Science Buddies: "Ask an Expert"

I am doing an experiment testing how different kinds of battery affect the force of an electric car. I researched how a battery works, but I have another question: What gives different kinds of battery more power than others (the ability to give more force than others?)
Thanks

Sorry i have another question.
My science project is testing how different batteries affect the force of an electric car.
What do you think would be the best way to measure force? There are 20lb. Spring Scales for fishing and Penny gram scales, although im worried they might not be able to record high enough force.
thanks

I guess I don't understand the question too well. Are you testing different brands of the same type of battery (for example, alkaline AA)? Or are you testing different types of batteries (like alkaline, nickel-cadmium, etc)? Is a car the best way of testing? As to the scale, just hook the most sensitive scale to the car (with a battery in it but with the switch turned off), lock the car wheels (maybe by putting a toothpick in the gears). Pull on the scale and note the reading when the car just begins to skid. Do you see the problem?

Hi Wittle4 - I've combined both of your "Battery Power" questions into one topic. Your questions are related to the same project, and so it will help the experts in assisting you if you post all your questions in one thread.

Amy
Science Buddies

wittle4 wrote:What gives different kinds of battery more power than others (the ability to give more force than others?)

Excellent question; however, the answer involves learning about several underlying principles.

An understandinc of Ohms Law is needed to understand the relationship of Voltage (Electro Motive Force), Current (electron flow), and Resistance (things that affect the flow of electrons). Do you own searches for "Ohms Law" for some online materials.

A simplified understanding of battery chemical reactions and how it relates to the production of free electrons at one electrode (cathode) and the "borrowing" of electrons from the other electrode (anode). The important things to appreciate are how the surface area of the electrodes and the ability of the electrolyte to allwo ionic flow affects the rate at which the chemical reaction can occur and thus the production of external electron flow.

If you look for some battery specifications on the various manufacturers web sites, you can find some power curves for various loads.

Your question also involves the interaction of the battery with a DC motor. You are also going to have to read about motors and how torque, speed, current, back emf, locked rotor current, and other motor properties to understand the load characteristics of DC motors.

Fundamentally, different battery designs exist for different loads and how well a given battery design works with a given load will be a function of how well the power supply properties of the battery match the power demand properties of the load.

Internal battery resistance has a lot to do with the answer to your question, but the internal battery resistance is not constant and changes as the chemical reaction depletes more and more of the electrode and/or electrolyte ions, whichever is limiting at the moment. And as you guessed, different battery designs behave differently.