Octavia MK 3 Scout, 2l 184bhp DSG .RH drive (UK)

Replaced the battery at c. 85,000 miles when I bought the car early 2022.

Installed a Lucus AGM Lf096, marked with 'Stop Start' on the casing. Got it from Tayna, with 4 years warranty. It replaced a similar AGM (can't recall).

A friend who's an RAC man, helped me with the install because I was concerned about coding the new battery.

He was adamant that coding was unnecessary as the car would learn, and the battery was very similar (different brand but same spec).

It's just started struggling to start the engine a few times this last few months, since autumn, taking as much as 3-5 seconds compared to previous almost instantly every time since install.

This Christmas got a dashcam. The accessories socket stays live 24/7.

Installed VIOFO A329S on Christmas Eve. Drove Christmas Day, & then not until 31st Dec. Absolutely dead flat battery.

No central locking, nothing.

1. Unlocked driver's door using the physical lock under the cover.

2. Other doors don't open/unlock even using inside handles. Tried a 12V 2.1A battery into cigarette socket. It was enough to trigger alarm, and allow alarm off using key fob, but not to unlock central locking before the cigarette socket accessory plug melted.

3. Can't open bonnet with passenger doors closed. However the lever does clip off if you pull it away from the panel. Pair of square nosed pliers then allowed me to turn the mechanism & release bonnet catch. Handle just clips back in.

4. Multimeter measured 8V across battery posts.

5. Used charger for 12 hours. 12.8V.

6. Removed charger. Left battery overnight to rest. Remeasured, 12.4V. Should be 12.7V or more.

7. Reconnected charger another hour or so until it turned off. Removed charger. Left few hours. Remeasured, 12.45V.

8. Drove to Bedford Battery Co in Northampton, they checked it. Defo knackered, 12.3V & other KPIs low.

9. Bought new Yuasa 9000 (similar spec) AGM.

10. Fitted it myself. Contacted an ex VAG engineer, adamant does not need recoding. The self learning is enough alledgedly. Sure enough, like last time, all warning lights went out just fine.

11. Tayna will honour the warranty subject to their tests & despite my honesty telling them I left dashcam on for 6 days.

HOWEVER, the recoding thing bothers me. So much disagreement out 'there' as to the importance & effect, including AI chats etc.

I don't have any software tools... yet.

Arh - the "car will learn" way of doing things.

No - sorry; I don't buy that. Yes, eventually the car does learn, but it never fully charges or optimises the battery.

Get somebody with ODBEleven or VCDS and properly code up the correct battery type and capacity.

59 minutes ago, AdoksNick said:

So much disagreement out 'there' as to the importance & effect,

And you'll get exactly the same divided opinion here.

I'm in the 'car will figure it out just fine' camp.

No-one ever really produces any proper evidence either way.

1 hour ago, varaderoguy said:

Arh - the "car will learn" way of doing things.

No - sorry; I don't buy that. Yes, eventually the car does learn, but it never fully charges or optimises the battery.

Get somebody with ODBEleven or VCDS and properly code up the correct battery type and capacity.

If the battery is of the same type, eg., EFB or AGM as the old one and the same capacity and cold cranking amps, then there is no need to recode it.

2 hours ago, Breezy_Pete said:

I'm in the 'car will figure it out just fine' camp.

I agree no one has offered any evidence either way. However I still prefer to play safe and do the coding.

No-one has ever said doing the coding is bad in any way.

I fitted a new AGM battery, same type and capacity, with 6 months the stop start failed to work and bat capacity was at 70% even on after a long run.... i then coded it and re charged it.

Has been fine since.

Evidence perhaps not but considering the OP has had issues without a coding, it does seem to point to that batteries need coding upon replacement.

AGM batteries usually sit at 85% charged capacity. Not coding in your battery will also mess up stop/start and you may also get voltage spikes on the car electrics due to the BMS struggling to know what the current charge or voltage is or should be. This may also throw low voltage codes.

31 minutes ago, varaderoguy said:

AGM batteries usually sit at 85% charged capacity. Not coding in your battery will also mess up stop/start and you may also get voltage spikes on the car electrics due to the BMS struggling to know what the current charge or voltage is or should be. This may also throw low voltage codes.

If the new battery is the same as the old one then the system should be OK. Maybe the system also takes the age of the battery into its charging routine, so maybe if you wanted to code it, just change the last 2 digits of the battery number and leave the others alone. That way the system will now know the battery is new?

On 04/01/2026 at 10:00, Graham Butcher said:

That way the system will now know the battery is new?

If you go for the same make and battery type that is a goerz otherwise you really need to code it in properly.