My battery (TDi) is starting to get sluggish starting the car.

I'm guessing it's starting to go, but having a battery charger at home I'd like to try giving that a try before buying a new one.

 

So, if I pull the battery out and charge it, what kind of issues will I have when reconnecting it? Minor things like clock reset I'm not worried about, more if any major systems would need some kind of external influence to reset them?

 

If this is difficult, could the battery be recharged while still in the car without effecting the modules in the car?

 

Thanks

Would have been best to keep with your existing thread probably, but yes you can charge on the car.

Positive to the postive pole on battery, and Negative to chassis, not to the battery negative pole.

 

Ideally, go to the car, and take a picture of existing battery and also of the battery area so that you can see the negative clamp and the area behind if possible (don't zoom in too close, need a general overview)

Do not charge the battery off the car.

 

the car keeps track of the batteries charged capacity, if you remove it and charge it off the car it will loose track.

 

Do not connect the negative to the battery terminal directly! This will bypass the current monitor sensor.

Instead connect it to the ground point on the bulkhead.

 

positive can go to the positive terminal 

I made the mistake of not charging my battery properly, went on the neg terminal.

 

How to I 'reset' it all.

 

Charge unplugged from car and then run an adaption and make out it's new?

14 minutes ago, RoddersUK said:

I made the mistake of not charging my battery properly, went on the neg terminal.

 

How to I 'reset' it all.

 

Charge unplugged from car and then run an adaption and make out it's new?

If you have driven it a few times since, then I would not worry about it.  The car soon figures out what is what from measuring, sure it might think it has X stored when it is Y, but the system will soon balance to Z.

 

I wouldn't otherthink it myself.

Ok, just thought as my battery sits quite low, that may have been why.

I'll carry on as normal!

Just now, RoddersUK said:

Ok, just thought as my battery sits quite low, that may have been why.

I'll carry on as normal!

Depends on what you mean by low, and how long you leave before measuring etc.

I dare say you will be ok, even more so coming into warmer weather.

12.2v after a while, I thought it's a bit low, but reading other threads, the car consumes power the second you open it, or after you've stopped.

 

We do quite a few small journeys.

 

Battery is coming up to 2 years old.

 

Never starts slow, but I'm sure I remember seeing 11.9v on crank once.

40 minutes ago, RoddersUK said:

12.2v after a while, I thought it's a bit low, but reading other threads, the car consumes power the second you open it, or after you've stopped.

 

We do quite a few small journeys.

 

Battery is coming up to 2 years old.

 

Never starts slow, but I'm sure I remember seeing 11.9v on crank once.

I would say 12.2 is a little on the low side for a 2 year old, but not terribly so.

 

My 7 year old AGM would be 12.1V left for a week in the cold.  Still started, but you could feel it was getting a little wheezy, so I replaced it.

I'm not overly convinced it was great from new, maybe I should have questioned it. 

I think it has a 4 year warranty, will have to check, just in case....

8 hours ago, varooom said:

I would say 12.2 is a little on the low side for a 2 year old, but not terribly so.

 

My 7 year old AGM would be 12.1V left for a week in the cold.  Still started, but you could feel it was getting a little wheezy, so I replaced it.

My AGM battery is now on 12.2V. Hasn't been run for last 24 hours.

13 hours ago, ApertureS said:

Do not charge the battery off the car.

 

the car keeps track of the batteries charged capacity, if you remove it and charge it off the car it will loose track.

 

Do not connect the negative to the battery terminal directly! This will bypass the current monitor sensor.

Instead connect it to the ground point on the bulkhead.

 

positive can go to the positive terminal 

But if you charge the battery in the car with the car off, is it still going to be checking?

The battery has a SOC (State of Charge) value that is low, but not on deaths door.

 

11.7V = 0% SoC

12.7V = 100% SoC

 

So each 0.1V adds 10% SoC to the value, the car during normal operating will aim to keep the SoC at 80%, so 12.5V, this allows regeneration from braking to not overcharge the battery.

 

12.2V is a little on the low side after 24hrs, and would suggest it is heading towards the end of life, but doesn't mean it's right now, mine I swapped at 12.1V after sitting for a week.

 

I would charge it on the car once a week, for say 2 weeks, and then take some daily readings after that to see how it is now.  It might breath some extra life into it.

 

 

I did charge my new battery off the car before fitting, no ill effects seen (though I did adapt battery with VCDS)

 

It is the "correct" method to charge on the car ideally, but won't exactly break it's brains if you don't.  The car just won't know right away what's stored.

Considering my battery is for start/stop, which I always turn off.

Even after 2 years of shortish journeys, mixed with some long, I wouldn't expect it to be near end of life.

2 hours ago, RoddersUK said:

Considering my battery is for start/stop, which I always turn off.

Even after 2 years of shortish journeys, mixed with some long, I wouldn't expect it to be near end of life.

It might be the bad move maybe, as they are designed for deep discharge.  Perhaps keeping the stored energy and not letting it depelete harms AGM?

Sadly don't know the correct answer to that, just I rarely disable SS in normal driving, and my batteries have lasted years.

Not sure, thought I was helping it not cycling it too many times.....maybe that's wrong.

1 minute ago, RoddersUK said:

Not sure, thought I was helping it not cycling it too many times.....maybe that's wrong.

Maybe it needs the drainage to act like exercise, either way this could be fascinating reading to know for sure.

I think it's @ords who has the record of longest running AGM iirc, hopefully he will respond with how long his battery has been alive for.

1 hour ago, varooom said:

Maybe it needs the drainage to act like exercise, either way this could be fascinating reading to know for sure.

I think it's @ords who has the record of longest running AGM iirc, hopefully he will respond with how long his battery has been alive for.

It was 10 yrs old in January going by the mfg code. Car was registered in Mar 2013 and I bought it as an ex demo in Sept 2013.
Its always had long periods of discharge of between 3 to 4 months and has always had enough power to start up. Start stop has always been used.
These days, because I know I'm on borrowed time with it and hardly using the car, I'll start it up after about 6 weeks and run around for an hour or so. I can't use a charger without taking the battery out.
My previous 2005 Octavia 1.6 petrol had exactly the same treatment and the battery was ok at 8.5 yrs old when I sold it.

17 hours ago, RoddersUK said:

12.2v after a while, I thought it's a bit low, but reading other threads, the car consumes power the second you open it, or after you've stopped.

 

We do quite a few small journeys.

 

Battery is coming up to 2 years old.

 

Never starts slow, but I'm sure I remember seeing 11.9v on crank once.

I've just had my 4.4 year old battery replaced, was at 12.28v prior to starting, had s/s fault come on a few times, prior to starting. After testing it with my multi meter, then had it load tested at my local garage whom also confirmed it needed replacing. It's an EFB battery, new battery replaced, now reading 12.6v at rest, s/s light not come on since and my s/s now seems more reliable. 

New battery has a 2 year guarantee. 

Just been looking at when I bought my battery, 3rd aug 2021 I chucked one of these in:

E39 Varta Start-Stop Plus 096 AGM Car Battery 12V 70Ah and recoded it.

 

Just gone and sat in car, warmer weather clearly helping. Started @ 12.34v, then as lights went off etc... 12.5v.

 

That a do!

Edited 12 May, 20233 yr by RoddersUK

2 hours ago, RoddersUK said:

Just been looking at when I bought my battery, 3rd aug 2021 I chucked one of these in:

E39 Varta Start-Stop Plus 096 AGM Car Battery 12V 70Ah and recoded it.

 

Just gone and sat in car, warmer weather clearly helping. Started @ 12.34v, then as lights went off etc... 12.5v.

 

That a do!

If it has a 4 year guarantee, may be worth having it load tested. As I'd say it was a little low at 12.34v, swapped mine at 12.28v. Mine being an EFB, yours an AGM. I was quoted a £10 difference between the two, fitted. 

I either need to send it back @ £20 or get it load tested locally and pay for that.

Probably easier to wait a while and buy  a new one then send it off.

I have a load tester at work, but it's not calibrated with any way of printing a result out, so the company I bought my battery from won't accept it.

Alright, so found out you can't use a normal 12V charger to top up an AGM battery.

 

And as it's at 60%, and my uncle works for a battery supply company, I've decided to get a new one.

 

Considering the original is almost 8 years old and I've only disabled stop/start since I bought it 3 years ago, I suppose it isn't bad.

 

Anyway, the replacement I've lined up is another AGM similar to what I've got, but the AH & CCA are different (now higher)

 

68AH to 70AH

680CCA to 760CCA.

 

Are these different enough to need to get an adaptation done?

 

Thanks

13 minutes ago, wagonist said:

Alright, so found out you can't use a normal 12V charger to top up an AGM battery.

 

And as it's at 60%, and my uncle works for a battery supply company, I've decided to get a new one.

 

Considering the original is almost 8 years old and I've only disabled stop/start since I bought it 3 years ago, I suppose it isn't bad.

 

Anyway, the replacement I've lined up is another AGM similar to what I've got, but the AH & CCA are different (now higher)

 

68AH to 70AH

680CCA to 760CCA.

 

Are these different enough to need to get an adaptation done?

 

Thanks

You'll need to get an adaptation done because you're fitting a new battery. The CCA isn't something the BMS knows about and the difference between 68AH and 70AH is so small there's no need to change the AH details so all you need to do is change the serial number - just change 1 digit that's enough.

3 minutes ago, PetrolDave said:

You'll need to get an adaptation done because you're fitting a new battery. The CCA isn't something the BMS knows about and the difference between 68AH and 70AH is so small there's no need to change the AH details so all you need to do is change the serial number - just change 1 digit that's enough.

So if the AH is so small difference, then does it really matter then if the serial number is correct? Sorry, it kind of seems contradictory.

I saw something on a vid about some people putting the installation date in there instead of serial number, so that might be kind of useful to work out how long it lasts.

5 minutes ago, wagonist said:

So if the AH is so small difference, then does it really matter then if the serial number is correct?

Yes, it's the serial number that tells the BMS a new battery is fitted. If you don't change the serial number then the BMS will assume the old failing battery is fitted and is likely to start turning off systems to protect the old battery that's no longer fitted.