# Help choosing motor and question.



## Tesla (Jun 27, 2008)

The specs for this motor seem shady http://store.kta-ev.com/motors-dc-motors/amd_motor_k91-4003.aspx They're saying that at 48 volts and pulling 400 amps it can peak at 35hp(26kw). From what I've always understood if you took the volts times amps to get watts then divided by 1000 to get kw then that will usually be a bit higher than the actual output of the motor. 48*400 != 26kw it's 19.2kw(25.7hp). At any rate I'm looking for a cheap small DC motor that can peak at ~40hp(30kw) and preferably with the smallest voltage pack possible. Around what voltage would it be possible to get that kind of power with? I'd like to keep the pack small, this motor is almost entirely for acceleration; it can have a continuous rating of >= 8hp. Another motor I was looking at was D&D ES-15A-6; I guess my main question would probably be what voltage should I be shooting for then I'd find the motor that operates in that range that can output what I want.


----------



## frodus (Apr 12, 2008)

I didn't see anywhere it said 35HP @ 400A & 48V. It just says its a 48V motor, and that it'l do 400A intermittently. I've had this running at 96V, and just a hair over 400A (not at the same time though). It just cannot sustain that HP for long periods without overheating.

For an ACTUAL torque curve, look here:
http://www.evparts.com/img/mt2113voltagecurve.PDF


Actual output of the motor = Power in - Mechanical and electrical losses.

So efficiency at 400A, if you extended the graph, would be about 65%.

96V x 400A = 38.4kw = 51.5HP going INTO the motor. Efficiency of the motor lets say is 65% at that point, that would be roughly 34hp, so its not that far off.


Good luck finding a cheap AND small electric motor that can do 40HP peak.

Might as well get an Agni and be done with it.


----------



## Tesla (Jun 27, 2008)

Ah, yeah I forget their inefficiency at times. The reason I called their spec's shady and I'm sure it's unintentionally misleading is that they say "*Operating Voltage: *48-96 volts DC" then they go on to specifically say "*35 HP peak at 48 volts"* for that motor to produce 26kw at 48vdc with 65% efficiency it'd have to pull 833amps which is double what they've stated. Looking at the extreme price difference between the two motors I've found and the more powerful ones with higher efficiencies (agni) I've decided I should be able to make one of these two work  Thanks for the document, for some reason I couldn't find anything for the life of me


----------



## frodus (Apr 12, 2008)

Not a problem. The only reason I have it, or know where it is, is because I used to have that same motor in my motorcycle..... So I'm pretty familiar with it.

Its 56lbs, but its got a TON of torque (if you can supply the amps). The HP is fairly high too, right around 30hp or so at 96V.

Whats it going into?


----------



## Tesla (Jun 27, 2008)

I've got a grand scheme to make my old metro a plug-in-hybrid and I'm getting back into the hardware to see what's available. I haven't looked at this stuff in at least a year. The car would be driven by a 16hp engine over 35mph or so, it's matched to the power requirement to travel just over 70mph (after some aerodynamic work) and the motor would make up the lack of HP to accelerate. That's the reason I was shooting for ~40hp so that when they're both going full throttle it'd add up to ~56hp which is actually a tad more than the metro has stock. The current condition I've been driving it in I doubt it's producing anywhere near 50hp though so I would probably see an increase in performance lol


----------

