Luna BBSHD Ludicrous V2 controller documentation

[StvMan]

Interesting info...so taking it further....the old adage that the bbshd loves higher rpm is more of a heat prevention measure, rather than an effective use of available power to the dirt....correct?

[marcos]

Exactly. At low speed you get full *phase* Amps (torque-producing Amps), but not full battery Amps (power-producing Amps?). You would be using low battery current, but your motor would have to endure very high currents, which gets it hot and lossy.

The electrical battery power is (Voltage * Current), its efficiently converted to mechanical power at the wheel which is (torque * speed). So at zero speed you make zero power, which is also reflected in the battery current.

[StvMan]

Marcos...you mentioned “battery current is pretty much proportional to speed, so if you want lower battery current you can lower the motor speed.”... I am sure you mean this as a general rule of thumb, but I have to ask...Does this mean that if I load up the motor at wide open throttle but don’t reach full RPM (steep hill with tall gear) will I not be reaching full Amps?

[marcos]

Oh cool. Keen to see how that combo performs

[xcnick]

2p of Samsung 40T - high drain 21700 Li-ion cells. In theory they are 35amp cells so 70 amps are available.

here is a test to see if they are really this good: https://www.thunderheartreviews.com/...00-li-ion.html

The pack is made by one of our members who has posted in this thread. The web page: https://bicyclemotorworks.com/produc...ttery-72v-8ah/

He says 80 continuous and 120 burst. Should be interesting....

Paxtana, have they shipped my egg yet? just kidding. I will be patient, it is just a hobby.

[marcos]

you mentioned 20s2p, go easy on that battery because the controller can crush it. At your speed it will run more efficiently I think, but with only 2p the sag is substantial so you should limit battery current to something like 30 or 40A, you can PM me and we can setup that.

[xcnick]

Altitude is correct, I am high all the time, ask anyone. But we have learned I can only be an idiot for a minute before overheating. You have opened my eyes to how these temps and field weakening information could be useful on a display.



This is the data about my bicycle that should go with the log:

26" wheel, 48 tooth front sprocket, 13 tooth rear cog, equals 97.5 gear inches; Then 150lb (me)+65lb (bike)=215lb load. (Sorry it is not Metric)

https://www.sheldonbrown.com/gear-calc.html


When the egg rider arrives, 72 volts on the exact same task!


I haven't been on this forum in while. Is anyone seeing my pictures? In the old days I just copied a link from the picture displayed in Google Photos, but with all the changes to google photos, maybe this won't work anymore.

[paxtana]

Wow that is some impressive data analysis. Really cool to see that is possible.

[marcos]

Another thing I didn't notice before is the altitude, is that GPS data correct?



You were at 2000m over sea level (6500ft), and climbed 117 meters in 130 seconds (380ft). It was a 7% incline and it was done at full speed, pretty though.

[marcos]

I can't see your images, but from the CSV I can get a ton of data.

So first, the controller is throttling down the phase current because the motor temperature is exceeding the max limit:
More accurately, you have 100% torque available at 100°C. At 110°C you have 0% torque available (its a linear derating). At 110.00001°C the controller asserts the overtemp fault I pointed out in the image.

My initial thought was that you were running a too low gearing and using too much phase current, so I was going to suggest to shift gears to keep the motor at higher RPM... but then I realized the speed was very maxed out.

I can tell speed is maxed out because the duty is near 100%, the controller can't push more volts into the motor. This made me wonder if the V2 was under field weakening, and voila, it is:

k

Field weakening is what makes your motor run faster than stock, but its also very punishing because those -30 Amps are heating up the motor, and don't provide any torque.
For example, if you had a higher voltage battery, for the same speed you wouldn't need any field weakening current and those 30A could be spent providing torque.

Right there you sustained about 70 phase amps for a minute or so at max speed, and the motor got too hot. In winter/rain/low altitude etc it would take it longer to hit temp limit, but we can't do magic with thermodynamics.


Now... about your battery. At only 60 battery Amps the voltage is sagging down to 44V, I think it's not pushing more phase Amps because the battery can't supply them.

The battery voltage cutoff starts at 44.2V (100% torque available) and at 40.3V it drops to 0% torque available. You are not quite reaching this, but its on the very edge.

I think that if your battery could provide a stiff 54V you would be zapping around at 150 phase Amps. I don't know much about batteries, but I know controllers struggle to push amps when the battery voltage is low.


So... I can't tell if your battery is underperforming because I'm not a battery expert, but I can tell that the first 60 seconds the battery was limiting your current throughput because it drooped too low, and after those 60 seconds it was the motor temperature that produced the torque reduction.
Hope it helps!

[xcnick]

I have something, Here is the two temps like your example:




Here is one of amps:



This not how I use my bike. Normally I PAS the approach so I have power to brap around when I get there.

Wolf setting, two mighty minis in parrallel, 14s4p of 30Q cells. Level 9, so something is capping me at 50 amps. 56volt to start

What else should we look at? How do I tell how my battery is performing?

csv file attached

[marcos]

I was going to post instructions on how datalogging works in the ludi v2, but there were already written in the first post of this thread.

So instead I'll focus on what can you get from the logs.

Example 1:
See how much battery current are you using over time


This what I'm used to see in flat ground, lots of short (few seconds) bursts of power coming from the battery.

You can zoom into the plot to take a closer look:

If you are climbing a mountain the battery current draw will have a higher baseline and you will be able to see how much you are really asking out of that battery.
Pro-tip: battery current is pretty much proportional to speed, so if you want lower battery current you can lower the motor speed.


Example 2:
You can analyze your drive unit temperatures, for instance comparing mosfet and motor winding temperatures:

The BBSHD has the motor temperature sensor very poorly located, so there is a huge lag between the moment of maximum power and the sensed max motor temperature. In the new bikes we sell with the ludi v2 install the sensor properly and also upgrade the nylon gear.

You can see in the plot that the mosfet temperature is snappy and the motor temp lags a lot. If someday in summer you experience a power loss, you can check in the logs if you were experiencing motor overtemperaure, which will progressively decrease motor current. The V2 controller is overbuilt and I could never hit max mosfet temp with an ebike motor, I reached its limit driving an impeller on water with a huge motor.

Example 3:
Its pretty difficult to get the speedo reading right, as it depends in gearing. From the logs you can compare and fine tune the gear ratio to match controller-estimated speed with the phone GPS data:
Of course this works best when there is a single gear ratio.

Example 4:
Stats!

Using GPS data you can take any segment of the logging and vesc tool integrates the data to show efficiency, average speed, distance, etc
Battery current is an indirect measurement, not as accurate as phase current but its still very usable. I found that logging with the phone on my pocket was okay, but GPS was more accurate when it has line of sight with the sky.
If you would like a slow walk through the datalogging feature, in this video the VESC architect explains how to use it: https://www.youtube.com/watch?v=1dm12zB78Ic


So all of this is already built in, running under the hood and ready to use, and its pretty fun to get to the stats of your rides. You could find ways to make your riding more efficient, compare paths, see how badly you are punishing your battery, etc.

I'm keen to see your plots! I haven't seen a ludi working in the snow, or climbing in very hot weather, the more we know the safer it is to increase power on future firmware deployments.

[xcnick]

You got it. I need the controller to be smarter than the rider who just holds it wide open and hangs on. The snow bike is a hard tail so it jumps around. Watch video of early 1900 motorcycles hill climbing. I will use the steel gear for this but the controller should be ready to be unloaded and loaded as it bounces up and down. thanks so much for you help, but even more for sharing the fun we all are having out here.

[marcos]

the motor only cares about phase current, so it can put out more power for longer if you run it at higher voltage. As for the battery limit, you would have to check how much current each cell is delivering and see if that's safe or not.
I'll try to prepare a post about data logging to show how you can analyze your power draw over time with some graphs, because full throttle doesn't necessarily mean full power.

[xcnick]

Does the 72 volts allow one to hold full power for longer because it runs cooler? I hill climb, it is the only way to loose the yuppies with the spandex, turbo levos, and private school dogs. Five minutes of full power would be very useful.