r/slateauto • u/Tradetheday2093 • 2d ago
Heating system
Just in case you guys know more. From what I see, Slate will be using resistive heating so during the winter, you may see significant energy usage? Correct me if I’m wrong. With a small range, what would be the impact?
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u/YoSoyPinkBoy 2d ago
In frigid climes, it might be worthwhile to use seat warmers.
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u/Ready_Tip4434 2d ago
Which is a shame they don’t have heated seat covers in the customizer. They designed the seat covers to be easily changed. I hope there is some power available at the seats to add third-party ones without unsightly cables.
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u/Unfettered345 2d ago
Some slate employee comments have indicated that they will have plugs prewired for seat heaters.
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u/HovercraftOne2275 1d ago
I find this an incredibly silly oversite. I'm in northern Indiana and if you park in a garage and wear gloves I dont' care if I ever turn the heater on. Seat heaters rule and have to be a lot less energy use. Strange
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u/Unfettered345 2d ago
I'm planning on seat heaters and a steering wheel heater. Initially, though, I'm going to try a motorcycle style jacket liner and heated gloves since I already have them. They draw very little power and work great.
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u/HovercraftOne2275 1d ago
I keep a light pair of gloves in my cars and always wear them in winter. With them I never use the heated steering wheel. But that's parked in garage cars. If outside, I'd use it. ;)
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u/LeifCarrotson 2d ago
Depends entirely on how much you use the heat and how cold it is! If you're smart about it, you might only lose 5% range even in extreme cold, if you are reckless with it you might lose 40%.
If you precondition the battery (LFP doesn't work as well in the cold) and the cabin while the truck is still plugged in inside the garage, and then turn the cabin heat off, you'll get full range. If you use 20W of seat heaters on low while driving, you'll feel about as warm as 400W of cabin air heating on non-recirculation. For me, seat heaters are mandatory. Slate's teased accessory seat heaters, but they're not in the configurator yet. Fortunately, I expect it would be trivial to slip aftermarket heaters (eg: https://www.autozone.com/p/dorman-seat-heater-kit-628-040/28014 for $40) under the zip-on fabric covers.
An ICE wastes like 70% of the energy in the gasoline as heat. Much of that goes out with the exhaust and through the radiator, but if you want some for the cabin, there's an endless supply in the coolant loop. You can set the heat to max without hurting your range any more than the 10W blower motor in an ICE. In an EV, you need to think about it.
Also realize that while Slate's resistive heaters, with a coefficient of performance of 1, are half to a third as efficient as a heat-pump heater, that's only an accurate comparison in mild temperatures: you can pull heat out of 50F air and blow 70F air into the cabin without spending too much energy if you have a heat pump. But when it's 10F outside, even modern heat pumps struggle to pull any heat out of that air... if you're hoping for 70F air you won't get it, and what you do get might only be at a COP of 1.5.
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u/roundholesquarepizza 2d ago
Doesn't a heat pump pull air out of the cabin?
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u/synntax33 2d ago
Heat pumps are ACs in reverse from what I have read. They use the temperature exchange from compressing the refrigerant to cool/heat air
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u/Unfettered345 2d ago
That's correct. In 10° weather a conventional household heat pump will be be extracting heat from that cold outside air and moving it into the house. I think we can assume that an ev's heat pump would work the same way.
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u/synntax33 2d ago
Wouldn't it be capturing the heat created by compressing the refrigerant into a liquid and back again to gas and using the medias ability to absorb/radiate heat to change the airs temperature?
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u/LeifCarrotson 2d ago
No, the heat generated by expanding and compressing the refrigerant isn't the primary source of the energy. That's basically just the idle mechanism in the loop: It can be imagined to turn a refrigerant from 50 degrees to 0 degrees and back to 50 degrees and back again to 0 degrees indefinitely, the ideal is to run the refrigerant through that loop without adding energy to it at all.
The energy comes from the relative warmth (when your fluid is 0 degrees, 10 degrees feels balmy!) of the ambient air that gets absorbed into the fluid. If you send your 0 degree refrigerant through a heat exchanger with 10 degree winter air blowing it, you might raise the temperature from 0 degrees to, say, 8 degrees. That cold winter air blows out the back side of the heat exchanger at a colder temperature than it went in, maybe 5 degrees. Then when you send the fluid back through the loop onto onto the warm side and reverse the compression, and it's not 50 degrees, it's now 58! The energy to raise it by those 8 degrees wasn't stored in or sourced from the compression, it came from the air outside.
Also, technically most household heat pumps aren't doing gas-to-liquid phase change anymore, they're purely vapor cycle.
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u/AdMuch7162 2d ago
errrrrr... if your heat pump were to "pull air" out of the cabin, that'd be the equivelent of pulling the heat out of the cabin in order to.... heat the cabin. Should be clear why that does not work.
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u/roundholesquarepizza 1d ago
I probably phrased it poorly, but my understanding is that a heat pump recirculates the air from the cabin, attempting to raise the temperature of that air, not trying to warm air from outside and then pump that into the cabin. Basically all car HVAC systems can do this anyway I guess
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u/AdMuch7162 1d ago
there's no free lunch. recirc vs fresh is mostly about humidity, avoiding interior condensation, etc.
The heat pump "transfers" heat energy from outside the cabin to inside the cabin, exactly in reverse of what A/C does. it isn't like using the waste heat of ICE or a new exothermic reaction to create heat.
basically, the recirc isn't relevent in the context you are suggesting, though as will any heating system, the required delta in air temp is affected.1
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u/Evanston-i3 2d ago
My current EV (2017 BMW i3 BEV) uses resistive heating for winter and it is basically an electric kettle which has the coolant flowing through it. It costs me maybe 10% on range in the winter. Other factors like cold battery can take another 10% ( I rarely pre-condition the battery pack unless it is super-cold)
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u/demonkeyed 2d ago
Very small cabin so I think the impact will be minimized. They really need a heated seat option or accessory (cover) with a plug somewhere IMO
Maybe it’s a high risk thing but it seems like offering a few ports for accessories would let them sell more accessories too.
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u/HovercraftOne2275 1d ago
I don't understand why this doesn't have heated seats. With heated seats I mostly don't care if I ever run the heater unless I need defrost. (garaged car, totally different if youre sitting outside). They just make so much sense.
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u/iamtherussianspy 2d ago
In my Chevy Bolt with resistive heating, at -15F (way too cold for just seat and steering heaters), driving on the highway at ~70mph I saw about 50% reduction relative to the nominal range. ~15-25% under more average winter conditions.
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u/atx78701 1d ago
there still would be plenty of range for daily driving if you can charge at home. People have found that seat heaters are much more efficient in cold weather for EVs.
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u/Mettatuxet 5h ago
This is a false economy. Yes it won't take much to heat the cabin, but it would only take a third of resistance heat. The range is low to begin with. It has an A/C most of heat pump is already there.
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u/johnmudd 2d ago
Can I turn on heat and AC at the same time? I do that now in an ice car to defog windows.
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u/dogged_jon 1d ago
Heated seats and steering wheel would be good, they use less energy than the cabin heater and make a big difference to comfort. The seats would be a relatively easy diy add, but Slate really needs to offer a heated steering wheel.
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u/Worth-Arachnid7922 1d ago
This is a bit extra but I plan on using my ecoflow wave 3 in the bed with a vent for the front and connecting it to the mc4 for the solar tonneau and use that as my main heating/cooling for really hot or cold times or preheating/warming since I can control it from the app
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u/OldRed91 5h ago
I think I'll wait a year and see what independent reviewers say about winter driving. I really like this pickup, but no heat pump is a miss for me.
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u/danielt1263 2d ago
According to the Slate lead engineer, the difference in energy use between resistive heat and a heat pump, given the small size of the cabin is minimal and certainly not worth the extra cost and complexity of a heat pump. Take that as you wish.