[Loring]

A few interesting observations about maintenance battery cooling of a Bolt EV in extreme temps:

We have a JuiceBox 40A L2 charger which produces some very useful data on their phone app used for controlling the charging process and recording detailed info on each charging episode.

We were traveling away from our home in Tucson, AZ for the month of June, so we left our Bolt plugged in, in our garage. Temps in early June were very moderate by our standards, and cooling wasn’t needed until June 6, but from then on there were from one to four cooling episodes per day for the rest of the month as the outside temps went above 100F degrees on a daily basis. Each cooling episode drew about 5 amps at startup, lasted about 9 minutes and drew about 1/3 of a kWh. The total additional energy for cooling during our absence is estimated at about 30 kWh for 27 days of cooling. Interestingly, but unrelated to this test, there appears to be a cooling cycle at the end of each regular charging cycle, at least during warmer weather, probably to bring down the elevated temps caused by the charging.

After this test, I have greater confidence that the on board cooling system will protect my battery from our very high summer temps.

 

[raitchison]

The Bolt does indeed do a good job of cooling the battery when you're plugged in and not charging. The problem is for people who have to park our cars out in the sun where we can't plug them in. The car will allow the battery to get VERY hot (I've seen mine as hot as 37C without the car doing anything to cool it).

A simplified description of how the Bolt's battery cooling works.

• If you're plugged in and not charging the car will maintain the battery at about 27C.
• If you're not plugged in but the car is turned "on" the car will maintain the battery at about 31C.
• If you're not plugged in and the car is not turned "on" the battery will not cool the battery at all (at least that I've seen).
• You can trick the car into cooling the battery while charging by leaving it "on" with the passenger A/C turned on while you're charging.

Another challenge for those of us with 2017 or 2018 Bolts even if we have the ability to plug in where we park if we want to let the car keep the battery cool we have to let the car charge the battery all the way up to "full" so just under 90% with Hill Top Reserve enabled, so we have to choose between keeping the battery cool but maintaining a relatively high SoC or maintaining a lower SoC and letting the battery get hotter than it should. Lithium Ion batteries don't like to be charged to or stored at higher states of charge and they don't like to be hot but the Bolt is still very new and we don't really know whether it's better for the battery. People with 2019+ Bolts don't have this problem, since they have the target charge setting they can always specify a lower maximum SoC and allow the car to keep the battery cool without charging it higher than they might want to.

 

[Raymondjram]

I wonder how the Nissan Leaf 2 and the Tesla Model 3 survive the heat without being plugged in. GM is one of the best manufacturer involved with cooling, as they had two brands (Harrison and Frigidaire) and the latter is still one of the best brand in cooling appliances. The Bolt EV will never catch fire accidentally!

 

[raitchison]

I wonder how the Nissan Leaf 2 and the Tesla Model 3 survive the heat without being plugged in. GM is one of the best manufacturer involved with cooling, as they had two brands (Harrison and Frigidaire) and the latter is still one of the best brand in cooling appliances. The Bolt EV will never catch fire accidentally!

The leaf doesn't, the batteries get way too hot, especially with DCFC and the capacity and range plummets..

As for the Tesla, Tesla's BMS is far more aggressive in terms of prioritizing keeping the battery cool, the car will regularly use battery power to cool the battery if it's parked and not plugged in. The downside is that Tesla owners complain about "lost range" after being parked on a hot day because the car used a noticable amount of battery power for battery cooling.

 

[NoMoPetrol]

...As for the Tesla, Tesla's BMS is far more aggressive in terms of prioritizing keeping the battery cool, the car will regularly use battery power to cool the battery if it's parked and not plugged in. The downside is that Tesla owners complain about "lost range" after being parked on a hot day because the car used a noticable amount of battery power for battery cooling.

Tesla owners complaining about "lost range" need to consider the alternative.

Regarding the original post:
In our household we have one garage stall but two EVs (Model S and Bolt). We made the Bolt purchase with the understanding that during the hottest days of summer the Bolt would have priority for the garage so we could plug it in to keep the battery properly cooled. It involves a little Musical Chairs routine in our condo parking area, but is a very small price to pay for the enjoyment my wife gets out of driving her Bolt.

 

[SeattleRic]

I live in Florida and left my 2017 Bolt plugged into a JuicBox 40 for two weeks during a trip to Boston. Average high temperatures in Orlando were in the mid-90s. Upon returning, I noticed a faint burnt electrical smell in the cabin of the Bolt. I am expecting that it will dissipate over time, but am wondering if this is normal. I have not noticed any adverse effects. I have another 2 week trip coming up to Seattle. Just wondering if it is a good idea to leave it plugged in.

 

[ButchAZ]

So if I set my target charge to 80% and just leave the car plugged in every time I pull into my garage (in Tucson, in hot weather), it will keep it charged to 80% and use current from the plug to run the battery cooling system?

 

[tangolima]

Kids came running saying the car was going nuts in the garage. It was hot summer evening. The car was volt. It has been fully charged a few hours ago and was still plugged in.

100% soc, high temperature, and long period of time is not kosher for battery life. The car was trying to save itself by taking away one of the 3 elements, I suppose. It always turns on the cooler when it reaches 100% soc. But we just hadn't seen it doing it hours afterwards. So far I haven't seen one doing it unplugged. Perhaps it hasn't been bad enough for it to use its own power to cool itself.

-TL

Sent from my SM-N960U using Tapatalk

 

[zzzing]

So if I set my target charge to 80% and just leave the car plugged in every time I pull into my garage (in Tucson, in hot weather), it will keep it charged to 80% and use current from the plug to run the battery cooling system?

Yes, that is correct, if battery cooling is needed it will use wall power if plugged in

 

[ButchAZ]

Good information! Thanks.

 

[NoMoPetrol]

I have a question on behalf of a friend who just bought a 2020 Bolt. Is there still a problem with no battery pack cooling for a parked car unless it is plugged in?

 

[NewsCoulomb]

I have a question on behalf of a friend who just bought a 2020 Bolt. Is there still a problem with no battery pack cooling for a parked car unless it is plugged in?

Was there ever a problem? Humans literally couldn't survive in the types of temperatures required to actually damage the battery, and even then, yes, the battery will prevent damage to itself. Ideally, you want to leave it plugged in, though, because it will more aggressively condition the battery.

 

[NoMoPetrol]

Was there ever a problem?...

If that were true, the Leaf would not have battery packs that seriously degrade within a few years of purchase due to heat exposure in hotter regions. It was my understanding that if the Bolt's cooling system does not operate when parked, it is essentially on a par with the Leaf for those hours of non-operation.

 

[ARob]

It was my understanding that if the Bolt's cooling system does not operate when parked, it is essentially on a par with the Leaf for those hours of non-operation.

Only when SOC is low. If battery temps rise to about 95F, and there is 40% or more capacity in the battery, TBMS will occasionally kick in. But, GM designed it so less frequent conditioning when unplugged, to preserve range.

That is why most comments you will see on the topic suggest leaving it plugged in, hot or cold. Even if charging is disabled, being plugged in will provide enough energy to run TBMS.

That being said, parking in the hot sun for extended periods with a 90% or greater SOC may also be problematic. Same with extreme cold at high SOC. If you are going to leave it parked and unplugged, best to do so with 40-80% SOC probably.

 

[NoMoPetrol]

Only when SOC is low. If battery temps rise to about 95F, and there is 40% or more capacity in the battery, TBMS will occasionally kick in. But, GM designed it so less frequent conditioning when unplugged, to preserve range.

That is why most comments you will see on the topic suggest leaving it plugged in, hot or cold. Even if charging is disabled, being plugged in will provide enough energy to run TBMS.

That being said, parking in the hot sun for extended periods with a 90% or greater SOC may also be problematic. Same with extreme cold at high SOC. If you are going to leave it parked and unplugged, best to do so with 40-80% SOC probably.

Thanks to both you and Newscoloumb. I will pass this on to our new Bolt owner/enthusiast.

 

[p7wang]

If that were true, the Leaf would not have battery packs that seriously degrade within a few years of purchase due to heat exposure in hotter regions. It was my understanding that if the Bolt's cooling system does not operate when parked, it is essentially on a par with the Leaf for those hours of non-operation.

Yes, but the Bolt battery will never experience the extremes that a Nissan Leaf battery had to endure. Agree that while parked, it is possible that Bolt battery would experience elevated temps if the battery charge is below 40%, otherwise, my understanding is that the liquid cooling would cool the battery. When driving in 115F heat, though, and the Leaf battery will definitely be hotter than 115F while the Bolt battery would be much cooler.

 

[NewsCoulomb]

If that were true, the Leaf would not have battery packs that seriously degrade within a few years of purchase due to heat exposure in hotter regions. It was my understanding that if the Bolt's cooling system does not operate when parked, it is essentially on a par with the Leaf for those hours of non-operation.

During heavy operation (or normal operation in very hot regions), the LEAF's battery will reach internal temperatures of over 125 F. While monitoring the Bolt EV's internal battery temperatures using Torque Pro, I've never seen it exceed 105 F.

 

[ARob]

During heavy operation (or normal operation in very hot regions), the LEAF's battery will reach internal temperatures of over 125 F. While monitoring the Bolt EV's internal battery temperatures using Torque Pro, I've never seen it exceed 105 F.

I believe it was @Wolfy who documented his Leaf trip (which lead to his trading in for a Bolt) that his Leaf battery temps were staying up in the 125F range and throttling the charging rate down to something like 10kW.

I haven't paid attention to Bolt temps, but knowing TBMS kicks in when needed is reassuring enough for me.

 

[Wolfy]

I believe it was @Wolfy who documented his Leaf trip (which lead to his trading in for a Bolt) that his Leaf battery temps were staying up in the 125F range and throttling the charging rate down to something like 10kW.

I haven't paid attention to Bolt temps, but knowing TBMS kicks in when needed is reassuring enough for me.

We completed a road trip in our Bolt late Monday night. I still have one more video to create (meant to today, but work was ****), before I begin cleaning up the clips and combining them to a trip vlog. Our Bolt's battery saw a maximum of 93 degrees. We heard the car cycle on the A/C pretty much immediately on charge two on our drive down to Hampton, VA. Temps were floating around 90 degrees that day, much like they were on our LEAF drive to TN. The drive home from Hampton, VA via the Chesapeke Bay Bridge Tunnel up to Wilmington, DE., was approximately four hours shorter than the drive home from TN, which was a similar distance, despite being routed through a notably slow stretch to get from Wilmington, to I-76 in PA, and a throttled charge from EA as the chargers were undergoing "maintenance". Actively managing battery temps made a massive difference in our trip. Having the capacity to charge "up to 100kw" as was advertised in the LEAF, is useless when subsequent charges are tortuously slow from an overheated battery. The Bolt's "inferior" 55kw charger was faster overall because it could do the same thing, every charge. Faster charging might be nice in the Bolt. The distance we can drive between charges, combined with our slow and steady style, spreads them out to where they can easily be planned around lunch and dinner stops. This seemed to fit well into the time required to receive the desired state of charge. The only time they get to feel long is during "lost time" stops where everything is closed, something really only felt when we had the third late night charge on the final stretch home. Still, I was happy to have a 30 minute slowish EVGo (40kw charger) over what would have been a 90 minute or more stop in a deeply throttled LEAF.

 

[NoMoPetrol]

So, just to condense the above responses regarding this issue:
1. The Leaf's battery problems were generated as much from overheating while the car was being operated as from when it was parked all afternoon on a hot summer day.
2. A parked Bolt will actually cool the batteries on a hot summer afternoon so long as the battery has a SOC of <40% sufficiently to avoid the battery pack damage that might otherwise occur.