We have used a few different displays with our ebike builds but a common favorite is the Color 850C display. however recently we have had two separate screens die. the first was seemingly after only a few weeks use, and it wasn’t subject to any water damage, the other was lent to us by a local rider who also came back to a working screen after a while not being used to find it completely dead.
In both cases the screen would not power up, there was no power on the USB port, and swapping the switches out for a known working set made no difference.
So recently i took the plunge and decided to open one up to see if there was anything visually wrong. Totally expecting to see either water damage or maybe a broken solder joint, I was surprised to see an immaculate PCB with no obvious issues.
I checked the continuity on all pins back to the PCB to rule out any brakes in the wire or connectors, but again all looked fine.
I then noticed a small lithium battery soldered to the PCB and thought why not try shorting this for s few seconds? My thought being if the Microprocessor was not booting for some reason maybe this battery was holding it in a bad state and shorting the only visible power supply might reset it?
(The battery is the small silver disc need the edge of the bottom of the PCB)
Well much to my delight. yes. right after the screen would boot fine over and over. So I did the same on the second screen and yup exactly the same.
So if you do have a similar screen and its refusing to boot, as long as you are happy to pop of the plastic screen surround and use a little hot air around the main screen to soften the glue and separate it from the case. it’s a quick fix.
Tip: you might want to use a little silicon to help seal the screen afterwards as the glue will never work as well on its own.
Empowered People 
That’s a great tip. Thank you.
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il mio non tiene piu la data e ora… puo essere questa batteria tampone che è scarica??
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Hi,
how did you made a battery shortcut and not drain the battery for good? Or it was just a millisecond shortcut?
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Yes only shorted if for about 1/2 second. Enough to reset the chip.
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Hi,
great!!! The same approach worked for me! It was the same, 850C display. Thank you!
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Ahh great glad it helped 👍
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how do you short the battery
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I just bridged the positive and negative pins for a fraction of a second using something metallic like a screwdriver.
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I had two screens die with claims from the seller they are being replaced with upgraded versions. Since I got tired of waiting and not being able to use my bike, I did the procedure and it worked fine. Furthermore, I soldered two small wires to the battery and routed them to the exterior of the unit and taped them to the harness. If it happens again, I just need to touch the two wire ends together for an instant rather than taking it all apart. I has been two weeks and still working.
Thanks for the info.
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Many thanks, worked for me to with non-responsive 850c display. The steps I went through:
1. Plugged a Bafang programming cable into the green cable where the display plugs in. This is to determine what was not working. This cable shorts two pins and bypasses the display (allowing the motor to work without a display). The motor worked when I turned the pedals. This meant the problem was the display and/or switch and not the motor / controller.
2. I tested the switch for continuity using a multimeter and it was ok.
3. Removed and took apart the 850c, found the battery and did a very rapid short across the terminals (I guess you could cut one wire from the battery and resolder?). Just to clarify, to open up the unit, it is first necessary to unclip an outer plastic housing and only then separate the clear screen using a blade and heat. Then remove two small screws to lift the board.
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Great to hear it worked for you billybib. Yes you could desolder one leg of the battery. And to be fair that would be a better option really. But like you say the short only needs to be performed for a very short time, so should be safe. The screens I have done it to are still going strong. And haven’t had the issue again. And yes your steps to open the unit are correct and like you say does require a little heat and a blade. So weather resistant may be compromised slightly.
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This was a great piece of information to find. I went through all the troubleshooting steps to find the display was the problem on both bikes my wife and I own. First her bike wouldn’t power up, then a week later mine did the same thing. I found this to be extremely suspicious, almost as if there was a warranty timer to expire the displays.
Anyway, thank you greatly for posting this and saving me the money on two new displays. It would seem a simple reset button would solve this issue and a clear design flaw. Maybe they left it out to sell more displays,…I am so cynical 🙂
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Genius solution! Well done and thanks, worked exactly as you described. I now carry my bafang programming cable on rides as a back up to bypass the controller and get me home should it fail again,
Cheers!
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how to you connect the program cable to do this. does the throttle and pedal assist work and can you still use the different power levels up and down on the throttle. thanks trevor
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You are a LEGEND, thank you so much!
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I’ve done this twice now, last time after not using the motor for 7 months, this time after about 6 or 7 weeks not being used.
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Hi! This works! Let’s see for how long (: Thanks
My set up suddenly didn’t power up but shortening the (850) display battery made the motor work again as usual bullet proof
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what is the voltage for the lithium battery? I guess 3.6?
I have a P850C and the power/voltage at my battery is 1.18 V. 😦
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can you short it from the wire by just sticking two pins into the correct holes and touching them. that way you wouldnt have to take anything apart. if so witch ones if the slot was facing up on the 5 pin display connector. use the trottle one or the one to the battery?
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Good tip. This worked for me also.
Not too difficult. Could have added a reset button on this display
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