Very recently my Nexus has had trouble charging. It does it verrrrry slowly. A charge now takes maybe 3-4 hours, and the screen has to be turned off for it to do this. I've actually seen the batter life go down while it's been charging with the screen on. This is a very recent change, and started maybe a week ago. Prior to this I had no issues charging. I've tried multiple chargers so that is not the issue.
That's not good your Nexus is taking longer to charge. You did well trying other charges, this narrows the issue down to either the battery or the device. Do you know anyone else that has a Nexus, may want to try and use their battery to see if this still occurs. If not other batteries are available to test, I'd recommend taking the device to a Sprint Service center and have them diagnose it. They should be able to tell you if it's the battery or something else like the charging port.
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There is a factory defect with the USB charging port, you can replace it yourself Dock Connector Charging Port Flex Cable Ribbon for Samsung Galaxy Nexus GT I9250 | eBay or take it to a sprint store
I've noticed that too when it was charging via PC, the battery actually discharging while it was plugged in. I have better luck using an AC charger.