$7E8 $7EA Red Triangle Of Death

OK this has happened three times to me with slightly different symptoms and could use some assistance. 2007 Prius. This happens after the car sits idle for a day or two. Replaced the small battery about 12 months ago and the big battery about 4 months ago. 185K miles.
First time: car sat for most of the weekend. stopped at a stop sign, car produced the red triangle of death, the screen said the informative word, "Problem" and the car stopped dead. OBD reader said $7E8 and $7EA. Tried a jump and clearing the codes to get it working (not sure it needed a jump). Ran fine for a week.
Second time: car sat for the weekend again. Stopped and got red triangle again along with the yellow exclamation point. Problem read on the screen but the car kept running. Clearing the same codes and it ran fine.
Third time: car sat for about 2.5 hours. Got a check engine light and the car wouldn't start when I got in. Clearing the same codes once again and it ran fine after that.

What's going on here?

 

Thanks, I'll look into getting one. I got the battery from Greentec Auto. I thought the service guy was pretty knowledegable so my confidence in the replacement was pretty high. Yes, my mileage has dropped a bit but I assumed it had more to do with a long drive where I was going at higher speeds for an extended period of time. I would guess I may be about 5-10% lower than what I usually expect. No fan noise, but I'll be honest I haven't been paying that close of attention.

 

I contacted them this morning and were extremely helpful. They first asked for the codes before they can issue a warranty replacement. I have a Mini VCI on order and will go from there. Greentec's warranty is 18 months so that was a nice time cushion (bought 4 months ago). I'm hoping this will be the solution and I'll keep you posted on this thread.

 

Well, Techstream came up with no fault codes. Called Greetec and they suggested looking at the oil level and it was low. So far, so good but I'll keep an eye on things. This does beg the question: it appears that my Prius is burning oil. Probably at a rate of about 1 quart per 2500 miles. Cause for concern? I'm fine checking/filling it once in a while but is there a reason to think it may have a serious issue?

 

OK the battery check didn't indicate any problems. I checked the voltages and the difference between the highest and lowest value was slightly higher that 0.2 volts. I ran the battery down and got the attached values. I'm really not sure if this is considered a problem or not. My work develops products that are battery operated and I've seen far larger swings in battery voltage when a system is under load. Any thoughts?
So far, no new instances of the Red Triangle (since adding oil) but I will be keeping an eye on it and report back.

 

So far the battery looks about the same. I took a 1500 mile trip over the weekend and the Prius performed flawlessly. I checked the oil this morning and I'm down about half a quart. I think I'll be monitoring that going forward and if the battery acts up, I'll give Greentec a call. It seems that the battery may have issues down the road but the real culprit for all of the problems I had, was the oil level. Thanks to all!