Battery advice needed

Technical Advice, Faults and How-To Information.
Post Reply
Millwheel
Posts: 88
Joined: Fri Dec 21, 2018 9:08 pm

Post by Millwheel »

I’ve started getting a low battery warning when starting my V6 340 2016 coupe after leaving the car overnight.
The car starts fine though. The dealer checked the battery circuit, says the battery is good, and they can’t find anything wrong. They reset the battery control module.

Checking today, I had 12.11 volts on the battery with the low battery warning on the screen (engine off). From the manufacturer data this shows a level of battery charge of around 30%. I then drove two hours at speeds up to 70mph. I checked the battery voltage again with the engine off and found 12.88 volts which would indicate a fully charged battery. I then connected my CTEK MXS7.0 smart charger and it showed the half-charged symbol, and two hours later was still not at the three quarter charged symbol.

My challenge is understanding all this. Do I actually need a new battery? Or is this a calibration problem? As the battery is four years old it might not be a bad idea to replace it anyway, but it’s an expensive decision if it s still effective. If it’s not the battery, what could drain the battery by 70% overnight that I’m not noticing? And why does the CTEK charger think the battery is only half charged when it appears to be fully charged? Is this anomalous battery behaviour indicating an internal fault in the battery? Beats me.

All suggestions welcome.

User avatar
scm
Posts: 5032
Joined: Fri Aug 10, 2018 11:39 am
Location: Southampton, UK

Post by scm »

I'd be inclined to fully charge the battery, even doing a recondition phase on it, and take it from there. If everything else is apparently working it doesn't sound as if a module is "stuck on". I had a recent flat battery, but that was predeced by a n "SOS System not available" message which was persistent (I occasionally get it after leaving the car for three days but it clears when I start the engine) and it stopped recording my journeys. When the flat battery was recharged all the modules started behaving and I've had no recurrence.

A further thought on the battery vciltage, do you have the second battery for the stop/start system? Is so that might give a high voltage reading even if the main battery is low. I'd trust CTEK over a multimeter regarding the battery health.

On the US forum, the advice for resetting everything is to disconnect the battery and short the leads together - they have noticed that if the OBD socket is used and not disconnected properly it will run the battery down, I think the symptom is the Park or Hazard light doesn't go out (can't recall which).
MY18 F-Type V8 R AWD in Glacier White
Lots of leather and toys, and loads of noise!
User avatar
Dan_Veluwe
Posts: 1180
Joined: Wed May 02, 2018 5:30 pm
Location: Dutch Highlands [Veluwe]

Post by Dan_Veluwe »

I have been driving around with a voltage meter plugged into the dash outlet. This gives wonderous readings. It can go down to 11 volts and up to 14,6 volts for no obvious reason. The first mechanic told me that several electronic controls do different things at certain moments that let the voltage jump about. Also the outlet seems not to be stabelised and doesn't give the direct battery voltage.
Range Rover P400e autobiography Loire Blue (2019) :P
Mazda__MX30_RED___2021_ BEV
FT jag _P300 _Ultra Bleu, 2018 ___________SOLD :(
D5 lr__SD4__Corris Grey, Blck roof, 2018_SOLD :roll:
FP Jag – 25t _Loire Blue ,2020 ____________SOLD :|
Millwheel
Posts: 88
Joined: Fri Dec 21, 2018 9:08 pm

Post by Millwheel »

I bought a battery analyser (about 10% of the cost of a new battery), and after some trials I got a consistent reading of battery health of about 48%, with a “replace” recommendation from the tool. It charges fine though but quickly loses its voltage. Also bought a voltage meter for the power socket which mostly showed a voltage of 11.3v, seems low with the engine running, with occasional jumps to 13v or so. (why?) Analyser says charging circuit fine though, and there are no warnings on the car display. Tried the reconditioning function of the CTEK charger but there seemed to be no change in readings; unclear if it works with AGM batteries anyway. Final result is that I’ve decided to buy a new battery. As the car is still under extended warranty I’m going with another Jag battery despite the £100 premium over a branded Varta, and as the new battery requires a battery management system reset it will be done by the dealer. Got a sort of deal from them which helps a little. Checking the car history shows that it probably spent about four months in stock before it was originally sold and it had off road periods at various times, which based on prior experience probably means the battery went fully flat at least twice which would have not helped its long term life. Also the battery was made in Italy which really boosts my confidence in its reliability.

It does seem strange that these complex computers on wheels still rely on a box full of lead and acid which dates back over a hundred years. If I was keeping the car for the future I think I’d go lithium ion, as it is with some simple TLC the new one should do at least five years.
User avatar
scm
Posts: 5032
Joined: Fri Aug 10, 2018 11:39 am
Location: Southampton, UK

Post by scm »

Some folks on the US forum have changed to Li-on batteries and had no problems. Main benefit it seems is to save (a lot of!) weight.
Regarding CTEK, the ones designed to cope with AGM have a specific AGM mode you can select (e.g MXS 5.0)
MY18 F-Type V8 R AWD in Glacier White
Lots of leather and toys, and loads of noise!
User avatar
Tel
Posts: 2383
Joined: Sat Apr 19, 2014 7:26 pm
Location: Deepest, Darkest, Darzet.

Post by Tel »

Millwheel wrote: Sun Jul 07, 2019 10:02 pm I’ve started getting a low battery warning when starting my V6 340 2016 coupe after leaving the car overnight.
The car starts fine though. The dealer checked the battery circuit, says the battery is good, and they can’t find anything wrong. They reset the battery control module.

Checking today, I had 12.11 volts on the battery with the low battery warning on the screen (engine off). From the manufacturer data this shows a level of battery charge of around 30%. I then drove two hours at speeds up to 70mph. I checked the battery voltage again with the engine off and found 12.88 volts which would indicate a fully charged battery. I then connected my CTEK MXS7.0 smart charger and it showed the half-charged symbol, and two hours later was still not at the three quarter charged symbol.

My challenge is understanding all this. Do I actually need a new battery? Or is this a calibration problem? As the battery is four years old it might not be a bad idea to replace it anyway, but it’s an expensive decision if it s still effective. If it’s not the battery, what could drain the battery by 70% overnight that I’m not noticing? And why does the CTEK charger think the battery is only half charged when it appears to be fully charged? Is this anomalous battery behaviour indicating an internal fault in the battery? Beats me.

All suggestions welcome.



ALWAYS CARRY A SMALL ADJUSTABLE SPANNER IN THE CAR...

I can explain the above in great detail, and there's many factors that can give very false readings including the CTEK. But to begin with, let's start with the basic routine of a "Reboot"

1. Disconnect the positive terminal (with the aforementioned adjustable spanner) from the battery for 10-60 seconds. This will reset many of the subsystems.
2. Reconnect above, makes sure both terminals are tight
3. Ensure the connections from the CTEK are tight
4. Leave the CTEK connected whenever you can, but certainly for a couple of evenings
5. Take the car for a run and report back
2016MY V8R IRR
ITG Maxogen Cold air intake kit
Billet OBD lock
Forged lightweight Blades
Full custom Xpel Ultimate PPF wrap
Piano Black badges
17mm MST Hubcentrics
Smarttop remote
Black exhaust tips
Porterfield RS-4 Carbon Kevlar pads
Mich PS4S's
+ more 💩
Millwheel
Posts: 88
Joined: Fri Dec 21, 2018 9:08 pm

Post by Millwheel »

Did that before my last post, including 48 hours on AGM setting after the reset. Ah well I’m resigned to the replacement. Looked up a Lithium battery but fell over at the price. Roll on the supercapacitor!
davyrobo
Posts: 11
Joined: Tue Apr 26, 2016 7:19 pm

Post by davyrobo »

Hi. I am having a similar problem. Can anyone tell me if I disconnect the battery to carry out the reboot will I have to carry out any other tasks after reconnecting i.e. radio codes or will the car return to normal. Don’t want to take it to the dealer. Don’t trust them. Thanks.
User avatar
scm
Posts: 5032
Joined: Fri Aug 10, 2018 11:39 am
Location: Southampton, UK

Post by scm »

You might have to reset the windows, details should be in your manual, see "Windows - reset" in the index.
MY18 F-Type V8 R AWD in Glacier White
Lots of leather and toys, and loads of noise!
Post Reply

  • You may also be interested in...
    Replies
    Views
    Last post