Why does my iPhone randomly turn off?

I've had an iPhone 3GS for a while but now it'll just randomly shut off and i have no idea why. When i try to turn it on the apple symbol appears and thats it until it just goes black again and won't turn back on until you plug it into the charger. I already tried hard starting it and nothing. It can be at 90% battery and it'll do that can anybody help?

Unfortunately these "fancy devices" have a limited life span. The battery charging cell stops holding a charge and you can replace it but I believe it's very expensive and not worth it. Unlike some electronic devices that you might expect 5 to 10 years of useful life, iPhones and iPads aren't these types of devices. I've had two "dead" iPhones and one "dead" iPad. Unless you have bought an extended warranty (but now Apple only offers a max of 2 years and no longer 3 years) you just have to buy a new one. It's a bummer.

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