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This is a good thread-starter/post because it puts the Bolt's 'slow' 55kW DCFC in context. IOW, at one point in time not all that long ago, 55kW DCFC was perfectly acceptable.

Of course, time marches on, and now it's considered the Bolt's Achilles Heel relative to the advent of much faster DCFC stations and capability of other, newer BEVs. The silver lining is that any bad publicity the Bolt might receive over this apparent detriment can lower Bolt demand/increase supply/lower the price for the savvy BEV shopper.

As it is, the Bolt is a pretty **** good deal right now with the return of full $7500 federal tax credit eligibility, particularly if DCFC is not all the necessary for the owner's needs.
In my travels throughout New Jersey and New York, I don't think I've ever used a DC fast charger that could max out at more than 75 kW or so. For all this talk about 350 kW DC charging, there aren't really all that many dispensers out there that are even available for drivers that exceed 55 kW -- other the the usual Tesla superchargers. So, the 55 kW max for the Bolt isn't really all that big of an issue.
 
Discussion starter · #42 ·
If there's no valve for the cabin refrigerant loop, are you introducing latent heat from the cabin into the battery loop and then your confusion between the cabin and battery conditioning would still exist?
If there was a valve to cut off the evaporator from the AC loop, the chiller wouldn't work at all. An AC loop requires a condenser, and an evaporator to function. It doesn't require the battery chiller, which is just a heat exchanger block with the AC line in one side, and the battery coolant line in the other side.

 
In my travels throughout New Jersey and New York, I don't think I've ever used a DC fast charger that could max out at more than 75 kW or so. For all this talk about 350 kW DC charging, there aren't really all that many dispensers out there that are even available for drivers that exceed 55 kW -- other the the usual Tesla superchargers. So, the 55 kW max for the Bolt isn't really all that big of an issue.
(excluding Tesla Supercharger)
I'm guessing that's a regional or network provider-specific thing. I'm in the SF Bay Area.

I've never seen a single Electrify America site that had below 150 kW DC FCs. I'm not aware of EA installing ANY DC FCs with <150 kW anywhere in the US. The sites with 350 kW DC FCs are definitely more limited.

Within a 6 mile drive of home, I can think of 3 EA sites, all with 150 kW DC FCs. If I expand it to maybe 11 miles, that adds on 4 more, 1 being EVgo.

There were 2 50 kW EVgo DC FCs <6 miles from home but they were removed, leaving no public charging there at all.

For non-EA CCS providers, ones with even 75 kW or more DC FCs is limited.

If you've ever used Electrify America to DC FC, you used at least a 150 kW DC FC.
 
(excluding Tesla Supercharger)
I'm guessing that's a regional or network provider-specific thing. I'm in the SF Bay Area.

I've never seen a single Electrify America site that had below 150 kW DC FCs. I'm not aware of EA installing ANY DC FCs with <150 kW anywhere in the US. The sites with 350 kW DC FCs are definitely more limited.

Within a 6 mile drive of home, I can think of 3 EA sites, all with 150 kW DC FCs. If I expand it to maybe 11 miles, that adds on 4 more, 1 being EVgo.

There were 2 50 kW EVgo DC FCs <6 miles from home but they were removed, leaving no public charging there at all.

For non-EA CCS providers, ones with even 75 kW or more DC FCs is limited.

If you've ever used Electrify America to DC FC, you used at least a 150 kW DC FC.
Wouldn't it be fascinating to learn that when some (if not all) of the big DCFC players replaced their lower-power stations with higher-power units in higher demand areas (i.e., SoCal), they reused and relocated the lo-po stations to other parts of the country for initial installations?
 
(excluding Tesla Supercharger)
I'm guessing that's a regional or network provider-specific thing. I'm in the SF Bay Area.

I've never seen a single Electrify America site that had below 150 kW DC FCs. I'm not aware of EA installing ANY DC FCs with <150 kW anywhere in the US. The sites with 350 kW DC FCs are definitely more limited.

Within a 6 mile drive of home, I can think of 3 EA sites, all with 150 kW DC FCs. If I expand it to maybe 11 miles, that adds on 4 more, 1 being EVgo.

There were 2 50 kW EVgo DC FCs <6 miles from home but they were removed, leaving no public charging there at all.

For non-EA CCS providers, ones with even 75 kW or more DC FCs is limited.

If you've ever used Electrify America to DC FC, you used at least a 150 kW DC FC.
I’ve actually never used an Electrify America dispenser. Those aren’t situated anywhere near where I’ve driven. California has a much more well-developed charging infrastructure than other areas of the nation.

I’ve used EVGo, Chargepoint, Volta, and EVConnect fast charging. The highest rated dispensers I’ve used say 200 kW on the machine, but due to the cables they used max out at 74 kW. I know this is the max because that’s what even Rivians were getting with these dispensers. Those are the EVGo chargers near my house.

There are a lot of EVs in New Jersey, but our state didn’t invest in infrastructure like California did, so we’re far behind when it comes to charging.
 
@GJETSON Since there was no prior response, I'll provide the conclusion. There's no valve isolating the cabin refrigerant loop from the battery loop in a Bolt. You are introducing latent heat from the cabin into the battery loop and your confusion between the cabin and battery conditioning still exists. This is especially true when the cabin fan is engaged to move cabin-air heat across the evaporator.
 
@GJETSON Since there was no prior response, I'll provide the conclusion. There's no valve isolating the cabin refrigerant loop from the battery loop in a Bolt. You are introducing latent heat from the cabin into the battery loop and your confusion between the cabin and battery conditioning still exists. This is especially true when the cabin fan is engaged to move cabin-air heat across the evaporator.
Actually, it's been discussed in many previous threads. But it's always worth referring questions to the expert: Dr. Kelly at WeberAuto.

Edit: the only real difference between the older and newer ones is that the lower drivetrain cooling is no longer there in the newer (22+) models.
 
Discussion starter · #49 ·
@GJETSON Since there was no prior response, I'll provide the conclusion. There's no valve isolating the cabin refrigerant loop from the battery loop in a Bolt. You are introducing latent heat from the cabin into the battery loop and your confusion between the cabin and battery conditioning still exists. This is especially true when the cabin fan is engaged to move cabin-air heat across the evaporator.
The confusion I was referring to was that if I had the AC turned on, there would be no way to know if the battery system had requested continued cooling, not how effective it is.

So you are suggesting that GM spend the money to have two separate refrigerant loops? This would require an additional evaporator and extra valving, at a minimum. This is the same company removing map pockets, rear door buttons, and motor/gearbox cooling to save a buck.

I am sure all these compromises will be addressed in the Ultium system. ;)
 
@usedBolt Agreed. However, drivetrain cooling has nothing to do with the refrigerant loop.

@GJETSON Ah. I now see what you were trying to achieve. However, running the cabin fan also extended the battery conditioning.

I'm still confused by your 2 earlier posts though. Why do you believe that single a valve to isolate the cabin-loop from the battery-loop requires another evaporator (at a minimum) and you also implied that currently there is not already 2 evaporators in the AC loop? A single valve between the existing cabin-loop and battery-loop is all that would be needed. I totally agree with your assessment of GM cost savings though.

As an example, with the OEM design, if the battery is being cooled the cabin will also be cooled. That may not be wanted and adversely, cabin heating may then be needed. In any case, with the cabin in the loop, battery conditioning will be extended. The same can be said for cabin dehumidification in the winter while the battery is being heated.
 
Discussion starter · #51 · (Edited)
@usedBolt
Why do you believe that single a valve to isolate the cabin-loop from the battery-loop requires another evaporator (at a minimum)

you also implied that currently there is not already 2 evaporators in the AC loop?
You may be an AC expert. I certainly am not. But google says, "The condenser coil releases heat to the outside air, while the evaporator coil absorbs heat."

It does appear that Tesla has valves to cut the cabin evaporator out of the loop.

 
Discussion starter · #52 ·
Sorry for thinking out loud here. I had assumed that the temperature difference, which is necessary for the refrigerant to absorb heat from the battery coolant, required the liquid to vaporize. And that required a space with greater volume. Are the high pressure lines the same size as the low pressure lines? Is the pressure difference just created by the compressor pulling in refrigerant? There is no expansion chamber/evaporator? needed? AC experts?
 
From what I have been able to find, the Bolt has two evaporators: one for cabin cooling and one for battery cooling.

I don't know for sure, but I would suspect that there are one or two valves to control the refrigerant flow into these evaporators.
 
Discussion starter · #54 ·
From what I have been able to find, the Bolt has two evaporators: one for cabin cooling and one for battery cooling.

I don't know for sure, but I would suspect that there are one or two valves to control the refrigerant flow into these evaporators.
It has a traditional refrigerant-to-air evaporator in the cabin, for the cabin. It also has a chiller, which I have come to understand is a refrigerant-to-coolant evaporator for the battery coolant loop. These two are in series, with no cutout valves. They both run any time the compressor is on, which is a pathetic design, but cheap.
 
It has a traditional refrigerant-to-air evaporator in the cabin, for the cabin. It also has a chiller, which I have come to understand is a refrigerant-to-coolant evaporator for the battery coolant loop. These two are in series, with no cutout valves. They both run any time the compressor is on, which is a pathetic design, but cheap.
It's also consistent with a "reheat" HVAC system, which GM started using back in the 1960s. The a/c is always on if HVAC is on, with heat added from the heater core to adjust temperature.
 
It has a traditional refrigerant-to-air evaporator in the cabin, for the cabin. It also has a chiller, which I have come to understand is a refrigerant-to-coolant evaporator for the battery coolant loop. These two are in series, with no cutout valves. They both run any time the compressor is on, which is a pathetic design, but cheap.
It does seem odd to me. But, I suppose that "simpler is better" can be applied here.
 
This is the same company removing map pockets, rear door buttons, and motor/gearbox cooling to save a buck.
And to pass that savings onto the consumer. We paid $25k for a loaded 2021 Bolt EV LT, with no tax credits or rebates. Just a straight up $15k off MSRP. And then GM dropped the MSRP two years in a row.

Thank You GM for removing features I can live without, in exchange for a lower price!

The motor/gearbox cooling was retained on our EUV. It was only dropped on the lighter EV. I suspect it was considered overkill, but I guess time will tell.
 
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