After battery replacement, phone keeps rebooting

The original battery on my iPhone 4s had degraded a lot and so I ordered a battery from eBay a cheap $8 one. This battery worked fine for about 6 months until it also degraded and drained very quickly upon use. Then I ordered a replacement battery here from iFixit in hope of getting a higher quality OEM battery, when I put this battery into my phone however the battery percentage would not change, and only change when I restarted the phone. On shutting down the phone I also found that it wouldn't stay powered off, simply rebooting after 1-2 seconds. It would however stay shut down if it was plugged into the power. Also as well as the battery percentage not changing the phone begin to reboot every 5 or minutes, with the screen going slightly brown briefly beforehand. I then replaced the iFixit battery with the $8 one and all these problems stopped. Is there an issue with the ifixit battery, or can anyone help me with what the problem is?