Ebike power loss question and a possible fix


New member
Local time
5:00 AM
Apr 6, 2024
Largo, Florida
Ok so here's the deal with this ebike:

It's a 48V, 20Ah, 1200w with a G51 LCD display/controller. I let a coworker ride it to do a run for our job. Shouldn't have been anything crazy, literally just a lil stop and go riding down a couple city roads and into parking lots then back, nothing that would be hard on it by any means and he couldn't have been gone with it for more than 10 to 20 minutes. When he got back he said that it wouldn't reach full speed and was cutting out. This is where everything began. I don't know what he did to it, if he did anything to it or if this is just the point in which it decided it's going to start going bad or something not good. Regardless of anything he may or may not have done to it, i still have this issue going on now and I'm trying to figure it out. I got to messing with it and besides the battery being fairly low when he got back (I had done a decent amount of riding before he used it and not really charged it much) there was nothing I could see that would be causing the issue. I still haven't quite fully figured out what's going on with it. I have since played with the settings a lot and went through all of them over and over until I now understand this thing a lot better than I did before, I've read articles, other people's problems, researched, etc, and have not found this exact same issue anywhere else nor anything even close to the solution I have found (so if I don't end up getting help here I may possibly have found something that will help others, instead). Now, here is what it's doing currently. After it gets turned off, switched off, times out and turns off, it doesn't matter how it turns off but when it does and you turn it back on with the display it will be at about 1/3 power. I am a pretty crafty and clever fellow though so I have figured out a trick that gets it back to full power and everything seems to function properly but it's quite a pain as i have to do this every time I power it up. I'm hoping someone else has a solution that will prevent me from having to do this every time.. So, when I turn this thing on I will press and hold up and down to go into the settings menu. I'll type in the 2020 code to get me to the settings menu, starting at P01 obviously, then I will click my way through to P07. As far as I know this setting is for testing or something like that and refers to the magnets and something to do with those, I'm not quite sure exactly how it works or what it does but I do know that higher wattage bikes will use I think it was 47 as the number on this setting and most others will use 1. If 1 doesn't get your speedometer working properly then you try 86. So at first it wasn't working right on 1 so I tried 86 and bam, problem was solved, speedometer worked great and everything was fine for a few rides. Now It's not doing that anymore and instead it is now 1 that I need as that setting in order for my speedometer to work properly, only as I stated above anytime I turn it on I have about 1/3 power. So, I found a little trick to get back to 100% power. I go into the settings and find P07, which is always set to 1 like it was when it was shut off. Then I just hold up and the number will quickly go up. Now once it gets to about 80-ish it will go from a really slow speed (about 1/3 power) to I'd say maybe 2/3 power. I'll keep my finger on that up button and the numbers will continue to climb. I've heard that some of these bikes stop at like 150 or something like that, mine has 255 as the highest number for P07. Once I hit about the number 150-ish it will suddenly increase to full power. Now if I leave it set at any of these higher numbers above the 150-ish mark it will keep at full power but my speedometer will be way off so what I do to keep the full power but at the same time have a working speedometer is I just keep holding it until I get close to 255 and stop. I click it up 1 number at a time when I get to this point and let it roll over back to 0 and then finally till I get back to the original number that I started with, which is 1. Presto, the problem is gone, no more 1/3 power, it now has full power again, a properly functioning speedometer, the ebike is happy, I'm happy (also slightly annoyed) and I'm good to ride. I found out that I have to stop before 255 because if it rolls over and goes past 1 to lets say number 8 (which is very easy to do cuz the numbers climb pretty fast) then the speed drops down low and It goes back to about 1/3 power again, If I go back down to 1 from the number that I went past it to, which in this example was 8, It will not work and stays at 1/3 power. I literally have to start at 1, go all the way up until it reaches the top number of 255, let it roll over and get it to 1 again or else it doesn't work properly. Does anybody know why this is happening? I would really rather not have to do this every time I start this thing, it's really rather quite aggravating. Any help is greatly appreciated and I thank you for it.
Such a bummer it happened when you loaned it. Having the battery "lower" when they returned is a sign that your battery mount was loose. I suppose wiping out or the right pothole could have the same effect.

The 1/3 power thing makes me think that your controller is changing your bike to a lower voltage, like 36v and it should be 48v. However you stated your speedometer was being altered by the P07 setting as well. The speedometer thing is usually done by changing your wheel diameter settings.

Its possible the controller on your bike is going bad, and it's not able to save the settings. You should probably post the make/model of your bike. Maybe someone here has some experience with it.

Good luck