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... there is an insulating pad between the heat transfer plate and the bottom case. It's pretty minimal to be sure, but it's clear that there is no direct conductive or radiative heat transfer from the battery case to the batteries themselves.
Uh, d'oh! I did watch the video but must have dozed off during that period. The first eentsy-weentsy bit of insulation will be a boon. Yay!

"Never mind." :D
 

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Considering GM made the Bolt for the US, Korea, and other countries, I doubt they left off battery insulation thinking of only mild west coast climate use.
Korea can indeed be cold, but not quite as cold as ND, and it has some pretty serious mountains, but they aren't the Rockies. Also, Korea is highly urbanized. Picture yourself the combined population of the US West Coast (51M) living in a compact, NC-size (40K sq. mi.) country. Throw in the higher gas prices and the denser DCFC network, and the proposition of a 120-150 mi only winter range becomes even more reasonable for many Korean drivers.

Or, GM had other priorities in 2012, when the started working on the Bolt.

Superficially it may seem odd that people would give up on commuting but then some DC area commutes are flat insane-- a road trip, every day. Plus, there's no room for mystery or being inert by the side of the road in daily life. That kind of risk-aversion isn't too surprising when I think about it.
That's exactly right. The usual argument for the utility of the short range plug-ins "An average US commute is 31 miles" is somewhat like the "average temperature of the patients in the hospital is 98F". I would say, at least 50% commutes into DC and Northern Virginia are 80 mi round trip or better … in winter the safety cushion is already slim, and if you have sit for an extra hour in a heavy traffic, eating 3-4 kWh to heat the cabin .... uh-oh. There are a few DCFC's, but you may need 10-20 minutes to navigate to one, sometimes 10 minutes to get the machine going, and then 30 minutes to add 25 kWh … that's too much for someone who's been up since 5AM to get to work by 7AM.
 

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Korea can indeed be cold, but not quite as cold as ND, and it has some pretty serious mountains, but they aren't the Rockies. Also, Korea is highly urbanized. Picture yourself the combined population of the US West Coast (51M) living in a compact, NC-size (40K sq. mi.) country. Throw in the higher gas prices and the denser DCFC network, and the proposition of a 120-150 mi only winter range becomes even more reasonable for many Korean drivers.

Or, GM had other priorities in 2012, when the started working on the Bolt.
GM made the Bolt and intended it to be sold nation wide, when they started this project. Regardless of the Korean or
other countries. The Bolt was designed for all climates we encounter here in the US.
 

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A few thoughts:

-as was pointed out by Bolterado, there already is insulation on the bottom between the cooling/heating plate and the battery pan

-Over the holidays, I got to drive the same 300km route five times. On one of those trips the outside temp was just below freezing. Using Torque Pro I watched the battery temperature throughout the drive and during a brief DCFC stop (splash and dash?). There are a few different battery temp sensors and I'll use the highest, but the trend was the same for them all. Preconditioning turned on the battery heater and brought the temp up to somewhere around 15C. Driving at 100 km/h for two hours caused the battery temp to increase to about 20C. The battery heater didn't come on. The charge stop brought the temp up to 24C, again no battery heater. What I gather from this is that around freezing keeping the battery warm while you drive isn't a problem. Maybe it is when ambient is -25C. I'll probably get to find out if we get a cold snap.

-I too have noticed that even when fully charged, the car periodically sips power in cold weather, presumably to keep the battery warm. The colder it is, the more frequently it takes a sip. As our car often sits for days without use, this represents a large portion of the car's total consumption. When it's warmer outside, maybe above 10C, it doesn't do this at all.
 

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It would be terrific to have a PID or whatever for internal resistance dissipation in the battery. It should be possible to get close to a decent number working from stated capacity, external dissipation but remembering to gather that info at the right time is a bit tough.

The battery is a fascinating thermodynamic topic-- more data in general would be nice.

JPT: I too have noticed that even when fully charged, the car periodically sips power in cold weather, presumably to keep the battery warm. The colder it is, the more frequently it takes a sip. As our car often sits for days without use, this represents a large portion of the car's total consumption.

I think this will become a focus of engineering effort (really just small a fist-full of dollars) as the overall hit from this increases w/EV population. After this thread started I've been bothering to look at the display showing battery happiness consumption and indeed as Camano and others have mentioned, it's more often and more lengthy than when I last looked. It's the kind of thing that bugs engineers extra much because it's such an easy lift to improve.
 

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Insulation of heater and coolant loops.

This thread reminds me the insulation job on my 2012 Mitsubishi iMiEV. It was not about battery insulation but rather PTC heater and the pipes. The insulation made a big difference.
Similar to iMiEV, the Bolt's heater is un-insulated. Unlike iMiEV, the labyrinth of pipes in Bolt is so much more complex.
I have used various materials for Bolt heating system insulation. The PTC is padded with polystyrene foam and self-adhesive tape from another plastic, covered with aluminum foil (Home Depot). The pipes are covered with Armacell foam and the coolant reservoir - don't laugh - covered with wool sock.

How much energy am I saving? Well, if you can help me measure it, that would be appreciated. I am in NJ and the heating is not used much. It must be below 40F outside for me to start thinking about it. And, if I am alone in the car, it is always off, only to manage window defogging. So OK, seriously, if I were in ND or Manitoba, how big of an impact would it make?
 

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The radiant calculation is relatively easy, StanJ. Get rough dimensions of the tubing, heater block etc., derive area from those. W/IR thermometer, measure temperature of block, tubing, other significant exposed bits. Measure temperature of what those objects are "seeing," (what's in line of sight of the objects) then apply Stefan-Boltzmann equation (which is quite a simple expression). Radiation will be a bit more significant here than for lesser cases like the battery, because of the large difference in temperatures between what's radiating on the high side and what's re-radiating on the low side.

It's figuring the loss via conduction/convection that is hard. A calorimetric rough-in is somewhat possible but only if one knows the flow rate of the liquids.

It would be interesting to know to what extent the subcontractors who produce the heating system model these things, versus just "let's put a honking high-rate resistor in there and call it good."
 

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-I too have noticed that even when fully charged, the car periodically sips power in cold weather, presumably to keep the battery warm. The colder it is, the more frequently it takes a sip. As our car often sits for days without use, this represents a large portion of the car's total consumption. When it's warmer outside, maybe above 10C, it doesn't do this at all.
If your car sits for days without being used, AND you know 30 minutes to an hour or so in advance that you are going to leave, AND you don't need more than 100 miles of range in the winter ...

you can save a lot of energy by filling it up to about 60% SoC and just leaving it unplugged until an hour or so before you want to leave. Then you plug it in, and "remote start", which will start the battery heater and will put some electricity into the car. When the "remote start" times out it will continue to charge (which will heat the battery a bit). About 10 minutes before leaving, hit "remote start" again, which will start the battery heater again (if needed).

You won't save much energy if you are driving it every day, but if it sits for days without being used, there's no reason to leave it constantly plugged in (unless the ambient temp is always under 0C).
 

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The temperature of the surface below the battery makes very little difference in battery temperature. Heat transfer from radiation is minimal compared to convective heat transfer, especially when the vehicle is moving.

Added insulation is a two-edged sword. In cold weather, it will help keep the battery warm, but in hot weather it will also reduce heat transfer, reducing the ability of the battery to avoid overheating. The added insulation will also reduce ground clearance.

Any such modifications will obviously void the warranty on the vehicle. Just let it be, and deal with it.
 

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Discussion Starter #30
GlenandhisBolt1! stated; "Any such modifications will obviously void the warranty on the vehicle"

According to the "Magnuson-Moss Warranty Act" of 1975, user modifications made to a product only voids the warranty of the damaged parts only if the manufacture can prove damage was caused by the modification.
 

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The temperature of the surface below the battery makes very little difference in battery temperature. Heat transfer from radiation is minimal compared to convective heat transfer, especially when the vehicle is moving.

The older we become, the more often we realize the answer is "it depends." A cool battery compartment over warm pavement will become warmer even if it were in a vacuum. That's fairly simple thermodynamics. Radiation happens, cool things become warmer when exposed to radiation.

Doing actual numbers is helpful. Typical summer pavement temperatures in warmish and above climates potentially adds a noticeable load to cooling requirements, if one thinks of a couple of hundred watts as significant. That input happens even if the car is going 1,000 mph.

As to insulating the battery pack causing problems w/impedance of heat transfer out of the battery, once ambient temperature rises above the target regulation temperature of the battery pack that of course is no longer true, with leakage adding to the task of thermal management. Again, it's simple thermodynamics.

Anyway, dismissal of the potential for improvement of battery insulation is pretty much nullified by the appearance of a cost-tolerance question in a survey by GM. Clearly there's a question in play about adding money to fix what is perceived to be more or less of an issue, one that can be addressed with money.
 

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Insulation of heater and coolant loops.


How much energy am I saving? Well, if you can help me measure it, that would be appreciated. I am in NJ and the heating is not used much. It must be below 40F outside for me to start thinking about it. And, if I am alone in the car, it is always off, only to manage window defogging. So OK, seriously, if I were in ND or Manitoba, how big of an impact would it make?

That's exactly what I am thinking of doing to my 2019 LT.

The biggest issue for me so far was access to the heating module from all sides.
Nicely done. I bet it adds a lot Wh's in very cold days as the box is made of aluminum and it is nice and warm. The lines are lesser of a problem, but once parked - it all looses heat quickly.
And I think this is the MAIN reason why Bolt (Ampera-e) scored so low. Lots of heat is wasted into the air.



My view on the battery - I did not look under the car so closely yet (I got it in Jan 2020, so it was cold...), but I'd add 6-10 mm self adhesive, aluminum layered pad to the bottom of the pack and then stuff some foam as a wind buffeting aid over the sides to limit air flow over the battery when driving (if there is any gap). Probably leaving some small gaps in the back for water drainage.
 

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I used two 4'x8' sheets of black coroplast to make a belly pan for the Bolt. It will be interesting to see if the average miles per kW increases any over the next two months.
 
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