Please point me to the correct post if my question is a duplicate as I could not find what I was looking for.
Say I have the following:
1. Motor, 12v, 50amp draw max, 600watt
2. battery, 12v, 100AH

My calculation to determine how long I can run this battery at full draw is 100/50 = 2. This tells me that I can run this motor at 50amp for 2 hours (in a perfect world). Is this really correct?

I multiply it by a factor of .8 for inefficiency. 2*.8 = 1.6 hours.

I put it to the test. Here are my set up.
1. motor is connect to a gear reduction.
2. 5lb weight attached to a pulley system that just goes up and down.

Result:
30minutes

What could be contributing to this?

 

What could be contributing to this?

Batteries lose capacity as they get old and they are not rated for amp-hours at a 2 hour rate of discharge.
You would get better results at a 5 hour or a 10 hour rate of discharge.

 

When you're trying to calculate "usage", does the watt matters at all?
Here is a website for example:
http://www.1800wheelchair.com/product/drive-cobra-gt4-heavy-duty-4-wheel-power-scooter/
The wheelchair spec is:
Max Speed 10 mph
Driving Range 35 Miles
Battery Type 12V 75Ah
Motor is around 700watt

35/10 = 3.5hrs. So does this mean that theoretically this scooter can go on at 10mph for 3.5 hours. Is this correct?

If the motor is rated at 12v, 700watt, then does this mean that 700/12 = 58amp max?

For the scooter to go on for 3.5 hours at 10mph, it must mean that the motor must be pulling
75Ah/3.5 = 21amp. Is this correct?

Please bear with me as I am pretty new and curious to this.

 

The 35 mile range is probably not at maximum speed.

 

Okay say they were traveling at 5mph.
This give operation time of 35/5 = 7hours and the motor pulling at 75/7 = 10.7amps.
I make the assumption that it carried a person at 150lbs.

Does this make sense that it can carry a pretty heavy weight for 7 hours?

 

10.7A for 7 hours gives 74.9Ah which is very close to the stated battery capacity. The battery capacity is probably given at the 10 hour rate so it is still probably optimistic but a lot closer to reality than taking the stated numbers as applying simultaneously.

 

Hmmm. Interesting. As long as this theoretically checks out then I'm satisfied.

thanks!