@msfujino sorry to ping you directly, but since you created the original post, I thought you may have some insights on what could be wrong.
I am new to the forum, so I could only post two links in the post. Here is how I soldered the battery and the performance graph of the sgm6029. As you can see the performance should be > 90% with a load of 250uA and an input voltage of 3.7 .
