New Hummie Hubs!

ESK8 Innovations
1078

i ran a comparison for 10S vs 12S… 60a motor limit 60a battery limit for both…

the electrical to mechanical conversion efficiency in the motor doesn’t seem to be affected (green line top left chart)… but you lose a few miles an hour of top speed with 10S.

system-wide it would appear you may lose a little bit of efficiency with 10S because, as seen in the bottom right chart, at 10S you have to draw a few more amps from the battery at all speeds to maintain the same 60a motor amp limit in the motor, and consequently you generate a bit of extra heat in the battery wires with 10S compared to 12S, lowering the system-wide efficiency.

6 Likes
1079

Capture

real world who knows what was going on and hard to get a true test done but here’s a simulation with the only variable changed being the voltage. same speed. look at the bottom and it breaks it down

total system efficiency with the 10s is better and it ends with a lower motor temp. this is just a change of voltage first shot

this one here is an increase of kv and has similar results.
Capture

1 Like
1080

interestingly I did a second 12S vs 10S comparison with 60a motor limit and 30a battery limit (instead of 60a motor 60a battery)

in the new comparison you get higher motor efficiency with 10S above the speed that you hit the 30a battery limit because above this speed you get less motor current at the same 30a battery amps with 10S… and less motor current means less heat generated and consequently greater efficiency.

(notice the green line top left chart – motor electrical to mechanical conversion efficiency – gets a slight boost with 10S)

1 Like
1081

what i posted and @professor_shartsis posted show to disagree. i have more faith in the simulation i posted due to who made it, jason lee who owns endless sphere, and its widespread use, vs shartis’ which hasnt been through nearly the trials and oversight and it’s not as encompassing.

one thing that could be happening in personal experience showing more range with higher voltage is the cells are not being sucked for amps as much for the same performance and with less peak current draw a cell will produce more mah. if you suck a cell at its peak possible current it will produce less energy than if you were to discharge it at less current. so maybe with a lower discharge cell such as ion vs lipo, it would be even more advantageous to have higher voltage. but assuming a cell is not decreasing its total output due to this phenomena then the graph i posted should accurately reveal the range

1082

@Hummie here’s all the formulas used (and verified)…

let’s take 50v @ 20mph from the graph (30a battery limit & 60a motor limit, 0.07ohm winding)

20mph @ 83mm diameter = 2057.30454rpm

2057.30454rpm / 85kv = 24.20358v back emf

50v * %55.91814 duty = 27.95907v effective voltage

((27.95907v effective voltage) - 24.20358v back emf) / 0.07ohm = 53.64984a motor current

27.95907v effective voltage * 53.64984a motor current = 1500w electrical watts

1500w electrical watts / 50v battery = 30a battery current

(53.64984a motor current)^2 * 0.07ohm = 201.48142w ohmic heating & copper loss

(2057.30454rpm * 2 * pi) / 60 = 215.440427 rad/sec angular velocity

60 / (2 * pi * 85kv) = 0.11234 newton meter torque per motor amp

0.11234 newton meter torque per motor amp * 53.64984a motor current = 6.02702 newton meter torque

6.02702 newton meter torque * 215.440427 rad/sec angular velocity = 1298.46376w mechanical watts

1298.46376w mechanical watts / 1500w electrical watts = %86.564 electrical to mechanical conversion efficiency

1298.46376w mechanical watts + 201.48142w ohmic heating & copper loss = 1500w electrical watts

if you can find an error in any of these please let me know.

4 Likes
1083

Holy crappers what did I start lol

4 Likes
1084

a shartis storm

17 Likes
1085

heres another comparison at partial throttle which will be a bit different than the other graphs which had full throttle for the 10s and a bit reduced for the 12s to get the same speed. when able to go full throttle the switching in the esc is …not switching and more efficient. so here the difference between the two is less as theyre both at partial speed. the lower voltage is still wining in eff and somehow killing it in range.Capture

1086

@Hummie that chart I showed is both at full throttle… so what happens if you put both at 100% throttle for an apples to apples comparison (same speed and same throttle, different voltage)?

1087

so youre saying change the kv then? how could they both be 100 throttle and same systems and motors and speed with diff voltage? at a reduced throttle youre losing eff in the esc

1088

2 charts ago you posted a chart showing both at full throttle, and a 2% gain in efficiency for the 10S…

the last chart i posted at 20mph also shows a 2% gain in efficiency for 10S… so what I don’t understand is why do you say the charts don’t agree?

1089

2 charts ago while it says 100 throttle…it cant be! unless it was a different kv motor how could they have the same speed with different voltage? … it must be at like 90 percent throttle or something to get the results and not show on the throttle settings

but as far as yours disagreeing…i thought that’s what you said. I cant read yours its so small!!

1090

i said…

then you said…

your chart shows 2% gain in efficiency for 10S at full throttle:

this chart also shows 2% gain in efficiency with 10S at similar speed at full throttle:

1 Like
1091

in the first graph you posted you said you saw

1092

shartsis’s 100 throttle means pulling the trigger all the way down. not at top speed, if you look at the table you see that 12s can reach higher speed. and I assume the 100 throttle different speed is calculated for instantaneous moment as suppose to be constant speed.

1093

when the amp limits are 60a motor and 60a battery there is no change in efficiency, but when the limits are 60a motor and 30a battery, then the 10S gets greater motor efficiency because above a certain speed, the amps in the motor are lower for the same # of battery amps.

1 Like
1094

it looks to show on the grin sim that the battery amps will be lower and motor amps higher across the board comparing the 12s vs 10s at the different compared speed with same load, and with the 10s having the lesser motor amps

getting confusing

1095

correct, the charts I posted show acceleration not constant speed.

@Hummie it’s also important to make sure you aren’t confusing constant speed values with acceleration values.

1096

can you do a graph for constant speed at different throttle % ?

1097

but how to account for the different throttle output of 10s vs 12s. i think i did. in the last graph its the same speed and varying throttle setting to produce the same output I believe. here it is again Capture