# Electric cart circuit, editied [duplicate]

I am trying to make an electric go-kart. I am new to the forum, so I may be missing some information but any help is greatly appreciated. After doing some math and discussing with friends I found the following with the given information. I have 4, 24V 14A motors, all connected to a read drive axle. I have 2 pairs of motors on each side of the drive axle. The motors have an 11 tooth sprocket that is chained to a 68 tooth sprocket that is connected to the drive axle. I currently have 2, 12V 7Amp 20 hour lead-acid batteries, which provide my 24V. Each pair of motors is connected in parallel to ensure they both get the 24V. However, the motors do not spin, even when there is no load (The wheels aren't contacting the ground). I believe that this may be because the motors do not have enough amps, only receiving 7 Amps of the 14 Amps from the batteries, because there are 2 motors in each pair. My main goal is to get the kart moving. I weigh about 130lbs, and the kart is likely around 30lbs. Would getting a battery/batteries with move amps (28A) allow the motors to run properly? Any advice is really appreciated.

All the information I know

Each motor is a DC motor that needs 14A and 24V The motor has a sprocket of 11 teeth The Watts of each motor is 250 The motors are rated to have an RPM of 2750 or around 45.83Hz

The drive axle has a sprocket of 68 teeth. The 68 toothe sprocket is 5.5" The wheel diameter is 10"

If my math is correct, given the ratio of the motors to drive shaft. Each motor produces 5.45Nm of torque, and after the sprockets, the torque is 33.69Nm. I don't know what impact the 4 motors would have on the torque, nor do I know what the torque is for each side. I really just want this kart to move.

Would removing motors allow my vehicle to move? I think that my power supply does not provide enough amperage to my motors. Would having 1 or 2 motors be better in this situation?

• I'm very sure those batteries are 7Ah (Amp-Hours), not 7A, which only says something about their capacity, not the maximum current. Also, running 4 x 14A motors with 7Ah of battery capacity only allows you to run them for a very short time (like less than 4 minutes at ~50% of capacity) if you want to keep them healthy. Do you have a picture of those batteries, or their datasheet? You'll have to use thick cables and probably some beefier batteries to be able to supply 4x14A of current for any amount of time. – StarCat Sep 23 at 7:16
• This is a duplicate of your previous question 24V 250W motors. If you want to add additional information then edit that question, don't post a new one. – brhans Sep 23 at 12:17
• What kind fo motors are they? Are they BLDC motors? Those will each need a custom controller. – Brian Drummond Sep 23 at 12:58
• You edited the wrong question. You need to edit your existing, open question, not this closed duplicate. – Chris Stratton Sep 23 at 19:04

In order to drive your 4 motors at their rated power you will need 4x14A=56A at 24V. I am not clear what rating your batteries are but I am assuming they are capable of 7A of continuous current (they will also be rated in Ampere Hours which will give you the capacity i.e. how long you can get out of them e.g. 70Ah would imply 10 hours at 7 amps if you could fully discharge the battery (which you cannot do without damaging it so the actual duration will be less).

If you connect your 2 batteries in series you'll have a 24V 7A capability. You are going to need a lot more batteries-16 in total. The reason the motors are not running is the batteries are completely overwhelmed by the load. You could try measuring the Voltage under load, I suspect it's way under 24V. Perhaps try making the measurements with 1, 2, 3 and then 4 batteries to see the effect.

• See my comment, I think this is a (common) misunderstanding. Those batteries are probably 7Ah instead of 7A. – StarCat Sep 23 at 7:17
• I half suspected that in which case the batteries are way way underspec – mhaselup Sep 23 at 7:34
• @StarCat interestingly my motorcycle battery is 12V 11.2Ah quite a bit bigger than the OPs batteries. The manufacture Yuasa claims a cold-cranking amperage of 225A which really surprised me. – mhaselup Sep 23 at 8:36
• Lead Acid batteries, even small ones, can deliver large currents but not for very long (effective capacity will be a lot lower than with smaller currents). 7Ah is a very common capacity for small applications. I've found a datasheet which states a maximum 5-second current of 70A, so really not suitable for longer operation at high currents. – StarCat Sep 23 at 9:43

It really depends on what you're trying to do, but I'd say your system as you envision it is seriously underpowered.

A real go kart (e.g. a petrol-powered one) has somewhere between 4.5 to 27 horsepower, with 6-9 hp being typical for rental karts. At full power your electric motors have barely 24Ã—14Ã—4 = ~1.3kW, which is less than 2 hp. Actual e-kart designs from major brands like Sodi, CRG, OTL etc typically use

• one large electric motor, 5kW is typical, air-cooled (water cooling is rare)
• one large motor controller (Sevcon, Curtis), sized appropriately
• reduction gear, usually toothed belt type, around 3:1 reduction typically, but it really depends on the motor chosen
• batteries are typically 4x12V lead-acid, somewhat reminiscent of normal car batteries in size, but they are deep cycle ones. So something like 48V at say 30-40 Ah. Some newer designs use Li-Ion and the battery is detachable, but that is considered high-end. Using lead-acid for this application is fine.

With what you specified I think your kart will move, but it won't be fun to drive - it will be sluggish.