Battery issues and Auto Stop/Start not working

[PetrolDave]

5 minutes ago, ords said:

However, some have said that in normal circumstances the battery is never 100% fully charged to allow for a small amount of regenerative current to be put into the battery

It's been said many times on here that the BMS only charges the battery to a maximum SoC of 80% to allow for this (very minor) regenerative braking effect.

 

Certainly on my previous 1.4TSI which was old enough to be able to see SoC on the maxidot I never saw a value above 80%.

[Nirrain]

15 hours ago, nta16 said:

To me this sounds like something is wrong, as with the OP here and another thread.

 

I'll give more details later if wanted but to me it sounds like the initial battery swap and or charging by car and/or battery charger.  I've got to go now but if you want to leave more details.

 

I'd appreciate more details, thanks!

 

In my case the rough timeline is the following

1. My 2018 Octavia was not driven much during the first Covid lockdown in 2020 and when driven (short and long trips) the start-stop function did not engage

2. At one point the car reported low battery but could still crank, but on that trip it suddenly went into "safe mode" and the mechanic said it was a broken spark plug. They said it was not related to the low battery, but I am inclined to think it is related.

3. Since then the start-stop was only rarely engaged even when I charged the battery with a smart charger so I concluded that the low battery situation had damaged the battery so I replaced it in dec 2021 and everything worked fine for a while

4. In the summer of 2022 I noticed the start-stop again did not engage and I suspected the "Skoda Connect" dongle that Skoda installed to be leaking power so started monitoring the battery and charging whenever it went to 12.3 or below - resulting in external charge 1-2 times a week.

5. I measured voltage across all fuses while the car was tricked to sleep mode, but could not find any leaks

6. Then I noticed that even after a 45 min drive the battery quickly went from 12.6 to 12.2V while parked for 2 days and that the 2Amp charger only took an hour before reporting the battery as full

7. Then I tried to leave the charger on maintenance mode for 48 hours and since then the voltage dropped from 12.6 to 12.5 after 3 days parked

 

14 hours ago, ords said:

I just thought that if you have 2 smart devices connected there's potential conflict. If the battery is fully charged with one terminal disconnected, then the BMS should also read as fully charged when connected as you say.

 

As I understand the BMS does not only use voltage to gauge the SoC of the battery, so if the battery is charged to full while bypassing the BMS I would fear that the BMS thinks the battery is only at 80% or so and end up overcharging the battery?

[varooom]

1 hour ago, Nirrain said:

3. Since then the start-stop was only rarely engaged even when I charged the battery with a smart charger so I concluded that the low battery situation had damaged the battery so I replaced it in dec 2021 and everything worked fine for a while

Did you adapt the battery when you changed it?

What sort of battery is on it now, EFB/AGM and Ah ratings etc (picture is quick if you prefer)

 

 

1 hour ago, Nirrain said:

As I understand the BMS does not only use voltage to gauge the SoC of the battery, so if the battery is charged to full while bypassing the BMS I would fear that the BMS thinks the battery is only at 80% or so and end up overcharging the battery?

I charged my battery when I got it to 100% SOC off the car before fitting, not once was I worried about overcharging.  Not sure how often it updates the ECU/Gateway as to the SOC, but I suspect it's probably several times a second.  So even a car that thinks it has 60% SOC will soon clock on to the fact it has more SOC than it was thinking and dial back the Alternator.

 

 

I did some testing in the car just yesterday, on idle it was reporting the Generator as making/supplying 500W and it has to have some real time values to even show that.  I then turned on heated rear and front windows, and that figure jumped up to 2,000W (Alternator is 180A for reference) and again the value dropped off the instant I turned them both off back to 500W.  So the car knows fairly well how much SOC is in it, and can show in real time the values.

[Nirrain]

1 hour ago, varooom said:

Did you adapt the battery when you changed it?

What sort of battery is on it now, EFB/AGM and Ah ratings etc (picture is quick if you prefer)

The first battery was an 69Ah Varta EFB OEM battery, the second was a Varta Blue Dynamic 70Ah EFB battery for cars with start-stop.

 

I asked the shop to register the new battery with the computer as I installed it myself but have not (yet) dived into VCDS etc. Is that what you mean by adapt the battery or is that something else?

[varooom]

Just now, Nirrain said:

I asked the shop to register the new battery with the computer as I installed it myself but have not (yet) dived into VCDS etc. Is that what you mean by adapt the battery or is that something else?

Yes getting the battery paired to the car was what I was referring too.

 

If you have VCDS, it's worth double checking, as someone recently had their 70Ah input as 7Ah @DuncanDisorderly

[Nirrain]

2 hours ago, varooom said:

If you have VCDS, it's worth double checking, as someone recently had their 70Ah input as 7Ah

I do not, but have considered it. What would be the minimum required hardware and software purchases to be able to check it?

[varooom]

7 minutes ago, Nirrain said:

I do not, but have considered it. What would be the minimum required hardware and software purchases to be able to check it?

A quick Google of VCDS will show you, it doesn't need much power to run the program.

 

There are other tools other than this, so perhaps look down in the diagnostic section of the forum to ask anything you need.

[nta16]

Please note - I am not a mechanic or expert in anything.

 

5 hours ago, Nirrain said:

1. My 2018 Octavia was not driven much during the first Covid lockdown in 2020 and when driven (short and long trips) the start-stop function did not engage

2. At one point the car reported low battery but could still crank, but on that trip it suddenly went into "safe mode" and the mechanic said it was a broken spark plug. They said it was not related to the low battery, but I am inclined to think it is related.

As I often put here, just because the car starts and the lights seem bright enough it doesn't mean the battery has enough charge to keep the VW computer programs happy and they can throw up all sorts of unexpected issues even before giving warning warning lights and messages.

 

Reading the Owner's Manual and referring to it when required will mean that you will know about your car more than many long term owners, in it is a section on the battery and checking it, personally I'd not put all my faith in the battery indicator but it's better than nothing and reading the section will tell you the procedure required to test it correctly.

 

 

5 hours ago, Nirrain said:

3. Since then the start-stop was only rarely engaged even when I charged the battery with a smart charger so I concluded that the low battery situation had damaged the battery so I replaced it in dec 2021

 You were right the battery had been damaged but you might have been able to recover it for more life out of it with a suitable charger.  This gives you some detail and some idea of some of what's available. - https://www.rac.co.uk/drive/advice/know-how/car-battery-conditioners-and-trickle-chargers-everything-you-need-to-know/

 

 

5 hours ago, Nirrain said:

6. Then I noticed that even after a 45 min drive the battery quickly went from 12.6 to 12.2V while parked for 2 days and that the 2Amp charger only took an hour before reporting the battery as full

7. Then I tried to leave the charger on maintenance mode for 48 hours and since then the voltage dropped from 12.6 to 12.5 after 3 days parked

A general note just driving the vehicle is often not not enough to help with charging the battery and might even deplete it more.  The 2-amp charger only taking a hour does tell you there's a problem.  There are possibly ways around this depending on what charger this is and what else is available.  See RAC link for 7.

 

Edited 27 January, 2023 by nta16
ETA: Please note - I am not a mechanic or expert in anything.

[nta16]

Please note - I am not a mechanic or expert in anything.

 

Nirrain, it'd help if you added your car details and if you want location to the wotits that are at the left side of the posts.  2018 Octavia Mk3 - what engine, gearbox, trim level.

 

Also if you could put a link up to the 2-amp charger or its make and model.

 

You are doing the right thing by having a low amperage but you're not applying it at the right time and possibly not correctly.

 

I suggest for now you read the Owner's Manual about disconnecting and reconnecting the battery and possible resets on the car and you disconnect the battery, and leave it on charge again until full.

 

For the sake of the little effort and time required whilst the battery is disconnected - [ETA: - carefully bridge/join the positive and negative battery leads post clamps together to complete a circuit ] - turn the ignition on, press and hold the brake pedal down so that if the battery was connected the brake lights would be on, turn the headlights on, after about 20 seconds, turn headlights and ignition off.  This might reset some of the many computers that might have been upset or just a refresh of 'turning it off 'n' on agen'.

 

Edited 18 February, 2023 by nta16
ETA: an important bit I missed out

[Nirrain]

  

12 minutes ago, varooom said:

A quick Google of VCDS will show you, it doesn't need much power to run the program.

 

What I meant was if there is a cheaper solution than the 3/10 VIN Hex-V2 from RossTech https://store.ross-tech.com/shop/vchv2_ent/ as that sounds more "pro" than my mechanic skills justify 😀

 

18 minutes ago, nta16 said:

Reading the Owner's Manual and referring to it when required will mean that you will know about your car more than many long term owners, in it is a section on the battery and checking it

I have read the manual in particular regarding batteries and fuses, but the way the BMS really works is still a mystery to me.

 

The next step I plan to take is to do a long maintenance charge on the old battery and then somehow check the capacity if I can find a suitable 12V consumer to see if that battery may still be of use while I monitor the behavior of the new battery in the car to see if the BMS just lets it unload gradually or actually keeps it in decent shape from here.

[Nirrain]

1 minute ago, nta16 said:

Nirrain, it'd help if you added your car details and if you want location to the wotits that are at the left side of the posts.  2018 Octavia Mk3 - what engine, gearbox, trim level.

 

Also if you could put a link up to the 2-amp charger or its make and model.

 

You are doing the right thing by having a low amperage but you're not applying it at the right time and possibly not correctly.

 

I suggest for now you read the Owner's Manual about disconnecting and reconnecting the battery and possible resets on the car and you disconnect the battery, and leave it on charge again until full.

 

For the sake of the little effort and time required whilst the battery is disconnected turn the ignition on, press and hold the brake pedal down so that if the battery was connected the brake lights would be on, turn the headlights on, after about 20 seconds, turn headlights and ignition off.  This might reset some of the many computers that might have been upset or just a refresh of 'turning it off 'n' on agen'.

Really appreciate your help!

 

It is a 2018 Octavia Mk3 Combi, trim level "Style" with a 1.0 TSI engine and Manual 6 transmission gearbox

 

The charger is an Einhell CE-BC 2 M 'smart charger' where I connect the + on the charger to + on the battery and - on the charger to the "ground point" of the engine mentioned in the manual. I then connect the charger to mains and have set it to "winter mode" for normal charging and "maintenance mode" for the long 48 charge while the car was shut down (e.g. all doors locked and the bonnet clamp activated with a screwdriver as mentioned in a different post regarding "correct way to measure battery drain" on briskoda. What should I be doing differently?

 

When doing the trick with the ignition, brake pedal and headlights is the ECU using some internal battery to be able to register that it is being done?

[nta16]

Please note - I am not a mechanic or expert in anything.

 

9 minutes ago, Nirrain said:

I have read the manual in particular regarding batteries and fuses, but the way the BMS really works is still a mystery to me.

Good for reading the Owner's Manual but best done when you first get the car or better still before buying the car as they're available on line.  I'm not immune I sometimes forget and think I know and then have to go back and refer to it when I find I don't fully know or have forgotten something.

 

The VW system is very complex, over complex but I won't rant on about the falseness of it all, see here for 2009 thinking. - https://procarmanuals.com/self-study-program-426-start-stop-system-2009-design-function/

 

 

11 minutes ago, Nirrain said:

The next step I plan to take

See my previous post.

 

[varooom]

16 minutes ago, Nirrain said:

What I meant was if there is a cheaper solution than the 3/10 VIN Hex-V2 from RossTech https://store.ross-tech.com/shop/vchv2_ent/ as that sounds more "pro" than my mechanic skills justify 😀

Gotcha, well there are other similar tools, OBDeleven?  Not one I have ever used myself.

 

The other way I justified my expense many years ago was thinking of how many dealer/independent workshops visits would it take to cover the expense of purchase.  Mine has done me a massive service for the time I have used it.  They also do hold up on resale value quite well if you left the VAG stable.

 

And of course, the other way is to pay a forum member that's local if possible some beer tokens for a scan here and there.

[Nirrain]

33 minutes ago, varooom said:

The other way I justified my expense many years ago was thinking of how many dealer/independent workshops visits would it take to cover the expense of purchase.  Mine has done me a massive service for the time I have used it.  They also do hold up on resale value quite well if you left the VAG stable.

 

That is a very good point, I am just a bit overwhelmed. Also heard some that recommends Carly https://www.mycarly.com/plan/?c=DK&b=vag&n=Volkswagen but the very different pricing models (VIN#, subscription, "per click credit" etc.) make is it difficult to identify what makes sense for my limited need - I do not think I am ready to take over servicing my two cars at this time so will have normal interval service at the mechanics regularly.

 

I am located in Denmark so I doubt there are many local members around

[varooom]

2 minutes ago, Nirrain said:

That is a very good point, I am just a bit overwhelmed. Also heard some that recommends Carly https://www.mycarly.com/plan/?c=DK&b=vag&n=Volkswagen but the very different pricing models (VIN#, subscription, "per click credit" etc.) make is it difficult to identify what makes sense for my limited need - I do not think I am ready to take over servicing my two cars at this time so will have normal interval service at the mechanics regularly.

 

I am located in Denmark so I doubt there are many local members around

Yes, not sure they would accept 20 Euro for a "quick" scan 😆

 

Well you might be better making a new thread to discuss some of the tool choices here...

https://www.briskoda.net/forums/forum/23-diagnostics-amp-vcds/

This way some members can make recommendations on the Pro's and Con's of each.  My only things I have heard about the "one-click" type solutions is they can make mistakes and then to unravel it can be harder (if you are making coding changes) but for scanning also, not sure on how they are with the manufacturer fault codes.

 

Make a post is what I would recommend, then sift through the replies to ask more questions, or make an informed decision.

[nta16]

Please note - I am not a mechanic or expert in anything.

 

On 27/01/2023 at 14:22, Nirrain said:

The charger is an Einhell CE-BC 2 M 'smart charger'

I note from the Manual for the charger that it is designed for up to 60Ah, your battery is rated at 69Ah so using the formula in the manual if the battery is fully discharged it will take 34.5 hours (at 2-amps) to get it to 80% charge (about 12.4-12.5v).  In maintenance mode at a maximum of 1-amp the time doubles.  These times will be increased if the battery is connected to the car and has a constant drain on it.

 

The charger does not seem to have a recondition mode so once you have the battery as fully charged as you can from the charger it would possibly help to use the car to cycle the battery's discharge and charge, from the alternator, as the battery is designed for.  Use the least consumers and battery consumption as you can until you put the battery on the charger again, to fully recharge the battery again to hopefully have regained as much of the battery capacity as you can.  If required you could repeat use of the battery on the car and then another full recharge using the battery charger.

 

The maintenance mode is really for when the car is not used for long periods, as noted in the car's Owner's Manual but the battery is designed for cycling so should have some discharge.

 

Winter mode is for when the ambient temperature is below (+)5c, if the temperature was above 5c last time of charging I would not worry about it given the state of your battery.

 

Manual.pdf

 

 

On 27/01/2023 at 14:22, Nirrain said:

When doing the trick with the ignition, brake pedal and headlights is the ECU using some internal battery to be able to register that it is being done?

My terminology will not be correct - but - the idea is just to fully deplete the electrics so that you get a reset of the computers, to have a clean start when you reconnect the charged battery, it might not do much, or nothing, but as I put before when the battery gets in a low state of charge it can cause all sorts of unexpected computer or program issues so best to have them cleared if possible and speed up getting back to normal operation.

 

 

On 27/01/2023 at 14:22, Nirrain said:

It is a 2018 Octavia Mk3 Combi, trim level "Style" with a 1.0 TSI engine and Manual 6 transmission gearbox

Thanks.  Now if you add that to the information with your site name it will show at each post you make (when viewed on an appropriate device(?)) as example. -

 

 

Edited 30 January, 2023 by nta16
wording

[BigEjit]

On 27/01/2023 at 07:47, Nirrain said:

 

I'd appreciate more details, thanks!

 

In my case the rough timeline is the following

1. My 2018 Octavia was not driven much during the first Covid lockdown in 2020 and when driven (short and long trips) the start-stop function did not engage

2. At one point the car reported low battery but could still crank, but on that trip it suddenly went into "safe mode" and the mechanic said it was a broken spark plug. They said it was not related to the low battery, but I am inclined to think it is related.

3. Since then the start-stop was only rarely engaged even when I charged the battery with a smart charger so I concluded that the low battery situation had damaged the battery so I replaced it in dec 2021 and everything worked fine for a while

4. In the summer of 2022 I noticed the start-stop again did not engage and I suspected the "Skoda Connect" dongle that Skoda installed to be leaking power so started monitoring the battery and charging whenever it went to 12.3 or below - resulting in external charge 1-2 times a week.

5. I measured voltage across all fuses while the car was tricked to sleep mode, but could not find any leaks

6. Then I noticed that even after a 45 min drive the battery quickly went from 12.6 to 12.2V while parked for 2 days and that the 2Amp charger only took an hour before reporting the battery as full

7. Then I tried to leave the charger on maintenance mode for 48 hours and since then the voltage dropped from 12.6 to 12.5 after 3 days parked

 

As I understand the BMS does not only use voltage to gauge the SoC of the battery, so if the battery is charged to full while bypassing the BMS I would fear that the BMS thinks the battery is only at 80% or so and end up overcharging the battery?

 

1, Lockdown killed off plenty of batteries due to inactive vehicles. After approx 6 weeks layup with the battery connected, they will be in a discharged state with sulphates growing and hardening = unrecoverable capacity losses result ultimately requiring an early life change of battery if not fully charged ASAP!

 

2, Low battery warnings frequently coincide with other abnormal electrical warnings.

 

3, The principle signature of a discharged damaged battery is failing stop start esp if all other consumers are off. Do you know if the new battery was stored fully charged before you bought it or its age? Did you use the vehicle frequently after fitting the battery before having to externally charge? If no to either of these, this is the most likely root cause.

 

4, What sort of usage pattern do you have with the vehicle? Approx annual Kms/miles and downtime between journeys as an average? This is another key indicator of response and performance from the battery you are reporting and also a common root cause of early life failures.

 

5, Current draw is more important than voltage loss when vehicle is fully asleep - should be around 0.014Amps if i remember right. Any more and the battery discharges sooner requiring more use or charge cycles to compensate or even more unlikely, indicates a consumer is failing to switch off correctly (Dashcams are prime favourite here)

 

6, A fully discharged battery needs 24hrs to recharge and saturate the plates. a few hours run time won't have much lasting affect and leave the battery back in the original discharged state very quickly if the usage pattern stays the same.

 

Frequent full recharging from fully discharged by just running the vehicle on periodic long journeys can also increase wear rates on the battery and lead to moisture loss and overheating. Heat from frequent and brutal alternator based recharging from fully discharged state and/or intense summer temps also damages the battery from moisture loss and by turning the plates to mush losing capacity, which then usually shows in winter when cold. Overcharging a battery results in surplus energy being turned to heat..., which boosts waterloss..., which pushes things closer towards self detonation if there is a significant presence of internal damage already.......

 

 

 

 

 

 

[Nirrain]

On 01/02/2023 at 00:21, BigEjit said:

3, The principle signature of a discharged damaged battery is failing stop start esp if all other consumers are off. Do you know if the new battery was stored fully charged before you bought it or its age? Did you use the vehicle frequently after fitting the battery before having to externally charge? If no to either of these, this is the most likely root cause.

 

4, What sort of usage pattern do you have with the vehicle? Approx annual Kms/miles and downtime between journeys as an average? This is another key indicator of response and performance from the battery you are reporting and also a common root cause of early life failures.

 

5, Current draw is more important than voltage loss when vehicle is fully asleep - should be around 0.014Amps if i remember right. Any more and the battery discharges sooner requiring more use or charge cycles to compensate or even more unlikely, indicates a consumer is failing to switch off correctly (Dashcams are prime favourite here)

 

6, A fully discharged battery needs 24hrs to recharge and saturate the plates. a few hours run time won't have much lasting affect and leave the battery back in the original discharged state very quickly if the usage pattern stays the same.

 

First of all thank you @varooom, @nta16 and @BigEjit for all your detailed suggestions tailored to my specific situation, I really appreciate it.

 

ad 3. I recall that the battery had about 12.5V open circuit when I received it and that the manufacturing date code was about 3 months prior to the date I received it.

 

ad 4. I drive the car for approx 7000 km/year where most of the trips are 40 min mostly highway, but also occasionally short trips. The car frequently stands still for 5 days at a time but it is rare that it exceeds a week.

 

ad 5. I have not put an amp meter directly in circuit as my multimeter is rated only for 200mA and from other posts I understand that the sleep current may fluctuate (e.g. when the 4G SkodaConnect dongle wakes) so I have only measured the current draw indirectly by measuring voltage across the fuses and kept track of the battery voltage over time while parked. The latter being a poor indicator if the total capacity of the battery is nowhere near 70Ah anymore

 

ad 6. Since I left the charger on for 48 hours in maintenance mode even though the charger reported the battery as already full, the battery seems to be in better health. After 3 hours parked the voltage is 12.59V and when parked for 24 hours it is now 12.52V. So much better than previously, but still either the current draw is high or the capacity of the battery is low as the energy loss from 12.59 to 12.52V is about 5Ah if the battery capacity is 70Ah when full which would suggest a current drain of about 215mA while parked.

[nta16]

Please note - I am not a mechanic or expert in anything.

 

On your 2-amp charger once it shows full then does it go into maintenance mode which is only keeping it topped up to that full so the 48 hours does not really matter once you remove the charger as whatever the full is it is not being added to in that 48 hours.

 

If your car is parked up for for 5 days could you remove the battery from the car to fully recharge it on your 2-amp charger in more stable and perhaps warmer conditions in home (I have no idea where you are and how cold it is).  Then you can check what full is and how it holds over a period of the next couple of days off the car.  Once the charger shows full you can disconnect it and take a reading about 12 hours later after the battery has settled from the recharge and take another reading(s) 12/24 hours after your first reading with the battery rested and off the car. 

 

Charging the battery again to full will be good as you have used the car since the previous time so the battery has had the cycles it is designed for and you have discharge so you can top it up.

 

Are you taking the voltage readings from your 2-amp charger as well as your multimeter?  Do you have another multimeter to check the readings?

 

Do you have access to a battery tester for state of charge and state of health?

 

[Nirrain]

49 minutes ago, nta16 said:

On your 2-amp charger once it shows full then does it go into maintenance mode which is only keeping it topped up to that full so the 48 hours does not really matter once you remove the charger as whatever the full is it is not being added to in that 48 hours.

 

If your car is parked up for for 5 days could you remove the battery from the car to fully recharge it on your 2-amp charger in more stable and perhaps warmer conditions in home (I have no idea where you are and how cold it is).  Then you can check what full is and how it holds over a period of the next couple of days off the car.  Once the charger shows full you can disconnect it and take a reading about 12 hours later after the battery has settled from the recharge and take another reading(s) 12/24 hours after your first reading with the battery rested and off the car. 

 

Charging the battery again to full will be good as you have used the car since the previous time so the battery has had the cycles it is designed for and you have discharge so you can top it up.

 

Are you taking the voltage readings from your 2-amp charger as well as your multimeter?  Do you have another multimeter to check the readings?

 

Do you have access to a battery tester for state of charge and state of health?

 

The charger has protection against overcharge and goes into trickle charge mode once full, I have, however, not been able to find out if that is the same as the explicit "maintenance mode" so I have manually changed it to maintenance mode once the normal (or winter mode when below 5C) charge reported the battery as full.

 

From the SkodaConnect app the voltage fluctuates while in maintenance mode, see attached image showing 1 week measurements where the middle part was the long maintenance mode charge and the other peaks have been while driving.

 

It is about 0-5C currently in Denmark, but I would prefer to keep the battery in situ rather than taking it indoors - our infrequent use of the car is not always planned ahead.

 

The voltage readings have been from my multimeter as well as the "SkodaConnect" dongle that seem to be in agreement as long as the car is forced to be fully asleep (e.g. doors and bonnet hatch activated)

 

I do not have access to a battery tester, but considered testing the capacity by a real load like turning on the headlights (or full beam lights) for a set amount of time and then based on the OC voltage and time until the charger reports to battery as full estimate the capacity - I do need to somehow find the headlight wattage though.

[J.R.]

On 27/01/2023 at 15:09, nta16 said:

You are doing the right thing by having a low amperage but you're not applying it at the right time and possibly not correctly.

 

When is the right time for applying a low current charge and what is the incorrect way of applying it?

[RIncewindwiz]

On 26/01/2023 at 11:47, varooom said:

Understanding really, you want to have peace of mind that it will work on the turn of the key.

 

 

Shop around, as batteries have been hit with the oh so wonderful inflation

https://www.tayna.co.uk/car-batteries/types/096-agm/

https://batterygroup.co.uk/batteries-power-electronics/agm-batteries/9483/varta-start-stop-silver-dynamic-agm-e39-12volt-70ah-760a/en-570-901-076-starter-battery-096?number=110058

 

I took off my factory fitted Varta after 7 years (it was not fully dead, but not happy) and fitted a Varta E39 you can see on the above list, as whatever is inside must be good to live that long IMHO.

So I see you guys have been having fun with my thread 🙂 - good interesting stuff

 

I decided my battery was effectively dead (in that it would not drive start/stop and gave up the ghost after parking for short period swith the lights on) biught a new one , adapted it and start/stop works fine again. Thanks to all that contributed.

[nta16]

@Nirrain as the car is not being driven a lot but could be needed at short notice lets try a different approach,  Looking further at the manual for the battery charger you have it is undersized in its capacity, it is not the 2-amp but the 60Ah and 32Ah in "Maintain" mode .  How about replacing it with a different charger that is capable of charging a 12v battery above the 70ah you have now and for convenience go to a 4-amp charger and maintainer.

 

From the pdf of the manual for your charger. - 

 

How good your battery is now is difficult to know so that makes it more difficult to know how much your problem is related to the battery or the car and in what proportion.  I'm not sure about the accuracy of doing your test and if you do the battery is as it is at the moment.  

[Nirrain]

58 minutes ago, nta16 said:

How about replacing it with a different charger that is capable of charging a 12v battery above the 70ah you have now and for convenience go to a 4-amp charger and maintainer.

 

 

My understanding is that the upper limit it is more of a "convenience" to avoid too long charge time and that the lower current charger will all else equal be better for the battery no matter the size.

 

For comparison the higher amp chargers have the same low limit capacity for  maintenance mode, though they do have a RECOND mode that could have been relevant.

 

At the moment I am leaning towards the battery no longer having its full capacity but still with significant life left and the main problem is that the BMS only charges towards 80% (or less) which is not ideal when the car is not driving every day. I wonder if a HEX-V2 and VCDS would enable me to increase the charging target to 90 or 95%.

 

But otherwise the extended charging sessions while the car is parked may just be a necessary hassle to keep the battery healthy which only used occasionally.

[RIncewindwiz]

I did ask yuasa in my discussion with them about the state of my battery. They said

"With regards to charging, our normal suggestion would be 1/10^th of the label rating for general recharging. If the voltage is sufficient, you will charge a battery even if the current is lower, it would just take longer to do so.  To much current is not recommended as this can cause thermal issues inside the battery if used too frequently. "

So it seems that 7A not that critical and 8A, if not used too often, will be fine

 

Edited 3 February, 2023 by RIncewindwiz