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Batteries
14 questions By Tony R. Kuphaldt
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Question 4 of 14
Draw a schematic diagram showing a DC generator charging a battery, and another schematic showing a battery discharging into a resistive load. Be sure to include arrows in your drawing showing the direction of charging current.
Reveal answer
Follow-up question #1: how must the battery and generator voltages compare in order for the battery to have current forced “backward” through it?
Follow-up question #2: which is the source component, and which is the load component in a circuit where a generator charges a secondary-cell battery? Explain your reasoning.
Notes:It is very important for students to understand the direction of current through a battery, both when charging and when discharging. A helpful perspective on this topic is to think of the battery either as being a source of electrical energy versus being a load. Under which conditions (charging or discharging) is the battery playing the role of source versus load?
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Question 5 of 14
What does the amp-hour capacity of a chemical battery represent? What does it mean if a battery is rated at, say, 150 amp-hours?
Reveal answerThe amp-hour rating of a battery is an approximate indication of it’s useful lifespan per charge.
Follow-up question: why not just rate batteries in terms of hours, instead of amp-hours? Since time is the value we are most likely interested in, why bother to refer to current (amps) at all?
Notes:Although the basic concept of an amp-hour battery rating is simple, it is important to realize that real battery discharge characteristics are very nonlinear, and therefore the simple “amps times hours” approach may yield grossly inaccurate predictions regarding battery life.
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Question 6 of 14
What is the best-performing secondary cell technology today, in terms of energy stored per unit mass?
Reveal answerThere is no point in giving an answer here, as it will change as battery technology evolves. However, in your answer you need to specify an actual numerical figure for energy density, for comparison against other classmates’ research!
Notes:Questions like this are fun, because they allow the students to do research on state-of-the-art technology. Ask them where they obtained their information for the answer!
sometimes battery with small capacity (Ah) has a high Cranking Amperes (CA). for example Motorcycle battery 4 Ah has 140 CA. Automotive battery 35 Ah has 350 CA. 35 Ah is more than 8 times of 4 Ah but the CA just only 350 CA