bad 18650 battery. fix or throw out?

Got a bad draw and ended up a bad 18650 Ultrafire 4000mAh battery. Fully charged, it gets 3.7V, but it wavers when you physically shake the battery. It goes to 3.5 and then 3 and then 2.8V. You shake it and it could give you anything in between. The other identical one of the pair I bought is fine. However, I feel something in both these 4000mAh moving when I shake it compared to the completely solid red Ultrafires 3000mAh I have.

The broken one results in a really dim light. So dim that staring at the lit flashlight LED doesn't hurt your eyes. Modes don't work.

I got a refund on both already.

So anyway to fix it? If I chuck it, is trash fine?

Thrash it, it is dangerous.

Two things , If it has a protection circuit - try it without it ...

Or wrap the + - in tape and recycle it .

I got flat top ones. How do you try it without protection?

From what I've heard, the "4000mah"s should have been tossed in the garbage bin as soon as you received them...

--Bushytails

Toss it!