# Power-to-weight ratio | Good Motor?



## major (Apr 4, 2008)

I like the AC-15 for karts and bikes. I think a single motor will compare favorably to that 70 kW ICE. Good luck.

major


----------



## Sunking (Aug 10, 2009)

Ditto, the _*AC15 motor from HPEV*_ is what I used in a racing golf cart. Don't be fooled by part numbers as the AC9 and AC15 are the exact same motor. Only difference is what voltage you use. AC9 is 48 volts, and AC15 is 96 volts. Only real difference is what Power Graph you look at. The AC9 is a 27/10 HP motor, and the AC15 is a 60/15 HP motor.

Motor weight is not your concern, battery weight and the space it takes is what will bury you. Take note here if you use one of the AC Induction Motors is going to require you to use a 3-phase AC motor controller, and those cost big bucks. A good 650 Amp @ 96 volt battery is going to cost you $1500 to $2000 vs say $400 for a like DC motor controller.

The AC15 motor is intended to run at 96 volt battery. With a 650 Amp Controller means a minimum 80 AH LFP battery. A 96 volt 80 AH Lithium Battery is going to cost you some $2000 and weighs in around 200 pounds. Do not even think about using lead acid. Sure a like Pb battery only cost 1/3 as much, but weighs 3x and takes up 3x space that you cannot afford. The bike would be so large and heavy, it would not work if you used Pb batteries. So forget lead acid. . 

I know you think money is no object and that is a good thing, because if you go with an AC15 motor, 500 amp controller, and a 96 volt 80 AH battery is going to cost around $5000 just for the motor, controller, and battery. 

Where you can save some money and weight is with an AC motor, does not require a transmission. At 10,000 RPM, you can go direct drive and the only transmission is a differential or in your case chain/belt and sprocket. 

Now if you want to Drag Race and do not need distance, then you can use a lot smaller battery, but very specialized LiPo Batteries made for RC Airplanes and Toy trucks. Will buy you 150 pounds less weight and only requires 1/5 the space. Catch is a smaller LiPo will cost as much or more for a battery 1/10th the size. LiPo batteries C-Rate is 50/100, so you can get away with say 96 volt 10 AH battery, vs a 96 volt 100 AH LFP battery. A high discharge _*4S 7.7 AH Lipo*_ cost $250 each and you would need at least 7 units or $1500 worth of batteries. What you gain, or I should say loose is going from a 200 pound battery to 12 pounds. But you give up a lot of range and money for performance. But if you are drag racing, no big deal, you just use several battery packs and change them out between races.


----------

