Need advice on Prius with dead batteries

....existing battery may be the original, hence >10 years old... Sounds like the other stuff after I get it running isn't that different from what you would do with any car that has been sitting way too long....Why would gas without ethanol be better?

OK! A new battery is in your future.
This is the battery I have used in the past, my experience with these goes back 4 years and so far so good. According to their literature "they can last up to 10 years"

Power Sonic PHR-12200 Rechargeable SLA Battery 12V 192 Watts/Cell T6 Terminal - $168.01

PriusBrit posts gave me the idea to try a "mobility battery" type. The battery he suggested back then was not available in the US market.

After searching/reading other posts settled on this one because it does have a high charging rate: Up to 16A. Why does the charging rate matter? The Prius can send a 30A+ into the battery, a youtube video showed that. It is also the one with the lowest internal impedance. 10Y sounded very attractive. I actually do not like futzing with the car for those kind of items. My aim is to usually help the longevity of the car. It is heavier so naturally you can expect some kind of drop in MPG.

The PHR-12200 battery is not a direct fit. I simply used 1" M6 screws with stainless steel washers and a split lock washer at the head to connect the pencil type battery connectors to the T6 terminals. It barely fits inside the allotted space and it is a bit higher.

I am attaching a spreadsheet made out of reading many posts, blogs and figuring out what is available in the US market, etc. I hope it helps you pick a battery. I have not used the spreadsheet in quite a while lol. The item marked in yellow is the one I bough showing the price back then. So far I have bought two of these batteries. One for my 2009 Prius (4 years ago) and another for my brothers 2015 Prius (2 years ago).

Why is ethanol gas better? This is what I have gathered:
a) It will age much better if some reason you wind up delaying the repair of the car.
b) It will burn better and help the engine start more easily: Right now I think you need to increase the odds in your favor.
c) It burns cleaner, I can clearly see that at the tail pipe of all my vehicles.

I hope this helps!

 

1. New meaning new Toyota cells, not refurbished, reconditioned, used or repainted? Warranty on anything but truly new means little to reliability other than "maybe" another swap.

2. Conked out in two minutes? What does that mean? Engine was running for two minutes? Engine never started but was in Ready? Or codes and lights while dropping Ready? It is very important to know what happened and if your batteries, both now "new" with warranties are still good.

3. Was the two year old gas replaced?

Sounds like your guy is not hybrid experienced. But anybody with a shop can read codes in five minutes, write them down, clear them with a 12v disconnect and try again. Often it takes several tries after a 12v disconnect.