Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
Replacement AGM battery
Yesterday after being parked for four days my battery was down to 10.5 V (cig voltmeter reading). Although it barely managed to start the engine I think it might be time for a new battery before the temps drop to permanent subzero.
I thought about fitting an AGM battery as LR and other brands now do. I read that an AGM battery must not be charged with more than 14.8V. I remember my D3 sometimes charging with over 15V. I know that the D4 is somewhat different so could this be a problem or are there any changes to be done in the CCF regarding battery type? Also how about fitting a battery with higher capacity than the original one, could this be a problem with the D4s high tech battery system? Life in the slow lane
17th Jan 2014 8:03 am
stick
Member Since: 13 Jan 2010
Location: hants
Posts: 604
I know that you can put an AGM on but does anyone know how to tell the car it has a different battery?d4 HSE
17th Jan 2014 5:03 pm
D4mation
Member Since: 29 Jul 2011
Location: Ruralshire
Posts: 593
My cig voltmeter reads 15v and I have had an AGM battery from new.MY12 D4 HSE Ipanema Sand
18th Jan 2014 12:33 am
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
You are correct that AGM batteries are less forgiving when it comes to charging voltage even though they store energy quicker. When they first became mass-market products the manufactures acknowledged that ideally they needed a little more voltage than traditional types (nominally 14.7v rather than 14.4v). As with everything the nominal voltage is just that as temperature (and in extremist pressure altitude) makes quite a difference too. Quite a few smart chargers changed or introduced specific AGM charging strategies.
As time has progressed they have become less sensitive to nominal voltage but they do not appreciate the large voltages that could be tolerated by traditional batteries. Given their key strengths they became essential for the world of stop-start and ECM controlled charging strategies have become very clever and totally dynamic.
The D4 charging system is very different to the D3 and it also varies over the model years, CCF settings, software loads and BMS. By MY12 you effectively have most of a stop-start system installed, by MY13 it is a reasonably mature but not active stop-start system and by MY14 it is a fully functional stop-start. Along the way you have more and more energy recovery being used to reduce alternator load and therby reduce emissions. The earlier years of D4 had a few issues with the BMS and the programming and some owners were plagued by 'low battery' messages. I presume LR would have gone live with stop-start earlier if things had gone better.
As for the car settings the lengthy explanation above gives you an idea that the answer is 'it depends'. The CCF has an entry for the type and capacity of the battery installed so the ECM can adopt the correct stratergy. For example my MY13 D4 with an AGM battery has the following CCF entry at 0x12:
Quote:
H8HD 90Ah 950 Cold Cranking Ampere
On top of this setting you have the BMS revision and ECM version playing their part. The BMS is supposed to be reset when a new battery is installed so it can re-learn the capacity and discharge rate. As for voltages seen when driving I typically get less than 13v. When I take my foot off the gas the energy recovery kicks in and demands more from the alternator giving voltages nearer to 14v. Of course, with the new charging strategy the ECM is not trying to achieve a full charge as the last few % takes a lot of power, so the system keeps the battery a bit below it max capacity. I never get anything like the charging voltages seen on the D3 so this should give the AGM battery an extended life. I still use a Ctek charger to provide conditioning charges each season to keep the battery in tip-top health.
Drivesafe will be able to give more of an insight into battery and charging developments in the last 2 years as the pace of change has been remarkable.
Hope this helps.Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 13 Jan 2010
Location: hants
Posts: 604
Thank you Robbie for the description.
As I have a MY10 and have put an AGM on without any problems, it sounds like I would be best to leave the BMS alone, so the new battery's a secret!d4 HSE
18th Jan 2014 6:17 pm
viethson
Member Since: 13 Jan 2009
Location: Bavaria
Posts: 136
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