Help needed possible battery failure and dealer is trying not to honor warranty

Hello, I'm a lurker here but have never posted. Anyway, last Sunday I was driving to the park and the red triangle came on as did the check engine light and the car light with the ! in it (hybrid system failure I believe). So the car would still run but not go into gear and wasn't drivable. My car has 85K miles on it and I have done all scheduled maintenance. Since it's still under warranty and the hybrid system light was on, I had it towed to the dealer the following day. The dealer called me and told me that I had diesel fuel in my car and that my tank needed to be drained and I needed new plugs, my injectors cleaned, and a new fuel filter. This assertion made me immediately suspicious because the gas station where I fill up doesn't even have diesel fuel. I nonetheless thought that maybe their tank was somehow contaminated and almost believed the dealer. They wanted almost $500 and that included the $90 diagnostic time. That day I had it towed to my mechanic who also happens to be my brother. The only reason why it wasn't towed there in the first place is because I thought that what needed to be done to the car was warranty work. Anyway, when my brother received the car, he immediately drained some fuel from the line and saw/smelled no evidence of the presence of diesel fuel. He then hooked up the scan tool and the only code that was showing at the time was P0A80 (something to do with the battery). When he cleared the code the car started running just fine. The plugs weren't fouled and there seemed to be no problems at all. I called the dealer and they said for sure there was diesel in the car and I of course asked them why it ran just fine now after clearing the code. I told them that I was suspicious that the code camp back up as pending. They told me to bring it back to them. To make a long story short, they were not friendly nor helpful. The pending code seemed to have cleared itself but the original codes from the dealer when I brought it in were
P3190
B1271
B1421
P0125
P3000
P0A0F
B1200
P0A80
B1207
If any of those codes are brake or speed sensor codes, that would be from the tow. Also, if one of those codes is an A/C code the tech said that happens when you bring it inside the shop or something. It's some sensor. When my brother initially cleared the codes the battery wasn't really charging as it idled in his shop. If it charged at all it would drain immediately. It now is charged and is acting/running normally. The P0A80 code that was pending has cleared. I have no idea what's going on but I suspect it has something to do with the battery. Any help would be greatly appreciated.
Thanks

 

I just did the test and the battery was at 11.9 and dropped to 11.8. Since it's below 12v I assume that it's failing? Is the 12v covered by the 8 year/100,000 mile warranty? Also, I'm calling the dealer Monday, could you either point me to a website with the codes or tell me what they were because I'm still wondering how they were trying to tell me that my car had diesel fuel in it. And lastly, thanks for your quick response.

 

Well, I'm am idiot because I retested my battery because I realized that the A/C was on the first time I ran the test and got 11.8-11.9v. When I retested it it was at 12.4v so I don't think that the 12v is the problem. I'm going to take it to my brother's place tomorrow and he's going to load test it. Thanks for all the help so far.