Final answer:
The lowest acceptable overvoltage category rating for a tester to be used on electronic equipment and circuitry is typically Category II, which is suitable for appliances and portable tools. This ensures safety against transient overvoltages.
Step-by-step explanation:
The question pertains to the overvoltage category rating for testers used in assessing electronic equipment and circuitry. In the context of such testers, the overvoltage category rating is a crucial safety classification regarding the tester's ability to withstand transient overvoltages like spikes that occur in electrical systems. The lowest acceptable overvoltage category rating for testing electronic equipment and circuitry is typically Category II, which is designated for appliances, portable tools, and similar devices. However, for a more precise answer, one must consider the specific environment and the nature of the electronic equipment being tested. The context provided indicates that the devices in question are battery testers, which use small load resistors to draw current and test internal resistance of batteries, indicating their strength through terminal voltage measurement.