Which statement about hydrometer readings for a lead-acid battery electrolyte is true?

• A. A specific gravity correction should be added to readings if the electrolyte temperature is below 59°F
• B. The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80°F
• C. The hydrometer reading will give a true indication of capacity regardless of electrolyte temperature
• D. Temperature corrections are routinely required at all temperatures

Answer: (B)

Temperature affects the density of the electrolyte, so a hydrometer reading can shift with temperature. Hydrometers used for lead-acid batteries are calibrated to a standard reference temperature, commonly 80°F (27°C). When the electrolyte is at that temperature, the reading already matches the reference chart, so no temperature correction is needed. That’s why a statement saying no correction is required at 80°F is correct. If the electrolyte is colder or hotter than 80°F, you would apply a temperature correction to estimate what the SG would be at the standard temperature. The other statements aren’t correct because they either rely on an arbitrary temperature threshold or claim corrections are needed at all temperatures, which isn’t the case at the reference temperature.