Stromer Troubleshooting and Diagnosis Part 1

So, I have done a bit of research in my off time to get more acquainted with the Stromer electric-assist bicycle.  It is the other brand of ebike that we carry in our shop and is notable for its price point and performance.  Not only will it go quite a bit faster than the Turbo (about 50kph or 31mph), but it also comes in at a price point of about $3,500 USD versus the $5,999 tag on the Turbo.  Both equate to an amazing experience on a bicycle, but this option seems more affordable than the Turbo without sacrificing quality.  I like to think of the Turbo as an ebike with style where the Stromer is a workhorse that won’t quit and won’t deteriorate under pressure.

That being said, I wanted to go over a few parts of the Stromer that I have worked with and what expect for a long term review in the future once I ride them a little more.  The Stromer is designed by BMC (the company chose to call itself the initials of its UCI code), a Swiss manufacturer that’s founder was the owner of the famous 711 racing team.  They make two models: the ST1 and the ST2.  Both can be configured with various options from a suspension fork or carbon fiber fork to three levels of motor power and two battery levels.

Stromer ST1 Specs

Stromer ST2 Specs

The ST2 is an upgraded version that has a possible range of 150km on one charge.  That is on of the longest lasting battery specs on the market with 814 Wh.  The newest model has a smartphone integration for real time stats and data.  With built in lights, fenders, and a rear rack, it is a notable competitor for the Turbo S and when the newest model hits our shop, I’ll be posting a review on it.  Until then, I will be dealing with troubleshooting the Stromer ST1 and ST2 from prior years since they are more common.  Having all the information I have gathered in one place will help both you and myself as it expands.  From past research, I have not found very useful information on the Stromer on the Internet and have relied mostly in swapping components from a new build to the repair and having replacements sent from the representative for the company in the USA.  That being said, there is still a great deal of information that can speed up repairs and diagnosis and keep your customers happy and riding.

Much of the issues I have come across seem to deal with replacing the display unit or cleaning connections.  One issue dealt with a bad charger (It should be noted that the charging process of the battery off the bike is very specific).  First, plug the adapter cable to the battery.  Then plug the opposite end of the adapter cable to the charger plug.  Next, plug the power cord into the opposite side of the charger from the adapter cable.  Lastly, plug the power cord into the wall.  You should see a red light appear in the LED bubble on the side of the box charger.  After a few seconds (up to about 5 sec), it should change to either an amber color (signifying it is charging) or green (Stromer recommends leaving the charger on while the LED is green for about an hour for maximum charge level).  If the charging connectors are not plugged together in the correct sequence, damage can occur to the charger and the battery and result in a solid red LED on the charger box.  If this is the case, consult your dealer for a replacement charger.  I have had confusion come from customers on the charging process and it has led me to have to deal with recharging a supposedly malfunctioning battery with a new charger.  In these instances, I also try charging it through the bicycle, which helps to eliminate the battery being the issue.  Here are the photos in order of the process.

Cleaning the connectors should be done carefully and with the battery out of the bike.  While an electrical discharge is not likely, be safe and take the battery out first.  This also provides an opportunity to check the connections for the battery inside the frame and on the battery itself.

Here are a few photos of the various electrical connection on the bike.

The two main issues of display replacement have been related to the information messages shown on the display.  One issue of NO_BATT appeared on the display after only a couple of weeks of use.  I checked the battery both in and out of the frame and the connections leading from the display to the battery.  All of them seemed clean of debris or liquid and were securely connected.  The next step was to reset the display to see if the system would correct itself upon start up.  I removed the display from the handlebars by disconnecting the wires and taking the two anchor screws out of the band mount.  Once removed, I used a quarter to turn the battery cover to the open position underneath the circular gray foam pad protecting it.  Taking a scribe, I popped the cover open and removed the CR2032 battery and inspected the two terminals inside the battery compartment.  Both also seemed clean and correctly positioned for contact.  Taking a new CR2032 battery, I installed it carefully and then put the battery cover and foam pad back.  Mounting it back onto the handlebars, I proceeded to carefully connect all of the wires appropriately and turned the system on.  The message of NO_BATT remained and I contacted the rep about a replacement.  In the short-term, I went ahead and connected a brand new display from a model not yet built to this Stromer and everything seemed to work great afterward.  The replacement unit came in and I reinstalled it onto the new build without issue as well.

Another issue I came across (though I believe it to be from either improper assembly or repair in its past and not from a defect) was a mechanical one.  The spacer nut on the rear axle drive side that correctly positions the freewheel away from the frame was completely missing.  I was able to find a suitable spacer and nut at a local hardware store and the wheel spins freely once again.  As the wheel was initially mounted, the high end of the freewheel was locked against the inside of the rear dropout on the frame and scored a fine line into the metal.  If this had continued, the frame would have likely had to been replaced.  You can see it in the photos here.

I am still not finished with the diagnosis of this particular model.  It has seen quite a few miles of use and also has an issue with the display showing an information message of NO_COMM.  This error means that there is a disruption in the communication between one or more of the components.  I scanned through the connectors, but could find little evidence of a bad wire or connector.  The only connection that seemed to have suffered from the weather was the connection to the rear dropout shown above in the right photo and above on the inside of the chainstay.  I question whether attempted use of the bicycle with the freewheel in its original condition as it came to the shop would have overloaded or shorted the sensor in the frame.  This information has been forwarded to the rep for possible solutions and extra wires to swap and test.  Otherwise, I will attempt to receive a replacement display to test (the models in the shop utilize a 2 wire display, where this model uses a display with 4 wires).  My general feeling is that correction of the rear wheel axle assembly and replacement of the display and rear dropout wire will fix all of the issues.  The bike has had a replacement rear wheel already, so the motor should be in good working order.

I will add to this article as the project progresses!  Feel free to message or comment any questions or suggestions.

– SNC

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5 thoughts on “Stromer Troubleshooting and Diagnosis Part 1

  1. Hi, I have recently ran into the “No Comm” error message. My stromer ST1 platinum was purchased in Dec 2014 and I have 7000 miles on it. But recently when I was on a 45 mile ride (have an extra battery), on about mile 42 I got the message and the bike shuts down. I was able to let it cool for about 5 mins and complete my ride in Eco mode. It seems to be getting worse, as the last two times it happened were on much shorter rides, and then today happened after only 12 miles.

    What did you determine was the issue?

    Unfortunately, I no longer live near an ebike dealer, so have to do my own trouble shooting.

    1. I have seen this once and usually is either a bad LCD or LCD battery (on bottom side of display) or the bike has not been charged in a long time (a month or so without turning on or charging) which causes it to go into a deep discharge state. This pretty much kills the battery. I haven’t ever been able to revive one that has done this. A similar issue that the LCD displays in the case the LCD is bad is a NO_COM message. Once the LCD was swapped, the bike worked fine. My immediate suggestion is to disconnect all of the exterior wire connections and affirm they are not corroded and then connect them all again.

  2. So would it be safe to assume that a bike that has been sitting for months, uncharged (and long enough for the LED battery to die), has a dead battery if the LED now has a flashing “no comm” and battery icon? It has less than 100 miles but has been sitting over a year. Asking for a friend 🙂

    Oh…..and is there a replacement battery that doesn’t cost $600?

    1. Yes. The battery is likely in a deep discharge state which ruins it. I am pretty sure 600 is about the going rate for a new one. I would have your friend go to a Stromer dealer and see what they can do if it is only a year old. Bring the purchase documentation as well. The company has great customer service and may have some options.

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