2005 with P3000, P0A80, rear fan running constantly--best option?

So my 2005 Prius with 187k miles recently displayed the usual four warning lights. These went back off for a day or two, then came back on, and this time car clearly often in limp mode, rear fan running constantly (with what seems like decent airflow). Display shows battery going between half-empty and full bars or just one down. I'm not sure it's shown a full battery since I got it from my sister in 1/20, and certainly hasn't recently. So that's also new. Shop pulled P3000 and P0A80, but no codes indicating a specific module.

The 12v battery is a few weeks past its second birthday. The in-car diag this morning (after the car had been sitting for a couple days) showed it at 12v initially then 11.6v after I hit the power button again (to switch to accessory mode). When the previous 12v battery failed I had various symptoms with the radio and such, but nothing like the above.

I've removed the interior trim. Everything looks fine.

So...any chance I'm not looking at a bad battery pack?

If I do have a bad pack, my options seem to be:

1. Get the diag tools and replace one or more modules myself. I don't know which modules available on ebay and such are good and which are from iffy sources.

2. Shop that pulled the codes says they've replaced individual modules in about 50 Prii, and only one came back later, and that was four years ago. They have a tech certified in hybrid battery repairs. They'd want $900 for diag and to replace up to two modules. A reduced charge (but well above zero) if it did have to go back for the same problem afterwards.

3. Buy a reman pack from someone like Green Bean, $1524, with a "lifetime" warranty. F grade on BBB because they haven't responded to a few complaints. Judging from the forum here, their packs do sometimes fail within just a few months. One concerning wrinkle: no refunds once you pay them, even if it turns out that the problem wasn't the battery pack. There are some other sellers with similar pricing, but no lifetime warranty.

4. Toyota battery for about $3000, which includes five hours of labor. Cosmetically the car is just fair, so even in today's market it's worth...maybe $4000? Also, the pack is currently on backorder.

Reading the forum, I see many claims that 1-3 tend to be a waste of time and money. But the local shop is confident their repair will last.

So...what makes the most sense? Any further tests I should perform / things I should try before pulling the trigger on one of the above?

 

By "new" you mean only Toyota, or also the company making new lithium packs? I don't know the price there.

I have the money, but struggle with putting $3k into a car that MIGHT be worth $4k.

I suspect Green Bean's $1500 is at most $1000 for the battery itself, the rest being mobile installation and warranty.

 

Does anyone think that #1 or #2 is a viable way to go? Or does replacing individual modules rarely work for long?

 

Ann Arbor, MI.

I did remove the interior trim today, but haven't removed the fan yet. Flow out of the exit seemed good.

I'll check the socket and connector.