How long should the new iFixit battery in my iPhone 6 last?

I replaced the battery in my iPhone 6 with the iFixit battery and it only lasts about 9 hours. I don't use my phone very much, the original battery would stay charged for a day and half at least when it was new. I followed the instructions, ran it down to 10% then charged it to full. If I use my phone I can watch the battery percentage drop, one phone call takes up 5% or more of my battery life. Is this a weaker battery than the original one?