Battery replacement, BMW or?

[TitanTim]

As you said earlier, gone are the days when a fella could rattle a 10mm spanner for a few minutes and job done!

My first car I replaced the battery in 2 minutes but then wind up windows was an option back then

Tim.

[ronk]

I could manage the mechanical bits - bur the electronic witchcraft is not my cup of tea!

[TitanTim]

Bit of an update.

Made a booking with AA mobile battery service who called today with a view to replacing the battery. They tested the battery and and it's charge state was at 100% and was charging ok from the alternator and said the battery was all good and didn't need replacing

Odd thing is if I connect a CTEK charger it will charge the battery to 100%, it should also indicate if the battery is going bad which it doesn't. When I disconnect the charger and then start the car I get a warning on the iDrive straight away saying battery is discharging and after a drive and switching off I then get the message "Battery Discharged"



I have a P3 dash gauge which is plugged into the OBDC and is indicating the battery is being charged at 14.2 volts with engine running so within healthy range.

The AA chappie suggested it might be a bad intelligent battery monitor that thinks the battery is discharging when it isn't. Could also be potentially a comfort access module gone bad that doesn't turn off and drains the battery but this doesn't explain when the battery charge is at 100% why the battery discharging warning appears straight away when the car is started or why at the end of a journey its saying the battery is discharged when it's being charged at 14.2 volts with the engine running.

It's due a Service and MOT next months so BMW can take a look and then charge me ££££s, I do have extended warranty though

Tim

[pvr]

My son’s 140 did exactly the same, so we just replaced the battery anyway. The extended warranty doesn’t cover the battery anyway and as due to the age you are on borrowed time I would do it anyway

[TitanTim]

My son’s 140 did exactly the same, so we just replaced the battery anyway. The extended warranty doesn’t cover the battery anyway and as due to the age you are on borrowed time I would do it anyway

Thanks for the info, I mentioned to the AA chappie about the age of the battery but he said as its testing fine he said he wasn't comfortable charging me £251 to replace a battery which he tested as being good so unsure. End of the day think you're right as the battery must be on borrowed time now, 7 years old. Think I'll hang on a few more weeks until the service/MOT and see what BMW say, just in case it might be something else and what they charge for a battery.

Doing some searching, I've read that once the battery reaches a certain age regardless of it's condition you will start to get the battery discharging warnings, so basically a way of saying you need a battery even though it might be perfectly healthy, might be a bit cynical way of looking at it I don't know if that is really true.

Tim.

[smorris_12]

Dunno about AGM ones but generally it's the voltage off charge that's of interest. 14.2v basically means the alternator is working and the battery isn't open circuit.

A good lead acid battery will fall back to about 12.6v off charge. As it starts sulphating up this drops towards 12 or high 11s. The voltage then (or the rate of change of drop) is all the computer can measure, nothing magic.

Saying that, 7 years isn't bad for a fair weather car. Even work long, daily trips, 10/12 years is about the best achievable. My second battery in the 320d died an early death due to lack of use in COVID and not thinking to put it on charge quick enough. And I am paranoid about battery care!

[pvr]

The easiest way to see if the battery is any good at all, is if start / stop still works. On my son's 140, that was the first thing to no longer kick in and that was about 2 months before the battery warnings came on.

[ronk]

I hate the stop start function but I think I will use it this morning for a battery test!

[TitanTim]

Thanks for the replies.

Used the car last night and this morning and the battery warning messages have disappeared

I did notice yesterday when I pulled the car out for the AA chappie I didn't notice the battery warning nessage but just thought I'd missed it but they've definitely gone for now so will see.

The AA chappie did test to see if the battery was holding its charge and it tested good.

This morning the CTEK was indicating fully charged,


I understand if it the error light is lit and doesn't get past stage 2 on the staus lights the battery is past it and if the error light is on and it stays on stage 5 then the battery isn't holding its charge.

Will see how it goes, haven't tried stop/start as never use it but will try it next time and see if it works, thanks for the tip.

Just thinking with the hot weather combined with using the CTEK alot the IBM on the car was giving a false message on battery status or threw a wobbly. The CTEK should take this into account through the charging cycles during hot and cold weather.

Tim.

[pvr]

I would not rely on the CTEK status though. I have the same on the Golf battery, and it always shows 100% fine and on the service a few weeks back, the VW dealer said that the battery was in a very poor condition and needed replacing (they offered to do it at some rather inflated price ...)

[TitanTim]

I would not rely on the CTEK status though. I have the same on the Golf battery, and it always shows 100% fine and on the service a few weeks back, the VW dealer said that the battery was in a very poor condition and needed replacing (they offered to do it at some rather inflated price ...)

You're talking about a franchised dealer though ££££s partly why I didn't want to go to them in the first place for the battery to be honest, not that I don't trust them

It's a difficult one but at the moment the AA testing seems to match what the CTEK is saying or vice versa. I was quite impressed with the AA chap as he was honest and mentioned he wouldn't fit a new battery if the test results are indicating the battery on the car is good, he said I would be ripping you off otherwise. Which is honest to be fair.

I'll probably break down tomorrow

Tim.

[ronk]

Ive been getting these messages on my 335 - so I went out this morning and taking pvr’s advice tried the stop start test.
It didn’t work properly. The car cabin fan doesn’t want to switch itself off and the cabin fan speed won’t adjust.

Thd air con has decided to start blowing warm air from the drivers side vents.

I hope it’s a battery problem !

I have a Bmw warranty on this car and the Z so I think I will call assist after lunch

It’s either the Battery or an ECM - The Battery is about 6.5 yr old

Ps I don’t intend to hi Jack your thread Tim - it’s just there are so many fault similarities

[TitanTim]

Ive been getting these messages on my 335 - so I went out this morning and taking pvr’s advice tried the stop start test.
It didn’t work properly. The car cabin fan doesn’t want to switch itself off and the cabin fan speed won’t adjust.

Thd air con has decided to start blowing warm air from the drivers side vents.

I hope it’s a battery problem !

I have a Bmw warranty on this car and the Z so I think I will call assist after lunch

Thanks Ron, keep us posted how you get on.

I'll try the stop start next time I'm out and see if it works. Everything else on the car is working normally including comfort access which I think is one of the first to stop working with battery issues.

When I got the warning above saying battery was discharged and certain functions have been switched off ie air conditioning etc it was all still working as normal which has got me thinking the messages were false or theres possibly an intermittent fault with the intelligent battery module that's on the battery, they can go faulty on BWWs as a bit delicate giving false warnings so will ask for it to be checked come service time.

I didn't really want to spend nearly 300 quid on a new battery if its testing ok and its possibly another issue throwing the warning messages

Tim.

[ronk]

My Stop/Start didn’t seem to function properly this morning.

There’s what seems to be a cabin fan running with no key etc - the system won’t shut down.
With this in mind I gave BMW Breakdown a call and they are comming out this evening

[ronk]

My Stop/Start didn’t seem to function properly this morning.

There’s what seems to be a cabin fan running with no key etc - the system won’t shut down.
With this in mind I gave BMW Breakdown a call and they are coming out this evening