[PLP]

Or could it be in regards to heat load? For example, in the -5C scenario, does it try to warm up the coolant further to transfer more heat to cabin air if you switch from recirc to external? What about if you crack open the windows for a while?

Hmm. That's not good, I wonder if it might be possible to add a barrier between that part of the powertrain compartment and the rest of the vehicle.

Heck, it may simply be that you'll get significant improvement by doing what some diesel truck drivers do in extreme cold weather - block off the radiator to reduce airflow through the engine compartment. Just don't forget to remove it when it starts getting warmer!!!!

The radiator has flaps that close. Nothing more can be done.

Maybe the heat load does something.
Problem is I have no clue - I cannot hear any change - when it is in recirc or fresh air mode. I tried manually switch it and either it is so quiet or... does not work
I did not try to crack a window, though.

A forum member did a pretty good job of it.

Yes, I saw it a while ago.
And while it works, it just looks... bad.
I am beyond the "half ass solution" stage in my life.
When I do it - I do it once and good. Duct tape? Some pieces flying here and there? No, not really.


There is still a part of me that is thinking - is the whole ordeal worth it?
Let's look on it.
From my driving in winter, about 20-25% goes to heating.
Just for the math itself assume I did 120 miles on average 2.0 miles/kWh. Very cold period.
I used 60 kWh, 25% heat, 15% battery. That means: 36/15/9 kWh for driving/climate/battery respectively.
Theoretically it means I drive at 3.3 miles/kWh - about right: winter tires, snow...

Now, insulation would drop what? 10% of the total heat? I mean, how much is actually lost there? Heck, lets assume even 20% which is VERY generous in my opinion.
New numbers are like this: 36/12/9 kWh for the total of 57 kWh.
Now I can drive extra 6 miles and my 2.0 becomes 2.1 average. I guess it is pointless...


It will NOT resolve a heat delivery delay. It will not resolve overall heat loss due to parked car.
In order to warm up the 2 liters of water (glycol needs less energy, has lower specific heat or heat capacity if you will) you need theoretically 90 Wh of energy. That is from 10 C to 50 C
Based on my measurements it takes about 3 minutes, short of 1 mile ride at full power of 7.5 kW.
It means that all the pieces around need heat as well. Pump, tank, heater, pipes...
That gives a total of 375 Wh.

Each time you park or drive a short distance, all the 375 Wh is lost.
No insulation will help. I mean, insulation will slow it down... but after 8 hours at work - it makes no difference.

Make it 5 trips (days), 10 total of cycles - you just lost 3.75 kWh just there.
That is what makes this system inefficient.

PTC heater does not have this problem.

 

[Entropy512]

Looking at that setup (and I'll take a closer look at my car when I get back), all of the parts of the heater system seem to be separate enough from everything else that you could just put bulkheads separating those components from the rest of the compartment rather than insulate the components themselves. Biggest issue (would need to look more closely) would be potential heat loss through the sheet metal on the side.

As to the frequent-short-trips-cycling issue - yeah, a problem, but not the one the OP appears to be trying to solve as he drives throughout the day. After all, don't forget that in addition to that glycol, you also have to warm up the battery if it's brutally cold, and its thermal mass is WAAAAY beyond the HVAC system.

I'm pretty sure Tesla went the glycol way too?

 

[GJETSON]

I'm pretty sure Tesla went the glycol way too?

Yes. They use the motor for their "tankless heater", deliberately running it inefficiently to generate more heat.

 

[Entropy512]

Yes. They use the motor for their "tankless heater", deliberately running it inefficiently to generate more heat.

Yup, although for the most part probably only a minor improvement over a standalone PTC - most notably that at lower power levels you can use the motor's base inefficiency, but that's likely insignificant at cruising speeds.

Let's say the motor system is, at best, 95% efficient (I think Tesla is actually better than this, I need to check but calculations for the Bolt compared with some of my past driving data imply even the Bolt is at 97+). So if you're cruising the highway at around 15 kW (and you're likely actually below this unless 70+ MPH, at which point aerodynamic drag starts dominating your efficiency), then you've got only 750W of waste heat.

The big thing for Tesla now is the heat pump. I know there were some analysis that claimed we weren't missing out on much, but the behavior of the Bolt when trying to defog makes me think otherwise - yes, heat pumps don't perform as well when pumping against brutal cold. But that ignores that they have a secondary function in cold weather - dehumidification, which if the system is configured correctly, allows the system to recirculate the majority of air without fogging.

As that Reddit thread I linked mentioned, there appear to be some federal laws regarding some minimal amount of outside air, but Tesla may have designed their system such that outgoing air goes over the evaporator and incoming air over the condenser, effectively making a heatpump-augmented HRV setup.

If there are any true game-changers to be had for Bolt climate control, it would be some form of HRV augment and/or a dehumidifier augment.

 

[TFPDrive]

ut that ignores that they have a secondary function in cold weather - dehumidification, which if the system is configured correctly, allows the system to recirculate the majority of air without fogging.

But the reason the AC dehumidifies is because it chills the air and causes water to condense and drain out. If the cold side of the heat pump is on the exterior, how is that going to dehumidify the interior air?

 

[GJETSON]

Ummm.

 

[GJETSON]

But the reason the AC dehumidifies is because it chills the air and causes water to condense and drain out. If the cold side of the heat pump is on the exterior, how is that going to dehumidify the interior air?

I don't think they can have the outgoing air blow over the evaporator. That would dehumidify the the air on its way out of the car, doing nothing for dehumidification inside. But I do think they could use the evaporator on the incoming air, as the Bolt does, but reduce the heat loss by pulling the incoming air over the condenser on the way in.

 

[Entropy512]

If the cold side of the heat pump is on the exterior

They don't. Air passes over the evaporator, water condenses, then air passes over the condenser and warms up. Tesla calls it "COP=1" mode (there was a post on InsideEVs a few months ago talking about it)

The whole point of the "octovalve" was to be able to connect either the evaporator OR the condenser OR both to the interior. (Well, not directly, via glycol loops for both.)

Run interior recirc air over both the evaporator and the condenser (or separate glycol loops connected to each) and it becomes a dehumidifier - and a side effect of them is that they heat the air going through them. Win/win in this case.

A 500W dehumidifier in addition to what we already have would be a game-changer for the Bolt - enough to prevent fogging in most use cases would be my guess, allowing full recirc to be used almost all the time. Unfortunately it seems like 12v phase change dehumidifiers don't exist, AC ones are huge, and all of the Peltier ones are poorly designed low-power (50w or less) units that are unlikely to be anywhere close to sufficient.

300W of Peltiers arranged in a counterflow setup like US4065936A - Counter-flow thermoelectric heat pump with discrete sections - Google Patents would be interesting - either just loop the cold output back to the hot side, or find a place in the Bolt where you can expel cabin air over the cold side to the exterior and intake outside air over the hot, creating a Peltier-augmented HRV. Optionally doing some tricks involving more Peltiers in a 2S3P or 3S3P arrangement to get better COP might be beneficial (TBD) - COP isn't super-important for this use case, but may allow improved moister removal rates for a given amount of input wattage and/or significantly more air exchanged in an HRV implementation. (remember, 300W of Peltier input will not only add 300W of heat to the vehicle, but also move 300+W of heat from input to output depending on how hard they're run and the temperature differential from hot to cold, and in an HRV application, the temp differential should be very low.)

 

[OneEV]

127 + 2.9 x 16 (44+16=60kWh battery) 46.4 = 173 Miles Outside Temp was 15-20


I made a total of 30 stops picking/dropping off passengers, cold air constantly coming in and the PTC heater did great ..at one point I measured a high vent temp of 94 degrees! I'm going to need to put a temp controller on it as it is going to get too hot (when we get into the mid 20's low 30s)inside the car (I can just power it off and on) but it would be nice to have it regulated at 78 or so.



If I didn't have the passengers I could have maintained 3.5 mile kWh but sitting and waiting for passengers cuts into range as well. But thats ok... 170 Miles on a 17-degree day running uber/Lyft., I'll take it. (I was out for 5 hours)

127 + 2.9 x 16 (44+16=60kWh battery) 46.4 = 173 Miles

 

[phuber]

What guage wire did you use to connect your inverter to the battery? I found that my pure sine wave inverter required too much from the battery and would shut down due to low voltage on the AGM battery. I remember reading that the pure sine wave inverters are not as efficient resulting in the greater draw on the AGM battery. I have ordered the same inverter as you use and plan to mount it in the cabin this time in order to capture the heat it generates. Also, did you leave the 1/4-inch gap between the heater and the board?

 

[OneEV]

What guage wire did you use to connect your inverter to the battery? I found that my pure sine wave inverter required too much from the battery and would shut down due to low voltage on the AGM battery. I remember reading that the pure sine wave inverters are not as efficient resulting in the greater draw on the AGM battery. I have ordered the same inverter as you use and plan to mount it in the cabin this time in order to capture the heat it generates. Also, did you leave the 1/4-inch gap between the heater and the board?

Morning Phuber
Yeah! I'll have someone to suppport what I am saying !

You'll be happy with the results ..

1. Not positive..they come with the inverter

2.Remember that Mounting in-cabin means longer cables to the battery = less efficiency

3. Basically just leave 1/8 -1/4 gap all around the heater and board ...that allows some cold dry outside air to by pass the heater and helps with defogging. Small gap


Very simple project.. the hardest part is cutting a whole through the rubber "grommet" in the firewall

When wil your parts arrive?

Keep us posted..

 

[Fivedoor]

Can I be skeptical here?

Show me energy used, miles, and the pie chart after driving 40-50 kWh of the battery. Then I will make my own decision if it really works.
I learnt one valuable lesson years ago - trust, but verify.

Any way to slide it somewhere near the heater core so that you are actually not warming it up? You see, the heater core is filled with cold liquid. In your case it will be a few degrees higher than ambient, so your initial hot air will be used to warm up the heater core. Then, without your approval, the coolant will start flowing freely in the system loosing all heat to the ambient. While it will not flow through the pump, it will use convection inside the about 1/2" tubing. Wide enough to create two layers of liquid and transfer the heat outside.

The difference is, he isn't trying to sell you anything or get nuclear disarmament... believe it or not as you like, I doubt if he cares that much.

Keith

 

[GJETSON]

2.Remember that Mounting in-cabin means longer cables to the battery = less efficiency

Yup. Running from the battery at 12 volt vs 120 volts for the invert means running those cables at ten times the amps. A guaranteed loss.

 

[phuber]

The inverter should arrive on Tuesday along with 4 AWG wire which I hope will transfer the power it needs to work correctly.

 

[Tyrelirwin]

The inverter should arrive on Tuesday along with 4 AWG wire which I hope will transfer the power it needs to work correctly.

It will be interesting to see how you route that much heavy gauge wire. I used 6 AWG when wiring my garage for 240, and it almost broke my spirit!

 

[phuber]

I'll report in about how it works. I plan to drill a hole through the large grommet on the driver's side.

 

[OneEV]

I'll report in about how it works. I plan to drill a hole through the large grommet on the driver's side.

Yeah it's a weird rubber ...not easy to drill.


Today at 28 Degrees I had 90+ air coming out..recirc on , fan @ 2


This is the type of weather 28F (the only thing that would have been better is if the sun was out..solar radiation ) that it really works great at because you are totally warm and extra range is really impressive. You won't need to pulse the car's heater at all .

 

[PLP]

believe it or not as you like, I doubt if he cares that much.

Keith

Keith,
it is not about believing. If one says - hey guys, I got a system that can increase your range by 30 miles in winter - I am like, heck I would love that.
It is about dry facts and evidence.
Whether I like it or not - that is not the point. I will make my decision based on numbers.

 

[OneEV]

Keith,
it is not about believing. If one says - hey guys, I got a system that can increase your range by 30 miles in winter - I am like, heck I would love that.
It is about dry facts and evidence.
Whether I like it or not - that is not the point. I will make my decision based on numbers.

You have the facts...you're just trolling now

 

[PLP]

You have the facts...you're just trolling now

Man, you showed so many screenshots, numbers, options (where some contradict each other) that I am not sure which one is right and the most current and actually what refers to what. And whatever data is there - is scarce.
I still cannot figure out how at 19 F outside you do not spend any time on battery conditioning.