Energy regeneration on Fardriver 72240

[Daniel2]

Hi, everybody! I have a question about energy regeneration and was wondering if somebody could be kind enough and help me. The specifications are as follows:
-My battery: 60V 30Ah
-Controller: far driver 72V240A
-Max line current:40A
-MAX phase current: 240A
1. I have turned on regen in function >follow >3EABS when release and in the energy regen section has set the following values
-Stop back current:5A
-maxbackcurr: 10 A
-Batt rated capacity: 30Ah
Now when I ride and release the throttle, I can see on display a charging sign indicating the battery is charging. All looks good here! However, after a while, the power started to be cut totally after a regeneration cycle and no response on the throttle . The only way was to stop completely and then the throttle starts working again. It happened several times.
My question however is:
-Why is it happening and what will be the max values I can choose for stop and max ensuring I do not damage the controller or battery?
-Additionally, I can't change the free throttle or any of the RPM variables in the energy regene section. If I enter a value, the value is not retained and always shows 0. Anybody knows the reason for it? is the section only active with the brake as a regenerator?

 

[Dui ni shuo de dui]

Could you post screenshots of all your settings in the fardriver app?
That should help diagnosing what the problem is.

Also, you should get some kind of error on the display, could you try to look up for it next time it happens?

 

[Daniel2]

Dui ni shuo de dui:
Could you post screenshots of all your settings in the fardriver app?
That should help diagnosing what the problem is.
Also, you should get some kind of error on the display, could you try to look up for it up next time it happens?
Hi, thank u for your response! I looked today. I finally figured out that the problem was a momentary low-voltage error. For some reason, the voltage will drop under the set protection level. Mine is set to 50 and I think the voltage dropped to 38-40V. Despite voltage recovery, the throttle does not work until I fully stop. It means the low Volt restore not working !! Do you have any idea why such a thing happens?

 

[Dui ni shuo de dui]

Dui ni shuo de dui:
Could you post screenshots of all your settings in the fardriver app?
That should help diagnosing what the problem is.
Also, you should get some kind of error on the display, could you try to look up for it up next time it happens?
Hi, thank u for your response! I looked today. I finally figured out that the problem was a momentary low-voltage error. For some reason, the voltage will drop under the set protection level. Mine is set to 50 and I think the voltage dropped to 38-40V. Despite voltage recovery, the throttle does not work until I fully stop. It means the low Volt restore not working !! Do you have any idea why such a thing happens?

You have a 72V rated controller and a 60V rated battery, ideally you'd need a 72V battery for things to go smooth.
So now what happens is that when you accelerate the controller demands too much power from the battery, which makes voltage sag.

First, I suggest you temporarily lower the low voltage protect parameter as low as it lets you, then ride a little bit and check how low the voltage gets once accelerating. I don't know how many cells in series your battery have, let's say it's a 20S for the sake of example.
If your battery is a 20S and you notice the voltage going down to 38V, then it means 38/20 =1.9V per cell.
In which case, that would mean that the cells in your battery reach a voltage of only 1.9V under load, which is way too low and is likely to damage the cells and potentially overheat them if you keep doing that for too long. That would indicate two things:
-your BMS is not doing its job to protect the cells
-you need a more powerful battery, or you need to tune down the controller power to reach safer cell voltage levels.

I don't know what your battery chemistry is, for instance LiFePO4 cells voltage can be lower than Li-ions.
Do you have any idea what cells are in there? chemistry used? how many cells in series?
If you don't, then another way we could determine it is by knowing what is the exact voltage the battery sits at right after it has been fully charged.

 

[Daniel2]

You have a 72V rated controller and a 60V rated battery, ideally you'd need a 72V battery for things to go smooth.
So now what happens is that when you accelerate the controller demands too much power from the battery, which makes voltage sag.

First, I suggest you temporarily lower the low voltage protect parameter as low as it lets you, then ride a little bit and check how low the voltage gets once accelerating. I don't know how many cells in series your battery have, let's say it's a 20S for the sake of example.
If your battery is a 20S and you notice the voltage going down to 38V, then it means 38/20 =1.9V per cell.
In which case, that would mean that the cells in your battery reach a voltage of only 1.9V under load, which is way too low and is likely to damage the cells and potentially overheat them if you keep doing that for too long. That would indicate two things:
-your BMS is not doing its job to protect the cells
-you need a more powerful battery, or you need to tune down the controller power to reach safer cell voltage levels.

I don't know what your battery chemistry is, for instance LiFePO4 cells voltage can be lower than Li-ions.
Do you have any idea what cells are in there? chemistry used? how many cells in series?
If you don't, then another way we could determine it is by knowing what is the exact voltage the battery sits at right after it has been fully charged.

Thanks for the nice info! I am not sure but I think it is 17 series and each group of cells is charged to 4,1v per cell. It is either LG or Samsung 18650 battries. The charger i have is 67.9V -10A. It also has a 6 pins sockets. I can still reduce the rate voltage from 72 to 65 . I agree it can be a battery issue and it is weak for the setup. Yet my problem or the thing i cannot understand is why this low voltage only happens after a long freewheeling (the 30s or more ). At all other times even at the highest speed, full throttle, and full Amp, I never saw the voltage drop below 57V. It is only something that happens after free wheeling/coasting of the 30 ec, regardless of whether the regen is on or off.i feel somthing more complicated cuasing the issue.
I also think the problem is that I adjusted the controller for maximum performance based on theoretical battery capacity. However, it seems there are moments at high speed when the controller tries to draw more voltage than the battery is capable of providing, while at this speed there is no need for a maximum amount of power to keep going. Yesterday I came up with an idea and want to test it. The arrangement of my speed ratio has put the motor in a state that tells the controller to provide Amps continuously even over the rated RPM. I think this setting is wrong and overloads my battery. As a new setting, I have decreased the max line current and phase percentage for both gears 1 and 2 to 65LC/P and 75LC/75%P respectively. At ratios in speed for gear 3, I also decreased the percentage of phase for 3000RPM to 90% and at 4000RPM to only 80%. Practically at this point, I don't think any more power should be sent through the controller, and any higher speed should originate from field weakening. I have not fully tested it yet. But today in one test run on gear 3 and after regeneration, I noticed only a delay (about 3 to 5 sec) from the time I applied the throttle to the flow of power, But I no longer got the symptoms of low voltage and a complete lack of power.

 

[Dui ni shuo de dui]

At all other times even at the highest speed, full throttle, and full Amp, I never saw the voltage drop below 57V. It is only something that happens after free wheeling/coasting of the 30 ec, regardless of whether the regen is on or off.i feel somthing more complicated cuasing the issue.

Ah ok, well in this case the battery probably isn't the issue then, 57V under load is not too bad. That being said, it's not 100% sure it can't be the cause, because it is a 72V rated controller, some controllers don't tolerate going too low in voltage evne though they theoretically can.

It's a weird problem, I don't really know what is going on there. Might be a firmware problem, I suggest you try asking whoever sold you the controller for help. I had an issue with my fardriver when I received it (the motor kept accelerating when I released the throttle, even though every parameter in the app was set correctly). The only way to solve it was to flash another hex file, the seller of my controller asked the fardriver factory to provide it, I flashed it in the controller and now everything works as intended.

Sorry for not having a better solution to propose, good luck