Jaguar Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
168 Posts
Discussion Starter #1
Hi all. I have a Icarsoft LR v2.0

I have recently changed my alternator (about 2 weeks ago) I made sure my battery was fully charged before I reconnected it and it was off the car for four days.
All seems ok and the car is running well. Someone has told me that when the battery is disconnected the BMS unit on the neg terminal looses its stored information and I need to reset it or the replacement alternator will burn itself out. I wasn't worried about this as I also read that the BMS learns all the settings as the car is used daily.
First off, if I do need to reset the BMS, will my LR V2.0 do the job or will I need someone with some other equipment to do it? If it will can someone let me know how I go about it please?
Thanks. Steve
 

·
Registered
2010 XFR Ultimate Black
Joined
·
1,410 Posts
There’s a BMS option on the iCarsoft, haven’t used it as of yet, but the option is there
 

·
Administrator
Joined
·
28,196 Posts
As I understand it, it will reset itself in a couple of days.
 

·
Registered
Joined
·
861 Posts
Both the above replies are correct. The icarsoft will reset the BMS or it will do it itself over time.
 

·
Registered
Joined
·
168 Posts
Discussion Starter #5
Thanks for the replies. I was under the impression too that it would reset itself after some uses but I've had a communication with someone who had changed his alternator and it failed again seven weeks after it was fitted. The mechanic who changed it again said the reason it failed was due to the BMS not being reset.

His backup info on this was that "If you disconnected the battery the BMS loses its memory and doesn't know how much charge your battery has. This in turn makes it constantly charge the battery." He goes on: "These have smart alternators"
"When you brake they charge when you accelerate they stop charging and when your cruising they only charge at 13v for systems. If you don't do the BMS it just charges at 14.4v+ constantly"
As I've just changed my alternator I thought I'd just come on to confirm either his opinion, or mine! I'm thinking that if the alternator was over charging wouldn't something come up on the dash as a fault? And would it wait for seven weeks before it failed?
 

·
Registered
Joined
·
1,673 Posts
"These have smart alternators"
"When you brake they charge when you accelerate they stop charging and when your cruising they only charge at 13v for systems.
Really???? My car likes eating fruit, would you believe that too? So, percentage wise of a motorway journey, of say 100 miles, how much would that be braking? 1% at most? And cruising, say 90%? With the load on the electrical system of average systems running I'd guess at 40 amps, how long would your battery last before it was flat due to lack of charge....... :rolleyes:
 
  • Like
Reactions: FCS and Gav

·
Registered
Joined
·
168 Posts
Discussion Starter #7
Yes, quite. It doesn't stack up at all. I had a regulator break down on my 97 XK and it sent 20 volts into all the modules causing all sorts of problems, and it didn't take weeks to have an affect. I think when an alternator fails, it usually takes immediate affect!
I do remember that somewhere I read that the BMS learns its roll over a couple of days of use and that it was more than a good idea to make sure the battery was fully charged before fitting it. The thing is, changing an alternator on our XFs is not a simple operation and I didn't fancy running about while the alternator fried itself only to have to do it all again.
So, not true I think and we all should beware of the mechanics who "pull the wool" so to speak by making it up as they go along. Thanks for all the help.
 

·
Administrator
Joined
·
28,196 Posts
No way will a BMS "learning" a new battery or resetting itself cause a healthy alternator to fail.
 

·
Registered
Joined
·
3,693 Posts
No, I suggest his mechanic didn't really know what he was talking about and just used it as an excuse. I'd suggest probably to cover up something he'd done wrong, or using second hand/unknown parts.

The BMS will constantly relearn and readjust itself and certainly won't cause an alternator failure.
 

·
Registered
Joined
·
3,580 Posts
+1!
 

·
Registered
Joined
·
1 Posts
Morning Ive just jump started my mates car of my xf 3.0 2012 and now the battery not charging warning is on, just to say, my engine was off
 

·
Registered
Joined
·
168 Posts
Discussion Starter #13
If you battery isn't charging that would be why your battery was flat in the first place! There's no point in jump starting a car if the battery on that car is flat. I suggest you charge the battery then have a load test done on the battery to find out if its any good. If its no good buy another and make sure its fully charged before you fit it. If the warning is still there then test the alternator. If you don't get anything from the alternator, buy one of those as well. Good luck.
 

·
Registered
Joined
·
10,658 Posts
Morning Ive just jump started my mates car of my xf 3.0 2012 and now the battery not charging warning is on, just to say, my engine was off
Check all connections for tightness but sounds like your alternator has failed :(
 

·
Registered
Joined
·
19,092 Posts
Morning Ive just jump started my mates car of my xf 3.0 2012 and now the battery not charging warning is on, just to say, my engine was off
Assuming the jump cables were connected correctly and you didn't accidentally create a short by touching the clips there should be no reason why this would adversely affect your car . . . unless the battery was on its way out anyway. Recently, I have had to do the same for my wife's car during the recent cold snap (new battery now bought and fitted) although I did keep mine running.
Try disconnecting yours (negative lead). Touch that to the positive terminal and reconnect. Otherwise, if the battery is still the original, a new battery is a starting point before looking at the more expensive possibility of a new alternator.

@stevexk I think the OP was starting his mates car, not the other way round.
 

·
Registered
Joined
·
168 Posts
Discussion Starter #16
OBC John
"I think the OP was starting his mates car, not the other way round."

Teach me to read more carefully! He may have performed a load test on his own battery by jump starting another car. Best to charge it off the car and start again after fitting it. It may be that his battery was on the brink of failure and the jump start showed it up though I suspect his car still starts and runs.
May be a good idea to just put a meter over the battery terminals to see exactly what the battery is doing in the way of volts.
These XFs have really sensitive electric systems. I personally wouldn't jump start another car from mine. These starter packs work quite well but some have had problems after using them. Just about all the car dealers use them though.
 

·
Registered
Joined
·
376 Posts
Check the small BMS wire on the battery, this is also a fuselink, if this is loose or blown the warning light will come on. The other place to look is the junction box near the battery, this contains mega fuses, you might have blown one!
 
1 - 17 of 17 Posts
Top