# Question about batteries for an electric cart project

• mp19393
In summary: Parallel stringing (five cells in parallel) will give you more current and voltage than series stringing (one string of five cells).
mp19393
Hi everyone, I am a senior Chemical Engineering student working on a project for a course of mine designing a remote control car. We have made 10 batteries from hand that each produce roughly 1.5 volts each. The car is fairly heavy and we only have a small electric motor to work with, and thus we would like to maximize the torque the motor produces.

My question is, to maximize torque, would we want to put the batteries in series to maximize the voltage applied to the motor or in parallel to maximize the current through the motor? An explanation of why or what either case does physically to the motor would be great. Thanks in advance!

With a fixed design of an electric motor the current it draws is directly proportional to the torque the motor is delivering. The motor speed is directly proportional to the applied voltage. Note that this is for a given motor design. "Within reason," a motor can be designed for desired speed and torque with given input voltage and available current. Of course you can't expect more output power than you supply, 1HP = 746Watts. To keep down the size of the wire and switches, thus their weight and cost, I suggest a higher voltage motor. Also figure out how you will charge the batteries (if rechargeable), most (all?) are very sensitive to being charged in large banks, either series or parallel.

What is the nature of your small DC motor ? As Tom.G points out there's more than one way to design them.
For high torque loads like vehicles one often chooses a "Series Wound" DC motor.

Tom also pointed out there's a voltage vs speed characteristic,
You might get fancy and start the cart with batteries in parallel for high current hence torque, then once rolling switch them to series for higher voltage hence speed. Diesel-Electric railway locomotives of the 1960's did something similar with their traction motors.

I suppose we should ask why you want to maximise torque ?

A lot depends on the voltage range the motor is intended for. Model car motors are typically in the 6-7V range so one option might be to put two strings of five cells each in parallel?

## 1. What type of battery should I use for my electric cart project?

The type of battery you should use for your electric cart project depends on the specific needs of your project. Some common types of batteries used for electric carts include lead-acid, lithium-ion, and nickel-metal hydride batteries. Consider factors such as cost, weight, and energy density when choosing the right battery for your project.

## 2. How long will the battery last before needing to be replaced?

The lifespan of a battery for an electric cart project can vary depending on several factors, including the type of battery, usage patterns, and maintenance. Generally, lead-acid batteries have a lifespan of 3-5 years, while lithium-ion batteries can last 5-8 years. Regular maintenance and proper charging practices can also prolong the lifespan of your battery.

## 3. How do I charge the battery for my electric cart project?

The charging process for electric cart batteries varies depending on the type of battery. Lead-acid batteries typically require a slow and steady charge, while lithium-ion batteries can be charged more quickly. Always refer to the manufacturer's instructions for the specific charging requirements of your battery.

## 4. Can I use solar power to charge the battery for my electric cart project?

Yes, it is possible to use solar power to charge the battery for your electric cart project. This can be a more environmentally-friendly and cost-effective option in the long run. However, it is essential to ensure that your solar panel system is properly sized and installed to provide enough power for your electric cart's battery.

## 5. How do I dispose of the battery when it is no longer usable?

It is crucial to dispose of batteries properly to avoid harm to the environment. Many types of batteries used for electric carts can be recycled, so it is best to check with your local recycling center for specific disposal guidelines. Never dispose of batteries in regular household waste or burn them, as this can release harmful chemicals into the environment.

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