Computer Reset after Battery Change

[Barryp]

Last Wednesday my 2011 RRS wouldn't start, flat battery. After a half hour on the charger it started and I drove to Galston about 45 minutes. Turned engine off and dash message comes up "Start engine immediately battery low". Rang LR assist and was given options but decided to drive to Concord Land Rover as the better option as car was running. At Concord LR battery came up OK so they wouldn't change it. (It obviously had a surface charge which they didn't test for.)
Next morning no go, so ring LR Assist again and they sent out an Allianz van with a replacement battery. Excellent service. Asked battery fitter if computer required a reset and he said probably not.
Anyway I have a GAP IID tool so did some checking on voltages and a computer reset with the following results.
New battery with no reset it charged at 14.7V, after computer reset the charge rate dropped to 14.1V. Both voltages after driving for about 20 minutes obviously with engine running. Note that the old battery charged consistently at 14.7Volts.
So clearly new battery would have been overcharging without a reset. Could explain a lot of early battery failures after replacement if no reset!
Regards
Barry

[Graeme]

14.7V is normal during periods of high charge on these engines. Driving for another 20 minutes can change the charge environment significantly, so not comparing apples with apples. I have a LED voltage indicator that shows that the voltage often fluctuatutes widely.

[Barryp]

Yes, I was using a LED indicator as well and both voltages were steady for the period of each test.
I thought it a good opportunity to test with a new battery as couldn't find anything on the web re recommended battery computer reset.
Have you tried my test before and after a reset on a new battery?
Do you have a dual battery setup which will change normal charge behaviour?
Regards
Barry

[Graeme]

Voltages can be steady whilst idling but can also drop off suddenly, depending on what charge logic the bcu is applying. In my experience with my D4, doing 2 tests 20 minutes apart would prove nothing. My vehicle always charges at high voltages soon after startup and continues for several minutes on morning starts and for much longer if cold.

I have an aux battery connected via a VSR that disconnects within about 15 seconds of the engine stopping, noting that significant power is being drawn from the starting battery in this period which drops battery voltage quite a lot for 30 seconds or so then less draw for the next few minutes.

[trevorj]

As Graeme says: 14.7 is normal at startup, gradually declining to about 13.4, after driving for a while (while engine running). But there is sometimes some variability of .2 or so for no reason obvious to me. My D4 has traxide/optima yellowtop. On recent trip (12,000km, driving most days) battery state followed this pattern above. I have cig plug LED voltmeter which shows main batt voltage continuously when the ignition is on. After overnight standing and before starting engine, typically shows 12.6 (after a full days driving the day before) which I interpret to be a good SOC. At home, when the main drops to about 12.2 (a couple of weeks standing), then I hook up the ctek via tow plug and just leave it on, sometimes for a week or more. The key thing for my peace of mind is having the cig plug LED ($10 flea bay), which I leave permanently plugged in - no more ugly surprises (although now I know how to easily jump the optima to main, probably got it all sorted anyway - thanks Tim). But , really would have been nice to have an OEM Vmeter.

[Barryp]

Guys I have a permanent cig lighter LED display and understand how the system works.
It was 14.7 volts with the new battery, fully charged and no reset and went to 14.1 volts the lower voltage immediately after the reset with no other change, engine running the whole time during reset in line with GAP recommendations. My drive comparison was after the reset to check for stability in the reading.



The GAP IID instructions say that the reset is to clear the data in the computer memory bank which is held from the old battery.

Words from the GAP instruction manual below:

"-Battery Replacement
>> This routine will reset the stored battery monitoring data.
>> Use
>> This routine is required after the battery is replaced."


Remember that the voltage from the alternator is controlled by the computer system and jumps up when you take your foot off the accelerator and it goes into "battery regeneration mode", that crazy supposedly fuel saving system on most modern cars. This would explain Graeme's comments about voltage jumping all over the place. Watch you LED voltage indicator when you back off the throttle. (Even with a fully charged battery)
Regards
Barry

[Graeme]

A couple of points...

1. I hadn't noticed reports of newly-replaced batteries failing,
2. There is no reference in my 2010 3.0 D4's handbook to visiting a dealer to have the monitor reset if the battery is replaced even though fitting a new battery is covered,
3. My observations of voltage fluctuations are generally not on closed or reduced throttle although I have noticed this at times,
4. My Faultmate MSV, a predecessor to the IID tool, does not have a function for resetting the monitor but acknowledge this is inconclusive,
5. Your voltage dropping at the time you performed the IID function could be coincidental.

However the existance of the IID function indicates that it is a standard BCU function but perhaps similar to the reset of the auto gearbox's learnt values which will be re-learnt anyway over time.

[Barryp]

Hi Graeme,
Replaced battery in my D3 with no reset and battery overcharged and boiled letting acid down into the chassis rails below. I wonder who bought my D3 after trade-in?
As you say could be coincidental but better safe than sorry.
By the way, Concorde LR service manager told me that a reset would be required after battery replacement.
Each to his own I guess.
On my initial searches on the internet I pulled up the requirement for a battery reset on Volvo, BMW and Mercedes. The lack of any LR hits was what made me explore the issue further. All of the latest generation EU cars appear to use somewhat similar systems. My BMW X5 which I bought new is 8 years old and still on the original battery (exactly the same battery as fitted to my D3). It will be getting a reset as recommended by BMW when the battery finally fails.
Regards
Barry