Battery 'Good' - yet not full charge..?

shaun_from_Africa

Strider590 wrote: »

This isn't true, in the 8 years I owned my Vectra the battery failed twice and each time the first signs of failure were the car starting but the dash not working at all.

A battery can start the car, but if the voltage drop during starting is too great, it'll play havoc with the electronics.

My current motor is a Focus and this is exactly the same.
Due to working away from the UK for 4-6 weeks at a time, the first time after returning that I have to use the car, the battery voltage is usually too low to unlock the doors using the remote central locking and the radio normally needs the code re-entering but without a doubt, I know that the engine will always start on the first turn of the key.

Joe_Horner

bigjl wrote: »

Cars can play up when the battery is weak.

Current Jaguars are particularly prone and the car will start but all kinds of spurious issues and fault codes will manifest themselves.

As the reply to Strider, those effects are caused by voltage drop as the starter operates - which wouldn't explain the mirror issue.

The sad thing (from the MSE point of view) is that quite often changing a battery appears to cure the issue simply because it involves disturbing connections - particularly any additional feeds attached to the main connectors. So the myth that any electrical problem like this is cured by changing the battery as a first step is maintained.

Surprisingly often, it's actually those feed connections which are at fault in the first place, and a simple clean-up is all that would have been needed. A new battery may be a cheap (debatable) first step, but 10 minutes cleaning connectors is free. Used to be called "maintenance" y'know.

Strider590

Joe_Horner wrote: »

Agreed, but in the case of the mirrors they'd "played up" (failed to extend) before starting so it wasn't down to voltage drop from the starter.

And if the battery was too weak to extend the mirrors it would certainly have been too weak to crank the engine.

No because unfortunately these days all the electrics are controlled by the ECU or in this case the body control modules, these will have decided not to extend the mirrors. So it's not a case of not having enough power to extend them, it's a case of them not even getting the chance to try.

All this electronics in cars can cause problems that would ordinarily defy all logic.

bigjl

Joe_Horner wrote: »

As the reply to Strider, those effects are caused by voltage drop as the starter operates - which wouldn't explain the mirror issue.

The sad thing (from the MSE point of view) is that quite often changing a battery appears to cure the issue simply because it involves disturbing connections - particularly any additional feeds attached to the main connectors. So the myth that any electrical problem like this is cured by changing the battery as a first step is maintained.

Surprisingly often, it's actually those feed connections which are at fault in the first place, and a simple clean-up is all that would have been needed. A new battery may be a cheap (debatable) first step, but 10 minutes cleaning connectors is free. Used to be called "maintenance" y'know.

I wasn't talking from a voltage drop when starting point of view.

It's a well known problem with current Jaguars.

Nothing to do with connections.

It's apparently due to the number of ECUs on the vehicle.

My battery was discharged when the alternator pulley broke up, had to get off the A4 and by the time I did the battery was completely discharged, not even enough power to put on the ignition and get the gearknob to raise up to put in neutral! Even the rear air suspension dropped down.

My car was about 2 1/2 years old at the time. Even now the oldest X351 is a 59plate though they were usually Press cars and Demo cars with the first being sold retail on a 10plate.

After getting the car back Inwould get the "start engine" warning after a couple of minutes listening to the radio whereas before it would only come on after 20/30mins watching a DVD and charging a phone with the engine off.

I fully charged the battery myself and it improved but as soon as the weather got colder it struggled to start, despite charging properly every week.

At the same time it had a few issues. Jag dealer replaced a few sensors.

After replacing the battery with a new one it was fine till I got rid.

I did ask the Jag dealer that did the alternator change if they had charged the battery and they said no they just used a jump pack.

This isn't just an opinion, if you have a mooch around some Jaguar forums it is fairly common. Later XJLs with stop start have a second battery under the boot floor.

I think that is for the ECUs etc though i could be wrong. I looked at one once and it definitely isn't big enough to start an XJL 3.0d lump IMHO. It's about the size of the battery in my Picanto. If memory serves.

GoldenShadow

Thanks for the replies everyone, lots to think about.

When the Halfords man was doing the battery test he got me to turn the car on and off as it kept beeping as if something was 'on' in the car, but it wasn't that I could tell. He did say the tester just plays up sometimes too.

In my old car and my OH's car, the dashcam switches off when you lock the car, all electrics do. For some reason in the Fiesta they keep running so I do make sure I take the dashcam out. Although generally if I dive into Tesco for 10 mins I will leave it plugged in, could even that make a difference?

Re local garages, I've got the Ford down the road but aside from that the two I tried are really busy and said its probably just he battery, hence I went to Halfords to get it tested.

The battery doesn't look like an original. The guy said it is a Halfords one and would be £120 odd to replace as it was their premium one, so doesn't appear to be the original one.

I was struggling to identify the correct battery to be honest as by reg lots of websites tell me to get different sized ones. I guess I would just have to buy exactly the same size as whatever is in there.

Still not sure on my course of action...tempted to buy a charger/jump start box as would be good to have anyway?

arcon5

Joe_Horner wrote: »

As usual, all the completely non-MSE advice to "just buy a battery" is missing one very important clue in the OP, so I've made it a bit more visible below:



A battery that was so low on voltage that it couldn't operate the mirrors, or that lost the stored data in ECUs would NOT have enough power to start the engine.

Especially the ECUs are far more dependent on voltage than current to hold data, and they'll generally hold it down to around 10 volts - they have to because battery voltage can dip to that cranking on a cold morning while the starter's running.

But a battery that had dropped to 10V or below overnight simply wouldn't crank the engine in the morning.

Therefore, not a battery problem. Possibly a battery connection problem but more likely to be a poor earth somewhere in all that modern electronics which is depriving some electronics of voltage while allowing it to the starter because that's using a different earth.

You clearly don't know much about automotive technology so time too stop talking.
The ECU won't open the mirrors if battery voltage is below a certain threshold for the exact reason that power is being preserved for starting!

So maybe know your stuff before insulting other peoples advise

bigjl

GoldenShadow wrote: »

Thanks for the replies everyone, lots to think about.

When the Halfords man was doing the battery test he got me to turn the car on and off as it kept beeping as if something was 'on' in the car, but it wasn't that I could tell. He did say the tester just plays up sometimes too.

In my old car and my OH's car, the dashcam switches off when you lock the car, all electrics do. For some reason in the Fiesta they keep running so I do make sure I take the dashcam out. Although generally if I dive into Tesco for 10 mins I will leave it plugged in, could even that make a difference?

Re local garages, I've got the Ford down the road but aside from that the two I tried are really busy and said its probably just he battery, hence I went to Halfords to get it tested.

The battery doesn't look like an original. The guy said it is a Halfords one and would be £120 odd to replace as it was their premium one, so doesn't appear to be the original one.

I was struggling to identify the correct battery to be honest as by reg lots of websites tell me to get different sized ones. I guess I would just have to buy exactly the same size as whatever is in there.

Still not sure on my course of action...tempted to buy a charger/jump start box as would be good to have anyway?

Don't bother with a Halfords Battery.

Get online to EuroCarParts, put in your ref no and there will be a huge selection of batteries to choose from.

Use code SALE25 to get an extra 25% off.

If you are keeping the car go for an Exide or Bosch Battery personally with a 4 yr Warranty or 5 year Warranty if possible.

Strider590

GoldenShadow wrote: »

The battery doesn't look like an original. The guy said it is a Halfords one and would be £120 odd to replace as it was their premium one, so doesn't appear to be the original one.

Their premium will be a Bosch battery, basically a re-branded Varta that can be obtained online for less than half the Halfrauds price.

It's probably a type 075
https://www.tayna.co.uk/075-Car-Batteries-G25.html
or type 063
https://www.tayna.co.uk/063-Car-Batteries-G4.html

Richard53

The battery is 7 years old and has already been flattened once. By any measure, it is on borrowed time. Get a new battery and take it from there. It might solve the problem, but if it doesn't at least further diagnostics will be on the basis of a good battery and therefore mean something.


Incidentally, my Ford had its 12V power outlet permanently live, so I used to plug and unplug my dashcam every journey. Apparently, if you locate the relevant fuse there is an alternative position for it which makes the outlet a switched live rather than permanent. I didn't bother doing this, so just passing it on with no guarantees. But if you leave your dashcam connected, this may help, if Ford use the same logic on the Fiesta as the Mondeo.

Strider590

Richard53 wrote: »

The battery is 7 years old and has already been flattened once. By any measure, it is on borrowed time. Get a new battery and take it from there. It might solve the problem, but if it doesn't at least further diagnostics will be on the basis of a good battery and therefore mean something.


Incidentally, my Ford had its 12V power outlet permanently live, so I used to plug and unplug my dashcam every journey. Apparently, if you locate the relevant fuse there is an alternative position for it which makes the outlet a switched live rather than permanent. I didn't bother doing this, so just passing it on with no guarantees. But if you leave your dashcam connected, this may help, if Ford use the same logic on the Fiesta as the Mondeo.

The MK4 Mondeo onwards turns off the 12v sockets 15mins after locking the car. It confused me at first because I'm used to leaving my 5v charging adaptor plugged in.