Battery Climate Control?

[rklisch]

The Bolt is equipped with a battery climate control system. Yet there seems to be so little information on this, and no vehicle instrumentation for this. Battery temperature has everything to do with it's health, longevity, and range. So it makes sense GM has designed this in, but as an owner I can't seem to learn more about this. For instance, while charging a car in a cold climate, do they warm the batteries? It seems they do not because my cold weather range is terrible. One would think if you are plugged in all night, then why not keep the batteries at 60 or 70 F? I would then expect a pretty full winter range. What am I missing here? Also, it would be nice if the instruments displayed battery temperature, the sensor is already there. It's just a tiny bit of software. Maybe that is just too technical for the average owner.

How is this battery climate system controlled? When is it actually used? And how does one know it is in use and working?

Thanks,

Roger K

 

[GetOffYourGas]

This has been an annoyance of mine since I got the car. The Leaf had zero thermal management, but displayed rough battery temperature (in "bars") prominently on the dash.

Also, it would be nice if the instruments displayed battery temperature, the sensor is already there. It's just a tiny bit of software. Maybe that is just too technical for the average owner.

I like to think of this in terms of an ICE car - most cars show you coolant temperature. The Bolt is equivalent to only having an idiot light go one when it's too late.

 

[winterescape]

You might desire to understand more about the TMS in the Bolt, as do I, and as do all of GMs competitors, I don't think they are going to tell us much more than what is displayed in the efficiency screen showing the % of energy consumption used for TMS. There have been a few threads where folks have empirically determined it turns on when plugged in and the pack temp is below freezing. Someone with a current monitor on the EVSE posted plots of the TMS energy consumption "blips" amplitude and period at a couple of temps.

IMHO, if GM turned the TMS on frequently and warmed the pack to 60 deg as you suggest, there would be several threads complaining about how much energy the Bolt wastes conditioning the pack compared to how "smart" Nissan was in not adding the cost or complexity to condition the pack

 

[rklisch]

IMHO, if GM turned the TMS on frequently and warmed the pack to 60 deg as you suggest, there would be several threads complaining about how much energy the Bolt wastes conditioning the pack compared to how "smart" Nissan was in not adding the cost or complexity to condition the pack

I read one post here where a Bolt owner heats his garage to 60F though the winter. I thought to myself, how crazy to buy a Bolt for the reasons of reducing emissions, then heat an entire garage all night. GM could give the option to heat or not heat the pack. The extra range the next day would be useful. Also, the Volt (I have under lease), causes the ICE to run in the winter for heat. No option to turn that off. GM ought to give us EV pioneers more options.

 

[mwk]

I am sorry if I'm "hijacking" this thread, but it seems fairly relevant to my question. I am a new Bolt owner (Nov 1 2017). I live near Boston. For now, I just have been charging my car using the included 120v cable and an all-weather outlet on the side of my house near the driveway. I only have a 10-mile round trip commute, so I get more than enough range by plugging it in overnight. There's also an EVSE at my office I can use if I want.

Anyway, the forecast for this week is bitter, bitter cold with temps below zero a few nights. I'm also off work for the Holiday week and I'm not really going out very much, so the car is sitting in my driveway, un covered. Should I keep it plugged in to the 120v outlet when it's not in use, during this extreme cold snap? I'm worried about the batteries, obviously. Will it do harm to the EVSE cable itself if I leave it plugged in continuously?

Thanks.

 

[BikingManiac]

Yes, leave your Bolt plugged in. Here in Wisconsin when it is below zero the car draws about 4 KWH in 24 hours.

 

[LeftieBiker]

Also, the Volt (I have under lease), causes the ICE to run in the winter for heat.

IIRC there is a menu option to select two temps at which the engine will start. The lower one is 15F. You might want to make sure you have that selected. At least the Volt has a cabin heater! Our Prius PHEV has no electric heater, so you have to run the engine for heat at any temperature...

 

[Williams60]

As its been below -15 Celsius here for the last six weeks or so now (that's the daytime high, average nightly temp is below -25 Celsius), I can confirm the battery conditioning only kicks in when the vehicle is plugged in, or when the vehicle is running. The only advantage to leaving it plugged in when standing, is that the full regen takes some time to achieve if it hasn't been plugged in overnight. To quantify "some time", it depends on the temperature, but below -20C it takes around 5 to 8 minutes before the regen notification 'bar' starts creeping down the 'available regen' gauge to the right of the speedo, in a similar fashion to when you fully recharge the battery (as opposed to using hilltop reserve, which is all I usually use, less a charge to full capacity around once a month just for ***** and giggles and to see what the predicted range at full charge is at this temperature, just in case I need its full range at some time). Worst range prediction (at full charge) that I've seen so far was 214km, after leaving it outside overnight below -28C (-18F) with a min (max?!!) overnight temp over of -32C. That battery conditioning rarely gets above a few percent of the battery usage, as the climate and propulsion draw far eclipses it, other than for the first 10-15 minutes of use, or if you use the pre-conditioning function, but it soon drops down as a percentage on the 'energy use' information graph once the vehicle starts moving.

You can hear the battery conditioning in operation when you plug the vehicle in to charge, if its' been standing for a while in the cold; you can hear the coolant expanding into the overflow bottle as the battery charging kicks in.

The power output is also reduced (limited to 60kW initially) once you're down below -20C. This increases pretty rapidly as the coolant circuits warm up and is not really an issue; I had to push the car harder than I should have done in those conditions to find what it was limited to, as you can't/shouldn't really try to accelerate that hard when it's -28C in deep snow.....lol!

 

[LeftieBiker]

As its been below -15 Celsius here for the last six weeks or so now (that's the daytime high, average nightly temp is below -25 Celsius), I can confirm the battery conditioning only kicks in when the vehicle is plugged in, or when the vehicle is running.

Are you driving it daily? If so you may be keeping the pack warm enough to avoid the need for it to activate conditioning to protect the battery...at any rate, it seems clear that the system is at the least much more willing to come on when the car is plugged in.

 

[IMAdolt]

As its been below -15 Celsius here for the last six weeks or so now (that's the daytime high, average nightly temp is below -25 Celsius), I can confirm the battery conditioning only kicks in when the vehicle is plugged in, or when the vehicle is running.

Are you driving it daily? If so you may be keeping the pack warm enough to avoid the need for it to activate conditioning to protect the battery...at any rate, it seems clear that the system is at the least much more willing to come on when the car is plugged in.

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.

 

[GetOffYourGas]

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.

 

[gpsman]

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]

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.

 

[gpsman]

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]

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]

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]

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.

 

[SparkE]

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]

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?

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]

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.