AC always active when fan is on?

That's exactly how I'd expect it to work and how every other car I've ever had works. However, that is not what I'm experiencing in my 2023 Prime and doesn't seem to be what @Ronnie5 is experiencing. If you turn off "Auto" and turn the fan on, it will use both heat and AC to get the temp to the set point. The only way to stop AC and do pure ventilation is to toggle the AC on/off at which point the temp still shows on the "auto" section, but the AC isn't on and you get air at the ambient temperature.

At least it doesn't spew little chunks of ice out the vents like my 79 Corolla did.

 

They must've updated the environmental software; because I don't have to play with the AC button to get it to blow only outside air, on my 2021 prime. Auto off; fan on; adjust air output - vent, floor, defrost vents. As stated earlier; if outside air is cooler than set temp - heat pump will engage to warm the air, fast fresh air warm-up if engine is ON - NO AC function if button is OFF.

 

Speaking of heat pumps and such, does the Prime have a heat pump to heat/cool the battery as well as the people?

 

AFAIK , gen 4 heat and cools the battery by air provided from the cabin ( i.e the people) and assisted with 2 fans, for gen 5 it think it is liquid cooled .

 

Thanks. We are going to order a Prime soon and I'm wondering about the extreme heat we have here in summers now. We're on 54 days of 100º F or over so far and have plenty more coming. I figure cooling of the battery is essential in such a climate?

 

yes it is essential in your climate .

 

There is also a set of electric heat pads under each block of cells in the traction pack. The Gen 4 has options in the settings of the MID (on the left side of - and next to the speedometer in the Gen 5) for ON/OFF of both the traction pack heater and cooler.
It should be easy enough to tell if the Gen 5s traction pack is heated and or cooled by air or liquid. The air vents leading back to the traction pack in the Gen 4 are below the back seat just above the floor next to each back door and as soon as the back doors are open there would be to more vents each with a filter in it, in the plastic next to the back seat backrest just inside of the back doors at about waist height.
Or check the owners manual.

 

Only partially true. If you go into the center display and set it to ECO only, it will stay in ECO regardless of drive mode settings.

 

The gen5 Prime uses the heat pump to heat/cool the battery. I haven't checked to be totally sure, but I'm very confident that the car uses a single heat pump for both battery and HVAC; having two heat pumps would just lead to extra cost and weight.


edit: I'm going to walk that back just a tiny amount. The heat pump absolutely cools the battery, but I'm not 100% certain it also heats the battery. There's a separate electrical heating pad that does this. I don't know if the car's computer can use either system to heat or only the pad. I also believe the car can use the pad to heat the battery while the car is off(in order to start overnight charging in cold environments), but I don't know if the car can run the heat pump to cool the battery when the car is off. I'm not saying it can't, just that I don't have the answer.

Here are the refrigerant lines running back to the battery:



And here is the heating and cooling for the battery:
2. Cooling conductor bars
3. Cooler (refrigerant runs through the pipes)
1. Heater (electrically powered)

 

The heat pump is used to heat the cabin, along with heat from the engine coolant.

There are electric heater elements in the battery pack to heat the battery, same as the G4 plug-in.

The air conditioning compressor is used to cool the cabin and the battery - there is a liquid coolant path to the battery, instead of air vents from the cabin as in all previous Prius.

 

I'm fairly sure KMO already knows this, but in case other people have never dealt with these things before, air conditioning and heat pumps are basically the same thing.

The difference:
An air conditioner compressor can only move heat in one direction, while the term heat pump in the US is typically used to describe a compressor that can reverse directions to provide both heat and cold. Either collecting heat from the environment and moving it into the cabin(heating mode), or collecting heat from the cabin and moving it out to the environment(A/C mode).

So when I say the heat pump is cooling the battery, and KMO says the A/C compressor is cooling the battery, we're both saying the same thing. We're using different terms for the same device on the car.

 

For the heatpad , in gen 4 , it had to be activated in the menu AND it only works when the car is plugged in between 34degF and 38 deg F if i recall correctly. (temperature sensed on the pack itself)

 

Actually, I was getting a bit muddled. Yes, it's all one system with a lot of valves to control flow, and I was thinking of it as two.

But as you edited, it doesn't rely on the heat pump to heat the battery - the heat pump can't supply heat below -10°C, so it must have another mechanism for really low temperatures. Starting the engine is the other mechanism for the cabin, and the electric elements are the other mechanism for the battery.

And then it's easier to have the electric elements just do the whole job.

 

My understanding is what you were enabling in the menu was permission to use the electric heater while plugged in - cos it could be costing you money. (Or just confusing the charge station).

Once you're running, it can freely use the electric heater.

 

Well I had in mind charging at home , and the pad consumes around 200 Watts. A small price to keep the traction battery happy when the temperature goes down into minus territory .And the added bonus , while the car is plugged,it is also charging via the DC to DC converter in the charger, the 12V battery since the pad is fed by the 12V battery . Like you say the function must be activated for this to happen,and the battery pack is at the proper temp to turn on.

 

The cooling system is like the one in the Rav4 Prime, which might be easier to find descriptions of.

 

When I turn the car on the AC always defaults to the off position. I have the temp set for 67 and when starting the car I forget to turn the AC on. After 5 minutes I am cold and the is AC off. I don't need to turn it on. Why is this? Something is wired incorrectly.

 

Nothing is wired incorrectly. It's described in this thread and others, but there have been slight changes to the way the HVAC system displays its status compared to how it was done in the past.

Previously, when you placed the HVAC into auto, the display would show you what it was doing. Outside air vs. recirculate, fan speed, which vents were being used, etc. With the new philosophy, having HVAC in auto means about the only thing displayed is the temp setting. The idea seems to be, "If you placed the system in auto, did you really want to see exactly what the whole system is doing, or did you just want the car to do all the work behind the scenes?"

In the default settings, this includes the A/C. The HVAC doesn't tell you when it's off or on, it just does whatever it needs to do to keep the cabin at the set temp. If the owner doesn't like the car being in control of the A/C, there's a setting called something like either 'AUTO on A/C' or 'A/C on AUTO. It's enabled by default, but you can disable the option if you wish. Once disabled, the A/C functions just like previous models, and the A/C light shows whether the system is on or off.

 

Screw the AUTO, ECO, AC, FAN settings! Just roll down the windows.

 

What is the outside air temp?
On the gen 4; if outside temp is lower than set point - it would automatically warm the incoming air.
Since the gen 5 was probably sending a cooling stream to the battery pack; while charging. I wouldn't be surprised there's some residual left in the system.

Just playing "what if's"