Showing 11.99v on my multimeter and on the '743' menu before starting in the morning. I know these cars have 'marginal' battery capacity so don't want to get caught out for the sake of the cost of a new battery but then again don't want to buy a new battery if I don't need to! 2012 TDV8 Vogue (L322)

Funny you should ask this as it was asked on the RRS forum today too.

I know it doesn't exactly answer your question, but a forum member posted the below table...



I suppose it's more a question of risk. The lower you go, the greater risk of failure. Kev

2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

That’s very helpful! 2012 TDV8 Vogue (L322)

Those look about right for FFRR.
Once started and settled down, mine shows 14.7 v

The only way to apply the posted voltages is to remove the battery from the car, charge it, then leave it a while say a day - then measure.

The problem is unlocking the car to open the bonnet 'wakes' the car up, so there are already electronics (how many ECM's do you have?!) taking power and thus lowering the voltage you see, so you won't ever see the true value.
Or
You connect a cable to the battery to enable you to check the voltage whilst the car is still asleep - but i wouldn't recommend that.

I had similar thoughts - I bought a CTEK charger due to lockdown and even after a good run I'd plug it in and it would get busy charging the battery! wow I thought, my battery must be dying!

I've since read that the 2010 onwards 4.4TDV8 has an uprated alternator and a completely different charging algorithm - such that as long as the battery has 80% charge or more it's OK.
The battery charging takes advantage of over run - slowing down events to push charge into the battery - accelerating etc it doesn't charge to avoid extra load (worse fuel economy). this is all dependent on the current state of charge and load demand of course.
So when you switch off you'll never know for sure how much above 80% charge your battery is holding ready for the restart tomorrow morning!

Thus my first comment - you'll need to take it off the car to be sure. Also explains why my CTEK can always top off the battery.

I get the usual start engine messages due to low voltage etc if I turn on the ignition after about 1 min.
So far mine has always started no problem - no hint of struggling - I recon my battery is ok - it's just the way the software is programmed and the current load as soon as you wake the beast up.

My advice is buy a CTEK charger - they have an AGM mode - I plug mine in in the boot.

Hope that helps - I felt better about mine once I realised it's programing says 80% or more is OK. Anything can be made to work if you fiddle with it long enough (and have deep pockets|)
Current cars, 2011 FF 4.4 TVD8; Audit TT 1.8T convertible.

I treat batteries as a service item on any automatic car, you can't bump start them and jump starting can be a nightmare. Even an AGM battery doesn't cost much more than a tank of fuel so if you've got even the slightest doubt or are uncertain of it's age I'd suggest replacing it.

I too agree with the comments above.

I plug my CTEK in every now and then to maintain the battery, even moreso during the winter months. I also have a little BM2 battery monitor fitted to the battery to monitor the voltage of the battery over time. It works on Bluetooth Low Energy and transmits the logging data to my phone whenever I walk near to my car.

On my old Sport I actually permanently wired my CTEK in to the vehicle. If anyone's interested, here a link: https://www.rrsport.co.uk/forum/topic55319.html Kev

2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

I have an LED voltmeter I have plugged into a cigarette lighter socket in the central glovebox. Shows between 12v and 12.2v with engine off. Between 14.3v and 15v when driving. Higher charging voltage when coldest !

Never had a starting problem. Occasionally FBH won’t complete a cycle if charge level low.

You can charge it up to 100% using a ctek if you want. With normal driving it will be down to 80% in short order.

AGM charging MY10 onwards very different to lead acid models up to MY09.

AGM warranty is 3 years.
My first one lasted 8 years and only changed it as I thought it is just a matter of time before it fails, and when it did I did not want to be stranded.

The first batch of AGMs used by JLR had several faulty ones, which appeared normal and passed garage checks but faulty cells were breaking down under load. (That’s what the man from Gaydon told me back in 2011).

Not sure what the RRP is for a genuine AGM battery. I would guess somewhere between £150 and £200.
Ideally, the battery management software needs resetting to inform car there is a new battery, as this affects how the car charges the AGM.

How old is your battery?

The genuine LR AGM battery is an Exide EK950, with a Land Rover logo on the sticker

Exide EK950 @ £116.95 https://www.tayna.co.uk/car-batteries/exide/ek950/

Genuine LR LR094642 @ £220.33 https://rimmerbros.com/Item--i-LR094642 Kev

2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

After monitoring voltages and seeing how awkward it is to physically change the battery I think for peace of mind for a dead battery one morning when I have to be somewhere I’m just going to get a Nocoboost starter battery. 2012 TDV8 Vogue (L322)