Please read the description/textbox first. Question and (perhaps) fact: after the many years that these cheap garden lamps were produced (they surely were made/sold during the past 20 years, say from the 2000’s, at least in Europe): these cheap garden lamps are still “throw away products”. Almost all of them, though a tiny amount of these lamps are OK.
Of course I always (try to) repair them as long as possible and that is very easy. Bridge a corroded contact with a wire, etc. They are intrinsic good (!), corrosion is the thing that deteriorates them.
They work in general for (say) 6 months or a year, after that the moisture in the garden has eaten up all the electric contacts, so they are thrown away and new ones are bought.
Important: also LED garden lanterns were produced in China that lasted for 10 years or so. I had one of them, it even worked for 15 years (!).
Please note: when we look at “the bigger picture” you can consider this as a minor or even non existent problem: because millions of old smartphones on our earth are scrapped/thrown away and (of course) for a certain part recycled, where valuable metals (gold, silver, rare earths etc.) are re-used after this recycling process.
Whatever that may be: I think this is a serious problem and the components of solar cell garden lamps are valuable. They must not (!) be made with these cheap on-off switches, bad accumulators, bad flimsy wiring , lead-less soldering, etc. So that these garden lamps can have a normal life of say 8 years or so. And, after that, are recycled.
When you have questions about (certain analog) electronic circuits and how to make them: go to my Channel trailer (Radiofun232 on You Tube) and go to the “looking glass”.
Type there the keywords that you want/need like: “power supply”, audio amplifier, capacitor tester, oscillator, radio, shortwave, shortwave radio, or any keyword you like to find the essential info & schematics on my YT channel.
My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in. My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.
https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=Ko+Tilman
I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 23 april 2022.