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Bafang 500W Front Hub Controller/Display Issues

Posted: Jan 21 2020 2:01pm
by richj8990
Hello everyone, first time posting here. I've been lurking off and on for a while here to get info on how e-bikes work, and learned a certain amount, but not enough to do 'everything' myself for a build. Sorry if this is a really long explanation below but I'll try to fit all info on what happened and what's happening now to help you (hopefully) diagnose the problem. Before I start, I realize now, after the fact of course, that instead of pouring money into bike shop labor, two controllers, and two displays, I should have simply bought a new Bafang rear hub drive with controller and display, that's much more user friendly for hooking up, either by myself or by a bike shop. That controller only has 5 plugs and they are all color coded with where they are supposed to hook up (I believe one to the battery, one to PAS, one to throttle, one to display, and one to the actual hub drive). Conversely, the front hub wiring is a nightmare, at least to someone not mechanically inclined.

The original Bafang 500W had a Loltra / KT LCD3 display and a very, very generic 48V controller with 14 sets of wires. Unfortunately because I put velcro over it, I can't read the make/model but it's obviously KT-compatible because it worked. I put about 3000 miles on the hub / display / controller before the display started dying. When I cut away the controller's holding bag, part of it was fused to the three phase wires that were 1/2 melted. The controller still worked, but the display was dead. 1st replacement display ordered came as 36V and didn't work at all. Second was the Ebikeling 48V 1200W SW900 810 LED which I still have now. Remember that I was 'mixing' an Ebikeling display with a KT controller, because I could not separate the fused wires from the half-fried controller, and just wanted to test it and see if it was only the previous KT display that was bad or not, or if it was both the display and controller that had problems. The Ebikeling E10 error message came up of course, but I was able to do PAS-1 and throttle. I could not do PAS 2-5. Because the bike had previously been set to 750W, I ended up with around 75W PAS-1 (it didn't read watts at all on the display), or 750W (or at least 500W) throttle because Bafang hub throttles are not very subtle for feathering, they are pretty much full blast after you turn them 1/2 way. 75W or 500-750W --- doable on pavement, not so easy offroad.

While I was screwing around with the Ebikeling display, the original replacement KT display finally came from China after three weeks of shipping. Throttle worked, PAS didn't at all. I found that interesting because it's a KT display and KT controller, but the Ebikeling display at least got PAS-1 to work. At this point, I ordered a KT replacement controller that has not arrived yet, and took the bike to the shop, the one that originally did the wiring. I should NOT have done that, I should have read the writing on the wall, returned the two displays back to Amazon, and simply ordered a rear hub motor that comes with a controller and display and is 100% compatible. But hey it is what it is, I tried. I had a different hardtail in the garage that had better geometry, 27.5 vs 26, and a much better suspension fork, and was not using that bike currently, so I told the bike shop to switch over the battery, hub motor/wheel, front derailleur, and triple crankset over from the 26 bike to the 27.5 bike. I also had them switch chainrings from 22/32/42 to 24/36/48. And I could have 27.5 x 2.5 in back, 26 x 2.8 front. The bike was going to kick butt, right? This is where things go really south...

After $600 in bike shop labor, they did the front derailleur, the 3x crankset with new chainrings, and some minor stuff like bleed the brakes, new pads on back, cut the brake lines down to the correct length, add the PAS sensor, fix the 9-speed deore RD orientation and added missing limit screws, etc. Look, I've only been doing this a bit under four years, but I know what bike shop labor costs. All of the above could have been done for $150 labor or less. Those fixes above were simple and routine. I get to the shop, I see the bike, it's only got the battery on it, no controller or display, no throttle or display buttons, nothing else except the battery on the down tube. WHAT??? $450+ labor for that? And they could not even get it to work? I told them this was a waste of money. $450 could have bought a whole new hub drive / display / controller. They said no, we worked for 7-8 hours on the bike and it's almost done, they just need the right controller and display. Yeah, well tell me that BEFORE I bring the bike in. Or at least tell me that after you test the bike and can't get PAS to work (remember I could at least get the throttle to work). They really should have looked at the controller and said hey, we are not even going to try anything until you get the right controller/display combination. Maybe they did try their best, and they were in the dark like me on how to fix the problem. But don't waste my money on 7-8 hours of labor to get something to work with a half-baked controller. That's just stupid. They should have given up after one hour, not eight hours. Their excuse was now that I somehow fried the phase wires and that's not their fault. I explained to them that when I first got the bike converted by them 16 months ago, I realized the PAS-5 and full throttle was 1000W, not 500W. I even checked the Bafang hub and it clearly says 500W on it. Someone at the shop juiced it up to 1000W and put in a 25A fuse between the battery and KT controller. They then got defensive and said 'they' would never do that to any conversion. But they did. I didn't even know how to power down the bike to 750W until I read stuff online several months later, I swear I didn't juice it to 1000W. Anyway, what's done is done, but they handled this really bad. $450+ labor for nothing.

Everything is hooked up between the hub motor, battery, controller, and display except for 5 wire sets on the controller and one on the display. I'm (now) very confident all wires are connected properly including the PAS. I got the throttle to work, and used an off-brand one on my garage shelf which was nice because it stays at one level of wattage, as in it sticks where you put it and doesn't spring snap back to 0; it's around 10 different levels total from 1/4 to 100% on. For some reason it's dependent on the PAS even though the PAS itself doesn't work. If I do the P10 function throttle only, it still doesn't work, I have to do throttle plus PAS to get the throttle to work. Higher PAS = more power, although at peak throttle PAS-3 is about 750W, PAS-5 is close to 1000W, so most of that is a function of the throttle position only. PAS1 sometimes does not give any throttle response so I start out in 2-3 instead. Can I use a volt meter to see if the PAS sensor / wire is bad? I'll try to live with the throttle only, it works pretty good on pavement, we'll see on dirt soon.

Re: Bafang 500W Front Hub Controller/Display Issues

Posted: Feb 05 2020 1:50am
by richj8990
I fixed it. KT controller came in, same problem as before: throttle worked and PAS didn't work, even with the KT LCD3 display.

So I started messing around with the parameters, because the KT controller has about twice as many parameter options as the Ebikeling controller. One of the parameters, P2 is the number of pulses per wheel revolution. I have no idea how many pulses to set, all I know is that I have 8 magnets in the PAS sensor. Range was from 0-6, default was 0. Turned it up to 6. Turned the pedal backwards and the front tire went forwards. OK, getting somewhere. It was reversed. Turning the pedal forwards didn't do anything.

C1 is the throttle start up setting parameter. However, it also affects PAS, even though it doesn't say so. Besides possibly C2, C1 is the only obvious forward/reverse option to mess around with. Default was 0, which is all forward (5, 8, 10 signal, whatever that means). Turning it up to 5 makes the reverse signal. I turned it up to 5. Turned the pedals backwards, nothing. Turned forwards, success!!!

Now...the question is...if the bike shop had both the Loltra/KT LCD3 display and the corresponding controller, could they have figured this out. The EBikeling display doesn't have the parameters needed to reverse the signal. The KT does. I for sure would recommend the LCD3 display/compatible controller over the Ebikeling SW900 display/compatible controller.