12V Battery Replacement Questions

[RecoverE]

I am into my sixth year with my 2015 eGolf @44Kmiles and want to replace my 12V Varta AGM battery with a Duracell AGM. They both have the same form factor including the mount holes for the terminal covers. The Varta is a 58Ah unit and the Duracell is 60Ah.

I plan to maintain voltage in the system during the exchange via a third battery appropriately connected via terminal clips. Can I expect a clean swap without the need for a service visit to register the new battery to the car? If there is a mis-registration with the new battery, what are the consequences until the issue is corrected? Is the car still usable?

I want to take this action now to see if a fresh battery (higher terminal voltage) will help with my occasional charge fault issues; i.e., failure of the power plug locking pin extending/retracting. So, I would appreciate any comments.

Thank you

 

[Spektre]

YMMV, but in my experience, replacing the 12v battery requires coding at the dealership (or DIY if you have OBDeleven or equivalent.)

I experienced the same disturbing behavior - bucking, error messages, etc - after replacing the battery as I did before removing the bad battery. Once I had it towed to the dealer, they coded the new battery in the system and it's been fine ever since.

I was able to find quite a bit of relevant info with this search.

 

[RecoverE]

Spektra, thanks for your response. When replacing your battery, did you maintain 12V battery voltage on the system when swapping batteries?
I am really torn on doing this exchange now given no obvious low voltage issues. However, my local VW dealer has little eGolf experience, so this fact is concerning also. In the absence of any additional encouraging comments, I probably will wait until I need dealer service for break/cooling system fluid replacements.

Thanks again.

 

[f1geek]

I believe coding is an absolute requirement so the car computer knows you installed a new battery. Not coding will probably lead to continued problems. I imagine the coding for an e-Golf is identical for an ICE Golf for a new 12 V battery.

 

[somethingcool]

Uh, definitely YMMV. I've had the 12v disconnected for more than a few hours on multiple 2019 eGolfs without issue. Sometimes you get the Christmas lights on startup but a turning it off and on a few times and a drive around the block always returns everything to normal in my experience. Maybe it varies per year, but I think you are reading way too much into a few people that had issues, the car was not designed to need "coding" for a 12v battery swap, not sure what that even means? The car has no way to tell one 12v battery from another.

What seems more likely to me is codes got thrown on cars that were running with bad 12v batteries, putting out low/unclean voltage and causing issues unrelated to the swap. Which would indicate your plan to swap before issues arise is a good one.

I would also not recommend this third battery to maintain voltage idea, seems way too likely to cause issues if you don't know what you're doing. Just swap one for one, no need to maintain connection at all times.

 

[RecoverE]

Thank you gentlemen for your comments. I did not realize that VW Golf MK7 ICE models had coding info. Interesting reading for me. Given the negative terminal current shunt, it seems that there is an effort to optimize charging as the battery ages. I will continue my research and again welcome further comments. I suspect that if I replace the OEM battery with one with similar specs, no coding will be necessary.

 

[Spektre]

Uh, definitely YMMV. I've had the 12v disconnected for more than a few hours on multiple 2019 eGolfs without issue. Sometimes you get the Christmas lights on startup but a turning it off and on a few times and a drive around the block always returns everything to normal in my experience. Maybe it varies per year, but I think you are reading way too much into a few people that had issues, the car was not designed to need "coding" for a 12v battery swap, not sure what that even means? The car has no way to tell one 12v battery from another.

Disconnecting the same battery and replacing the battery are two very different things. No one is reading anything into this, it is fact. There are 4 fields in VCDS that must be updated when replacing the battery, especially if it varies from the specs of the one you are replacing. At the very least the serial number field must be changed to let the car know it is a new battery.

https://www.golfmk7.com/forums/index.php?threads/how-to-retro-fit-a-bigger-capacity-battery-to-a-mk7-golf.320084/

 

[f1geek]

Some more information:

http://wiki.ross-tech.com/wiki/index.php/Battery_Replacement

and

https://www.youtube.com/watch?v=IJAScg6JrYI

At least you need to let the 12 V battery management computer know you installed a new battery and let it know Ah of said battery. It is most certainly easier to do nothing but swap the battery. If you've already spent money on a new battery, why would you not want to let the computer know you've done this so that the new battery is charged correctly?

 

[somethingcool]

If you've already spent money on a new battery, why would you not want to let the computer know you've done this so that the new battery is charged correctly?

Because the eGolf does not have a BEM system requiring this coding change. It's specifically for vehicles with stop/start systems. It won't hurt anything, but it also doesn't do anything, waste of time and effort.

Even for vehicles with start/stop/BEM not coding is fine, the ECU adapts to the new battery with time, making this coding useful but not required.

 

[somethingcool]

Disconnecting the same battery and replacing the battery are two very different things.

No, they are the exact same thing. This coding is for BEM equipped cars with start/stop feature. Does nothing in the egolf and is not even required in BEM equipped cars. You are misapplying information here without understanding the context.

The link you provided even acknowledges this: "Any VAG “MQB” platform cars (not Hybrids or Electrics)."

 

[f1geek]

The link provided to the golfmk7 forum says coding is necessary for cars with stop/start as well as for regular Golfs and e-Golf. It seems the coding is different, but still required. Also, you say coding is "useful". Why do think it is useful if you also say it is not needed? thanks!

 

[RecoverE]

To continue with my original post, I should receive the OBD11 Pro dongle today and will post my battery replacement experience by this weekend for anyone interested.

Thanks again for the comments.

 

[RecoverE]

I successfully replaced the original JCB 58ah AGM battery with a Duracell 60ah unit. I maintained voltage on the system with a third 12V battery and cables. After the exchange there were no codes indicating that the vehicle detected the change. Lastly, I used the OBDEleven dongle to define the new battery to the system -- amp hours, SN, and MFG. As an interesting observation, the dongle reports a battery voltage roughly 0.3v lower that that voltage measured at the battery terminals with a DVM.

 

[somethingcool]

necessary for cars with stop/start as well as for regular Golfs and e-Golf.

No it doesn't, I already quoted that post: "Any VAG “MQB” platform cars (not Hybrids or Electrics)."

I said it was useful as changing the battery serial number resets the capacity measure, but it's not needed because the car will learn it over time without a reset. I guess y'all are made of money if you're dropping all this extra money and effort for a placebo. To each their own, I'm just posting for the people who aren't suckers.

 

[f1geek]

$100 for software and dongle is a pittance. The e-Golf has a list price of over $30,000. I got OBDEleven to be able to read cell voltages, check on SoH, etc. Being able to properly code a new 12V battery is a benefit I did not anticipate, but I am glad I will be able to use it.

 

[BomBoi]

With weight in mind as well as longevity, what about Lithium ion batteries for our cars. i would think that little extra money and light weight can save time and hassle the long run.

 

[f1geek]

Makes sense, but I wonder if the typical super hot environment under an ICE car's hood is too punishing an environment for Li-ion, and thus few battery companies offer 12V Li-ion batteries?

 

[BomBoi]

I never thought about that . I guess as long as the company offers a good warranty, thats a great piece of mind . I was thinking about getting a battery from Antigravity Batteries.

This is their warranty info on them.

"Antigravity Batteries LLC warrants to the original purchaser that our batteries are free of defects in material and workmanship for the
Prorated term of 5 years. This will encompass a 3 year Direct Replacement period, with the final 2 years being prorated. All batteries
must be registered within the first 30 days from the Original Purchase Date or Original Purchaser must provide a copy of the Original
Receipt in order to be eligible for a warranty claim. Only the Original Purchaser will have the Warranty Coverage. Warranties are
non-transferable. Returns will only be accepted from the Original Purchaser. The Applicable Warranty Period begins from the date of
purchase with Original receipt. "

 

[f1geek]

Sounds good! I have an Antigravity Li-ion jumper battery for my wife’s fossil gobbler and it has been good so far, though I have only used it a few times to jump start a car. I’m guessing these are LFP cells which are very durable.

 

[BomBoi]

I just saw this last night and saw the post about FCP and programming the battery on MK7

https://www.youtube.com/watch?v=0T2LQNbjABM

No need to program the batteries unless it has battery management. It looks like a small control module on the negative terminal. Typically if you have start/stop it will have it though, in that case you need to have it reprogrammed at a shop or dealer after reinstall.

So i have a battery management module on my egolf.

I will be taking the plunge with an Li battery once the time comes.

Wish me luck!