LR4 possible alternator issue

[BlackOmega]

So I have been chasing gremilns in my 2012 LR4 and priginally I would get a christmas tree of lights and a laundry list of error codes but the LR4 would stay running, see my thread here - https://www.landroverworld.org/threads/strange-errors-occurring-randomly-2012-lr4-hse.48890/ - while that seems to have been a ground issue and seems to be fixed, I noticed some weirdness while watching the alternator and battery and it was suggested I replace the battery (which was already replaced 2 months prior) and I did, this time to an AGM battery. Since that replacement and the fixing of the ground I noticed that the headlightlights brightened when I reversed out of the driveway. Keep in mind it has barely been a week on the new AGM battery. I then checked with the IID tool and confirmed with multimeter 12.4v at the battery while running, decreasing as it ran. So I disconnected the terminals and charged the battery to full with a charger that can handle AGM and reconnected everything and initialised it as a new battery. The IID tool picked it up at 98% charged, 14.9v (the graph was showing an obscene voltage), battery current at 6.0A, and alternator at 43.0A, so I let it run while watching the graphs (see attachments) and I saw the battery current steadily drop by an amp every minute or two until it got to 1A and held steady there. Then suddenly at 24 minutes I heard the motor sound change, almost kind of sluggish in a way and a sudden drop of ALL values but battery state of charge. Checking with a multi-meter shows the battery now at 12.4V. I did order an alternator but could this be anything else? Thanks!

 

[itsaguything]

Please remind me, was the original battery scoped to your vehicle an AGM? The charging requirements are quite distinct from a lead-acid battery and generators are tuned to each situation...
The battery's discharge rate may be managed by a BMS. Furthermore, the variable output of the generator is dependent on load and capacity.

Of course, you did the right thing by fully charging the battery, then connecting. It will take a minute for the system to learn and equalize to the new situation and your observations demonstrate that.

The section "Battery and Charging System - General Information" in the Workshop Manual is a good read. Also the section describing the spec'd battery.

 

[Rover Range]

Check the battery monitoring wire that connects to the positive battery cable.
There's a fusible link in the wire that can burn out.

 

[BlackOmega]

Check the battery monitoring wire that connects to the positive battery cable.
There's a fusible link in the wire that can burn out.

Thanks for that advice, the fusable link is still good, when the LR4 cools off the alternator puts out again and around 20 minutes in the alternaotr drops to zero, but I never get an alternator light which is weird

 

[powershift]

What brand battery did you buy?

 

[txfromwi]

My 2013 came with an AGM, I would think that the 2012 was also OEM AGM.

You are in deeper than my knowledge, but I do know that loose battery terminal connections cause cause strange things.

I note that the AGM replacement that I use from Auto Zone has tapered terminals and I have had fully tightened connections slide up the terminal until it became loose.
i was taught always to grease the terminal before installing the cable and tightening.
That might have been OK on the batteries I learned on in the '70's, but it is decidedly bad advice on the tapered terminals.
Now I leave them dry and grease it up only after everything is fully tightened.

 

[TexanRover]

I've replaced several alternators on LR3s, RRS, LR4s. The first couple were aftermarket and didn't work. I had to go with OEM options. It seems the PWM control in the OEM alternator is far more reliable and specific to these models. Maybe someone else has had better luck with aftermarket, but I will only go OEM Land Rover on alternators and starters. Hope this helps...