ElectricScooterParts.com Support Center

A gear motor would be required to obtain the needed gear ratio for a 3.5-4 MPH top speed. All of the gear motors that carry have sprockets for a chain drive. 

Here are some calculations based on your parameters:

The calculations above are based on using our MOT-24450SP gear motor. For a 3 hour runtime on flat ground a 24 Volt battery pack made from two 12 Volt 44Ah or larger batteries would be needed. The closest battery size we carry is 50Ah. The dimensions of our 50Ah batteries are 7-3/4" long x 6-1/2" wide x 7" high and they weigh 32 pounds each. We added 75 pounds of rider and cargo weight to the calculation above to account for the weight of the battery pack and motor. 

A 14 tooth sprocket for #420 chain has an outside diameter of 2-1/2". This sprocket would have 3/4" of ground clearance when used with 4" wheels. Would the battery size and ground clearance be acceptable for the project?

We can get the 14 tooth axle sprocket for 1/2", 5/8", 3/4" and 1" axles. The 14 tooth sprocket for 1/2" axle has a 1/8" x 1/16" keyway for a 1/8" machine key. 

Our sealed lead acid batteries are designed for use and transportation in any position, however, charging the batteries in the upside down position should be avoided.

Depending on how hard the hand cart is used, two 35Ah batteries may be able to provide a 3-hour continuous runtime and they weigh 23 pounds each. For a 3-hour runtime under demanding conditions, we recommend the 50Ah batteries though. 

There are lithium battery packs on the market which are lighter than lead acid battery packs, however, our brushed motor controller which is needed to run the gear motor has a low Voltage battery protection level of 20.5 Volts which is designed for lead acid battery packs so we can not make a gear motor kit that would be designed towards using a lithium battery pack which typically need an 18.5 Volt low Voltage battery protection level. Lithium battery packs also cost around 3 times more than lead acid so for a 24 Volt 50Ah battery pack you would probably be looking at a cost of around $720 for a lithium battery pack compared to $240 for lead acid battery pack.

Please let us know if you have any questions.

The width of the 14 tooth sprocket is 7/8".

The 24V 35Ah battery pack is 18 pounds lighter than the 24V 50Ah battery pack. The dimensions of the 35Ah battery are 7.70" long x 5.12" wide x  6.26" high and it weighs 23.2 pounds. The motor weighs 11 pounds. 

The #420 chain has 1/2" long links so fine adjustments are not possible by adding or removing links. Due to this the position of the motor or axle will need to be adjustable in order to properly adjust the chain tension. This is often achieved by making a motor mounting plate that has oval-shaped holes for the motor bolts to go through so the motor can be moved towards or away from the axle as needed. 

Regarding the parts list and prices, I would like to gather a little more information before I get started on that so I have a few questions. 

Do you need the motor to go forward only, or to have forward and reverse?

Do you want a twist throttle or thumb throttle?

Do you want a panel mount key, or rocker, or toggle power switch, or handlebar mount key or rocker power switch? 

Please let us know if you have any questions. 

The thumb throttle is similar to the throttle on an ATV where moving it by thumb varies the speed of the motor. 

All of our throttles and handlebar switches fit 7/8" handlebars and are one piece designs that need to slip over the end of a tube to install. Due to their one-piece design, they cannot be installed on a continuous tube-shaped handle. 

We carry a cable pull throttle that can be connected with a cable to a mechanical throttle or lever so that may be a solution if you are not able to change the handlebar design to have open ends.

With a dead battery the cart could be moved by hand, however, there will be extra drag from the motor. The motor will not lock up the wheels though and they will be able to be turned. 

We can break the chain to any number of links that are needed so that is no problem at all. 

If you are not sure which throttle or power switch will work right now then we can go ahead and put together a quote without those parts. Do you want to purchase all of the parts and wire them together yourself or would you like them as a kit which has been pre-wired with matching connectors on all of the parts?

I have the price quotes prepared. Both of the quotes below are for kits that are pre-wired and have matching connectors. The 10 tooth motor is included with the motor so it is not a separate part. The power switch and throttle both have 60" or longer cables. 

Here is the quote with 35Ah battery pack:

1 qty. MOT-24450PL motor $159.95

1 qty. SPD-24500B controller $39.95

1 qty. THR-38 thumb throttle $19.95

1 qty. SWT-23 power switch $14.95

1 qty. CHR-C24V4AXLR charger $74.95

2 qty. BAT-12V35AB batteries $79.95 x2

1 qty. HNS-127 battery harness $12.95

1 qty. CNX-XLR10 charger port $3.95

1 qty. SPR-42014H 14T 1/2" ID sprocket $14.95

1 qty. CHN-420 x 32 Links $5.76

1 qty. Kit Labor $35.00

Total = $542.26

10% kit discount = $54.23

Grand total = $488.03

Here is the quote with 50Ah battery pack:

1 qty. MOT-24450PL motor $159.95

1 qty. SPD-24500B controller $39.95

1 qty. THR-38 thumb throttle $19.95

1 qty. SWT-23 power switch $14.95

1 qty. CHR-E24V7AXLR charger $149.95

2 qty. BAT-12V50A-ITP batteries $119.95 x2

1 qty. HNS-127 battery harness $12.95

1 qty. CNX-XLR10 charger port $3.95

1 qty. SPR-42014H 14T 1/2" ID sprocket $14.95

1 qty. CHN-420 x 32 Links $5.76

1 qty. Kit Labor $35.00

Total = $697.26

10% kit discount = $69.73

Grand total = $627.53

Please let us know your thoughts on these kits and we can take it from there. 

We have got the kit finished. It is our item # KIT-24450G-30. Here is the link to it: 

KIT-24450G-30: https://cart.electricscooterparts.com/24-volt-450-watt-custom-kit-for-hand-cart

Please let us know if you would like any changes made to the kit, or if you have any questions.