Just received a Bafang SWXH 36v, 250w.

[jbond]

I took the bike for my first test ride today. quite a heavy wind and -18 celsius.

I tried quite a steep hill and experienced some weird behavior. Or maybe its not weird..? It was like pulses. Like 2-3 seconds of power and then maybe 0.5 sec of no power and then 2-3 sec of power and so on.. Almost like the motor was skipping or something.. This was at quite a slow speed.

I reckon something is hitting a low voltage limit. As it's very cold, and this happened at full power, I'd guess voltage sag in the battery is reducing the voltage below the controller's low voltage limit. The controller probably has a block time of 2-3s on this setting so you get power for a couple of seconds, then it trips, the battery recovers and then the cycle repeats.

 

[NRG]

No but my test ride was without pedal sensor. Only a thumb throttle, controller, motor, battery. And i'm certain i didnt open the throttle due to pedaling.
It was like a "skipping" feeling.


Maybe i'm just getting it wrong, bear with me. I just get the impression from what you write, that its either a pedal sensor that you use or a throttle.. I thought the pedal sensor worked as an On/Off switch, and the Throttle controls the speed. Isnt it? That you can use both of them if you want.

I've experienced the same a surging or pulsing, for some reason my Peugeot is doing it and I suspect as JBOND has hinted at its the block time causing it...not sure its a LVC cutoff as that would be a very harsh power off feeling and I know my battery is good. As I've been messing with the controller parameters I'm fairly sure its the block time setting.

The Pedal sensor will have a short cadence ramp to bring the motor up to full speed. This varies from controller to controller, on my Alien GSII with the original controller the ramp was short but more progressive compared to the E-Crazyman replacement I fitted to it a while back. The E-Crazyman ramps much faster and is much closer to an on/off switch but there still is a ramp up of sorts.

You will probably find the throttle will over ride the pedal sensor when the sensor is some where on its cadence ramp up but only to increase motor speed, you can't for instance use it to slow down.

Also its worth mentioning again that these motors are speed controlled by the current controllers they do not offer true power control of the motor.

 

[Deleted member 4366]

No but my test ride was without pedal sensor. Only a thumb throttle, controller, motor, battery. And i'm certain i didnt open the throttle due to pedaling.
It was like a "skipping" feeling.

I'm not sure I understand what you're doing. I can't see how you can have the motor going without a pedal sensor and without opening the throttle. Did you have the throttle wide open when going up the hill? Is the pedal sensor connected and operating? If the pedal sensor wasn't even connected, then you can disregard what I said previously. If it's skipping with the throttle wide open, then it could be what Jbond suggested, or a connection fault. Some of the Chinese hand-soldering is not very good, so it's possible that you have a dry joint in the throttle. All the ones I've looked at have been dodgy. The controllers that I've seen are mainly wave soldered and appear to be done to a higher standard, so I think much less likely (though not impossible) a problem there.

To answer your point about the pedal sensor, depending which controller you have: If you install the pedal sensor, it's much easier to ride the bike. You only have to pedal and the controller gives lots of power when you're going slow and the physics of the system gradually reduces power as you get nearer the limit (14mph?), although it depends which controller you have. Some give a more gradual increase of power with increasing pedal speed. The throttle might give more power than the pedal sensor, so it can act as a boost when you go up steep hills. Sometimes, when you need to drive slowly in pedestrian areas or wherever, it's better to use the throttle because you can feed in just enough power to trickle along and, as I said before, it takes precedence over the pedal sensor, so stops that immediate accelleration with full power.

 

[Deleted member 4366]

You will probably find the throttle will over ride the pedal sensor when the sensor is some where on its cadence ramp up but only to increase motor speed, you can't for instance use it to slow down.

On all three of my bikes and my neighbour's the throttle can indeed be used to slow the bike down at any time, and it gives exactly the sysmptoms the OP is experiencing. When pushing hard up steep hills, it's easy to accidently open the throttle a little intermittently, which feels like the power has been cut intermittently.

 

[NRG]

Indeed and interesting, what controllers are these? IME, on the three different types of controller I have if the pedal sensor is in operation the thottle can only increase motor speed if motor speed is below maximum IE: On the cadence ramp for the sensor. Obviously this is not universal and it appears the operation varies from one controller to the next...

 

[jbond]

And another datapoint. I can't feel any power or speed limit variation with cadence on my pedelec sensor. It's full on or full off with nothing in between. This is with the LZDSZ controller on the Aurora.

 

[Deleted member 4366]

Indeed and interesting, what controllers are these? IME, on the three different types of controller I have if the pedal sensor is in operation the thottle can only increase motor speed if motor speed is below maximum IE: On the cadence ramp for the sensor. Obviously this is not universal and it appears the operation varies from one controller to the next...

They're just the regular cheapo Chinese controllers with no markings that give any clue to the maker.

 

[NRG]

Like the E-Crazyman controllers based on the xiecheng 116 controller chip?

 

[Trout]

I reckon something is hitting a low voltage limit. As it's very cold, and this happened at full power, I'd guess voltage sag in the battery is reducing the voltage below the controller's low voltage limit. The controller probably has a block time of 2-3s on this setting so you get power for a couple of seconds, then it trips, the battery recovers and then the cycle repeats.

This is probably the reason. I assumed that the battery was charged when i recieved it (measuring 39.9v) but i guess it wasnt charged.

Sunday evening i charged the battery full, and i measured the voltage right after the charge, it was at 42.0v. Yesterday, before i went for another test trip i measured the voltage and it was at 40.0v. (battery has been in "locked" position) I had a 45min trip, pretty much 50-100% power all time. but at the end of the trip the battery sagged and i experienced the same behavior. Also my 3-led thumb throttle turned off the "full charge-led" and i lost the power. It went back on as soon as i closed the throttle. and the sagging repeated. its a 36v 12Ah battery so i should have gotten more out of it. (asuming the motor being at a constant of 36v, 250w it should use 6.9A) Considering that it was -15 celsius it could have effected the battery drastically. when i got back home i measured the voltage and it was at 39.8v. To see if its just the cold, i didnt charge the battery yesterday and i'll try later today and see if i get maybe same amount of time of power. If i can ride it for quite a while, then its caused by cold.. If its fully drained when i start then theres something wrong with the battery.

I'm not sure I understand what you're doing. I can't see how you can have the motor going without a pedal sensor and without opening the throttle. Did you have the throttle wide open when going up the hill? Is the pedal sensor connected and operating? If the pedal sensor wasn't even connected, then you can disregard what I said previously. If it's skipping with the throttle wide open, then it could be what Jbond suggested, or a connection fault. Some of the Chinese hand-soldering is not very good, so it's possible that you have a dry joint in the throttle. All the ones I've looked at have been dodgy. The controllers that I've seen are mainly wave soldered and appear to be done to a higher standard, so I think much less likely (though not impossible) a problem there.

Sorry I missunderstood the open/close "term" of the throttle , i was riding with no pedal sensor and the throttle fully open.

 

[Trout]

Update: rode with the same uncharged battery for 35min at mostly full speed, mostly uphill. So I guess it was the extreme cold affecting the battery. But I feel that I have to invest in a watt meter.

 

[Trout]

I have a weird problem with the bike.

I charged the battery like a week a ago. And yesterday I took the bike for a trip, After about 2km of full power the green light on my 3-led thumb throttle turned off. and after about 1 km more, the bike completely lost power.
None of the leds on the 3led thumb throttle was on.
I first thought i had mistakenly pulled out the power cable or turned the key. But the cable was connected and key was turned to ON. I turned the key off and then on again and all of the 3 leds turned back on. 10 seconds later it turns all leds off again and i totally lose power. i turn the key off and back on, the 3 leds turn on and after 10 seconds they turn off and i lost power. This repeated forever.

Is there something wrong with the controller? Or any connections? or the battery?

 

[flecc]

That is typically the behaviour of a failed battery, voltage collapsing under load and low voltage cut-off operating. Switching off, then back on resets it.

It could be one cell failed, but there is still a possibility of a fault elsewhere such as in the controller. A poor connection can also do this sometimes, though with that fault it usually fails to deliver at all the moment the throttle is opened
.

 

[Trout]

Hmm ok.. What could i do with the battery to fix it?

 

[flecc]

Just to be clear, when you say "ten seconds later it turns the LEDs off again, is this ten seconds after you set off under power, or do the LEDs turn off after ten seconds when you are just standing still and not using the motor?
.

 

[Trout]

Its about 10 seconds under power

 

[Deleted member 4366]

When your battery goes flat, this is normal behaviour. It sounds to me like your battery wasn't charged properly for whatever reason. I have one battery that doesn't always connect to the charger properly. I plug it in and the charger goes from green to red and it starts charging, but later on it breaks contact and the light goes green as if it's charged. I got caught out once when the battery went flat after only 2.6aH, but now I always re-check by unplugging and re-plugging the charger: If the battery is fully charged, it'll only stay red for about 30secs, otherwise I leave it to charge.

 

[stevebills]

Its about 10 seconds under power

Charge it again and make sure its charging with amber light on till it goes green it should take 3 or 4 hours and get a volt meter and test the cells voltage

 

[Trout]

When your battery goes flat, this is normal behaviour. It sounds to me like your battery wasn't charged properly for whatever reason. I have one battery that doesn't always connect to the charger properly. I plug it in and the charger goes from green to red and it starts charging, but later on it breaks contact and the light goes green as if it's charged. I got caught out once when the battery went flat after only 2.6aH, but now I always re-check by unplugging and re-plugging the charger: If the battery is fully charged, it'll only stay red for about 30secs, otherwise I leave it to charge.

Charge it again and make sure its charging with amber light on till it goes green it should take 3 or 4 hours and get a volt meter and test the cells voltage

It could be that its not been fully charged. I honestly dont understand that chinese charger i received with the kit.

The charger has 2 LEDs on it. when i plug it in the wall the left LED is green and the right one is red (this right LED is constantly red, never changes color or go off while plugged in the wall socket). When i plug it into the battery to charge it, left LED goes red and i hear the fan start spinning inside the charger. After 1 hour or so, the left LED goes green and the fan stops, after about 20 seconds the LED goes red again and i hear the fan again for a minute or so. then the LED goes green again and fan stops. this repeats over and over for like 15 minutes. (I thought this was the charger balancing the cells......). After those 15 minutes the left LED is green and fan is not spinning.

I assumed that at this point the battery was fully charged...

Does it continue to charge? Am i doing anything wrong?

 

[Deleted member 4366]

I'm not sure about that charger - all mine work differently. When you think the battery might be charged, disconnect it and leave it for about 15 mins, then check the battery voltage with a voltmeter. It should be about 40v. If it's any less, it isn't fully charged.

 

[flecc]

The colour LEDs indication seems ok, but the charge total of one to one and a quarter hours seems very short. 3 to 5 hours is more normal for full charges from the point where a battery is cutting out at low voltage.
.