Apologies if this seems to be a really stupid question!

Car is ‘66 plate Octavia Mk.3

My car’s 12V battery needs

replacing. Rather than pay the dealer $$$ to do this, can I take the car to a 3rd party and do as I have done before and simply pop in a new one?

In other makes of car, when it is time to replace the 12V battery it is just a simple swap. Out with the old, in with the new battery.

From a brief bit of research, it seems that it isn’t that straightforward with a VAG vehicle? Something to do with the BMS??

Any advice welcome

Thanks, Zaph

2 hours ago, ZaphodB said:

My car’s 12V battery needs

replacing.

How do you know?

Not meaning to be "that guy", after all, I came to the forum seeking help, but with a car that is 10 years old on its original battery and getting the message each time that I get in the car, the centre display tells me the 12V battery needs charging it seems pretty conclusive to me.

So, returning to my original question now that is cleared up, is it a simple matter to swap out the 12V battery for a new one (assuming same size battery, same type, same capacity etc) or is it more involved?

A cursory internet search seems to suggest (like most things VAG) that you simply can't replace a part without some reprogramming involved.

Just seeking some clarification.

Z

47 minutes ago, ZaphodB said:

but with a car that is 10 years old on its original battery and getting the message each time that I get in the car, the centre display tells me the 12V battery needs charging

Ya...all good info to pop into the first post.

Agree, needs changing. I think you can just change but to optimise life of new battery, recode or at least tell the car its a new battery.

I think all you really need is to change serial no and make sure capacity (Ah or CCA) is correctly entered.

We don't know what your background info is and often when someone says, my car needs a new battery, a good diagnostic mechanic will ask l, how do you figure.

Plenty of punters say my car cranks for ages but won't start, must be the battery.

Or, my car won't start, what could it be....well...kinda anything....

Okay - replacing battery. Firstly; 10 years out of the OE battery - good going. You didn't say which version of the Octavia you have, but generally you need an 096 style battery. Please check before ordering anything.

I tend to use BOSCH or VARTA.

A7 Varta Dynamic AGM 096 Start Stop Car Battery 12V 70Ah...

A7 VARTA Dynamic AGM Car Battery <i>Innovation with Purpose, Premium Experience, Powerful History</i> VARTA was founded in 1887 Germany, and was established fully in 1904 by delivering the first elect

Once fitted, you need to tell the car that you have changed battery. You will need ODBEleven or VCDS to do this. The battery manufacturer is important - use VAR (as manufacturer) and AGM (each MY year has slightly different options) as your type. Change the ampage to 70Ah. The car should now start, run, and charge at 14.2V.

OPs original battery could well be EFB - but, if so, replacing with AGM will give better performance, but not especially necessary.

Agree that correct adaptation (coding) to the vehicles BCM is important - but actual battery manufacturer is not.

Critical battery adaptation information is -

• Type (AGM (fleece) or EFB.

• Capacity (Ahrs)

• Change battery serial number to inform BCM that a new battery has been fitted (this can simply be by changing the last digit of the existing serial number)

Thanks Blue for not talking what I posted the wrong way. Didn't want to come across as arsy!

On reflection, yes, the additional info (message in the display) would have helped!

Vehicle in queston is a 1.4 TSI Sport with an Exide EFB battery - top says "12V 59Ah 320A DIN" and "640A EN/SAE/GS" Dimensions are 278/175/190mm (L/W/H)

One question, if I may. WHY does the car need to know that the battery is an EFB or AGM battery? Does the stop-start battery management system take this into account? AGM (Absorbent Glass Mat) batteries appear to be necessary for cars with an energy recuperation system (eg hybrids) whilst EFB batteries are okay for "simple" stop-start systems. AGM have better cold-weather performance and cold-temperature cranking but are more expensive. The Varta Battery Finder suggests their DYNAMIC EFB 570500076 battery.

Given that the Exide EFB battery has lasted 10 years, I can't see any benefit in going AGM.

One further question - after I had used the Varta site. My (current) battery says '640A' on it but the EFB battery identified by Varta says '760A' Does this matter/make any difference?

Thanks in advance,

Zaph

On the subject of AGM being necessary for hybrid cars, these cars are actually micro hybrids as they also have energy recuperation "going on" - but 98% of people would probably dismiss the "micro hybrid" bit.

The "760A" on the Varta site is surely the "next size up" battery to the one currently fitted, so if you want to save money, just replace like with like, ie a 640A one.

Edit:- oh and EFB if that suits you - like the original.

Another Edit:- I would have thought, that your original battery is 242mm "long" and so a size 027.

Edited 30 January30 Jan by rum4mo
Missed out EFB

37 minutes ago, ZaphodB said:

Does this matter/make any difference?

oh yes. It is really important you tell the car what type of battery you have and replace it with. The alternator outputs different voltage/charging profiles dependant on what you tell the car you have installed.

Up until 2019/2020, you can use VCDS/OBD11 to code a new battery in. After this period, the car has a locked gateway and needs something like ODIS.

At least, my 2020 Octavia did.

4 hours ago, varaderoguy said:

oh yes. It is really important you tell the car what type of battery you have and replace it with. The alternator outputs different voltage/charging profiles dependant on what you tell the car you have installed.

It is hugely important. As an example, my father had an incorrectly coded the battery on his 2011 A3. For the next year, we had random issues - intermittent no horn, wipers, central locking or cruise control.

After taking everything apart, we finally figured out it was because the battery had been coded in wrong. First and last time we went to Halfords.

The car is smart. Very smart. It needs to know what is happening with the battery!

18 hours ago, OccyVRS said:

Up until 2019/2020, you can use VCDS/OBD11 to code a new battery in. After this period, the car has a locked gateway and needs something like ODIS.

You can unlock the gateway using ODBEleven.

1 hour ago, varaderoguy said:

You can unlock the gateway using ODBEleven.

That’s on me then.

This was over a year ago, shortly after I bought the car, and I was far less confident with it. I seem to remember scanning it, seeing the plethora of DTCs and absolutely shi***** myself!

If you get loads of errors; it is always worth making a note of them....send yourself a scan output; then clearing them, seeing what is left. Voltage issues will always errors on multiple errors.

My 2016 1.6tdi will be 10 years old in September and whilst I've not really had any battery issues it must be running on borrowed time so I have taken advantage of a 20% off code on EBAY and bought a Bosch 096 AGM battery from Tanya. Looks to be a fairly simple process to code it via OBDeleven

https://obdeleven.com/how-to-change-and-register-a-car-battery?tw_source=google&tw_adid=&tw_campaign=23520343912&tw_kwdid=&gad_source=1&gad_campaignid=23520351964&gbraid=0AAAAACmF5GW-gpPU1Jzz6Hl5BvJocEdfy&gclid=CjwKCAiAs4HMBhBJEiwACrfNZa-A8BY-ryW1D3FitmzNgCcB5MNVlaZPuoFSM2ctcstdAN6WiWjJyRoC8pwQAvD_BwE

A local VW independent specialst is fitting me a new battery and re-coding the BMS tomorrow

A total of £202 including battery, re-coding and VAT. Highly rated on trustpilot too I might add.

Zaph

Well, all sorted now and I was only charged £168 including battery, fitting and re-coding.

Zaph