Why traditional solar street lights were not that popular?
In the past, why people do not tend to choose solar-powered street lights is due to three major reasons,
1. Lighting bulbs are energy consuming
Both MH(metal halide) and HPS (high-pressure sodium), which were used as light source in streetlights at that time, are with the relatively obsolete lighting technology (60-80 lumens/w) compared with that of the LED. those bulbs/lamps usually require a large amount of energy per day from its battery bank, which is considered as a downright burden to its battery capacity.
2. The LED technology is newly-developed and pretty expensive
In those days, although LEDs had been on the market in commercial outdoor lighting for a few years, the technology was still not mature. Their lighting efficiency was only 100 lumens/watt (now, in 2019, it can be up to 200 lumens/watt). Furthermore, since LEDs were newly-developed at that time, the cost was rather expensive and the average man on the street could not afford to buy.
3. Lithium-ion battery technology is not well developed
The third reason is the solar battery. The lithium-ion battery has the longest lifespan as one kind of deep cycle batteries, but they were not stable and would fail to work under 0 Celsius. (now, the working temperature of ternary lithium battery: -30 to 65 Celsius)
However, Things have changed over years.