I replaced my iPhone battery last month with no success. It turns out it was the seller that was the problem.

I ordered a new battery from Amazon: Maximal Power Battery with Change Tool Kit and Photo Instructions for iPhone 3G, 3G S (Silver)

Worked like a charm. Battery is taking a charge and came with 50% which is appropriate. We will see how long it lasts, but at least it works.

So back to e_cell. Stay away from them. Horrible customer service and many reports on the web of the same problem I had. I should have listened:

http://modmyi.com/forums/hardware/695368-iphone-3g-does-not-turn-after-changing-battery.html

I think this bad company is also at amazon under the name eForCity but I cannot be sure.

Again. e_cell sells bad batteries shipped from the UK, so returning them is pointless.