Wierd Pedal Assist Problem

[turbulent]

Hello everyone,

So something weird is going on with my pedal sensor. A few things actually. when starting from stationary it works and as long as I keep pedelling it keeps power. As soon as I stop pedelling and restart pedelling it doesn't kick back in until i stop the bike and start again. Also, if I start off pedelling too hard it doesn't kick in at all. I've cleaned the sensor and magnets. Tried moving the sensor different distances from the magnets, nothing works.

Have any of you ever had this specific issue before and if yes, what was the fix, a new sensor or something else?

It's a bafang hub 250W 36V 11.5AH - on a Lombardo Valderice.

Thanks for any help you can offer.

 

[turbulent]

Here's a vid to show the problem

 

[Nealh]

You mentioned 3mm gap, it is to large push the sensor to wards the disc so the gap is 1mm or nearly touching.
At 3mm rotating fast the sensor simply can't pic up the magnet signal, rotating slowly is has chance and can do so.

 

[turbulent]

Hi, yeah that's not it unfortunately. Like I said, if I keep pedelling, it's fine. If I stop pedelling for just 1 second and continue, no more power assistance until I come to a stop. Then it kicks in again, as long as I don't stop pedelling I get power.
I tried moving it closer anyway, just to rule it out, but nothing.

Just praying it's not a controller issue as it's all built into the battery system, semi intergrated

 

[turbulent]

forgot to mention. The sensor has an LED which lights everytime a magnet passes. It's lighting up fine, so the sensor must be close enough.

 

[Sturmey]

I had a similar type (kingmeter) sensor with red led that started to behave erratically and finally totally failed. I did not know initially what was wrong but the bike worked on walk assist worked ok so I suspected the pedal sensor. Anyhow, I removed the sensor (by unscrewing the small screw) and found that it was very wet and the rubber sealant had broken down. I removed all the old sealant and dried the unit over the fire and had to resolder the cable. I put the whole lot together and used clear silicon bathroom sealant to seal as a temporary fix. Its still working. I reckon these units have a hard life and are exposed to a lot of water splashing.

 

[Nealh]

Likely as Sturmey says the final option is water ingress affecting the 5v line.

 

[guerney]

It might or might not be that the magnet isn't close enough - strange things can happen even if the sensor is lighting up as the magnet passes... the weird problems can occur at higher speeds. Even though it seemed that my magnet was close enough to the sensor, my display wouldn't register any speed over 28.7mph: just kept showing 28.7mph, then 0mph, then 28.7mph over and over again till I slowed down. I was going downhill and my bike is limited to 15mph on PAS, but I wonder how the controller's software would have applied power with a strange alternating hi/no speed calculation like that - in the event of a speed sensor error, or impossible/out of bounds speed calculation, a system shutdown of PAS until the bike sufficiently slowed down, stopped, or resumed normal speed calculations again, might be a sensible bit of built-in PAS system programming for safety reasons. After I moved the magnet extremely close to the sensor, the problem disappeared. I am about to apply some self-amalgamating rubber tape around the speed sensor connector, because I certainly don't want 5v line water ingress.

 

[turbulent]

Thanks for your help guys.
I'll be taking it apart tomorrow to inspect it for water damage. I ordered another one just in case it's beyond repair. Always good to have a spare anyway as they do seem exposed down there.
Hopefully it's that, sounds right to me.

I'll let you guys know.

 

[turbulent]

update:

It's not the sensor at all. It's the bafang hub.

I switched back wheels with my wifes bike and it gave the same issue. Wish I'd tried that first.

So, this just got a lot more complicated.

 

[Nealh]

Not much within a hub to go wrong.
Speed sensing magnet may have moved or dislodged so maybe is affecting the running.
Motor Hall sensors could be faulty, these are easy to test using a meter.

 

[Rapper]

I know I am too late to the discussion but @turbulent did you find any resolution? I am facing exactly the same problem with a Swytch conversion kit. It starts up fine and keeps going as long as I don't stop pedalling or don't brake. Also, the sensor is flickering red all the time I am biking, just no power. I too ordered a new pedal sensor and magnetic disk before finding this thread. Now I am just worried that the problem is deeper Would appreciate it you could let me know how you solved yours.

Thank you,
Ramya

 

[thelarkbox]

I know I am too late to the discussion but @turbulent did you find any resolution? I am facing exactly the same problem with a Swytch conversion kit. It starts up fine and keeps going as long as I don't stop pedalling or don't brake. Also, the sensor is flickering red all the time I am biking, just no power. I too ordered a new pedal sensor and magnetic disk before finding this thread. Now I am just worried that the problem is deeper Would appreciate it you could let me know how you solved yours.

Thank you,
Ramya

Hi Ramya Welcome..

Might be better if you post your own problem thread,, heads up - full details and pictures are helpful to the guru's in the know,, a snap of your handlebar display/controls, and the controller box label if accessible are generally very helpful too..

That way your bike issue will be the main focus and you can avoid issues of mixing the op's issue with yours in this thread. ..

 

[saneagle]

I know I am too late to the discussion but @turbulent did you find any resolution? I am facing exactly the same problem with a Swytch conversion kit. It starts up fine and keeps going as long as I don't stop pedalling or don't brake. Also, the sensor is flickering red all the time I am biking, just no power. I too ordered a new pedal sensor and magnetic disk before finding this thread. Now I am just worried that the problem is deeper Would appreciate it you could let me know how you solved yours.

Thank you,
Ramya

Try the new sensor before you start to panic.

The common problems for that are: Incorrect gap between the sensor and magnet disc (should be 1mm); slipping magnet disc caused by wear after it jams due to dirt; slipping due to jamming by dirt; water ingress after the hall sensor cover gets worn by grit or was knocked out of line and rubbed on the magnet disc.

Other potential causes ae: Damage to the cable when the chain came off; wires pulled so that the joints break; cable tie pulled too tight, which squished the wires in the cable and broke one inside the insulation to leave intermittent contact.

All those problems would be fixed by a new sensor when you fit it correctly and set it correctly.

There is nothing in the motor that could give the problem that OP describes. The control system cannot recognise the speed of the pedals, nor how much torque is applied. Probably, OP wasn't pushing the motor connector in far enough. 1mm short of the line can give all sorts of problems from intermittent running, through battery going down too fast or cutting off to complete destruction of the controller and/or motor.

Swytch has its own problems, depending on which version you have.

 

[Rapper]

@thelarkbox and @saneagle thank you so much for responding. I will start a new thread over the weekend with more details and pictures in case someone else faces this problem. I’m glad to hear that pedal sensor can still be the problem (it’s not the distance to the disc, already tried different distances)… I did notice that the pedal sensor had rubbed on the disc (not heavily though) so seems like your suggestion is likely correct. I already placed an order for a disc and pedal sensor. Will post back. Thank you again!

 

[Rapper]

Hello,

Back with an update:

Background: My ebike (converted using swytch kit) was having problems such that I would get power when starting up but if I stopped pedalling or braked (thereby stopping pedalling), I won't get any power until I would step down and start again from complete zero speed.

I am attaching the pictures of my old pedal sensor and the magnetic disc. The pedal sensor had clearly rubbed against the disc but to me it did not look major. But likely since the plastic wore off, maybe some water or dust entered it causing it to malfunction. I ordered replacements for both from swytch (cost 8 +10 for the two parts with 5 pounds for shipping) and today replaced them. Just gave it a test ride and it all seems to be working well!! So glad and relieved Will report back if it malfunctions.

Thank you so much @saneagle for asking me not to panic and suggesting that pedal sensor is still the likely culprit. It really helped me patiently for the parts to arrive instead of frantically looking for other solutions on the net. Thank you!

 

[Rapper]

I dont seem to be able to find any obvious way of starting a new post so continuing here. Today I road tested it to and from work and it's not fixed. As before, the pedal sensor lights up but I stop getting power after a while.

My next line of attack is to check the connection of the pedal sensor to the battery (though of course I only just re-did the connection). Any other ideas will be welcome! I am not sure if a normal bike shop will be able to repair a conversion kit, but will call up in case this doesn't fix it.

 

[saneagle]

I dont seem to be able to find any obvious way of starting a new post so continuing here. Today I road tested it to and from work and it's not fixed. As before, the pedal sensor lights up but I stop getting power after a while.

My next line of attack is to check the connection of the pedal sensor to the battery (though of course I only just re-did the connection). Any other ideas will be welcome! I am not sure if a normal bike shop will be able to repair a conversion kit, but will call up in case this doesn't fix it.

Did you check that the motor connector reaches the line?