Noob with a Q. re: Repairing Solar String Light

Hello! I want to repair two solar light strings. One has 120 blue LEDs and the other has 200 blue LEDs. The solar panels of both look fine and the light strings have never even been outdoors because they stopped working when I "tested" them ((covered the solar panel, Heh! )) I did of course try fresh batteries with no success.
Looking at the "innards", it looks to me like they were assembled using crappy hair-thin wires and even crappier soldering.
So then, my questions are this:
Should I try to disassemble the existing mess, strip the wires, clean up the mini-boards, and resolder? ((I've never soldered electronics, but I do very small stained glass items and I'm sure that adapting won't be too problematic.)) I have some solder that's called "waterproof silver solder", which I think has some copper in it as well; I also have some lead-free zinc solder, and some of the typical lead:zinc stuff.
*OR*
Would it be better to try to find new controllers? If so, should I switch the strings over to lithium batteries ((I'm looking at Amazon - yeah, I know, not the best but it's a place to start...)) since there seems to be a wider variety of those? Or if I want to be able to use the replacement NiMH bateries I just recently bought <!>, do I need to consider anything other than the voltage...? I'm sure the LEDs are connected in series, since the strings *do* use one 1.2V rechargable battery, but I don't know whether there is any limit on the mA that the simple charge-controller modules can put out. The whole reason I got these 2 strings was the length, since I want to suspend them over the pool and deck, which comes to at least 42 feet between where I can stick support poles into the ground.

I know I could switch to plug-in lights, but the lawn people ((my mobility is quite restricted so I can't do my own any more)) are so darned careless that I *much* prefer to not deal with electrical cords across the mowable areas
I also know I could buy new strings, but being on a fixed income now, that just gets annoying.
MORE than that, it's a matter of principle at this point: I much prefer to learn how to repair what I've got, than continually throw money at sloppy manufacturers. Ideally, I'd like to learn to build my own from scratch, but for now, I would be thankful for any and all possible repair suggestons

Thanks for reading!

Cheap electronic junk frequently does not work or fails soon because of design errors and poor parts and poor manufacturing.
High quality Name Brand electronic products are reliable and last for years. They are not sold on ebay, AliExpress or Amazon.

200 3V blue LEDs in series need 600V plus a current regulator that needs more voltage.
200 3V blue LEDs in parallel must all be matched for the same voltage and also use a current regulator. a circuit is used to boost the 1.2V from the battery to 3V for the LEDs plus maybe 2V for the current regulator.

audioguru said:

Cheap electronic junk frequently does not work or fails soon because of design errors and poor parts and poor manufacturing.
High quality Name Brand electronic products are reliable and last for years. They are not sold on ebay, AliExpress or Amazon.

200 3V blue LEDs in series need 600V plus a current regulator that needs more voltage.
200 3V blue LEDs in parallel must all be matched for the same voltage and also use a current regulator. a circuit is used to boost the 1.2V from the battery to 3V for the LEDs plus maybe 2V for the current regulator.

Click to expand...

- Thank you for your reply - I had not thought about a voltage booster.
- Re: components sources, well, the LEDs in these strings seem to be OK, even though they're cheap junk from Amazon. It's the power-related half of the unit that's wonky. If I do need a new power setup, of course I'll look at reputable sellers first; if I can't find small amounts for an affordable price, however, I'll just need to make do with what I can get. It's not as though I need to make ultra-reliable milspec items for NASA or similar; all I want to do is get two light strings working again so I can use them in my back yard.
-
- Meanwhile, I've already decided that the first thing I'll try will be disassembling, cleaning, fluxing, and re-soldering the existing parts. If that doesn't work, I'll try one of the new mini-boards. If that still doesn't work, then, in between the other things I'm doing, I'll look into making a set-up to charge, and utilize, a higher-voltage battery so I don't have to add a voltage booster.
- Apologies if this was the wrong place for my inquiry.

If you add a higher voltage battery then you must also add a current regulator to prevent burning out the LEDs. Without having part numbers and datasheets for the LEDs then how will you find out their suggested reliable current?

- I had decided last night to see what I can do with the existing parts, and hold onto the small controllers for now.
- Just in case this might help anyone else, I'll list what I've done so far. I'll get to the question of the resistance further down.
-
- I'm starting with the 120-LEDs string; I think they might be less than 3mm, but they're molded into the body of textured clear stars, so measuring them is challenging. After disassembling the body of the solar-panel 'box', I got hole of a 15X magnifier and a small but bright light, and examined the components. The existing resistor is color-coded as 560 Ω +/-10 and there are 2 diodes marked "1N50 M1C", so that gives me some information. There is a small IC marked "ANA6528 50074" - I couldn't see that before; I didn't see it show up in any of my searches ((yet)) but there is apparently a step-up/boost chips "ANA6518". An on/off button "KN-17", a "16V 47uF" capacitor, and a tiny thing in the "D2" place with a translucent reddish glass body and a thin black "cap"; the printing it too smeared for me to even see with a 15X magnifier.
- I still need to check whether all of those other parts have any resistance, but I assume all of that together will give me what I need to calculate the total theoretical resistance, and plan accordingly.
- FIRST, though, I finally separated that unit's board from the plastic enclosure by slowly and carefully prying-off the melted "pins" with a sharp knife; what was immediately obvious, when I turned it over, is that there is a wire that's partly stripped where it shouldn't be, and the wire-covering/coating around the "hole" looks like it's been melted and/or grated <!>. So that's the first thing I'll fix, and then then test the string again. If it works, I'll get everything back together and close it up, and that will be that. If it doesn't work, I'll think about what else I can do, and post more, just n case it if of any interest or help to others.
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- I'll eventually take the same approach with the next set, with the 200 3mm LEDs.
- FIRST, though, I have a small stained glass+Swarovski-crystals item I really need to finish by tomorrow with some soldering touch-ups, and finally, smoothing the solder and then applying the 24K gold leaf. Lastly, clip on the gold-plated-stainless snake-chain that will be the hanger.
- So I definitely won't get to the 200 light string until at least Wednesday.