Regen. braking cuts out unpredictably - Settings? Solution?

Hi, I'm test riding a new e-bike build, and this is my first experience using proportional regen. braking.

Is there a way to keep the controller from "cutting out" regen. braking when a current limit is hit?

I'm using the GMAC 10T geared hub motor, Phaserunner controller, Cycle Analyst v.3.1. I have a 10 Ah battery, so my regen. charging current is limited to 10 A. This can produce a nice strong braking effect at slow speeds, but not very much at high speeds (before the current limit is hit). That's fine, and I understand why (the hub makes more power/current at high speed, with less torque), but as a result the usability of the regen. feature for braking is badly compromised. It's disconcerting when you're trying to use regen. for braking, that the braking effect will surprisingly and abruptly just quit at unpredictable times, as you might proportionally increase braking (using the throttle), or even just as the bike starts descending faster (while you're holding the regen. braking constant).

(Less importantly, for me, this behavior also hurts the ability of regen. to return energy to the battery).

My ideal would be for the controller to be able to proportionally increase regen. current - braking - up to the set maximum, and when that maximum current is hit, just keep it there at that maximum current and not cut out. Have I missed some way to set it to behave like that?

By the way, I've produced this behavior on the bike with the motor and controller cool, and the battery partially discharged. So I don't think any temperature or voltage limits are being hit. Observing the CA3 readouts while riding, I think I'm just hitting my 10 A current limit.

Thanks for any tips!

Are you sure it's the current limit and not one of your cell groups hitting their max allowable voltage? Because if it's the latter it's working as it should to prevent overcharging that group. I know you said partially discharged, but unless you're able to monitor group voltages on the fly it's hard to say definitively.

Hi thanks for reply. I'm not sure of anything. But I do observe that the e-braking "cut-out" happens with all sorts of different voltages shown on the CA3, not any particular high voltage. However, there seems to be a correlation with the power/amps readout. When it gets close to 10, it cuts out. I use a 10 Ah Ping battery with the V5 BMS.

I'll report further, as I run the battery lower, to see if the behavior improves.

The past several days I logged data on this issue. I attach several files (two data runs, in original and in annotated .xlsx format).
Both rides are very short - about 90 seconds - simply getting up to speed and then using the e-brakes, increasing the e-brake power gradually until it cut out. Data was logged at 10Hz.
datalog 7 has the "begin max V" set to 42V (my original setting), and datalog 8 has it set to 43V. I wanted to isolate the possibility that the voltage limit was tripping the "e-brake cut" problem.

I think the data shows pretty clearly that the e-braking is abruptly "ended" when the current (A) is in excess of the limit I set to protect the battery (in my case: 10A). Nothing else was near any other limits set - not battery voltage, motor temperature, etc.

So my question remains... why can't or doesn't the e-braking continue at whatever maximum regen. power value was set? In my case, where my regen. limit is set to 10A, as I increased the demand for e-braking (using brakes and thumb throttle together), the phaserunner/controller ideally should increase hub power output to the maximum 10A, and then keep it there - i.e. continue e-braking for as long as the controls are demanding it, but not letting the regen. power go above 10A. Would the phaserunner not be able to "throttle" the regen. power like that? After all, it is able to throttle forward power being drawn from/out of the battery.

Am I missing a setting for controlling such behavior, or if not, is that something which could be improved in firmware?

Could it be the battery BMS (a Ping v5) triggering the regen. cut?

Thanks for any tips!

PS
questions/comments about the data file:
"1R" error flag - what could it mean?
"1W" error flag - happens when I pedal (PAS reads values), what does it mean?
(searching online, I was unable to find any documentation on the meaning of the various error/flag codes)

Try changing the limit to 5A. If it still cuts at 5A, it's probably controller related. If it doesn't, it's probably BMS related.

serious_sam: that is an excellent idea, and so obvious, I'm embarrassed I did not think to try that already. I finally got to it today... I set the Phaserunner to permit only 5A of regen. current, and indeed, now the regen. cuts out at about that value. (I was unable to record data on that today, but you can take my word for it

So, for what it's worth, I think I've narrowed the problem down to the Phaserunner: it will "cut out" regen. braking entirely, when the current limit is hit. This is unfortunate, because if you use regen. for the additional braking - e.g. getting a heavily laden bike down the hill safely, or aiming for and coming to a stop with regen. - then having that braking effect suddenly and unpredictably vanish does seriously erode what would otherwise be a useful functionality.

Now maybe it is still a problem with my setup - I don't know. Has anyone else observed this behavior?

If it is a bug/feature inherent in the current Phaserunner, could this be fixed in the firmware? The regen. feature would be so much more friendly and useful if, when the current limit is hit (or approached), the phaserunner would continue to supply regen. power at the limit value. (When the high voltage limit is approached, then it should phase out regen. braking gradually, to protect the battery).

thanks everyone!

retrocycler said:

serious_sam: that is an excellent idea, and so obvious, I'm embarrassed I did not think to try that already. I finally got to it today... I set the Phaserunner to permit only 5A of regen. current, and indeed, now the regen. cuts out at about that value. (I was unable to record data on that today, but you can take my word for it

So, for what it's worth, I think I've narrowed the problem down to the Phaserunner: it will "cut out" regen. braking entirely, when the current limit is hit. This is unfortunate, because if you use regen. for the additional braking - e.g. getting a heavily laden bike down the hill safely, or aiming for and coming to a stop with regen. - then having that braking effect suddenly and unpredictably vanish does seriously erode what would otherwise be a useful functionality.

Now maybe it is still a problem with my setup - I don't know. Has anyone else observed this behavior?

If it is a bug/feature inherent in the current Phaserunner, could this be fixed in the firmware? The regen. feature would be so much more friendly and useful if, when the current limit is hit (or approached), the phaserunner would continue to supply regen. power at the limit value. (When the high voltage limit is approached, then it should phase out regen. braking gradually, to protect the battery).

thanks everyone!

Click to expand...

Did you ever contact Grin or find a solution to this? Thanks

Just a quick update: I am talking to Grin about it, and they have allowed the possibility that my Phaserunner is faulty. That won't be settled until I can do some more tests. A recent crash (on another bike) is cause for some delays, as I recover from injuries. Please stay tuned and know that I will eventually post what I hope to be useful results.

Update: I have been running on a new 52V battery, with similar Ah capacity to the prior 36V battery. Though I get stronger regen. braking with the 52V battery, the Phaserunner still cuts out at the set power limits, which it is not supposed to do. I'm still trying to figure out why. Grin has not taken the phaserunner back yet, instead asking me to do some more experiments with it.

I've been experiencing the same thing- at about half of what I set the phaserunner to regen at. I recently set it to 30A since my BMS has a common charge port, and my cells all should be able to handle 1C charging (which is about 20A but I can't even get there). I can see 11a on the display before it drops off. There's definitely something wonky going on.

I, too, don't think it's the BMS since that fault will cause the voltage reported on the cycle analyst to drop- in my case the voltage is fine, the phaserunner just stops putting out power. I'll drop a line to Grin and get you a second patient.

Any news on this from anyone? I've not been able to do any more testing, as an OS upgrade on my laptop broke the ability to pull data from the Phaserunner. Grin wants more data before I return phaserunner, because of my "new" 52V setup. Due to other responsibilities, I've given up on the project... on the attempts to pull data. I feel like I've spent enough time on it.
With the 52V battery, the regen. braking is fairly strong/useful, but the fact that it "cuts out" unpredictably at the current limit is still a major issue. Regen. braking cannot be relied upon for steeper downhills, which is a primary reason I built with a regen. capable motor, to assist the regular brakes while heavily loaded on downhills.

The problem is solved. Robbie of Grin got back to me after noticing that in my PR settings, I had set different values for the "Throttle Start Voltage" and "Throttle Fault Range" - these two settings need to have the same value (at least for my setup, apparently). Below, I append Robbie's comments and instructions:

[Throttle Start Voltage and Throttle Fault Range] ...These two values must be equal, otherwise the system will fault when the CA forces the throttle to 0V (1.2V Start minus 0.9V Fault = 0.3V, the controller will fault any time it sees throttle voltage less than 0.3V, and when the throttle goes back to rest, will automatically reset the fault condition).

I would also suggest lowering the maximum throttle value to something where 5V actually faults (so if you set fault to 1.2V, max throttle should be something like 3.5V).


After adjusting the settings per these instructions, the problem is finally solved!

retrocycler said:

After adjusting the settings per these instructions, the problem is finally solved!

Click to expand...

It's awesome that you were persistent, and that you followed up and shared the results!! bookmarked

retrocycler said:

The problem is solved. Robbie of Grin got back to me after noticing that in my PR settings, I had set different values for the "Throttle Start Voltage" and "Throttle Fault Range" - these two settings need to have the same value (at least for my setup, apparently). Below, I append Robbie's comments and instructions:

[Throttle Start Voltage and Throttle Fault Range] ...These two values must be equal, otherwise the system will fault when the CA forces the throttle to 0V (1.2V Start minus 0.9V Fault = 0.3V, the controller will fault any time it sees throttle voltage less than 0.3V, and when the throttle goes back to rest, will automatically reset the fault condition).

I would also suggest lowering the maximum throttle value to something where 5V actually faults (so if you set fault to 1.2V, max throttle should be something like 3.5V).


After adjusting the settings per these instructions, the problem is finally solved!

Click to expand...

Hi, thanks a lot for this tip!
I couldn't understand why at 0,4V Regen kicks in but at 0,35 there is NO Regen at all.
So I followed your instruction, it works perfectly now!
Regards

I'm having a mysterious periodic and upredictable regen-braking cut off on my GMAC too, but retrocyler's solution did not work for me (my throttle start voltage and range were already set to be equal as they should be with the entirely default settings I have). I have an email out to grin and hope to report back once I get this urgently fixed (not riding it in the meantime as it's dangerous to lose ebraking suddenly).

NeezyDeezy said:

upredictable regen-braking cut off

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There are no details? Accelerating, decelerating, steady, do you have brake switches to invoke regen or are you using beta firmware with back-pedal, torque-sensing, cadence sensing, cargo bike with heavy loads, trike...

I could keep writing. Your reply could be shorter as you only need to list what is so for you.

when I use the ebrake lever to regen, the CA sometimes shuts down and needs to be powered back on, thank you!