Anyone else have a Hypermac not living up to claims?

[takeandbake]

I have a Macbook 4,1 (2008ish) and a MBP100 Hypermac (the original that came with the Magsafe cord). Hypermac was purchased in November of 2009.
Last September/October, I experienced significant decrease in performance and sent it back for warranty repair and received the product back in a timely manner.

However, I have always suspected that the product wasn't truly fixed and have been running multiple performance tests to confirm this.
Example: I start with fully charged Macbook plugged into Hypermac (charged for over 10 hrs), which is what Hypermac recommends for optimum performance. 50% brightness, web browsing. Hypermac lasts for 26:32 before it dies, so I will have approximately 4 hours total of browsing time with hypermac +fully charged macbook. The Hypermac website says that I should get 12.7 hrs battery life. Am I crazy? is it my laptop battery?

 

[thinh3d]

I suggest you check the health of your mac internal battery first. See how many percentage it has.

 

[takeandbake]

Coconut battery indicates that my internal battery is at 88% of the design capacity. To me, this doesn't seem significant enough to cause the poor performance I've experienced.
When I plug in the external battery when the Macbook's battery is close to being drained (not ideal) I get less than 10 mins out of it...