Which type of battery requires testing using a test light?

Conventional batteries, also known as flooded batteries, are designed with removable caps that allow for the addition of electrolyte. They can be tested using a test light because the test light can be used to assess the condition of the cells and the presence of charge by indicating the voltage through the battery's terminals.

In contrast, maintenance-free batteries are sealed and do not allow for electrolyte addition, making them unsuitable for testing with a test light in this manner. Lead-acid batteries encompass both conventional and maintenance-free designs, but the key distinction here is that conventional batteries have the physical characteristics necessary for using a test light effectively. Lastly, lithium batteries utilize different chemistry and require specialized testing equipment, so a test light would not be appropriate for them. Thus, the testing method aligns specifically with the properties of conventional batteries.