jkbrigman
10 kW
Using a CA to measure "freewheeling" speeds of the 2810 and 2812 motors at 18S (74V nominal) and 24S (96V nominal). To estimate real-world speeds in neutral wind, subtract 2 mph from these numbers on a recumbent, 3mph on an upright. I determined those "differentials" through testing on my SWB recumbent. I did not have a headwind at the time.
I made my 24S number "96V nominal" on purpose - I used 50% charged LiPo bricks to stay under 100V, I didn't want to risk damage to my controller, as I'm already well outside the voltages that the unit is warranted at with that test.
The purpose for doing this is because I have a front 9c 2812 in a 20" rim with a 1.5" Schwalbe Marathon. I need to estimate speeds for the 2812 on the various wheel sizes so I can do a spreadsheet to determine whether I should keep the motor in the 20" rim and run it at higher 24S, or have the motor moved to a larger rim and keep it at 18S. Since I've "standardized" on 18S, I expect the spreadsheet to "suggest" moving the motor and staying at 18S.
The test setup was using a 2812 on a 20" rim, and a 2810 on a 26" rim, so those numbers are actual. I changed the settings in the CA to simulate the speeds in 26"/700c rim for the 2812 and 20"/700c for the 2810. The "multiplication factors" I determined referenced to a 20" rim were 1.288 for the 26" rim and 1.374 for the 700c rim. Those numbers were consistent for both motors, as one would expect.
2810 @ 18S (74V)
---------------------
20" rim - 26mph
26" rim - 33.5mph
700c rim - 35.6mph
2812 @ 18S (74V)
---------------------
20" rim - 21.5mph
26" rim - 27.7mph
700c rim - 29.5mph
So the 2812 is roughly 6mph slower than a 2810 in the same rim at 74V.
2810 @ 24S (96V)
---------------------
20" rim - 33.5mph
26" rim - 43.2mph
700c rim - 46.02mph
The 2810 finally breaks the 40mph barrier at 96V. But at these speeds, wind resistance is to the cube of the speed increase, so I doubt my "2 and 3 mph rule" is going to work here. I will do real-world testing on a 10 mile loop tomorrow (4/15) to verify this.
2812 @ 24S (96V)
---------------------
20" rim - 28mph
26" rim - 36.2mph
700c rim - 38.5mph
The 2812 turns in respectable numbers at 96V, but this testing strongly suggests you won't join the 40mph club at anywhere under 24S.
Again, no clue how these numbers will hold up in the real world, but I expect you could see well over 20mph with a 2812 on a 20" wheel at 96V. It's curious to me that the differential between 2810 and 2812 INCREASES at 24S...I have no explanation for this and it doesn't matter until I do real-world testing to prove or disprove.
Note to self: check to see if you get any improvements in efficiency and distance capability at 72v vs. 96v. Seems reasonable to think you could see a range improvement given the same average speed and terrain.
I welcome questions or experienced feedback, especially if you can add to real-world experience that either modifies or supports what I've written. I'm not concerned about volts vs. S, my numbers are nominal.
I made my 24S number "96V nominal" on purpose - I used 50% charged LiPo bricks to stay under 100V, I didn't want to risk damage to my controller, as I'm already well outside the voltages that the unit is warranted at with that test.
The purpose for doing this is because I have a front 9c 2812 in a 20" rim with a 1.5" Schwalbe Marathon. I need to estimate speeds for the 2812 on the various wheel sizes so I can do a spreadsheet to determine whether I should keep the motor in the 20" rim and run it at higher 24S, or have the motor moved to a larger rim and keep it at 18S. Since I've "standardized" on 18S, I expect the spreadsheet to "suggest" moving the motor and staying at 18S.
The test setup was using a 2812 on a 20" rim, and a 2810 on a 26" rim, so those numbers are actual. I changed the settings in the CA to simulate the speeds in 26"/700c rim for the 2812 and 20"/700c for the 2810. The "multiplication factors" I determined referenced to a 20" rim were 1.288 for the 26" rim and 1.374 for the 700c rim. Those numbers were consistent for both motors, as one would expect.
2810 @ 18S (74V)
---------------------
20" rim - 26mph
26" rim - 33.5mph
700c rim - 35.6mph
2812 @ 18S (74V)
---------------------
20" rim - 21.5mph
26" rim - 27.7mph
700c rim - 29.5mph
So the 2812 is roughly 6mph slower than a 2810 in the same rim at 74V.
2810 @ 24S (96V)
---------------------
20" rim - 33.5mph
26" rim - 43.2mph
700c rim - 46.02mph
The 2810 finally breaks the 40mph barrier at 96V. But at these speeds, wind resistance is to the cube of the speed increase, so I doubt my "2 and 3 mph rule" is going to work here. I will do real-world testing on a 10 mile loop tomorrow (4/15) to verify this.
2812 @ 24S (96V)
---------------------
20" rim - 28mph
26" rim - 36.2mph
700c rim - 38.5mph
The 2812 turns in respectable numbers at 96V, but this testing strongly suggests you won't join the 40mph club at anywhere under 24S.
Again, no clue how these numbers will hold up in the real world, but I expect you could see well over 20mph with a 2812 on a 20" wheel at 96V. It's curious to me that the differential between 2810 and 2812 INCREASES at 24S...I have no explanation for this and it doesn't matter until I do real-world testing to prove or disprove.
Note to self: check to see if you get any improvements in efficiency and distance capability at 72v vs. 96v. Seems reasonable to think you could see a range improvement given the same average speed and terrain.
I welcome questions or experienced feedback, especially if you can add to real-world experience that either modifies or supports what I've written. I'm not concerned about volts vs. S, my numbers are nominal.
) and that opened up my throttle response. Tweaked a few other things in the CA and now the 9C is pulling like a donkey with 2kw starts easy. Happy kid here.
