How Do You Calculate the Variable Resistance for Optimal Battery Charging?

You will get a quadratic in R. Use the quadratic formula to solve this for R.In summary, the problem involves determining the variable resistance R in order to absorb 25 watts from a 10.5 V battery using a 0.035 ohm resistor and a 10.5 V element. Using KVL and substituting in the given values, the current was found to be 2.381 A. By plugging this value into the equation for current and resistance, a quadratic equation was formed. Using the quadratic formula, the value of R can be solved for.
  • #1
jesuslovesu
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0

Homework Statement


http://img2.freeimagehosting.net/uploads/bf073a5eb1.png
http://img2.freeimagehosting.net/uploads/bf073a5eb1.png

Determine the variable resistance R if the 25 Watts to be absorbed by the battery (0.035 ohm resistor and the 10.5 V element).

Homework Equations


V = IR
P = IV

The Attempt at a Solution



Well I did KVL clockwise current flow
-13 + 0.02*i + iR + 0.035*i + 10.5 = 0
2.5 = 0.02i + 0.035i + iR

Then factoring in 25W=10.5*i
i = 2.381 A which is close to the answer but doesn't factor in 0.035 and I'm not sure how to do it
 
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  • #2
jesuslovesu said:

The Attempt at a Solution



Well I did KVL clockwise current flow
-13 + 0.02*i + iR + 0.035*i + 10.5 = 0
2.5 = 0.02i + 0.035i + iR

Then factoring in 25W=10.5*i
i = 2.381 A which is close to the answer but doesn't factor in 0.035 and I'm not sure how to do it

The question was to compute R such that you got 25 W dissipated in the 10.5V battery. You computed what the current through this battery must be. Now use that in the equation with i and R you wrote above
 
  • #3


I would first clarify the question by asking for more information, such as the type of battery, the charging time, and the desired voltage and current for the battery. This will help determine the appropriate wattage for the battery charger.

Next, I would use the equations V=IR and P=IV to solve for R. From the given information, we know that the voltage is 10.5V and the power is 25W. Therefore, we can rearrange the equation P=IV to solve for I, which gives us I=2.381A.

Using the equation V=IR, we can plug in the values for V and I to solve for R. This gives us R=4.41 ohms.

However, it is important to note that this calculation assumes that the battery is receiving a constant current of 2.381A. In reality, the current may fluctuate depending on the state of the battery. It is important to monitor the charging process to ensure the battery is not overcharged, which can lead to damage. Additionally, the type of battery and its internal resistance should also be taken into consideration when determining the appropriate charging wattage.
 

Related to How Do You Calculate the Variable Resistance for Optimal Battery Charging?

What is the wattage of a battery charger?

The wattage of a battery charger refers to the amount of power it can provide to charge a battery. It is typically measured in watts (W) and can range from as low as 5 watts to as high as 100 watts or more.

How do I choose the right wattage for my battery charger?

The wattage of a battery charger should be chosen based on the battery's capacity. As a general rule, the charger's wattage should be at least 10% of the battery's capacity. For example, a 1000mAh battery would require a charger with a minimum wattage of 100W.

Can I use a higher wattage charger on my battery?

It is generally safe to use a higher wattage charger on a battery, as long as the voltage and charging method are compatible. However, using a significantly higher wattage charger may lead to overcharging and damage the battery. It is always best to use the recommended wattage for your battery.

What happens if I use a lower wattage charger on my battery?

Using a lower wattage charger on a battery may result in a slower charging time. In some cases, the charger may not provide enough power to fully charge the battery. It is important to use a charger with the appropriate wattage to ensure safe and efficient charging.

Can the wattage of a battery charger affect its lifespan?

The wattage of a battery charger does not directly affect its lifespan. However, using a charger with a significantly higher wattage than the recommended amount may cause excessive heat and potentially damage the charger over time. It is best to use the recommended wattage for your battery to ensure both the battery and charger remain in good condition.

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