The accuracy of the quartz movement was stated as within ± 20 seconds per month at a normal temperature range of 5 to 40 ☌ (41 to 104 ☏). The movement also featured an 'insufficient recharging' indicator. This battery type became available in the early 1990s, enabling an Eco-Drive 7878 movement to run 180 days on secondary power before requiring recharging via light exposure – a marked improvement in energy storage over previous light-powered watches. To store electrical energy the first Eco-Drive movements employed titanium lithium-ion rechargeable or secondary batteries. Though the Eco-Drive caliber 7878 movement solar cells remained slightly visible through the dial, the physical styling of the light-powered watch was no longer constrained by visible solar cells. By locating a sufficiently translucent dial material over the now more efficient solar cells, enough light could pass through the dial face to power the movement. This innovation was enabled by marked improvements in thin film amorphous silicon solar cells, which, by the early 1990s had become significantly more efficient.

Previous light powered watches from Citizen and other manufacturers had the solar cell(s) mounted directly on the dial. This movement was the first light-powered movement where the solar cells could be mounted under the dial. The technical platform that made the Eco-Drive concept possible was the Eco-Drive caliber 7878 movement. 2.4 Solar cell and secondary battery life expectancy.2.2 Temperature difference as power source.

Watch drive 2011