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Bosch cutting out

Old 06-15-24, 07:20 PM
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Bosch cutting out

My (our) e-tandem which has the Bosch Gen 4 Performace Line CX BDU450CX (copy/pasted from spec sheet) is cutting out on us, briefly and often, on hills. I had the exact problem with my e-MTB, also Bosch, but fixed it by putting an extra magnet adjacent to the original magnet on the spoke. The tandem has worked flawlessly for the first 2 years of riding but now cutting out, always on hills, and seemingly random. The speedometer flashes speeds over 20mph explaining why the assist is stopped briefly and annoyingly and not great for old knees. I've now put 2 additional magnets adjacent to the Bosch magnet and they have made no difference. The alignment of the magnet is the same as it has been and is correct according to the Bosch manual. Obviously Bosch has issues as this is 2 out of 2 bikes with their system. Suggestions?
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Old 06-16-24, 04:18 PM
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You did not say what make your tandem is. In looking up online tandems that have Bosch Gen 4 CX motors, found that a couple have their motor located at rear BB and a couple have their motor at front BB. Could not see whether those tandems have their sensor cable is routed in-frame or out-of-frame. The concern about motors located at the front BB would be that the cable for the rear wheel sensor would have to be extra long, with maybe a splice or connection before the lead plugged into motor terminal.

Bosch changed the sensor for Gen 4 Ė donít know how it mounts up versus how the earlier ones mount up. Have heard that the sensors are finicky about only using Bosch magnets. Also for Gen 4, the motor terminals got moved to the lower side of the motor Ė would watch for splash getting into this part of the motor during rainy day rides.

What Iím getting at is - maybe it could be the cable or the connection(s)?
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Old 06-16-24, 04:29 PM
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sounds like a connection issue or wheel sensor issue. what control do you have? the connections there could be an issue or the wheel magnet mine rotates on its own over time.
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Old 06-16-24, 05:22 PM
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Thanks for the reply. Ours is a custom tandem designed and assembled by a small bike builder and mechanical engineer. Overall it's been a great bike. This is our third tandem; without e-assist we would not longer be riding. The motor is at the stoker (rear) BB. Good info about possible water issue as the bike has almost exclusively been ridden in So Cal but is now in "damp" New Hampshire. I will buy another Bosch magnet and try it along side the original Bosch magnet. The two i added are not Bosch and they aren't as "long" as the Bosch magnet thus not getting as close to the sensor. They certainly did nothing to improve the drop out. The second magnet I added to my e-MTB was also not a Bosch magnet and one I found on an old bike. It worked to fix the drop out problem on that bike.

So now I will see if I can figure out accessing the cable connection ...

Originally Posted by TmMc
You did not say what make your tandem is. In looking up online tandems that have Bosch Gen 4 CX motors, found that a couple have their motor located at rear BB and a couple have their motor at front BB. Could not see whether those tandems have their sensor cable is routed in-frame or out-of-frame. The concern about motors located at the front BB would be that the cable for the rear wheel sensor would have to be extra long, with maybe a splice or connection before the lead plugged into motor terminal.

Bosch changed the sensor for Gen 4 Ė donít know how it mounts up versus how the earlier ones mount up. Have heard that the sensors are finicky about only using Bosch magnets. Also for Gen 4, the motor terminals got moved to the lower side of the motor Ė would watch for splash getting into this part of the motor during rainy day rides.

What Iím getting at is - maybe it could be the cable or the connection(s)?
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Old 06-16-24, 05:24 PM
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I will have to check out the connection. The magnet was and is perfectly aligned to the sensor.

Originally Posted by fooferdoggie
sounds like a connection issue or wheel sensor issue. what control do you have? the connections there could be an issue or the wheel magnet mine rotates on its own over time.
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Old 06-16-24, 05:25 PM
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this shows where the magnet goes. I used the circle at the end. oops.
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Old 06-16-24, 05:26 PM
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Originally Posted by BNB
I will have to check out the connection. The magnet was and is perfectly aligned to the sensor.
what control do you have?
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Old 06-16-24, 05:28 PM
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I have this exact drawing and the sensor is aligned exactly as in this image. I don't have calipers in NH to easily measure the distance but the wheel and frame have not changed.

Originally Posted by fooferdoggie
this shows where the magnet goes. I used the circle at the end. oops.
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Old 06-16-24, 05:32 PM
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Originally Posted by BNB
I have this exact drawing and the sensor is aligned exactly as in this image. I don't have calipers in NH to easily measure the distance but the wheel and frame have not changed.
then it's fine. the distance is not as critical. I love this stuff it seals electrical connections too. I used it to waterproof a garage door opener. I tested it without a case under water and it worked fine while under water.
https://www.amazon.com/gp/product/B0...UBCLUQU5&psc=1
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Old 06-16-24, 05:33 PM
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I don't understand the question ...

Here are the specs I have:Ebike motor. Bosch Gen 4 Performace Line CX BDU450CX

Ebike battery: 2X Bosch Frame-mount 500WH

Ebike kit Bosch Smartphone hub display; Bosch 4A US/Can

charger; Abus battery lock; assorted cables (NOTE:1

battery only; no Y-adapter or second battery mount)

Originally Posted by fooferdoggie
what control do you have?
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Old 06-16-24, 05:36 PM
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I'll check it out though must admit I would really not know what / where to use the stuff.

Originally Posted by fooferdoggie
then it's fine. the distance is not as critical. I love this stuff it seals electrical connections too. I used it to waterproof a garage door opener. I tested it without a case under water and it worked fine while under water.
https://www.amazon.com/gp/product/B0...UBCLUQU5&psc=1
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Old 06-16-24, 05:37 PM
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Originally Posted by BNB
I'll check it out though must admit I would really not know what / where to use the stuff.
How do you control your bike? is it a intuvia a purion a kiox or a nyon?

ops just saw a smartphone nub. that thing sucks I had mine replaced before my bike left the shop.
I don't know what these front two connections do since I never used it but the back connections check and make sure the screw is tight and nothing is cracked. with a Kiox or Nyon the pics can get gunked up since they are removable. if yo unwanted to try another one you can have mine its just sitting around.


Last edited by fooferdoggie; 06-16-24 at 05:45 PM.
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Old 06-16-24, 05:45 PM
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Well, I had to google those names. I honestly have no clue which control it is. I only use the most basic functions - turn on the system, speed and level of assist. If it does anything else I don't know and wouldn't bother to use it. Does it matter which control I have? Just curious ...

Originally Posted by fooferdoggie
How do you control your bike? is it a intuvia a purion a kiox or a nyon?
edit: here's the user manual image:

Last edited by BNB; 06-16-24 at 05:54 PM. Reason: add image
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Old 06-16-24, 05:51 PM
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Originally Posted by BNB
Well, I had to google those names. I honestly have no clue which control it is. I only use the most basic functions - turn on the system, speed and level of assist. If it does anything else I don't know and wouldn't bother to use it. Does it matter which control I have? Just curious ...
if you don't need more features like your cadence how much power you're putting out maps and such then it does not. do you put your phone in it at all? I asked because the type of connection would make a difference on them coming loose and causing the issues you describe. but I doubt your pushing the motor too hard. you have to put out serious power to bog the motor down. on my trek I was putting out 550 watts to go up a 20% grade and sinning at 80 rpm and even then I don't know if I hit where the motor maxed out. on the older bosch it was 450 watts. on our bosch powered tandem we have to be doing 20% grades to hit that.
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Old 06-16-24, 05:59 PM
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definitely not using any of the extra features even if it is capable. I doubt we're pushing the motor too hard but it is only happening on uphill - not on flat terrain even though we are getting assist on flat terrain. We are not pushing any harder than we did the previous 2 years; probably less and try to keep low gear / high cadence for knee pain reduction.

Originally Posted by fooferdoggie
if you don't need more features like your cadence how much power you're putting out maps and such then it does not. do you put your phone in it at all? I asked because the type of connection would make a difference on them coming loose and causing the issues you describe. but I doubt your pushing the motor too hard. you have to put out serious power to bog the motor down. on my trek I was putting out 550 watts to go up a 20% grade and sinning at 80 rpm and even then I don't know if I hit where the motor maxed out. on the older bosch it was 450 watts. on our bosch powered tandem we have to be doing 20% grades to hit that.
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Old 06-16-24, 06:10 PM
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just saw your pics ... maybe I can get clarification from you about this in PM? I'm fried and done for the day. Thanks for the offer to help.

Originally Posted by fooferdoggie
How do you control your bike? is it a intuvia a purion a kiox or a nyon?

ops just saw a smartphone nub. that thing sucks I had mine replaced before my bike left the shop.
I don't know what these front two connections do since I never used it but the back connections check and make sure the screw is tight and nothing is cracked. with a Kiox or Nyon the pics can get gunked up since they are removable. if yo unwanted to try another one you can have mine its just sitting around.

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Old 06-16-24, 06:13 PM
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Originally Posted by BNB
just saw your pics ... maybe I can get clarification from you about this in PM? I'm fried and done for the day. Thanks for the offer to help.
feel free. ya we are worn did about 40 miles.
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Old 06-16-24, 07:33 PM
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Originally Posted by BNB
definitely not using any of the extra features even if it is capable. I doubt we're pushing the motor too hard but it is only happening on uphill - not on flat terrain even though we are getting assist on flat terrain. We are not pushing any harder than we did the previous 2 years; probably less and try to keep low gear / high cadence for knee pain reduction.
yes not hard enough. so just to make sure check the screw that holds the wires in on the back of the smartphone hub. if they look fine I would get the bike checked it could be a internal wire issue.
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Old 06-17-24, 06:35 AM
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Originally Posted by BNB
The tandem ... now cutting out, always on hills, and seemingly random. The speedometer flashes speeds over 20mph explaining why the assist is stopped briefly and annoyingly...
First of all I want to say that I am a luddite – I don’t trust the latest in technology. That said, have you or your builder looked at whether the smartphone control system is giving you problems? E.g. wireless cutting out?

I have 3 Haibikes with Intuvia controls – all dead reliable, directly wired, no wireless linking to cut out. Have you or your builder looked into whether Intuvia would work with Gen 4 Bosch? Looking on the internet just now got me only vague info (gee thanks Google AI … but no, AI, that’s not what I’m searching for, lol).
One of the benefits of Intuvia is being able to tune the assist speed limit.

Last edited by TmMc; 06-17-24 at 09:31 AM.
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Old 06-17-24, 08:05 AM
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Originally Posted by TmMc
First of all I want to say that I am a luddite Ė I donít trust the latest in technology. That said, have you or your builder looked at whether the smartphone control system is giving you problems? E.g. wireless cutting out?

I have 3 Haibikes with Intuvia controls Ė all dead reliable, directly wired, no wireless linking to cut out. Have you or your builder looked into whether Intuvia would work with Gen 4 Bosch? Looking on the internet just now got me only vague info (gee thanks Google AI Ö but no, AI, thatís not what Iím searching for, lol).
One of the benefits of Intuvia is being able to tune the upper limit of assist.
the smartphone hub has been a big failure but it's usually for holding a phone poorly or breaking while holding the phone. but you can't put an intuvia on without new wiring and it won't let you change how the motor performs. only a nylon or kiox would do that and the poster doesn't do much of anything with the controls but the amount of assist so it would be pointless.
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Old 06-17-24, 09:42 AM
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Sorry fooferdoggie, my last sentence wasn't clear. I've edited it to clarify.

In the Intuvia menus there is a '"wheel circumference" setting. This setting gives a range of numbers. If you increase this circumference number to be higher than your bike's actual wheel circumference then the assist speed limit increases. For a 28mph assist limit, I've gotten the cutoff to raise to 30-31mph. The only downside is the speed shown on the speedometer is also raised and inaccurate - e.g. speedo reads 33mph at that 30-31mph.

Agreed that installing a Intuvia control would require replacing the smartphone hub control lead with an Intuvia lead from its bracket to the control terminal on the motor. From photos the control terminal on a Gen 4 motor looks similar to that on older 2 and 3 generations - but I cannot say they are the same for certain. And in this case - for a tandem with a rear BB motor, that lead would have to be extended.

Last edited by TmMc; 06-17-24 at 12:11 PM.
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Old 06-17-24, 07:16 PM
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I would take it to your local shop and see if they can take a look. The nice thing with Bosch is they have really excellent support all throughout but their newbie support is really truly top notch. They go through everything and are very thorough to the point of my old shop being annoyed dealing with it because we had already done those steps and more.

It sounds like the magnet is aligned which is good but you shouldn't need a second magnet that is an odd one. Make sure it is close enough and make sure the magnet is still there. If it is the display I would imagine swapping it out to Nyon or Intuvia or Purion would be a good option. I remember when the Smartphone Hub came out but didn't see it often and didn't order a lot of them. They were cool but I didn't see a long life for those. It should still work but maybe there is a an issue there or with some connection.

Do you have lights and do those work? If they aren't working that could be a sign of connections at the motor having issues and maybe some cleaning and electronic grease might help. Your local shop can help with that.

Beyond all of that it looks like fooferdoggie had some excellent ideas.
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Old 06-18-24, 02:10 AM
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I don't use any wireless feature - no smart phone connected to this Bosch system. The builder is suggesting getting the magnet closer to the sensor but I'm dubious this will work.

Originally Posted by TmMc
First of all I want to say that I am a luddite Ė I donít trust the latest in technology. That said, have you or your builder looked at whether the smartphone control system is giving you problems? E.g. wireless cutting out?

I have 3 Haibikes with Intuvia controls Ė all dead reliable, directly wired, no wireless linking to cut out. Have you or your builder looked into whether Intuvia would work with Gen 4 Bosch? Looking on the internet just now got me only vague info (gee thanks Google AI Ö but no, AI, thatís not what Iím searching for, lol).
One of the benefits of Intuvia is being able to tune the assist speed limit.
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Old 06-24-24, 09:22 AM
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Veganbikes finally gave the right answer. You can guess all you want but you have a better chance of fixing the problem with software diagnosis.

Go see the Bosch man! Look for his cert on the wall.

-SP

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Old 06-24-24, 06:06 PM
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That's the plan despite long drive to get to one ...
Originally Posted by speedy25
Veganbikes finally gave the right answer. You can guess all you want but you have a better chance of fixing the problem with software diagnosis.

Go see the Bosch man! Look for his cert on the wall.

-SP
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