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I would like to build a gocart using a 150W 24V DC motor. To power it I would like to build a battery pack using 2Ah rechargeable batteries. The motor will run about 2 hours at 50% capacity (the gocart if for a kid and doesn't have to run at high/max speed). This means it will require 150Wh. So, it seems that my 24V battery pack needs to deliver 6.3Ah. (EDIT: it seems I need to go for a lead-acid battery).

Question: Can I use a higher voltage (like 30V) and then a regulator or PWM?
If I used a 24V battery pack the motor will go slower as the battery gets discharged. But if I use a 30V battery pack I have a lot of slack.

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    \$\begingroup\$ "are only 2Ah" that doesn't tell anything about how much current they can provide. \$\endgroup\$
    – PlasmaHH
    Commented May 30, 2016 at 21:05
  • \$\begingroup\$ (1) Figure out how long you want the motor to run for at full power. (2) Convert this to hours. (3) Multiply by 150. That will give you the number of watt-hours (Wh) your battery needs to be able to supply. (4) Divide Wh by chosen voltage. That will give you the Ah (amp-hours) your battery pack needs to supply. (5) Add a margin to allow for battery deterioration. (6) Edit your question with these details and then ask a specific, non-opinion generating question. \$\endgroup\$
    – Transistor
    Commented May 30, 2016 at 21:16
  • \$\begingroup\$ How long do you expect this to run? That is what do you require? \$\endgroup\$
    – WhatRoughBeast
    Commented May 30, 2016 at 21:17
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    \$\begingroup\$ Normally gocarts use 48 vdc batteries and a charger, with a 48 volt motor. DC-DC converters supply power for 12 volt devices such as radios. I mention this because there is a huge market in 48 volt products for gocarts. \$\endgroup\$
    – user105652
    Commented May 30, 2016 at 21:25
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    \$\begingroup\$ A 150 watt motor is about 1/5th of a horsepower. You may be able to walk faster than your cart... \$\endgroup\$
    – user105652
    Commented May 30, 2016 at 21:33

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The batteries you specified are specified at a discharge rate of 500 ma, so you will need a pack of about 300 of them to deliver 150W at this rate no matter which voltage configuration you would use. They may operate for shorter periods at higher rates but too much current will lead to the cells heating up.

The PWM scheme you are suggesting is the normal approach for controlling motor speed so no real issues there as long as you watch the current.

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  • \$\begingroup\$ Thanks for your answer. Are you sure the rating for that eneloop bat is only 0.5A ????? Even a small digital camera will draw WAY more than that! \$\endgroup\$
    – IceCold
    Commented May 30, 2016 at 21:41
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    \$\begingroup\$ That is the current at which they rate it at the Ah rating. They will generally run for higher current at a cost of shortened life and cycles. Also, be wary of running at high current continuously to prevent cell overheating. I would put in the PWM regardless of your approach so you have a way to limit current. \$\endgroup\$
    – John Birckhead
    Commented May 30, 2016 at 21:47
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    \$\begingroup\$ @SolarWind - Here rightbattery.com/wp-content/uploads/2013/11/… is a set of test results. You see that once you get more than about 1 A the voltage starts to drop. And how long do you want your go kart to run for? \$\endgroup\$
    – WhatRoughBeast
    Commented May 30, 2016 at 22:07
  • \$\begingroup\$ @WhatRoughBeast-Thanks. The motor will run for about one hour. Max two hours. BUT probably not at full speed. \$\endgroup\$
    – IceCold
    Commented May 31, 2016 at 7:27

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