Sluggish Acceleration/Bad gas Mileage

It’s best to download Dr Prius and get one of their recommended obd. You really need to be able to see what’s actually going on with your battery. You won’t know any positive gains from cleaning the fan for at least another few hundred miles.

 

@ASRDogman Good idea on the ac filter material. I might try that too.

 

You'll notice NO gain whatsoever from cleaning the hybrid fan.
Unless it was completely clogged. And if so, the cells are probably covered with the same crud.
So you would have to remove the top cover of the battery housing and clean that out also.

 

You are likely experiencing normal Hybrid System behavior in intense heat (100°F+) due to a combination of the intense heat itself, AC Usage, and possibly a hot Hybrid Battery. These factors all compound one another.

The AC alone is a massive draw on the High Voltage system. If AC is maxed out, it can draw more than 3,000 Watts (4+ horsepower) of Power from the Hybrid Battery/Hybrid System. This will rapidly drain the Hybrid Battery at City Speeds, causing the Combustion Engine to turn on and generate High Voltage Power via MG1 to charge the Hybrid Battery and also force the Engine to supply Torque to drive the wheels that normally would be supplied by the Hybrid Battery and Electric Motor... So it's a Double Triple Whammy Effect... The Combustion Engine is forced to supply all the power to the wheels... While also generating power for the AC... While also supplying power to keep the Hybrid Battery above it's minimal voltage... Resulting in massive power and mpg loss as Electric Motor/Hybrid Battery Power is only reserved for "flooring it' in this condition.

At Highway Speeds, the Combustion Engine will work harder by supplying an extra 3,000 Watts of power to maintain the Hybrid Battery at 60%. Since the AC is putting an extra 3,000 Watt load on the Hybrid System, the engine needs to generate this via MG1 to keep the Hybrid Battery at a stable 60% while simultaneously driving the wheels down the road. So the engine will be generating 4 more horsepower than it normally would at all times during the highway commute, causing more gas consumption.

A Hot Hybrid Battery can compound this even further... as when the Hybrid Battery gets above 125°F Charge going in and out becomes fairly restricted.

Above 130°F Charge becomes severely restricted.

Above 133°F Charge becomes even more restricted and the Hybrid Battery fan kick on to high (you'll hear it screaming)

Between 133°F and 140°F, charge going in and out of the Hybrid Battery is virtually stopped. You will also notice severe hanging revs from the Combustion Engine at this point as the Prius begins to utilize the combustion engine for all power output and takes drastic measures to avoid drawing on the Hybrid Battery at all costs... AC use makes this effect even worse.

Above 140°F, this gets into overheating territory.

I believe your Prius is functioning completely normally... it's mainly just a combination of the heat and AC use causing your strange Hybrid System behavior.​

You can see in this Youtube link, the hanging revs im talking about:

 

When you put the hybrid safety plug back in, you have to insert it, close the tab, and then slide the plug to where it clicks in place. Sliding it finishes the circuit.