The Baghdad batteries and the Dendera light bulb have both been largely dismissed as 'ritual objects' by the mainstream - and yes, perhaps they are, but we're not talking computer chips here, both contain pretty basic technology that could have been developed long before the Napoleonic wars. And then there's a long standing 19th & 20th-century attitude that "everything we've invented is brand new so nothing like it could have existed before." A good example of this was the excavation of Caligula's pleasure yachts in Lake Nemi during the 1930s. Several bronze water taps were recovered from the wrecks that so closely resembled modern day faucets they were dismissed as recently dumped rubbish. The fact is, a solution to an ancient problem is going to end up looking very similar to the solution for a modern problem - this is why ancient ship anchors look the same as modern ones and why the 2000-year old Antikythera clockwork computer looks identical to 19th-century mechanical calculators. In the end, mainstream archaeology needs to be more open minded - if a mystery object exhibits modern day characteristics, then there's a reasonable chance it is an ancient solution to the same modern day problem.
So where does this leave the Dendera light bulb? There's no way every Roman household was crammed with batteries and light bulbs...but that's not to say this technology didn't have some important alternatives to household lighting - and that could at least explain the lack of physical evidence for an ancient light bulb in Roman cities. Think tunnels. During the Roman-era more road and water tunnels were dug than at any time before the 1800s. Mining was booming and shafts were going ever deeper - and ever darker. Logically lighting these shafts was with oil lamps, but air quality would have been appalling - to the point where excavations may have become impossible. And, well, that would have cost money. The Dendera light bulb may have been a solution - and probably an expensive one. But was it? I don't know, maybe we should look more closely at Roman mines or tunnels for glass, copper rings and iron spikes. However, chances are, if these objects have been found, they have probably been described as...ritual objects. For more on day to day Roman technology, you can read 'Mischance and Happenstance' available from Amazon, just follow the links