How to make power improvement for solar powered go-kart?

I have Model: MotoTec Solar Electric 24V Go Kart (http://www.bigtoysusa.com/mototecsolarelectricgokart350wred.aspx).
I need to make power performance improvement on it.
Please, make suggestions.

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skumu (author) 7 months ago

I am trying to make improvement by adding bigger Photo voltaic panels (my main focus to demonstrate sustainable (renewable) energy solution. Go-kart has solar panel (Integrated 4W Monocrystal Silicon (13 x 9 inch panel)) which delivers 1% power that it needs (350 Watt DC Electric Motor).

I tried to understand what is inside the controller.

Speed of Go-Kart motor is DC and controlled by Pulse Width Modulation (PWM).

Reasons PWM is used instead of potentiometer in DC motor speed controller

Power efficiency.

When controlling speed of motor with Potentiometer there is power and energy waste in the form of heat across the resistors. Resistors in series have a voltage drop, hence, there is heat lost.

The transistors in PWM mode have very low impedance and therefore a low voltage drop and low power dissipation.

When using PWM resistors in series are not used so no power waste. The motor is shuttled between on and off and the average gives the voltage.

It is considered that dc motor speed of go-kart is using PWM because on the controller of go-kart it is writing Brake Pulse Low.

Is this write judgement?

How to know if controller uses any input control for solar panel?

Like when using bigger solar panel an optimal controller, which controls the output power of the PV panel and the charging current for the battery will be needed.

rickharris skumu7 months ago


Look at the size of these things. You do not have enough space to carry a large enough solar panel let alone cope with the weight of the panel.


rickharris7 months ago

Within limits anything you do may spoil something else, assuming the design has been optomised for best overall performance.

far the most effective in terms of acceleration and top speed is to
change the gear ratio between motor and wheels, HOWEVER making a higher
top speed will effect the acceleration, making it go faster will
effect the top speed.

Building a light weight body will improve
aerodynamic drag and you will - if it isn't too heavy - go faster.
Carbon fiber would be the best option with fiber glass, foam board and
aluminum coming a close second.



You could over drive the motor BUT it will get hot and you will need to change the drive circuitry

You could change the motor for a more powerful motor but you will need a better battery AND drive system.

You could change the wheels for ones with lower drag/ rolling resistance.

skumu (author)  rickharris7 months ago

Thanks! Please share you knowledge about controllers on the comment above.

rickharris skumu7 months ago

The DC motor is controlled by a pulse width modulation (PWM) controller a google search will lead you to lots of these.


You need to pick one that can handle the voltage and current you intend to use.

PLEASE take note of all my comments You can't change one thing without changing others or you will break the cart.

Do you want to make it go faster or run longer.

If you want it to run longer you need to increase the battery storage capacity.

To make it carry more weight, bigger motor and power train, watch out for this as you can easily surpass the structural integrity of the frame.

You can make it go faster by changing the gear ratio but you will limit the weight it can carry.

skumu (author)  Josehf Murchison7 months ago

Thank you! Please, help me with understanding controllers on the comment above.

OK the solar panels are for powering the charger to charge the batteries while the cart is not in use.

In most of these carts, the battery is disconnected from the cart drive when connected to the battery charger.

To use the solar panels and the battery at the same time you need to bypass the charger and connect the battery and the solar panels in parallel.

Since the solar panels are only 4 watts you will get very little power for your effort, about 1% to run the motor 100% from the solar cells you need panels 100 times the size of the panels you have. At 50% 50 times, at 25% 25 times, and all of that added weight.

skumu (author)  Josehf Murchison7 months ago

Thanks! So does that mean the controller that go-kart has already connects solar panel to battery in parallel?

I put description controller below in the comments. Is there way to know how the controller is working?

If I get it right the solar panels power the charger.

The charger, charges the battery.

The battery when it is not connected to the charger, powers the motor controller.

Jack A Lopez7 months ago

OK. I gather from the words, "I have Model: MotoTec Solar Electric 24V Go Kart", this means you already own one of these.

I suggest removing the photovoltaic (solar) panel, because it is not adding a significant amount of power (4 watts, max) to the approximately 200 W, or so, needed to push this thing down the road. Honestly, I think the solar panel on this thing, is just there for show, to make this toy look like it's solar powered.

By the way, I don't actually know how much power (in watts), or current (in amperes) you're actually getting out of that 24 V lead-acid battery, but my estimate of 200 W comes from the numbers in the product page you linked to,

"The MotoTec Solar Electric Go Kart provides up to a 2 hour ride time
with its integrated 4watt monocrystalline silicon solar panel on the
rear wing that continuously recharges the go kart while in use. It's
powered by a 16Ah 24v battery pack and 350 Watt DC motor that can reach
speeds of 15mph. The solar panel can also charge the go kart while not
in use or with the battery charger in 4-6 hours. This go kart comes
standard with 9 inch pneumatic tires for a variety of terrain and easy
to use disc brakes."

Specifically I estimated watt*hour capacity of the battery as,

(24 V)*(16 A*h) = 384 W*h

Then I divided that number by the advertised "2 hour ride time" to get

(384 W*h)/(2 h) = 192 W

Then, I guess I just sort of sort of rounded that up to 200 W, just to give a nice round number.

Expected battery current to give 192 W, at 24 V, is of course,

(192W)/(24 V) = 8 A

But you know, this is just guestimation.

If you want to actually discover how much power is flowing into your motor, the way to do this is by putting your electrical test equipment on it; i.e. measuring the voltage and current going to the motor, while you're driving the cart.

Although maybe actual measurements are not what you want, because this seems too complicated, or you don't have the tools for this, or both, and instead you would rather just try replacing things, like for example, the battery.

You might get more power out of that motor (nominally 350 W, max) by throwing more voltage and current at it, by way of a bigger battery. That would probably be the thing to try first.

Seems like there are a bunch of 'ibles on this site, showing how to build your own battery pack, from individual lithium ion cells, usually, for electric motorcycles and similar things. So I suggest searching for those 'ibles, and doing the math for what it would cost to build or buy a battery with maybe 1.5 x the voltage, and current capacity (in A*h) , of your current battery ( 24 V, 16 A*h)

skumu (author)  Jack A Lopez7 months ago

Thanks! Yes , you are write 4 W does add any power. Please, share your knowledge about controllers for the comment above.

Downunder35m7 months ago

Please delete the other topic before it starts to get confusing with the replies.
If you buy a cheap toy you only get cheap hardware, especially if false advertising is used.
As Jack pointed out the solar panel is just a joke not even capable of fully charging the battery in one day and without using the cart.
To be able to run on solar power alone the panel(s) must be capable of delivering more than what the motor uses, then the battery is only there to care for clouds or the wrong angle to the sun.
Do to the intense sun down here people tend to use a big solar panel on their mobility scooter as a sun shade with added charging.
I modified a few for friends and neighbours over the years and although the panel does a good job chargin the batteries during a 2 or 3 day period of no use you won't really get more speed, distance or anything out of the system itself.
At least not to an amount really worth to mention.

One way that is used on solar karts is to use highspeed motors that require relative little amps and a suitable reduction gear system.
Basically comes down to finding the right motor/gearbox combo that allows the best use of the juice available.
Only other approach is to use more or bigger batteries, which these guys try to avoid due to the weight.
These days Li-Ion batteries offer a good power to weight balance but the costs are usually too high for a hobby level.
One nifty guy down here added a motor from a big model plane (petrol with nitro mix) to run an small alternator to assist when needed.
The motor is strong enough to get sufficient revs onto the alternator so it can supply over 10A for charging on the go.

skumu (author)  Downunder35m7 months ago

Thanks! I deleted the other post. As you said I am trying to go for bigger solar panels. Trying to come up with some type of renewable energy solution. However, It not quite clear for me how this go-kart works. Especially, function of small controller that it has. Please, make comments.