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Motor power, run time, and other specifics

Firstly, I have read through a ton of these forms.  There is a plethora of awesome information.  Thanks so much for all of the advice.  I'm hoping you can help me with a few questions have while I try to design a cart I have been wanting for some time now. Some background:

I am working on designing a custom cart; something like a hybrid of an electric wagon, and a table.  I know this sounds vague but i will give details on the important specifics:

Dimensions:: ~25" width, ~46" long, ~35" high

Weight: somewhere between 750 and 900 lbs.(this includes 244lbs of SLA batteries, if I go that route, more on that below)

Axle type: live axle - 1" width a 1/4" keyway

Tire size (on rear/live axle) - i'm thinking ~12"

Terrain: pavement and grass, mostly flat with some long, gradual hills

Top Speed desired: 10-12 mph

Desired run time of cart between charges: 3 - 4 hours 

I want to use one of your motors, speed controllers, throttles, switches, etc. The problems I am running into:

Motor: I am not sure which motor to install on the cart.  What are the differences between your 36v motors and your 48v motors?  How do i determine the torque required to push the cart?  Do you know the torque output of each of your motors?  Will either be able to push a cart weighing 900lbs?

Batteries: I am quickly learning that they will be the most expensive and heaviest part of the "motorization" of the cart.  What are my options? At first thought, going with a 36v motor means I can purchase/carry one less battery; what are the drawbacks of that vs going with the 48v motor (and consequently 4 batteries)?  I can't determine if I want to use SLA batteries or if I want to splurge on some 12v Lithium-Ion batteries.  It looks like they sell some for ebikes that come with a harness already attached to the battery (these batteries are in all sorts of weird/custom shapes) and then some Lithium-Ion batteries that closely resemble the SLA batteries that you sell on your site.  Will either work or do I have to stick with the ones that resemble SLA batteries?  Both seam ridiculously expensive.   How do I calculate how much motor run time I will get out of a given ah battery? Can you explain how different motor voltages will impact this?  

Sprocket:  I noticed that most of your 1000w and 750w motors come with a sprocket that fits 8mm chain.  I am having a hard time finding sprockets that will fit that that go on a 1' live axle.  Are there other options that you sell that can be installed on the motor to run more "generic" chain, such as bicycle chain?  

Thanks so much for all of your help with this.  If I have left out an pertinent information, please don't hesitate to let me know.   I can't wait to get welding!  

I used Azusaparts.com for my axle, bearings/hangers, sprocket/hub, key shaft, and wheels. I also opted for a 1" live axle and they cut me a custom 27 tooth aluminum sprocket for #415 chain. They have a bunch of sprocket options. Then took the hub from azusa to a local machine shop to cut it down to fit my small axle sprocket. Matching all the power transfer stuff is a pain. Good luck with the build. 

There are no major advantages or disadvantages between using a 36 or 48 Volt motor. The 36 or 48 Volt motor decision boils down to what Voltages the best motor for the project is available in, and how many batteries will fit best in the space on the vehicle that is alotted for the battery pack. For example, on some vehicles, three 20Ah batteries will fit better than four 15Ah batteries, so a 36 Volt motor is a better choice.

The torque needed to push the cart depends on many variables including top speed, rate of acceleration, and degree of incline that the vehicle is traveling up. We have what we call a 'grade power calculator' that takes all of these parameters into consideration which I will provide a link to below. 

Using our grade power calculator I found that a 900-pound vehicle could climb a 5-degree hill and be geared for a 10-12 MPH top speed if it has one 1600 Watt motors (or two 800 or 1000 Watt motors). Or could climb a 10-degree hill with a 10-12 MPH top speed gearing if it has two 1600 Watt motors.

Our 1600 Watt motors run at 5400 RPM so for a 10-12 MPH top speed a jackshaft would be needed to obtain the right gear ratio. However, our 800 and 1000 Watt motors run at 3000 RPM so they could be used without a jackshaft and with a single chain between the motor and axle for a 10-12 MPH top speed. 

We are having a batch of 10 tooth sprockets for #35 chain custom made right now that will fit our large format 500-1600 Watt motors. These sprockets will be available very soon. #35 chain is a common size for go karts and mini bikes so you should be able to find plenty of axle sprockets available for it.

The torque that our electric motors produce is relevant to their Watts rating. For example, our 500 Watt motors have a maximum torque rating of 1.4 ft-lb, and our 1000 Watt motors have a maximum torque rating of 2.8 ft-lb. Our 48 Volt 1600 Watt motors are brushless so they are more efficient than our 500-1000 Watt brushed motors and they have a maximum torque rating of 4.8 ft-lb.

We have created many online calculators for determining what size battery pack, motor, charger, and other parts are needed for various riding conditions. Here are links to some of these calculators:

There are more electric vehicle parts calculators and charts available on this page: https://electricscooterparts.com/electricscooterrepairhelp.html

Regarding batteries, both lead-acid and lithium, they have different maximum continuous current ratings which need to be observed when choosing the battery pack. Controllers have maximum current limit ratings which can be used to determine the maximum amount of current that the controller will demand from the battery pack. That rating can be used to determine what size batteries are needed to be able to supply that amount of current. For example, a 35Ah lead acid battery may have a maximum continuous output rating of 60 Amps, so it should be used with a controller that has a 60 Amp or lower current limit. This type of controller to battery pack current limit matching is especially important when using a lithium battery pack since they are very unforgiving to being overheated.

Please let us know if you have any questions.

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