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Troubleshooting A Dead BMW GS – What Finally Killed My G650GS?

In this article and video I’ll be sharing my experience of troubleshooting a mysterious problem with my 2011 BMW G650GS motorcycle that resulted in the motorcycle dying on me suddenly while I was riding. No lights would come on, and even the dashboard wouldn’t light up. I was concerned a new G650GS LED headlight I installed may have been the problem.

In the end the problem wasn’t my aftermarket headlight, a burnt fuse, rust in my fusebox, or a bad battery connection. I had an unusual battery condition which can very easily be missed when trying to diagnose your dead BMW GS or any other motorcycle. I’ll walk you through the steps I took to diagnose my issue, so you can follow this if your BMW GS, or any other motorcycle, ever leaves you stranded.

watch this video

Watch this video!


Getting the motorcycle running again

When your BMW GS, or any other motorcycle stops running and behaves like this, you always want to start with the most simple things first. I recommend starting by checking the terminals going to your BMW GS’ battery. Are they clean, rust-free, and connected tightly? A loose ground terminal can cause a total blackout of your motorcycle.

Next up, you’ll want to check the fuses in your fuse box. Are any of them burn out? If so, replace them and see if the problem reoccurs. I checked my fuses and despite the fuses being in good shape, I found corrosion in my fuse box. What’s that about?

BMW G650GS corrosion in fuse box

If your battery connection and your fuses are in great shape, then the next thing to do is get a multimeter. A multimeter is a very inexpensive tool used to measure your motorcycle battery’s voltage. They usually only cost around $10. When I measured my battery’s voltage it read 12.7 volts which appears to be normal. On about 90% of motorcycles, a battery reading 12.7 volts is 100% perfect for a lead acid motorcycle battery that has been sitting at rest for a few hours.

However, I noticed that my battery felt warm to the touch, which was strange given that the motorcycle had not been running for some time. That’s when I remembered the battery in my BMW G650GS wasn’t a lead acid battery, it was a lithium battery. Could things be different with lithium batteries?

I decided to take the voltage reading of another lithium battery. It read 13.3 volts, that’s substantially higher then the 12.7 volts of the battery in my GS. This is weird because at rest the two batteries should have the same voltage, if both of them are healthy. I remove the 12.7 volt lithium battery from my GS and put the 13.3 volt lithium battery in my BMW. Instantly the GS fires right up.

Figuring out the root cause of the problem

So now I know there was an issue with my battery, but I’m left wondering: Was the motorcycle failing because the battery had failed, or had the battery failed because of a problem with the motorcycle? Simply replacing a battery will only leave me stranded again if the root cause of my problem was a charging system issue. I need to get to the bottom of this, and if you have a motorcycle starting issue so should you.

A motorcycle’s charging system failing could cause a battery to fail. I also have that aftermarket LED headlight that I recently installed and if that’s drawing too much power it could also be causing problems for my battery.

Testing BMW G650GS Charging System

Time to once again take out the multimeter. I decided to test my motorcycle’s voltage at idle to see if the headlight was drawing too much power, but it wasn’t. I also tested my motorcycle’s charging system by making sure the voltage was within specifications while revving up my motorcycle, and it was. I have detailed instructions on how to test your motorcycle’s charging system here. Neither the headlight or my charging system seemed to have any problem. So why did a relatively new lithium battery fail?

Lithium batteries are tricky

Lithium motorcycle batteries are very different from traditional motorcycle batteries. First, they need to be charged using a different kind of battery charger than a traditional lead acid motorcycle battery. Second, the way they’re constructed is very different from lead acid batteries. A lithium battery has more technological components.

I reached out to the battery manufacturer and explained the situation to them. First they had tech support make me re-test my charging system over the phone with them. Later, they sent me an email asking if I could send them my lithium battery back. They explained that it seemed that my battery’s capacitor component may have failed, and that due to supply chain shortages they found a new supplier for these components which they were having some problems with. The manufacturer asked me to send them the battery back for testing.

Upon receiving the battery, the manufacturer let me know that my capacitor had been one of their new batch which they were having problems with, and they sent me a new battery at no charge.

The five lessons I learned

I’m sharing this experience diagnosing my dead BMW G650GS so that you can quickly and easily learn from me. Hopefully this makes diagnosing your own motorcycle much easier. Here are my five key takeaways:

1) 12.7 volts on a lithium motorcycle battery is not the same thing as 12.7 volts on a lead acid battery. A fully charged and healthy lithium battery should read 13.3 volts at rest. At 12.7 volts my lithium battery was as good as dead, whereas a lead acid with that voltage would have been perfect. Had I assumed my lithium battery was fine because of the 12.7 volts reading, I would have missed the problem altogether and spent a lot of time and money having a shop diagnose my issue.

2) A multimeter is still one of the best things you can spend $10 on if you want to be able to solve your own problems on your motorcycle.

3) Don’t just take a loss and think “Oh well.” A lot of people would have been too lazy to contact the manufacturer and mail a product back to them. Yes, I did have to pay shipping to send their product back to them, but it meant getting a brand new one shipped back to me for free. Definitely worth it.

4) The LED headlight for the BMW G650GS is a great upgrade! I’m still not particularly fond of the build quality, the LED color, and the installation, but it’s quickly becoming one of my favorite G650GS upgrades.

5) Never stop learning. Had I rested on my laurels I would never have second-guessed the voltage being bad, and I would never have questioned the manufacturer on why the battery failed. I’ve been riding for 16 years and I learn about new stuff every day.

If you want to learn more about motorcycling with me, subscribe to YouMotorcycle on YouTube. I have a ton of how to videos and other informative motorcycle content. Thanks for watching, ride safe, but have fun. Peace!

About Adrian from YouMotorcycle

I started riding motorcycles in 2007, founded YouMotorcycle in 2009, and was working in the motorcycle industry by 2011. I've worked for some of the biggest companies in motorcycling, before going full-time self-employed in the motorcycle business in 2019. I love sharing his knowledge and passion of motorcycling with other riders to help you as best I can.

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