I got a solar led light from Ali Express. These use a Li battery 3.7 V and 20 LEDs. Worked fine for 3 months but now stopped working.. Any ideas what to check for. Battery V checks OK.

 

Sun went down?

 

~90-days is actually an impressive run for such a device.

There are generally 2-solutions to your dilemma,
1) Buy another identical Light,
or,
2) Purchase top quality Components and build it yourself, ( probably ~40 to ~60 bucks ),
insuring that it is thoroughly weather-proofed in every way possible.
This will probably give You a ~2 to ~3-year life expectancy before failure.
Then build another one.

Solar Walk-way Lights are a gimmick,
but they can be had for soooo-cheap that people will buy them anyway.
And Grandma can install them, 'cause there's no Wires.

Electronic-Components don't like existing and operating in a hostile, wet, environment,
especially cheap-Electronics.
.
.
.

 

Wife buys those cheap garden figurines that light up. They quit working frequently. I've found the switch to be the major problem in many cases. In other cases, after a few years, they stop working because the battery is cheap. I'm talking about those 1.2V batteries, I believe they are NMH (Nickel Metal Hydride). Not positive about that - but - - - .

 

Yes, they are NiMh batteries.
Another common problem is that the solar cell’s internal joints open up.
The small control IC becomes defective.

As LowQ mentioned, these solar garden lights are designed to become E-waste in a single season.

 

NiMh

Thanks for the clarity.