Weird indications of impending battery failure

The other day the wife discovered that the front passenger electric window would not operate. Perhaps it’s the rocker switch thought I, but then it wouldn’t work from the driver’s side window control panel either. I’ll just check the others I thought. So the passenger side rear window won’t work from the drivers control panel either. Perhaps it’s a fuse or a relay me thinks. So then I try the drivers side rear window from my control panel, and low and behold, both rear windows go down ! Now I am confused. Happily, both the rear windows went up again upon using the rear left window up command from the driver’s panel.
Having returned home I thought I would investigate further. So I turn on the ignition to start the car and the windscreen wipers start operating all by themselves ! Before you ask, no I had not inadvertently switched them on. In fact I had to switch the wipers on, and then off, in order to stop them from working. The window situation was still the same although the driver’s window worked just fine. Additionally, when the front passenger door was opened with the engine running, the warning on the dashboard said that the driver’s door was open.
Being thoroughly confused by this time, and dreading the thought of the cost of having all the electronics checked over at the garage (the CT is due next month), I sought information from the internet ‘oracle’.

Happily, I found a YouTube explanation by a chap familiar with our make and model (Jag X308) who said that if you have a problem with the car, and you can’t see what has dropped off or is broken, then it is the battery. Checking the terminal voltage revealed only 11.6 volts despite the battery having had an overnight trickle charge a couple of days previously. With all this Covid business the car spends days on end without turning a wheel, and the car alarm and clock tend to drain the battery all the time of course, and with only then making short trips to the supermarket (there’s nowhere else to go is there), the 8km journey isn’t enough to put back into the battery what is taken out by starting the car on a cold day, especially when the heated seats are on as well as the headlights in this seasonally dismal weather.
So, I order and fit the biggest battery I can find (100AH) and all the problems with the windows and other electronics immediately go away.
I have to admit that in all my motoring years, which includes nursing along some real old crocks at times, it’s the first time that I have ever been alerted to impending battery failure by weird operating faults with electric windows.
All is just fine now, but I thought I would relate the tale in case anyone else might experience a similar situation.


Interesting, the electric window driver side on my 308 slides down ok but only comes up a few inches at a time so I need to push the button six or so times to close it. It used to be intermittent a few years back but all the time. I’m assuming it’s the motor.
Over the past eighteen months I had been getting messages on the screen saying that the ESP wasn’t working or various other spurious messages which made no sense as the car drove normally. About the same time the Stop - Start function of the engine stopped kicking in .
About a month ago I had to take the car in for new tyres , I explained the other problems to him and he immediately told me that the battery was the cause. He fitted a new battery and, hey presto everything works normally except the window which must have an indépendant fault.

The non functioning stop/start is usually a indication that the battery is on it’s way out, if the car is still getting a long enough journey to fully charge the battery and the stop/start still will not work, most of the times we would change the battery and it would start working again.
It usually was a defective plate in the battery and because the batteries have a higher capacity because of the stop/start then it stops working first.
I have seen 3-6 month old cars getting their batteries replaced by dealers.

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Be careful of just getting the biggest battery you can find and putting in in a modern car - increasingly the battery is not just connected to the alternator and left to its own devices but goes via a “charge manager” as part of the overall emissions strategy. This might not always be best for the battery though as it might wind up chronically undercharged to save 0.01mpg.

We’re not quite  at the stage of “smart” car batteries with a serial number and manufacturers ID, forcing you to buy a branded item but we’re close - the beemer has to have a new battery “coded” (i.e the car’s management system told that there is a new battery, what its chemistry is and what its capacity is).

True, seen a few BMW’S and Mercedes with boiled/buckled plate batteries.

It cost 300 quid to replace my wife’s BMW battery last month. Except in hybrids I think this start stop stuff is ridiculous. It also causes a dangerous lag with DSG boxes. For example at roundabouts and T junctions.

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The plates are wafer thin these days.

I feel your pain, we have a new Seat Alhambra with dsg + stop/start and it makes junctions and roundabouts a lottery at times, " I can see a car coming but I have plenty of time, FFS come on start and move you ba*****", or you go to move and it cuts out just as you go to pull away :face_with_symbols_over_mouth:
Forgot about the collision detection radar at the front that does not like the heavy metal plates they use to cover work at roadworks, twice it has thought the metal plates were a car we were going to hit, slamming on the brakes in an emergancy stop, just about gave us a heart attack.

I have experience of two implementations - BMW and Mazda.

The driving experience in the Mazda is very good, it is pretty unobtrusive, cuts the engine cleanly and restarts in a heartbeat. Given that the “signal” to restart the engine is pressing the clutch power is always there when you are lifting the clutch again to move off.

The BMW is good but not as seamless, possibly because the car is an auto so if you are stopped with your foot on the brake, but still in drive there is little time to get the engine going again before your foot is on the accelerator and want power - it has caught me a couple of times as I wanted to move off almost as it was deciding to kill the engine and, yes, that moments hesitation could be embarrassing. The engine also takes fractionally, but noticeably, longer than the Mazda’s to start running again. Funnily enough the switch to disable it is much more accessible on the BMW than on the Mazda.

Stop-start puts an enormous load on the battery though, loads of 50-80A on the battery while stopped but with fans, lights, infotainment etc running are quite plausible. You need something more akin to a deep-cycle battery (and it is why you do need to put the more expensive batteries in, if you have a car with stop-start).

Ouch - was that main dealer or independent?

For mine the battery needs to be 92-95A, 800A cranking current, “stop-start” construction. Just the battery is nearly £300 if you go for something like a Bosch, though maybe down to £200 for a lesser known brand. At the other end of the scale I found one Exide battery listed as suitable which is £540 retail :crazy_face:

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With DSG you don’t have a clutch pedal and it does not have a torque converter like an automatic box.

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The first time I encountered stop start was in a Hertz Passat in Brussels in 1981 (I’m getting more conscious every day that I’m starting to sound like an "I remember when… old fart :roll_eyes:). It worked OK, was clutch pedal operated but I guess emissions/consumption didn’t justify the cost and the standard batteries and starter motors at the time weren’t up to it.

My wife’s BM is clutch activated and is quite responsive. I’m just not sure all that churning saves that much, maybe on the official test cycle it does. We’ve a C350e PHEV which does start stop very well. First of all it has a traditional slushbox auto (albeit 7 speed) and secondly it can kick off in electric and start the engine on the move seamlessly. That all works very well.

The problem child is our Tiguan. It’s a DSG which is excellent 99% of the time but pulling away at roundabouts and T or Y junctions there’s a bit of lag while the clutches sort themselves out. It’s 240BHP so when you want to nip out you expect it to do so but the slight DSG lag can be annoying. Couple that with a start stop hiccup and it’s actually alarming. Especially if you’re dragging a trailer :flushed:

I’m familiar with deep cycle batteries. My boat had two to run lights etc. but a “normal” battery to give the short, sharp whack to start the diesel. The problem (I guess) with the big mother in Noelle’s (my wife) BM is that it’s trying to do both. We replaced it with a premium brand, Bosch probably, and their premium grade of battery but we had it fitted by an independent.

The battery in the back of the Tiguan is equally ginormous. Hopefully I’ll have moved her on before that needs replacement.

No worries there Paul. The car is 23 years old and needs at least a 90AH so the 100 I bought should be fine. I managed to find a Bosch online for €130 including home delivery which I thought was fairly reasonable as batteries go.

Incidentally, I have experienced the stop/start technology in some rental cars we have had and find it to be a nuisance. At the first opportunity I go through the vehicle handbook and find out how to turn it off, as well as turning off any other extraneous ‘automatic’ things such as windscreen wipers and lighting systems.
The new fangled thing that annoys me the most is when there is no ignition key at all, but just a key fob that allows entry to, and starting of the car when the car senses the proximity of the fob.
I like to check that the doors really are locked ( especially on a rental car with which one is unfamiliar), so one has to lock the car, put the proximity fob down on the kerb at least 15 feet away, and then go back and check that the doors are properly locked, before going back to retrieve the fob from wherever one had to place it.

Would you prefer a hole in the floor that you put your feet through and just run? So much more traditional than modern cars with engines!

I am not sure you will cope with a self driving Tesla if stop/start and auto-wipers are a concern. In 10 years standard cars will be very very different in terms of automation!

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I’m with Mat here - I find the rain sensor works well on both of our cars and the BMW’s auto full beam is, similarly, implemented well.

The stop-start on the Mazda simply does not impact normal driving, the BMW’s does occasionally verge on annoying but, as I said above, I think this is more to do with the car having automatic transmission and so less “input state” that it can monitor, but it has a nice, accessible and dedicated button for turning it off.

I prefer the BMW’s keyless entry though as you have to “do something” (either touch a sensor in the door handle or use the fob) to lock it - we do find ourselves fairly constantly asking “is the car locked?” with the Mazda. But, if you’ve walked away and aren’t sure it’s not necessary to go back to the car as the fob can be used to lock it in the “normal” remote-control manner.

The BMW is a nice car - I bought it to see why everyone raves about them and I can certainly see the appeal. That said I do find myself wondering whether to move on before it starts to needs repairs&replacements rather than just routine maintenance because it is going to get expensive when it does. Mind you no car is immune from big bills - the Mazda just needed a new turbo and it is not yet 5 years old, the Saab we had before that also blew its turbo (but at least it had the decency to wait 11 years).

I don’t have a problem with technology on our cars, auto lights, auto wipers, , keyless entry, distance control cruise on the Jaguar XFR and BMW 760Li, but the stop start when combined with DSG is just too much of a lottery when at junctions and roundabouts.
It is not confined to the Alhambra as I have driven quite a few VAG cars that have that combination and it just is not consistent in its use.

I used to be able to lock our BMW from my phone which was quite reassuring as I often would wonder the same question but be sat in a restaurant or cinema etc at the time.

Yes, I have the PC setup, not the phone at the moment as I’ve never needed it. It’s a bit disconcerting that the car is permanently connected to the internet and, no doubt, regularly phoning the mother ship.

"You should have seen the overtaking manoeuvre he did yesterday, that and the parallel parking he attempted, three goes and then he basically abandoned it and don’t get me started on when he pulled out from that junction and cut up that L driver I shut my headlights I couldn’t look " :yum::grin::laughing:


Sorry Mat, but I am of the old school that believes that the driver should be capable of noticing when it starts to rain, or visibility becomes poor, and also capable of operating the relevant manual switch. Even electric windows are a pain when one only wishes to open it half an inch and the darn thing insists on going all the way down on a wet day.
A great deal of this automation is just a gimmick. More things to go wrong and very expensive to repair.
We seem to have already established during this discussion that stop/start requires a special battery that is at least double the price of a standard one. The objective being to save half a cup of fuel during the journey. To my mind I feel perfectly capable of deciding when the engine should be running or not, and I can buy an awful lot of half cups of fuel for the difference in cost of battery replacement. If one day I am forced to have the stop/start technology, then I shall simply disable it and fit a cheaper standard battery when replacement time comes around.

I expect that self driving cars will have their uses such as on a well maintained motorway where the unusual is more predictable. There is however no substitute for the human brain that can instantly determine the difference between a small child and a dog, and thus decide whether it is worth it to swerve into the ditch (risking occupant injury) in order to avoid the ‘obstruction’ ahead.


I second that, I still regret the withdrawal of the starting crank handle on my Model-T!