Yes, a gel battery can lie flat without affecting its operation or performance. This is one of the advantages of gel batteries, as they do not contain liquid electrolyte that can leak, even when the battery is placed in different positions.

The electrolyte in a gel battery is immobilized in a gel-like substance, preventing it from leaking, even if the battery is lying flat. This makes gel batteries suitable for installations where space is limited and the battery needs to be placed in various positions.

However, it is important to note that the battery terminals of the gel battery are still susceptible to corrosion, and proper connections and terminal protection should be used to protect the battery from potential damage.

If in doubt, it is always advisable to consult the manufacturer's instructions for the gel battery regarding proper installation, storage, and use of the battery.