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Battery / Battery Charging Issue

4313 Views 13 Replies 6 Participants Last post by  Kasi
I’m after help regarding a battery /charging battery issue I seem to have on my 2009 A5 3.0 TDI

After 7 months of swapping the original battery out with a new Yuasa equivalent (as the car complained the old battery kept being low) the new one now dies without warning. At no point does the car even warn it is low and just fails to start.

I’ve done a bit of checking and this is what I’ve observed:
  • After starting the voltage at the battery is it 13.2v but then slowly rises over the course of a minute or 2 to settle at 14.5V
  • The battery voltage just after stopping the car will be at 12.8V or 12.7V but then will drop after about an hour, sometimes as low as 12.1V. I’ve done numerous long motorway journeys (2 hours+) but still the battery will not hold above 12.4V
  • The charge current to the battery after starting (measured by a current clamp meter on negative battery terminal) shows 15A on initial start but drops down to only 5A within 2 minutes. After long journeys (2 hour) still shows at 1.4A
I got the battery checked back where I bought it and they couldn’t find anything wrong when using there handheld Yuasa diagnostic tool.

Also while the battery was out I took the opportunity to checked the current draw for any potential leakage that maybe draining it but the max draw was only ~10mA after 2 minutes of the car being locked.

My initial thought is that this is all due to me not programmed a new BEM code after changing the battery, as when looking at changing the battery originally it seems to suggest I wouldn’t need to with my car being older and without stop start etc. Unfortunately, as Yuasa do not seem come with a BEM code (or at least the equivalent battery I bought doesn’t) I just changed the serial number of the battery in the hope that’ll help about 1 month ago at a garage, but still no change!

So can I please ask if anyone has any ideas on the following:
  • Why the battery is unable to hold more than 12.4V?
  • The car seems blissfully unaware when the voltage gets low?
  • Does anyone also know if what I’m seeing regarding the slow increase of voltage at the battery terminals from the alternator on start, and the quick drop off of charge current to the battery is normal?
My first thought was a faulty alternator but now I’m not too sure. I’m now thinking that it’s possibly not programming a new BEM code which has damaged the battery and hence why I’m seeing it not hold above 12.4V and it struggling to accept charge, even though it seems to test fine on the shop’s tester.

What are people’s thoughts on this?

If I have damaged to battery has anyone had much luck with smart battery chargers that are supposed to help condition batteries? Just wondering if it’s it worth forking out on one to see if that may sort the battery?

Any help on this will be greatly appreciated.

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Some more useful information in figuring this out might be the starter battery PR code for car (on the vehicle info sticker, starts with letter 'J') and the replacement Yuasa starter battery model number you installed. Do you have VCDS or equivalent VAG aware diagnostic tool ?

Battery (re)coding is only needed when the car is fitted with Battery monitoring control module J367 (on the negative terminal), though I suspect your A5 has this.

Re smart battery chargers, I think a good case can be made to have one of these around. The charger Audi sells (420093050E) is a rebranded CTEK MXS 5.0 (MXS 5.0 UK). We keep one connected to our A4 when the A4 is parked in our garage for an extended period (info HERE). We have another for conditioning the batteries for our sailboat during the off season. --g
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Hey. Not sure but sure worth hooking up to a obd2 thing and ideally VCDS to see if this can shed any light.

Also Yuasa are generally excellent quality batteries and the CTEK chargers are fantastic. I have several and they even managed to bring a large van battery back to life?
Thanks Both!

Funny enough I actually bought a CTEK MXS 5.0 straight after my original posting due to amazon having a deal on them. I plan to hook it up this week if I get chance to see if that will help.

I believe my car does have a battery monitoring control as I did wonder about the 2 wires coming from the negative terminal when changing it, which makes sense now.

The Battery code is J0Z (which I believe is a 110Ah?). The Yuasa I bought is a HSB020 (Here). Couldn't find the battery model on the Yuasa site so I think this has been rebranded/packaged. However I believe this is identical to the YBX5020 (Here)

I don't have a VCDS unfortunately, only a Carista. Luckily I'm quite friendly with the guy who runs the garage that services my car so he was happy to help change the serial number to see if that would make a difference. I have looked before to see if there were any VAG specific error codes regarding the battery, but noting that I noticed then. However I will check again tomorrow using the Carista to see if I've missed something obvious.

Does anyone know if changing just the battery serial number will help in this case? I presume in not changing the serial number the first time round has impaired the battery capacity possibly? I have tried to contact Yuasa on the off chance they could give me a BEM code for their battery, but so far I've not heard anything back from them yet.
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I remembering watching a youtube video about changing the serial number:
@ 7:35

he says it's not about changing the serial number, but he did it anyway. hahaha.
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This forum had another thread recently about the Halfords Yuasa flooded 110 Ah starter battery, which is equivalent to VAG 000-915-105-DL; it must be that Halfords has an arrangement with Yuasa for their HSB020. If your old starter battery was a conventional 110 Ah battery, changing the serial number by a single character is sufficient to tell the BEM that a new battery of the same type is installed. Interesting that the page for YBX5020 shows that Yuasa also sells a rebranded CTEK MXS 5.0 charger.

Re Carista, I have their BT adapter & app from years ago (got it when the full app license was US$20 for life), as well as VCDS & a couple other VAG-aware tools. It's definitely useful when we take long trips in our A4 or Golf Variant TDI. For an economical mid range solution that includes module adaptation & encoded, the XTool V401 is useful: XTOOL VAG401 OBD2 Auto scanner diagnostic tool for Audi/VW/SEAT/SKODA
In fact, I just helped a fellow in NZ recode his BCM using one of these so that the DRL control worked in the MMI Car menu again after a trip to the dealer for an unrelated matter (discussion over on Audizine). --g
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That's really good to know about the XTOOL DrGER, thanks for that. That seems to be able to do a lot for something that is quite reasonably priced (for a nice change).

Yes the old and new batteries are both 110Ah so I'm hoping that just changing the serial number now has possibly fixed the initial issue as you mentioned. Just got my fingers crossed that the CTEK charger can bring the battery back to life fully.

Does anyone happen to know if not changing the BEM code would also stop the car from warning of a low battery voltage? As I'm still not sure why the car has not warned me during when not being able to start.

Findalex that's quite amusing. Good to know the battery state is on 019. With my A5 being 2009 I'm not sure if it supports that but that's something else I can try and look at if the charger doesn't work.
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Mate I think that the car needs to kind of "recognize" the battery in order for it to be able to work 100% correctly. You know that these cars, if they see too little battery charge, start to shut down some non essential stuff in order to keep the charge for the important stuff. So I guess that if they dont know that the battery is good then you can have all sorts of (small ish) problems.
@A.D. Do your diagnostic scans mention “energy management active”?
So the plot thickens...

Checked to see if there were any OBD and Audi VAG Specific errors using the carista (I know it's not as good as VCDS but that's what I have currently) and couldn't see any mention of a 'energy management' or any battery related errors, which is good. @JohnS4 (or anyone else for that matter) Do you know if you can see a 'Energy management' fault on a carista or if there was a way of checking it the 'Energy management' is active?

However when checking for any errors I noticed that the voltage was only at 13.2V (engine still running after getting back from work). Normally when I've checked before the voltage is around 14.5V.

The next day I got the same low voltage reading when arriving back home so decided to check the current flow on the negative battery terminal and it was down to ~0.3A, which is lowest I've seen it. I was hoping that maybe the battery had fully charged and hence little current flow but when checking this morning the battery was down to 12.2V

Does anyone know if the voltage will drop once the car thinks the battery is fully charged? Or if the system will for some reason stop the battery charging? I'm somewhat confused with the low voltage.

I've now hooked up the CTEK charger in 'Recond' mode in the hopes that may help if the battery at fault
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Have a look at this recent thread over at Audizine: Voltage drop across alternator cable - bypassed stock cable with new cable

In that case, starter battery charging trouble was tracked down to a corroded cable terminal at the starter (from the alternator). In a 13+ year old car, these things can happen. Does Carista report charging voltage in the engine live data page ? --g
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Hi everyone, checking the parameters of my new Varta H15 AGM after making a trip of 220 Kms to charge it, I am not sure if the charging system works correctly.

In block 020 (I attach a screenshot of Vagcom) it indicates a real capacity of 72 Ah when I think that, being a new battery, it should indicate a value closer to 110 Ah, which is its real capacity.

Could someone who has recently installed an H15 send me that same Vagcom screen for comparison?

Thanks a lot.
Product Rectangle Azure Font Screenshot
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@Kasi : You don't say in your post what your application is (year & model) or the PR code for your starter battery from the vehicle information sticker, or whether you adapted the new starter battery to the battery monitoring control module J367 successfully. The Varta web site tells us that short code H15 is a 105 Ah AGM starter battery. --g
My car is an Audi Q5 from 2013 2.0 TDI quattro 177 CV S-Tronic MMI 3G+ and I have correctly coded the Varta battery: 000915105CF VA0 211207 xxxx
Any idea?
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