According to a pamphlet I picked up at the hardware store, the rechargable Nickel-cadmium (Ni-Cd
) batteries in many solar powered garden lights
only last 2 years. Apart from not represeting good value for money, Cadmium is a toxic heavy metal
. Ideally a wired light should be used, but failing that, using nickel metal hydride (NiMH) "Pre Charged
" would be better.
Nickel-cadmium batteries are among the longest-lasting of all batteries generally speaking. They have been demonstrated to endure thousands of charge/discharge cycles, and there are nicad batteries in service today that were made in the 1970s. So if nicads are used until they no longer do the job, they can be the greenest battery option available, with each cell replacing many NiMH, lithium, or alkaline rechargeable cells.
It is important to properly dispose of old nicad batteries due to the toxicity of the cadmium contained in them, but it's not fair to characterize a product with such long service life as an environmental hazard without taking into consideration the amount of comparable products it can replace.
If it is the solar-powered garden lights themselves that only last a couple of years, then the problem lies with them, not with the batteries.
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