tdv8 FF's used both batterys..

its all in the WM. ... - .- -.




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