Trying to guess amp draw on a DC motor

Does the scooter list how many amps the batteries have... and how long they should be able to run it? Could probably Cludge backwards from there..

55 Ah @ 24v. Range of 13 miles. It doesn't list a top speed so I am thinking 4 MPH? If that's the case 55 Ah spread over 3.25 hrs approx 17 amps. Figuring 2 of those for the complex ass lights and controls and 2 motors, 7.5 amps? Shit I have no idea if I'm even close.

>>1139892
Your best bet is to look for any identifying markings and hope you can match a part number. Motor ratings are pretty nebulous either way since they are limited by temperature.

The exact amount of current the motor will draw depends on its load, and the load it can withstand depends on the ambient temperature and how long you want it to run.

What is the easiest way to measure amps on DC? I have an amp clamp, but the one I have is AC only.

>>1139949
Wait till harbor freight sends out the coupon for a free electric meter.... maybe wear thick insulated gloves while using it though...

OP here. Finally found a way after googling the fuck out of it and finally asking an old guy down the street who worked on the the Chicago El years ago. If it's a DC motor it's voltage divided by static resistance of the motor. Dirt fucking stupid simple huh? That gives you peak amps the motor is capable of drawing. This formula is DC only though.

>>1139967
I mean, that will be the peak, but only for a fraction of time during starting. It's not a bad guess, but it's going to be a bit higher than the current when moving. I don't even know about whether it's under load or not.

>>1139967
>voltage divided by static resistance of the motor
That's LRA - locked rotor amps
You're looking for FLA - full load amps

FLA will only be a fraction of LRA

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>>1139949

>>1139892
12ga wire is only good for about 15A.

>>1139918
DC current is measured most commonly as voltage across a shunt.

You can put a multimeter in series (bat to - to + to motor to bat) and see the amp draw if it's 10 amps or less. If more just get a 100 amp shunted meter for like $20 on Amazon

>>1139892
Buy an cheap as analog meter and build yourself a circuit to extend it's range. You'll find that shit in old books or online, did that once to measure a 7A sign.
It has to be analog because it's basically an extension to the circuit that turns the needle. You will also need to measure the internal resistor of the analog multimeter or take a vague guess. You will need to buy precise power resistors, i'd say around 5W, where the value is calculated by the range you want to measure.

>>1139967
As others already mentioned, this is only the current that flows when the motor is locked, and it will likely burn out this way. If the motor is free to turn, the current will be very low, like 2A maybe. During actual operation, the current will be between those two extreme values, depending on how much torque you need.
On well cooled brushless RC motors, there is the rule of thumb that you can have 3W/gram. So a motor with 100g mass will be able to deliver 300W for a short time. Given the lower air cooling and efficiency of your motor, I would assume you might get 0.5W/gram tops. But your calculation with 7.5A goes into the right direction. This would be 180W which sounds reasonable.
So, in a nutshell, the current a motor takes depends on the load it has to deliver, and the load it can deliver depends on how well it is cooled and how hot it is allowed to get.

>>1139951

This meme is going to prevent you from buying an alright cheap meter.

>>1139892
12 gauge wire can handle 41 amps so I would guess 20 to 30 amps max.

>>1139892
I googled the numbers I found on a wheel chair motor that I got from a scooter rated for a 600lb person and it had a maximum draw of 8.3 amps at 24 volts dc.

>>1140002
Dangerous over-simplification. It depends on the length of the run.

>>1140909
It can handle 40 amps if you spring for the 200 degree insulation, but at that point it's cheaper to buy larger cables. However with a 5% voltage drop on 24 volts a 12 guage wire can only be run 25 feet at 15 amps.

If you're running 40 amps over a 12g wire your max run would be 9.5 feet. Buy yourself a code book

>>1139967
energy isn't free, it can't be created or destroyed
so
how much energy does it take to spin the shaft of the motor? get a stick and a force gauge to find the torque then work out the energy
now assume the all of the electrical energy is converted to mechanical energy (it's not, some is heat) to find the minimum power the motor will draw. you can do this with whatever load you have too and add them.

>>1139951
Bad idea.

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>>1140002

Depends entirely on some combination of length of conductor, insulation used, acceptable temperate rise, acceptable voltage drop, duty cycle, and amount of ventilation/cooling available.

Additionally, even by some of the most conservative ratings (the US NEC's listings for ampacity), 12AWG is good for 20A.

>>1142282
>>1140909
told

go to radio shake and find a 1 ohm resistor
connect it in series with battery and motor
voltage across the resistor is the current
V = IR