Greenworks Brushless Cordless Mower

I purchased the Greenworks 21" 40 v Brushless Cordless Mower with Two, 2.5 AH Batteries August 24th. It was easy to assemble and I immediately put the batteries on the charger so that I could cut the grass the next day. Both batteries showed fully charged, I placed both in the lawnmower and started her up. My grass height was right around 2 " tall, I managed to get right around 11 minutes of use on the first battery before it stopped working. Greenworks states that "Up to 55% of U.S. homes only need one charge to get the job done, Run Time: 70 min." If you look at the size of my front yard, one battery should have easily lasted long enough for me to cut it and still have remaining power to complete some or all the back yard. I took the spent battery back inside and placed it on the charger, in hopes that it would charge up enough that I could use it to finish the back yard in case the second battery already installed, did not last long enough for me to finish my back yard. The second fully charged battery lasted 14 minutes. Ugh! I went inside grabbed the 1st battery-tested the charge level, 2 dots...put it in the lawn mower and started it back up. I got 4 more minutes of use. Let the batteries charge over night and had to finish cutting the rest of my back yard the next day. I returned the batteries back to Amazon thinking, maybe they were not putting out the energy required- Greenworks/Amazon in turn sent a whole new lawn mower including 2 new batteries. Not what I was asking for but...ok. I first tried the new batteries in the original lawn mower and achieved a whopping 16 minutes of use while cutting the front yard before the new battery was spent and 13 whole minutes of use on the back yard. Again the back yard was not completed until the next day, after I had re charged both batteries. Next, I put together the new lawnmower (thinking maybe the issue is with the original mower, maybe its pulling too much energy and killing the batteries) and put the new, fully charged batteries in the mower...you guessed it not enough juice to complete my front yard...again. Greenworks, please reach out to me and lets figure out how we can get this lawn mower to behave as advertised!!