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Discussion Starter · #1 ·
Hi everyone, first post since joining, up until now the XF has been faultless. So my first question is.

Will the Alternator stop charging if you replace the battery and do not perform a BMS reset ?

Sounds like a simple question but after a lot of reading over the past week I have not found an answer.

My issue, I had Halfords replace my large battery last week, for no reason other than it was the original, car is a 2012 XF 2.2d. (with stop/start) 75000 miles. I enquire about resetting the BMS, "not necessary", the man says. The following day I get the "Battery not being charged" message displayed on the dash.
So I speak to Halfords, they send someone out who replaces the new battery with another new battery. I enquire about BMS resetting, "no need", he says. Warning light now off..... following day the warning is back on.

I check the output from the alternator, no output, the B+ terminal just shows battery voltage irrespective of engine rpm.

"Well I never did, imagine that, replace battery one day, the alternator packs up the following day, what a coincidence".

But then I think "Nah can't be a coincidence".

"I wonder if the BMS must be reset to start the alternator charging again ?" Lots of forum reading later, no answer.

My dealer says bring the car up for a Diagnostic check, it's only £150 and carefully avoids answering my question regarding the alternator output.
So it's booked in Thursday, I guess I'll get my answer eventually.
 

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What you need is a friendly and local FM with an iCarsoft LR v2 to perform said battery module reset and see if it cures the problem. Where are you located?
Oh, welcome to the forum!
 
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Hi Fred, welcome to the forum and sorry to hear of your woes..

The BMS does not 'need' to be reset.. though there are differing opinions of whether it's better to or it's not needed..

Nobody that I can recall has ever linked not resetting the BMS to having a 'battery not charging' warning straight/soon after...
 
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Discussion Starter · #4 ·
Thanks for the welcome guys. I'm in Telford, Shropshire. Could it be a coincidence ? ? ? I have read a fair few posts on the subject but I don't think anyone has ever asked the question I am asking. I tried to book the car into my local independent but there's a 2 week wait.

I understand the principal of a BMS system but I don't see the logic of switching off the alternator just because the ecm controlling the system has not been reset ? So maybe it is a coincidence ?
Wish I hadn't bothered changing the battery now :) just seemed like a good idea at the time.

Hope it's not a new alternator as I believe the bill will be around £800. :-(
 

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Fred do you have small battery ? If so check the voltage of this too. A healthy battery should be high 12’s
a low one 12.3V
 

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Very useful!
 

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Perhaps the fine wire that connects to the BMS module on the battery negative terminal been broken or left disconnected. I've read elsewhere that they're quite fragile.
 

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Discussion Starter · #9 ·
Thanks johnw777 that is interesting. Especially this bit.

If the fusible link becomes an open circuit, the RJB would detect communication loss with the BMS. The battery warning lamp would be shown in the instrument cluster message center, the system would default to a fixed charging voltage of 13.7 volts and a DTC would be set.

The voltage at the B+ terminal of the alternator is within 0.1 volts of the voltage measured across the battery terminals, so battery voltage allowing for 0.1 volts of drop across the circuit, ie. I'm measuring battery voltage.

The small battery is interesting in that it shows close to 13 volts when the car has been switched off for several hours but will show 14 volts with the engine at idle speed ? ? ? and yet the alternator B+ terminal will show battery voltage !

I'm preparing myself for a new alternator.
 

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Hi Fred another Fred here. I find it odd that you have 13 volts on the small battery after several hours. I presume you measured it across it's terminals. My first thought would be a reset as OBCjohn say's. The BMS can be a pain in the arse.
I find it hard to believe that places like Halfords don't reset the thing when fitting a new battery and do a full diagnostic on the charging system as we all know and they should the problems encounted by changing batteries on these cars.
If you havn't got one I would buy an icarsoft v2 they are a godsend with these cars.
 

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Hi Fred,
do mean, that one day you measured 13V across the battery terminals (small battery) while engine was running and the other day you measured 14V?
If you measure 14,0..14,4V across the terminals of the small (auxiliary) battery with a running engine, the alternator is working.
I just changed both batteries too. My Jag lost the ability of the central locking function. I reset the BMS via the icarsoft CRPro. But I didn't check the battery voltage and charging function
before or after the exchange. But I hadn't had any warnings regarding the batteries on the dash.
It might be a coincidence and your alternator is really defective. But I wouldn't believe that. I would check the BMS, the wiring and the control units via SDD.
 

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Discussion Starter · #12 ·
The car is now at my local dealer, Hatfields Jaguar in Shrewsbury, we drove the 11 miles there, with no message on the dash. Typical ! Oh well, all will become clear tomorrow.

The small battery had me very confused. When I got home from work, a 7 mile trip, the message "WARNING Battery not being charged" was displayed in between the speedo and rev counter, it had been on the whole journey. I left the engine running got my multi meter and measured the voltage across the terminals of the large battery, it was 12.2 volts. I measured the voltage across the small battery, it was 14.10 volts, strange ???
I lifted the bonnet and checked the voltage at the B+ terminal and the power steering pump case, it was 12.10 volts. I rechecked them, same results.
Switched the car off and went inside very confused. Came out half an hour later the large battery was 12.2 volts and the small battery was 13.10.
I really don't understand why the small battery was showing 14.10 volts with apparently no output from the alternator.

?
 

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An answer to the question about why the small battery voltage suggests the alternator is working while that of the large battery suggests the opposite may be found in that document posted by @johnw777 in post #6.

Calibration
Periodically the BMS module will instigate a self-calibration routine. To self-calibrate, the BMS first charges the battery to its full condition. Once the battery is fully charged, the BMS will discharge the battery to approximately 75% of its full state of charge, but never lower than 12.2 V. The time taken to complete this part of the routine is dependent on the electrical load on the vehicle and the length of time the vehicle is used.
 
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Discussion Starter · #14 ·
Interesting, Would the BMS commence a calibration routine at idle speed ? If it would I can imagine a scenario where you could be confused / caught out while measuring voltage and current across the affected circuits.
Interesting.
 

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Discussion Starter · #15 ·
The results are in for those interested.

The technicians report was - Investigated battery not charging fault on dash - checked for DTC's, PCM P0620-00 Generator Control Circuit, checked charge rate of alternator and found no charge coming out of alternator, checked LIN wire to alternator 7.4v - OK. Checked battery monitoring wire 12v - OK. Requires new alternator.

So, £225.00 for diagnostic, £366.54 for C2Z31658E Alternator plus £118.31 VAT comes to £709.85

In 5 years of ownership this is the first issue, can't complain really. They did put the car through the wash. :)

Thank you to those who took the time to give advice.

It is annoying though that the likes of Halfords don't feel it is necessary to reset the BMS, after all it's there for a reason with stop / start vehicles.
 

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The results are in for those interested.

The technicians report was - Investigated battery not charging fault on dash - checked for DTC's, PCM P0620-00 Generator Control Circuit, checked charge rate of alternator and found no charge coming out of alternator, checked LIN wire to alternator 7.4v - OK. Checked battery monitoring wire 12v - OK. Requires new alternator.

So, £225.00 for diagnostic, £366.54 for C2Z31658E Alternator plus £118.31 VAT comes to £709.85

In 5 years of ownership this is the first issue, can't complain really. They did put the car through the wash. :)

Thank you to those who took the time to give advice.

It is annoying though that the likes of Halfords don't feel it is necessary to reset the BMS, after all it's there for a reason with stop / start vehicles.
Thanks for letting us know the outcome. £700 lighter but at least you have a fault-free Jag again.
 

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Glad you got an answer Fred, even though it was fairly expensive, thanks for coming back with the result.
 

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It's certainly possible that the alternator was on it's last legs, but not yet done for as the old battery wasn't accepting much in the way of current anyway.

Now you've had a new battery fitted, it's stressed the alternator to destruction.
 

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I'm currently struggling with self-diagnosis of the same "Battery not charging" dash message. At rest, the main battery reads whatever is left in it (11.9v in this instance), and the small Stop/Start battery reads 13.1v or thereabouts.

With the engine running, the Stop/Start battery reads 14.3v but the main battery's reading doesn't change. If the alternator is defective, what causes the voltage increase in the Stop/Start battery when the engine is running?

Perhaps coincidentally, but I'm not so sure, from the start of the journey until around when the dash went red with the message (10-15 miles later), there had been a faint whining noise much like a worn bearing, matching engine speed in pitch variation and most noticeable at or near idle revolutions. From then, any trace of that noise has been entirely absent.
 

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Sounds very, very much like this post from earlier in the thread corned:
The car is now at my local dealer, Hatfields Jaguar in Shrewsbury, we drove the 11 miles there, with no message on the dash. Typical ! Oh well, all will become clear tomorrow.

The small battery had me very confused. When I got home from work, a 7 mile trip, the message "WARNING Battery not being charged" was displayed in between the speedo and rev counter, it had been on the whole journey. I left the engine running got my multi meter and measured the voltage across the terminals of the large battery, it was 12.2 volts. I measured the voltage across the small battery, it was 14.10 volts, strange ???
I lifted the bonnet and checked the voltage at the B+ terminal and the power steering pump case, it was 12.10 volts. I rechecked them, same results.
Switched the car off and went inside very confused. Came out half an hour later the large battery was 12.2 volts and the small battery was 13.10.
I really don't understand why the small battery was showing 14.10 volts with apparently no output from the alternator.

?
 
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