New HV battery, or something else? P300, P0A80, P3018, P0A84

Yes. Consider replacing a module or two, then top balance or cycle the pack.

Have you checked or cleaned the associated HV battery fan connection already?

Try removing the sticker and place a drop or two of machine oil on the fan spindle (with or without removing the circlip first).










Check all of the connectors on the left end (drivers side) of the HV battery, including the the harness and HV battery ECU (below) :

 

FAQ

If an 08 with 133k is in good shape otherwise, get a new battery (OEM or aftermarket) for the most reliability, performance (power wise it will feel and perform new again), and the least amount of downtime (for many jobs this is usually incredibly important).

Little funds, plenty of time, can afford for vehicle to be down for many days at a time? The Wack-a-mole approach of replacing the worst of the cells is often suggested (see above). This can cost as much as half of a new battery (aftermarket plugnplay solutions). I recommended (and practiced) this method many years ago but in 2022 (for a gen 2) I'd skip and get all new cells (aka new battery) or if you can find a complete, used but much newer HV pack. Sometimes one gets lucky and finds one for cheap for a complete swap but other owners and battery rebuilders/shops are always looking too.

GOOD LUCK!

 

The battery fan does need to work (and you need to do something with the HV battery itself.)

As mentioned, the connector near the fan itself commonly gets corroded from water leaks around the tailgate body frame. Then check the connection at the fan itself. Also might want to check the small relay that supplies power to the fan- in the wire harness attached to the air duct(?).

The battery ecu monitors the negative control side of the fan motor. With the fan off there should be near 14V at the ecu. When the ecu commands the blower "on" at lower speeds, the blower module partially grounds (pulse width duty cycle) the negative circuit. So there should be around 8-12V on the (-) monitor circuit, with voltage decreasing as fan speed increases. At 100% on, there should near 0V.

If the ecu doesn't see the voltage it expects (when it expects), then you get the P0A84.

For the HV battery, you can go for a new set of modules, Toyota, newpriusbstteries.com, or maybe projectlithium.com.

Almost any other replacement pack is likely some kind of "refurbished" (ie, used) modules. Maybe something ok, maybe something bad, nobody knows. Maybe the modules were tested, discharge - charge cycled, and matched to similar ones, or not- nobody knows. Expect a couple years at most, some don't last a month without problems. Understand the warranty because you will probably need it.

Get a complete set of (hopefully good) modules from a later wrecked Prius and swap those in. Can be Gen2, Gen3, and some (non Li-ion) Gen4.

DIY repair- swap modules, clean or replace busbars and harnesses as needed. Cycle the pack with grid charger or hobby chargers- or not.
Use the search function as there are hundreds of posts covering this topic.

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I live in your state's capitol and looks like @SFO and others have answered most of your questions. Hit me up if you need parts or need more help?

 

Refurbished batteries are good for 3 months to 3 years depending on the quality of equipment the rebuilder has. GreenTec seems to be the most popular in western Washington. And a new OEM or Project Lithium upgrade pack may cost more up front, but you can go a decade without much concern, as in fix it and forget it. Of course you'd have to pull the trigger on this one in less than a week because after that they'll be out of stock till November: https://projectlithium.com/?ref=9qLPw And OEM packs are backordered indefinitely as well.

As for the fan, I have a spare one, but use it to run Prolong charger on packs that aren't in a car... If you pull it out and test it with 12v wires going directly to the plug socket that will confirm if it works or not.

As for your symptoms of engine reving and lack of power, this is just the car detecting the bad module and going into safe mode that shuts down the hybrid system and turns on the fan full blast, which is another way to test the fan.

Usually the first module you replace in a pack is the one that keeps the pack going the longest. Of course your pack will need reconditioning (aka: deep cycling ) to restore capacity too. Depending on how close you live from me, I may be able to help with a spare pack, but would have to build it. Or could repair yours...