BionX Questions - Regeneration & Battery Cycles

[deardancer3]

How many pins does the cable have that you need?

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[cjr]

Interjection here in this thread, having similar problems with BionX that Canis Lupus posted earlier. We set up my Trice T with the BionX primarily as an equalizer so that hubby and I can ride together. (it's rev4) It is working like a charm on the hills, I can stay with him easily on level 2 assist, sometimes dropping to level 1. (He is riding a Catrike Speed). But, on the flats, it's a different story. If it is a slight downhill or a good tail wind, I spin out and can't get much past 16-18 MPH. (stuck with a 48 tooth ring on front). Spinning at 80rpms, plus, I'm not getting any assist to speak of. I see few/no bars of assist, and when I set the assist to 0, it doesn't feel any different than on level 4. I presume this is because there isn't enough torque for the sensor to signal the BionX to kick in. I gather that I am pretty much using my own power in this situation to keep that 60lbs of bike up with him. I think that a HSD would probably solve that problem, but still stuck with the 20mph restriction :-( . Now, the real problem is a day like today, we were riding into a stiff headwind, on flat to slight uphill grade, and I couldn't stay with him even on level 4.. but it doesn't seem to me like I am getting anywhere near 300%.. looking at the gauge, I"m seeing 0 to 1 bar.. we did 17 miles outbound against a nasty wind, and I still had 1/2 a battery left, despite using level 4 until I was so tired of trying to keep up and pushing that big gear that I dropped it down to level two and dropped the speed to about 10mph.. So, is this normal? I mean, he is stronger than I am, which is why we bought the system, but he isn't that much stronger, as evidenced by my ability to stay with him on some pretty good hill rides on no more than level 2. Could the fact that he is on a much lower Catrike, and I'm sitting much more upright, higher bike make that much difference in a headwind? I've read and messed with the various codes (0007 set to 3, 0008A set to 4, I think I have 1234 set to 3 or 4). We've also tried the trick with changing the wheel size to circumvent the speed limit, but it doesn't work. Any insight you could offer would be appreciated. I'll probably post a separate thread on this, but would be interested to hear your thoughts... -cjr-

 

[alan]

[...]If it is a slight downhill or a good tail wind, I spin out and can't get much past 16-18 MPH. (stuck with a 48 tooth ring on front). Spinning at 80rpms, plus, I'm not getting any assist to speak of. I see few/no bars of assist, and when I set the assist to 0, it doesn't feel any different than on level 4.
[...]Now, the real problem is a day like today, we were riding into a stiff headwind, on flat to slight uphill grade, and I couldn't stay with him even on level 4.. but it doesn't seem to me like I am getting anywhere near 300%..

There are a number of points to consider...

The BionX, as with nearly all ebike systems have a top "target" motor speed that is a function of voltage times the motor constant, Kv. That top speed is motor RPM, not MPH. Once you are above the voltage * Kv motor speed, there will be no assistance from the motor. The greater the speed difference between the motor RPM and the target speed (V*Kv), the greater the current. When the motor is turning slower than the top/target speed, then the battery will discharge, and when the motor is faster than its target speed, the battery will be charged.

A bigger wheel will have a faster top speed (at the same motor RPM) for a given motor/battery, but will have less torque. I'm guessing your top speed for your particular BionX motor and battery is about 18 MPH. BionX has two different battery sizes (24 and 36 volts) and, I'm guessing, six different motors (different Kv) for the three different wheel sizes they offer with the two different battery voltages (although there may be some overlap for one motor fitting more than one wheel/battery combo). With a properly designed system targeted for a legal speed limit, I assume BionX designs their systems to have a top target speed (V * Kv) just slightly higher than the cutoff limit, to optimize the overall system efficiency (to get maximum range with the battery).

The 300% assist at level 4 on the BionX system has many assumptions, such as the correct sized wheels for the motor/battery, and "normal" gearing. You should get that assist level (or 150%, etc. for the lower assist settings) from just above starting, when the assist begins. However, the closer you get to the top speed, the less assist you will get. This is true with nearly all ebike systems. For a throttle only system, the max assist will always be at lower speeds, with diminishing assist up to zero assist at the max speed.

Also, the BionX system using pedal sensing must assume a "normal" pedal cadence so that it can reasonably compensate for issues such as changes in torque with gear changes (pedaling torque goes up in lower gears), or a weak leg, while still being able to sense the input from the user (and not think that input is changing every time a gear change occurs). If the pedal cadence is too fast or too slow, there must be changes in the system response to avoid various risks. I'm guessing the BionX system is optimized for a 40-60 RPM cadence. So long as the user is shifting gears to maintain such a cadence, then the BionX system can automatically compensate for the changing torque from the pedals while maintaining a good assist level. A lot if this is a issue specific to BionX, as they try to maintain a consistent assist level even when the rider is shifting gears. Most other pedal sensing systems are either simple on/off systems that only detect pedal movement, or are sensing chain torque without compensating for the torque multiplying effect of gear changes, and just do not work as well as the BionX system.

When you changed your tire size, I assume you re-spoked the motor with a larger rim? Even though the max speed should have increased, the air resistance combined with the reduced torque could have left you with the same effective max speed. The target speed (V * Kv) is a no-load speed: the speed the wheel will turn when it is held off the ground at full throttle. Air resistance, tire rolling resistance, bearing friction, incline, and any other forces acting against your movement will only reduce the maximum speed from the target speed. That is why a larger tire, which will have a faster target (no-load) maximum speed, may not have any greater actual riding speed.

Except for the pedal torque sensing the way BionX does it, nearly everything else in these points are pretty much the same with all ebike systems that use a direct drive or a fixed gear drive motor (virtually all hub motors). There are various other considerations for systems that vary the gearing between the motor and the wheel.

-- Alan

 

[cjr]

Alan, thanks for the lengthy explanation.. I thought I should add some info/clarification. The BionX we bought is the PL-350. The Trice-T has a 20" wheel. When I said we changed the wheel size, what we did was change the wheel size settings in the console to try and defeat the speed limiter. We didn't actually change the physical wheel. This was based on instructions in various forum posts we've seen. However, there have been other posts saying that it won't work... Excuse my non-technical layman's wording. If I am understanding your information correctly, the motor has a top speed, which is RPM's, and it won't matter what settings you put in the console, it isn't going to go past that top design rpms. The only way changing the console settings would make a difference is if the motor has excess capacity and it is the settings in the console that are preventing it from reaching that maximum RPM.

 

[alan]

[...] When I said we changed the wheel size, what we did was change the wheel size settings in the console to try and defeat the speed limiter. [...] If I am understanding your information correctly, the motor has a top speed, which is RPM's, and it won't matter what settings you put in the console, it isn't going to go past that top design rpms. The only way changing the console settings would make a difference is if the motor has excess capacity and it is the settings in the console that are preventing it from reaching that maximum RPM.

The BionX and other commercially sold systems are required by law to have a speed limiter. It is 20 MPH in the US, and, I believe, around 15 MPH in most of Europe. BionX computes the speed from the motor RPM and the wheel diameter. You can trick the speed cut off by reprogramming the wheel size. That is what you have done. However, the max, non-cut-off speed of the system is only a bit higher than the cut-off speed, so it will not make much difference.

The other programmable settings that you may have been playing with can change the minimum speed that the BionX will start assisting (you don't want it kicking in from a dead stop just because something touched the pedal!), the sensitivity of the assist that varies how much assist each assist level setting (1 - 4) provides, the torque sensor sensitivity that adjusts how the assist changes with changes in the pedal torque, and other various settings. The factory defaults are pretty good for most people, and the few settings that the manual describe are all most people need to worry about.

In my case, I found that my ideal assist for my 11 mile commute was between setting 1 and 2; 1 was not enough and caused me to ride too slow, and 2 was more assist than I wanted most of the time. On the other hand, I really liked the more aggressive take-off power level 3 gave me from a stop. I played with my sensitivities (0007 and 0008 settings) until I got just the right assist for me. Now I have great take-off acceleration, and also full speed cruise (19-21 MPH) which allows me to keep my heart rate where I want it (which would be about 15 MPH without the BionX). This setting also gives me great range on my battery (better than the factory default for level 2 assist).

-- Alan

 

[DahonElectric]

Alan, thanks for the lengthy explanation.. I thought I should add some info/clarification. The BionX we bought is the PL-350. The Trice-T has a 20" wheel. When I said we changed the wheel size, what we did was change the wheel size settings in the console to try and defeat the speed limiter. We didn't actually change the physical wheel. This was based on instructions in various forum posts we've seen. However, there have been other posts saying that it won't work... Excuse my non-technical layman's wording. If I am understanding your information correctly, the motor has a top speed, which is RPM's, and it won't matter what settings you put in the console, it isn't going to go past that top design rpms. The only way changing the console settings would make a difference is if the motor has excess capacity and it is the settings in the console that are preventing it from reaching that maximum RPM.

Motor rpm limitation is imposed by the size of the wheel. You have a 20" wheel and if you trick the system into believing you have a 26" or a 700c wheel, you are not defeating the speed limiter at all. What you have done is simply telling the motor to keep turning until it reached a set distance for a complete 1 revolution of the 26" or 700c wheel! 1 complete revolution of a 700c wheel travels further in a straight line than 1 complete revolution of a 20" wheel. In order for a 20" wheel to reached a set distance equal to that of a 700c wheel, it has to turn more. I think about 3 to 4 times more, which means you are able to increase pass your 20" speed limit, but not pass the 26" or 700c limit unless it managed to reach it. Then the motor cuts out. Or when you are going down the hill, the motor cuts out because you reach max RPM faster than what the system expects it should be, a bigger wheel. So again, no assist.

Changing wheel size does not defeat any speed limit.

 

[Canis Lupus]

Alan, thanks for the lengthy explanation.. I thought I should add some info/clarification. The BionX we bought is the PL-350. The Trice-T has a 20" wheel. When I said we changed the wheel size, what we did was change the wheel size settings in the console to try and defeat the speed limiter. We didn't actually change the physical wheel. This was based on instructions in various forum posts we've seen. However, there have been other posts saying that it won't work... Excuse my non-technical layman's wording. If I am understanding your information correctly, the motor has a top speed, which is RPM's, and it won't matter what settings you put in the console, it isn't going to go past that top design rpms. The only way changing the console settings would make a difference is if the motor has excess capacity and it is the settings in the console that are preventing it from reaching that maximum RPM.

Hi CJR, the conflict between opinions about lifting the speed limit might arise from there being two different bionX systems - a new one, and a previous version. With the previous version, it was possible to turn the speed limit off, although the motor's inherent speed limit of approx. 32km still applied. With the new version, BionX have made lifting the speed limit impossible. I think this is mainly an issue with non-American users, such as in Europe, where there is slower legal limits with e-bikes.

If I had the new system and was limited to European (or Australian) legal limits, I wouldn't bother with the system. Nice to know for me that there is some benefit with the older system.

In relation to an earlier post of yours and your mention of the HSD, the following might be relevant to consider. I use the Schlumpf HSD, bought it especially for e-assist to help compensate for the loss of the 9 and 10 teeth rear gears, while still giving me the range to mountain climb even if the battery gets exhausted. One drawback has been the lack of assistance when putting the HSD in the top range. The torque sensor doesn't seem to be as sensitive as in the lower gear range. Assistance is no-where near comparable in overdrive, as the assistance given in the lower range, even when comparing gears which are close together and speeds well below the BionX speed limit ie. top gear in lower range compared to lowest gear in top range - the two being almost identical. I've experimented with this from slow starts.

From another forum I loiter in, I know this is not just my system acting in a funny way. Another BionX user who has a HSD has posted a thread seeking a solution to the problem. It doesn't worry me that much, I don't mind using the throttle in overdrive, although in the lower range I like having the assist to manage power input. So, the problem actually suits my way of working the system, but I can understand people who bought the system particularly for the pedal assist system might feel frustrated.

 

[Canis Lupus]

Just a little update concerning my own system - sorry, I don't wish to distract the discussion from CJR's posts.

I've had the system up and running nearly two months now as it was intended and designed to be, once I received all the right parts, the latest being the extender wire.

I've had so many problems with the system that when it comes on and operates as it should, I almost feel relief. Now that it is though, I am enjoying the system. The more familiar I become with it and the better at managing the small battery, the more I enjoy it. Because of the regeneration feature, pedal assist, and throttle, all can be used in different ways to make its use flexible ie. burn around as fast as possible or ration assistance to when the going gets hard and extend range.

So far, I've failed to exhaust the battery. Obviously if I was determined to do so, I could easily enough. But for the different type of trips I've made with it, I've had few problems in managing the system well enough. I was particularly impressed with a trip to a nearby town I made last weekend, which wasn't that far but did involve a big climb and then plenty of ups and downs. The last time I made this trip, I almost exhausted myself just getting to the highest point, whereas with the assistance it was a pleasant trip, while still giving me plenty of exercise. Using the regeneration as much as possible, meant arriving at my destination with the battery less than half depleted. Not a bad effort after nearly 30km I thought.

Management of the battery supply is easy when you know the distance and terrain you are going to travel, but where there is some uncertainty the regeneration adds a great deal to the management in not being caught with a depleted system.

I've also be doing some pretty rough trips on atrocious unsealed roads. So far, fingers crossed, the system as a whole has stood up to the battering.

Lastly, in getting my problems sorted out with the system, ultimately BionX came to the rescue through a dealer in Germany. It cost me nothing except postage there. It was frustrating doing without the system while it traveled back and forth, but I can't complain about BionX's warranty. Once I talked to the right person at BionX, all problems faded except the time taken.

I'm returning to Australia soonish. Unfortunately, BionX does not have a dealer there. I'm feeling a little vulnerable with the system if there is a problem, just like I have here in Greece. Hopefully, Bionx can get some dealers going in Australia again soon.

I still think the system is dreadfully overpriced, as their accessories are also. I would like to have another battery but I'm certainly not prepared to pay $1300 plus postage, or even $800 plus postage for a reconditioned one. I would be willing to pay a $100-200 for a clapped out battery with the circuitry still working, replace the cells with something of my own choosing.

At 50% - 75% of their present prices with a standard distribution through local bike shops, a BionX system would become a far more attractive system. Sorry if that is stating the obvious, but because of the price I would not make the purchase again, unless I picked up a heavily discounted system. To others, not as price conscious perhaps, and with a dealer on hand nearby, I see no problem.