Okay to run the AC at all times while driving?

[Candleflame]

Is it okay to run the AC at all times while driving? Even when it’s comfortable in the car, if I turn off the AC, it starts to get stuffy and the windows start to fog.

Is it bad for the car to constantly run the AC while driving?

Thanks

quite often the A/C is used to dry the air, not to cool it down. When I first switched to a car with automatic air conditioning I was wondering why even though the heating was on the AC would occasionally turn itself on too.

Living in the tropics I now understand - in the winter months I occasionally have the heating AND AC on at the same time as you otherwise get this really stuffy humid air coming from the heater.

 

[David99]

Related question: what is the 12V in the Model 3 used for? It’s not powering radio or AC so...?

It powers everything in the car except AC, heater and propulsion. The entire car electrical system is 12 Volt based like any other car. Fans, power steering, media, main computer, every light, power brakes, ABS, windows, power seats, all electric actuators, ...

 

[wdolson]

I guess I’m wondering if you just sat in the car for hours if it would run the radio etc until 12V depleted or if it uses HV battery to recharge 12V

I'm not sure, but I think it does periodically check the 12V battery and tops it up. I don't know about the Model 3 or the newest Model S/X, but the original Model S had a lead-acid 12V battery:
Syonyk's Project Blog: Tesla Model S 12V Battery Analysis

The good thing about a lead battery is it is less fussy than li-ion. It's fine being charged to 100% and sitting that way. It doesn't need any electronics to charge it properly. Tesla probably has some special, expensive part for the battery, but it's a pretty normal lead-acid battery like you'd find in any ICE.

 

[dgpcolorado]

I guess I’m wondering if you just sat in the car for hours if it would run the radio etc until 12V depleted or if it uses HV battery to recharge 12V

The 12 V battery is topped off from the main battery pack from time to time. However, Tesla is really hard on the 12 V battery because it is used for so many of the car's systems and the background electronics are always running to some degree, so it gets cycled a lot. My impression is that the Model S batteries need to be replaced every three to four years — in my climate I tend to get eight to nine years for a battery in an ICE car. Mobile service can do it, so a visit to a service center isn't required. For cars still in warranty 12 V battery replacement has been covered under warranty IME, although that could change I suppose.

When camping at an RV park I tend to charge the car while I am inside it using the screen, audio system or reading lights. That way the main contactor is closed so I figure that the 12 V battery can be topped off as needed and it might be less of strain on it.


It may be that the Model 3 has better control of the 12 V battery cycling and it will last longer. Too soon to say. Or, perhaps, they are using a different kind of 12 V battery than in the older models, although I haven't seen any reports of that.

 

[Trevor B]

I also turn off the AC a minute before I get home to air out the system and prevent any foul odors the next time I get in.

What foul odors? It's a brand new car ...

 

[David99]

What foul odors? It's a brand new car ...

I think that's the concern from the old days where ACs started to smell because when you stop the car, the condensor is still wet and the moisture will start to get moldy and you get that smell in the car. I had that in my cars sometimes 15-20 years ago but not with recent ones. I guess car manufacturers have found a way to prevent it.

 

[Tezlanian]

I think that's the concern from the old days where ACs started to smell because when you stop the car, the condensor is still wet and the moisture will start to get moldy and you get that smell in the car. I had that in my cars sometimes 15-20 years ago but not with recent ones. I guess car manufacturers have found a way to prevent it.

I've encountered it on newer cars. Not much you can do against mold on the evaporator coils if they don't get used often. You might be referring to the mold that develops in the ducts which is offset by always having some airflow regardless of what is on.

The 12 V battery is topped off from the main battery pack from time to time. However, Tesla is really hard on the 12 V battery because it is used for so many of the car's systems and the background electronics are always running to some degree, so it gets cycled a lot. My impression is that the Model S batteries need to be replaced every three to four years — in my climate I tend to get eight to nine years for a battery in an ICE car. Mobile service can do it, so a visit to a service center isn't required. For cars still in warranty 12 V battery replacement has been covered under warranty IME, although that could change I suppose.

When camping at an RV park I tend to charge the car while I am inside it using the screen, audio system or reading lights. That way the main contactor is closed so I figure that the 12 V battery can be topped off as needed and it might be less of strain on it.


It may be that the Model 3 has better control of the 12 V battery cycling and it will last longer. Too soon to say. Or, perhaps, they are using a different kind of 12 V battery than in the older models, although I haven't seen any reports of that.

They certainly have a need for an auxiliary unit without running the main pack but it seems strange they didn't just make their own cell (not necessarily even leadacid) if available car batteries were unsuitable.

 

[SoCalGuy]

Well I do remember Elon initially wanting the Model 3 to be without a 12V battery... but that went out the window early in design as did the HUD.

 

[dgpcolorado]

...They certainly have a need for an auxiliary unit without running the main pack but it seems strange they didn't just make their own cell (not necessarily even leadacid) if available car batteries were unsuitable.

Some people have put Li-ion 12 V batteries in EVs such as the LEAF. But they aren't practical for general use because they don't work in the cold — that's why the main battery pack is heated in very cold weather.

I would hope that Tesla could tweak the charging algorithm so that the 12 V batteries last longer but, perhaps, from Tesla's point of view 12 V batteries are cheap and replaceable. It may be that the Model 3 will be easier on the 12 V batteries than the Model S is.

 

[Tezlanian]

Some people have put Li-ion 12 V batteries in EVs such as the LEAF. But they aren't practical for general use because they don't work in the cold — that's why the main battery pack is heated in very cold weather.

Wasn't necessarily suggesting lion chemistry. I don't really know that much about battery chemistry but I recall the only advantages of lead acid is the slow discharge rate and high overcharge tolerance. Cells like NiCd and NiMH work in the same temperature ranges. Considering Tesla's top off the backup battery so often I am not sure that the discharge really matters much versus an ICE setup.

I would hope that Tesla could tweak the charging algorithm so that the 12 V batteries last longer but, perhaps, from Tesla's point of view 12 V batteries are cheap and replaceable. It may be that the Model 3 will be easier on the 12 V batteries than the Model S is.

They're still using a pretty high performance unit in the 3. Only time will tell how hard it is on it. Hopefully they have the battery warning implemented and it isn't an oversight missing from the 3 software. Might put in a garbage battery just to check

 

[Candleflame]

I think that's the concern from the old days where ACs started to smell because when you stop the car, the condensor is still wet and the moisture will start to get moldy and you get that smell in the car. I had that in my cars sometimes 15-20 years ago but not with recent ones. I guess car manufacturers have found a way to prevent it.

was quite happy to read this here as I have this issue in my car here in queensland. Obviously never been an issue in europe with our <7 days of aircon weather.

 

[SalisburySam]

OK to run your HVAC all the time? I've seen nothing explicit from Tesla that cautions any problem with that. I've had mine on since I got the vehicle in July, and it will likely not ever be turned off.

Coming from a 2012 Nissan LEAF with very restricted range coupled with an inefficient (non-heatpump) heater, the only time I turned off the HVAC in that vehicle was during cold weather when I needed every electron to get me to a destination. In other and previous ICE vehicles, I never turned the HVAC off but chose to take the hit to gas mileage instead.

Several posters mention the 12v battery as a possible concern. In the LEAF like the Model 3, the 12v powers almost everything except the vehicle traction motor(s), and I still have my original LEAF 12v battery working very well. I do use a battery tender frequently and I attribute my battery life partially to that device. The LEAF has lived in Ohio and North Carolina, fairly temperate environments so nothing like Hudson Bay or Phoenix. With the Model 3, I also expect to get a pretty long life, sufficiently so that I don't consider it in my HVAC usage.

Lastly, for my wife and me, comfort far outweighs other remote outcomes. The LEAF taught me to respect driving style and range awareness, and I've not forgotten those teachings with my Model 3. The 3 just gives me six times the range and its overall awesomeness.

 

[ngogas]

Run the AC... that is why it comes with it and that is why you have warranty.