Title: Module 2: Battery Chemistry & Electrolyte - Activity
Course: ASE A6 Battery Service > Section: Module 2: Battery Chemistry & Electrolyte

Q: What are the two roles of the electrolyte in a lead-acid battery?
- It lubricates the plates and prevents corrosion
- It carries ions between plates and indicates battery condition through its concentration
- It cools the battery and prevents overcharging
- It bonds the plates together and seals the battery case
A: It carries ions between plates and indicates battery condition through its concentration

Q: Why does the electrolyte's concentration decrease during discharge?
- The electrolyte evaporates from the heat generated during discharge
- Water is added to the cells automatically during discharge
- Sulfate ions leave the electrolyte and bond to the plates, reducing acid concentration
- The separator absorbs the sulfuric acid during discharge
A: Sulfate ions leave the electrolyte and bond to the plates, reducing acid concentration

Q: During discharge, what compound do both the positive and negative plates convert to?
- Lead dioxide (PbO2)
- Sponge lead (Pb)
- Lead sulfate (PbSO4)
- Lead oxide (PbO)
A: Lead sulfate (PbSO4)

Q: What happens to the electrolyte during charging?
- The electrolyte is drained and replaced with fresh acid
- Water is consumed and must be refilled after every charge
- The electrolyte freezes and must be thawed before use
- Sulfate ions return from the plates to the electrolyte, regenerating sulfuric acid and increasing specific gravity
A: Sulfate ions return from the plates to the electrolyte, regenerating sulfuric acid and increasing specific gravity

Q: At the positive plate during discharge, lead dioxide (PbO2) reacts with sulfuric acid to produce:
- Sponge lead (Pb) and oxygen gas
- Lead sulfate (PbSO4) and water
- Lead oxide (PbO) and hydrogen gas
- Pure lead (Pb) and more acid
A: Lead sulfate (PbSO4) and water

Q: During discharge, electrons flow through the external circuit in which direction?
- From the positive plate to the negative plate
- From the negative plate to the positive plate
- From the electrolyte through both plates
- From the separator to the electrolyte
A: From the negative plate to the positive plate

Q: A flooded battery sits overnight. Hydrometer readings show an average specific gravity of 1.190 across all six cells. What is the approximate state of charge?
- 100%
- 75%
- 50%
- 25%
A: 50%

Q: Using the reference chart, what open-circuit voltage would you expect from a battery with an average specific gravity of 1.190?
- 12.6V
- 12.4V
- 12.2V
- 12.0V
A: 12.2V

Q: A sealed AGM battery reads 12.0V after sitting for 24 hours with no load. What is the approximate state of charge?
- 75%
- 50%
- 25%
- 0%
A: 25%

Q: A technician wants to verify the state of charge of a sealed AGM battery using a hydrometer. Is this possible?
- Yes, all batteries can be tested with a hydrometer
- Yes, but only if the battery has been fully charged first
- No, because AGM batteries are sealed and the electrolyte is absorbed in the glass mat separators and cannot be sampled
- No, because AGM batteries use gel electrolyte instead of liquid
A: No, because AGM batteries are sealed and the electrolyte is absorbed in the glass mat separators and cannot be sampled

Q: A flooded battery has an average specific gravity of 1.190 across all six cells (approximately 50% state of charge). A technician wants to load test the battery. What action should be taken first, and why?
Feedback: The battery should be fully charged before any further testing (load test or conductance test). A battery at 50% state of charge should not be load tested because the results would be inaccurate and could lead to a false failure. Charging first ensures the test reflects the battery's true capacity rather than its current discharge level.

Q: A battery was removed from a charger 10 minutes ago and reads 13.2V. Does this voltage accurately reflect the battery's state of charge? Explain why or why not, and state what voltage you would expect after the issue is resolved if the battery is actually fully charged.
Feedback: No, the reading does not accurately reflect the state of charge. The battery has surface charge — a temporary elevated voltage caused by just being charged. It needs to sit for at least 12 hours (or have the surface charge removed electronically) for an accurate open-circuit voltage reading. If the battery is actually fully charged, the voltage should settle to approximately 12.6V or slightly above once the surface charge dissipates.

Q: A technician tests all 6 cells of a flooded battery with a hydrometer and gets the following readings: |------|---|---|---|---|---|---| What is the battery's approximate state of charge, and are the cell readings acceptable? Explain your reasoning.
Feedback: The battery is approximately 100% charged (fully charged). All readings are near 1.265, indicating a full state of charge. The cell readings are acceptable because all cells are within 0.010 of each other, well within the 0.050 acceptable variation threshold. Consistent readings across all cells indicate a healthy battery with no defective cells.

Q: A technician tests all 6 cells of a flooded battery with a hydrometer and gets the following readings: |------|---|---|---|---|---|---| Is there a problem? If so, identify which cell is affected, explain how you identified it, and suggest possible causes.
Feedback: Yes, there is a problem. Cell 3 reads 1.160, which is approximately 0.090 below the other cells (which average about 1.250). A difference of 0.050 or more between any cell and the others indicates a possible defective cell. Cell 3 likely has internal damage such as a shorted plate, sulfation, or plate shedding. The other five cells are consistent and near full charge, which confirms the issue is isolated to Cell 3 rather than being a general discharge condition.

Q: A technician tests all 6 cells of a flooded battery with a hydrometer and gets the following readings: |------|---|---|---|---|---|---| What is the state of charge, and what action should be taken? Explain your reasoning. |---------|-----------|--------|----------|
Feedback: The battery is approximately 50% charged (average SG around 1.190). All cells are consistent, within 0.010 of each other, so the battery is not defective — it is simply discharged. The technician should charge the battery fully and retest. If the SG readings rise evenly to approximately 1.265, the battery is healthy. The consistent cell readings indicate no internal cell damage, just a need for recharging.