GetOffYourGas
Posts: 1057
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Location: Syracuse, NY

Re: Battery Climate Control?

Tue Jan 09, 2018 12:45 pm

IMAdolt wrote:I was under the impression the TMS will kick in weather or not it's plugged in running or not running till about 30% SoC? Seems silly to allow for battery damage in extreme weather to save a few watts of power for driving.


It will, and I have seen it do just that (and reported in the energy use screen). The temperature threshold for the TMS is lower when the car is off and unplugged, but it will still turn on to prevent damage.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier

gpsman
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Joined: Thu Oct 20, 2016 9:10 pm

Re: Battery Climate Control?

Thu Jan 11, 2018 8:35 pm

Do the batteries really get damaged at any low temperature, or just become unusable?

These are “dry” cells. Not sure what, if anything can freeze.

GetOffYourGas
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Joined: Tue Oct 20, 2015 5:25 pm
Location: Syracuse, NY

Re: Battery Climate Control?

Thu Jan 11, 2018 9:11 pm

gpsman wrote:Do the batteries really get damaged at any low temperature, or just become unusable?

These are “dry” cells. Not sure what, if anything can freeze.


Our batteries have a liquid electrolyte, which can absolutely freeze. Lithium batteries without a liquid electrolyte are referred to as "solid-state" batteries. They are underdevelopment, but not yet employed by any EV on the road.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier

gpsman
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Re: Battery Climate Control?

Fri Jan 12, 2018 3:51 pm

OK... Cold REALLY affects DCFC.

I’m only in San Francisco cold. So overnight cold soaks in the 40’s.

When I DCFC the charge rate follows pretty much a bell shaped curve. Slow to start, fast in the middle, slow at the end. But on a warm day with warm battery, I start with maximum charge rate.

Today, the car cold soaked all night at 48’F or 49’F.
I drove it ~30 minutes on the freeway, which warmed up the cabin, and you would think, the use, would warm up the battery.

It’s now 52’F outside. I’m thinking my HV battery pack is at least this warm, probably warmer from the 30 minute drive.

On a 50kw DCFC just now (which delivers 46 kw to the car on a warm day), the car is only taking 32 kw.

DCFC rate is reduced by 30% with temperatures in the 50’s. Which turned out to be 15 kWh hours, or 25% charge in 30 minutes on the fastest DCFC available. (16% to 41% in my case)

As the battery warmed up, the charge rate gradually ramped up.

MikeDabrowski2017
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Location: North East Ct
Contact: Website

Re: Battery Climate Control?

Mon Jan 22, 2018 6:07 pm

We just got a break in some pretty cold weather here in new England.

From my observations during the coldest periods, the battery temperature seems to be maintained at a similar energy regardless of being plugged in or not.

I don't drive the car every day and I leave the car plugged in to my level 2 evse juicebox which logs all charging or conditioning in a graph
After watching the kWh drawn to condition the pack for several days plugged in, I unplugged the car for a similar period of time and based on the percentage of charge used for conditioning recorded by the car, i saw just about the same kwh used.
Looks like the conditioning cycles run at about 6 hours off 30 minutes to over an hour on or .7kw to 1.5 kw per cycle.
Thermal camera looking at the fluid hoses saw 70- 80 degrees on the exterior of the hoses while the conditioning was active.

gpsman
Posts: 491
Joined: Thu Oct 20, 2016 9:10 pm

Re: Battery Climate Control?

Fri Mar 02, 2018 3:25 am

How come on a cool 45 degree day I can regen at the full 70 kw but I can only DCFC at 32 kw?

I know charging warms the pack, but after 30 minutes I was only at 38 kw on a 50 kw DCFC.

My car was in the 26% to 50% range.

GetOffYourGas
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Location: Syracuse, NY

Re: Battery Climate Control?

Mon Apr 02, 2018 2:22 pm

gpsman wrote:How come on a cool 45 degree day I can regen at the full 70 kw but I can only DCFC at 32 kw?

I know charging warms the pack, but after 30 minutes I was only at 38 kw on a 50 kw DCFC.

My car was in the 26% to 50% range.


There are two types of "50kW" DCFCs. They can either be 100A / 500V or 125A / 400V.

If it's the former, your car is limited by the charger. The Bolt will pull 100A as the battery voltage slowly rises to about 370-380V before tapering down to about 66A. This means the max you can actually charge your car is the 38kW you have seen. I'm guessing this is what is happening.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier

SparkE
Moderator
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Re: Battery Climate Control?

Mon Apr 02, 2018 8:05 pm

GetOffYourGas wrote:
gpsman wrote:How come on a cool 45 degree day I can regen at the full 70 kw but I can only DCFC at 32 kw?

I know charging warms the pack, but after 30 minutes I was only at 38 kw on a 50 kw DCFC.

My car was in the 26% to 50% range.


There are two types of "50kW" DCFCs. They can either be 100A / 500V or 125A / 400V.

If it's the former, your car is limited by the charger. The Bolt will pull 100A as the battery voltage slowly rises to about 370-380V before tapering down to about 66A. This means the max you can actually charge your car is the 38kW you have seen. I'm guessing this is what is happening.



Actually, the car is limited by the charger in both cases that you stated - it's just that in one of the two cases the car is limited more. The Bolt appears to be limited to a max of 150A when using DCFC (based on reports of fast charging posted from Europe, where they have 100 kW+ CCS charging stations).

Yes, the Bolt aggressively steps down the amperage when fast charging at multiple points : somewhere around 55% SoC (dropping from "up to 150A" down to "around 100A") and then again around 70% (dropping down to "about 65A") and again near 85% ("about 45A"). So, if you are using a 100A DCFC, it will charge at a rate of 32-36 kW until it reaches about 70% SoC (the voltage goes up during DCFC charging while the amps remain constant, and thus the kW rate slowly increases). If you use a DCFC that can provide 150A (or more) then you will charge at a rate around 52-54kW until about 55% SoC, when the charging will drop to 100A.

Now, if your question was more "why did GM do it this way, since the battery will charge at 70 kW during regen", instead of "why can I only DCFC at 32 kw" - the answer is "because GM programmed it that way". My guess is that they did it that way to prolong battery life (but that's just a guess - nobody told me). The battery should be able to take short burst of very high-level regen (measured in seconds) with very little harm - much, much, much less harm than charging at the same high rate for 30 minutes or longer.

gpsman
Posts: 491
Joined: Thu Oct 20, 2016 9:10 pm

Re: Battery Climate Control?

Thu Apr 05, 2018 6:30 am

No. That wasn’t the case at all. I’m afriad you missed my point.

On the drive TO the 125A DCFC my Bolt would regen at 70 kw.

Once I got to the DCFC and hooked up, with a low to medium low SOC (right in the sweet spot) it would only take 32kw to 38kw.

The same charge station a day or two earlier / later and I was gettting 46 - 47 kw charge rate.

The difference was outside air temperature.
Cool, but mild. 45 outside but the battery had been in use for some time, the battery had to be in the 50’s or more. And my question was: why not limit regen at the same temperature and scale as DCFC?

GetOffYourGas wrote:
gpsman wrote:How come on a cool 45 degree day I can regen at the full 70 kw but I can only DCFC at 32 kw?

I know charging warms the pack, but after 30 minutes I was only at 38 kw on a 50 kw DCFC.

My car was in the 26% to 50% range.


There are two types of "50kW" DCFCs. They can either be 100A / 500V or 125A / 400V.

If it's the former, your car is limited by the charger. The Bolt will pull 100A as the battery voltage slowly rises to about 370-380V before tapering down to about 66A. This means the max you can actually charge your car is the 38kW you have seen. I'm guessing this is what is happening.

GetOffYourGas
Posts: 1057
Joined: Tue Oct 20, 2015 5:25 pm
Location: Syracuse, NY

Re: Battery Climate Control?

Thu Apr 05, 2018 12:39 pm

You're right, I missed where you stated that it was 125A and the fact that you had previously charged at 46-47kw at that station. Again, I have never seen a 125A / 400V "50kW" station, although I know they exist somewhere. But not where I travel in NY and New England.

As already mentioned, there is a huge difference between regen'ing and QC'ing at 70kW. In the former case, it's a matter of <10 seconds. In the latter, it's a matter of tens of minutes. It's simply not apples-to-apples to compare the two.

My question would be - why not use some of that power upfront to heat up the battery? It seems from others' experiments that the upfront investment of energy would actually save time in the long run.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier

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