# Turnigy RotoMax 150cc Size Brushless Outrunner Motor

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#### Vigilant1

##### Well-Known Member
I think you might have typo there, the HobbyKing web site says the motor is rated at 190 amps, or 9800 watts (roughly 13HP). If somebody is putting 360 amps through it at the same voltage, then it should be producing roughly 26 HP (for however long it lasts).

#### pictsidhe

##### Well-Known Member
I'm still pondering power options. If you buy two, the second could go on ebay for profit... I might get one to test ducted fans, though. Ducted fan math is horrible, btw...
The 120100 have a 50% longer stator than the '150cc' 12090 motors.

#### Sockmonkey

##### Well-Known Member
Remember the rule for electric and/or hybrid planes. If you don't want it to suck, you need to design the plane from the ground up to take advantage of the flexibility electric and hybrids give you.

#### pictsidhe

##### Well-Known Member
Remember the rule for electric and/or hybrid planes. If you don't want it to suck, you need to design the plane from the ground up to take advantage of the flexibility electric and hybrids give you.
And to avoid their bad points...

#### henryk

##### Well-Known Member
I'm still pondering power options. If you buy two, the second could go on ebay for profit... I might get one to test ducted fans, though. Ducted fan math is horrible, btw...
The 120100 have a 50% longer stator than the '150cc' 12090 motors.
-see FREERCHOBBY motors...(big power!)

#### proppastie

##### Well-Known Member
Log Member
Any good charts,...spread sheets,...on batteries required and running time......also different controllers? Seems like there are lots of variables and every installation I see is different.

Saw a reference to "junk yard Nissan Leaf".....is that an option for batteries or are those batteries too big....and are there really any "junk yard" stuff like that yet?

Lots of questions

#### pictsidhe

##### Well-Known Member
I'd favour 18650 cells rather than hobby ones myself.
Capacity is a tradeoff with max current.
The not-latest Tesla uses panasonic NCR cells, you may find someone splitting a pack on ebay. DeWalt 1.5Ah batts use LG HB4 cells.
Pick cells with a higher max current than you will use. Some on the web have tested many of these cells. Beware fakes! 18650 industry is littered with them.
This site has a big selection: www.imrbatteries.com

The math is pretty easy:
Wh required = A x V x hours run time.
750W = 1hp. The motor will be up to 85% efficient. So power draw will be around 900W per hp. Then you've got losses in the controller, lets say, to be safe and easy, a round 1kW from the batteries per prop hp.

Battery energy = Ah x 3.6V
A 3Ah battery will be 9.8Wh. Batteries will last much longer if you avoid full charge and discharge. Using only 2/3 or 3/4 the capacity will greatly increase their life.
So, lets say 20hp for 15 minutes.
20kW x 15 / 60 = 5kWh
Using 3Ah cells. 5000/9.8 = 510 cells. That doesn't include extra capacity so you don't fully charge and discharge, 510 / 0.75 = 680 cells. Yeah, that's going to be pricey at ~\$5 a cell. Time to see what is on ebay...

#### proppastie

##### Well-Known Member
Log Member
thanks much...... all in all great post.....

680 of the 18650 = 680 x Weight: 47.9g =31960g=71.8 Lb.

5 min = .33 x 71.8 = 23.7 lb.......not so unreasonable, especially if perhaps I only need 15-16 hp to climb and can throttle back after liftoff.

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#### pictsidhe

##### Well-Known Member
Most efficient climb will be at max power. You'll be putting a larger proportion of power into climb. For only 5 min, you need to be careful not to exceed the max current of your cells. If you only use 3/4 of the pack capacity, you'll need cells that run at 60/5 * 3/4 = 9C, where C is the cell Ah. A 3Ah cell would need to be good for 9x3 = 27A. They generally aren't, so you'll need to look at higher current, lower capacity cells. Such as 2Ah, 25A cells. Then you need 50% more cells to get the capacity. They are likely to be a littke cheaper each, though...