12V Battery Failure and Upgrade to Group 48 AGM

I experienced somewhat of a weak start one morning a few months ago. But it didn’t happen again. Weeks later, I was listening to music over my lunch break and the sound quit. That was strange. The stereo was still on and the time counter was still running. After a small amount of troubleshooting, I concluded that the battery voltage had fallen to a point that the Helix amp had shutdown and all I needed to do was start the car and recharge the battery. That was my hint that the battery was nearing the end of its lifespan… after just two and a half years. I went to a shop and saw that they carried Interstate batteries and asked about it a replacement. The shop owner said “If the car starts, then you don’t need a battery.” I heeded his advice to wait. Four months later, I got the dreaded “click” when I pressed the START button.

I was prepared to write an article about how the Helix amp served as a “tattle-tail,” a subtle warning that the 12V battery may be starting to fail. However, the stereo worked fine during this recent no-start event. The battery’s voltage was fine, but it simply had no “oomph” or cranking current left in it. I was interested in upgrading to a Group 48/H6 battery by Interstate. As luck would have it, the local Interstate dealer, which happens to be the same shop that told me I didn’t need a battery, is closed on the weekends. I visited this GolfMk7 thread to see what people were recommending as replacements and discovered this battery, which is carried by Batteries Plus. Guess who’s open on the weekends, including Sundays? That’s right: BATTERIES PLUS!

I drove my daughter’s 2015 Golf to Batteries Plus and grabbed their last X2Power Group 48 AGM battery. This is a dual-purpose battery, meaning that it serves as both a starter battery as well as a deep-cycle battery. It’s made by NorthStar, is leak-proof, and highly-resistant to vibration. It’s also expensive, but should easily tolerate the abuse that my electronics suite puts on my car’s electrical system. The Mk7’s battery tray features three holes for mounting the battery’s hold-down bracket. This allows owners the flexibility to either upsize to a Group 48 (from the factory Group 47) or downsize to something smaller, which seems to be of interest to those to track their VW’s.

The Group 48 battery is a tight fit, but it does fit in the tray and the factory retaining bracket holds it as designed. It’s difficult to install without bumping or sliding it on the airbox. I discovered that by accident while recording this video. This incidental contact, which can cause scratches on the top of the airbox, can be avoided by either removing the airbox or by placing a towel on top of it. I managed to install my battery with only the tiniest of scratches on my airbox (see photo). Lesson learned for next time. That said, this battery may last so long that I’ll forget about the challenge of installing it. HAHA!

Before starting the car, the CAN Gateway module must first be told that the battery has been replaced. I have both VCDS and OBDEleven. I prefer OBDEleven for most tasks because of the convenience it provides through my smartphone. Rather than detail the steps on how to update your battery information here, I will refer you to this discussion as well as my video, both of which should get VCDS/OBDEleven users through the process. If you don’t have these tools, then you either need to purchase one or go to a professional who understands modern Volkswagens. Now that I’ve done the battery adaptation, I’m not 100% certain that this step is necessary on cars that do not have the START/STOP feature, which also have the Battery Energy Management (BEM) system. The information that had been stored in my car did not match the labels on my factory battery. However, the fact that I was able to change the coding for the battery suggests that it either needs to be done or, if the information is ignored in non-BEM cars, that updating the info is not hurting anything. I recommend storing the factory information, just in case, and then entering the new data. See my video for an example.

Upgrading to a Group 48 battery will render the stock cloth-like battery cover useless. It’s designed for a Group 47/H5 battery and will not fit a larger battery. I’ve had a few people with sharp eyes notice the battery cover that I’m using. I actually installed this cover months earlier because I was looking for a solid place as close to the battery as possible to mount the 100-amp circuit breaker that serves the electronics panel in the back of my car. The cover is a little too long for the stock battery, but it still worked fine. It’s a perfect fit for the Group 48 battery. I bought mine through AliExpress, which sells a multitude of products that are shipped directly from manufacturers in China. These items sell out and reappear under a new heading too frequently to maintain links on my site. Click here to search AliExpress for “Volkswagen Battery Cover” and then scroll through the results. You’ll find several samples. I usually avoid “knock-off” products. But this is a piece of plastic, not a turbo or wheel. Feel free to buy this with confidence, especially at its low price. It fits fine and is held in place by small retaining nubs.

Fully Charged,


About Scott

I grew up near Houston, TX and served in the U. S. Coast Guard for over 30 years. I have an electronics background and continue to work in the electronics engineering field. I taught myself the basics about automotive systems as well as how to perform some of my own maintenance (cars and bicycles). I became involved with Amateur Radio and computers in 1995. The explosion of technology has made my job and several of my hobbies quite interesting. My hobbies include Volkswagens, bicycling, photography, electronics, amateur radio, web management, and reptiles. Visit my websites to learn more.
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