Extreme Desert Heat

I posted some of this in a trip report I wrote, but I'm now getting a bit confused and am not sure what to do.

I live in the Palm Springs area. Our temperatures are already over 100F, and now up around 105F. Over the summer, they will get upwards of 121F on some rare days.

According to the manual, when the temperature is about 90F is says that it is best for the battery to leave the car plugged in. I've also been told that it would be best to set the car on Hill Top Reserve to preserve the battery.

So, if I leave the car in Hill Top Reserve, should I leave my Bolt plugged into my charge station (240V, 40 Amp) and on "Charge Immediate" or should I only have it charge overnight when the temperature drops to the mid to low 90's.

It seems sort of contradictory information as I have also heard that charging when it is extremely hot outside is also bad for the battery.

I think I need help understanding what to do and sorting this out.

Delayed charging is fine (as is hilltop reserve).

The car will use the high voltage battery to help keep the battery cool even if it not plugged in, but when connected to 240v power will be more aggressive in it's cooling since there is an "unlimited" source of power to do so. No need to worry about the owner coming back to the car and finding not enough charge to reach their destination. If not plugged in, no conditioning will take place if the SOC is <30% (IIRC).

DucRider said:

Delayed charging is fine (as is hilltop reserve).

The car will use the high voltage battery to help keep the battery cool even if it not plugged in, but when connected to 240v power will be more aggressive in it's cooling since there is an "unlimited" source of power to do so. No need to worry about the owner coming back to the car and finding not enough charge to reach their destination. If not plugged in, no conditioning will take place if the SOC is <30% (IIRC).

Click to expand...

So I suppose the best course of action is to not allow the Bolt to sit in the hot garage plugged in and charged to 100%, but keep it on hill too reserved and plugged in and on immediate charge so it has plenty of electricity to cool? I have heard that charging when the temperature is high is also bad for the battery?

Two threads, similar topic ... :mrgreen:

I just posted this on the other thread :

iankh said:

Actually the manual says that the car should be plugged in when it's above 90F. Does this mean is should be in a charge mode or not in a charge mode?

Click to expand...

It doesn't say, but I would assume it doesn't matter. I *believe* that when the car is plugged in, it will pull energy from the wall (via the EVSE) to cool down the battery instead of using the energy stored in the battery itself. (Does anybody know if the battering conditioning starts *earlier* {or cools to a lower temp} if the car is plugged in, compared to it NOT being plugged in???) At any rate, I would *expect* that the battery cooling system would turn on and cool the battery if the car is plugged in - whether the vehicle is currently charging or not.

Note that even if you set delayed charging (using the Departure charge mode, Latest Possible Charge Completion) the car MAY start charging immediately (or at least sooner than you would expect) if the battery is pretty empty because it calculates how much time is needed to fully charge the vehicle (or charge to 90% if hilltop mode is set) and will start charging so that you have a 'complete charge' by your set departure time.

Also, there is a 'Priority Charging' setting which will immediately start charging your battery if it is below 40% full (if it is set); it will ignore the delayed charging and charge until the battery gets to 40% (if needed) then stop at 40% and resume charging once the 'delayed charging' parameters are matched.

I'm not sure how 'bad' it is to charge a low-SoC (State of Charge) battery to 40% when it is really hot outside (say, over 90 degrees). Which is worse : letting the battery get hot, or charging when it is hot? I don't know. It might be a good idea to use the 120V EVSE that came with the vehicle in such cases : the battery would be protected (because it is plugged in when hot) and the battery would be charging at a very low rate (120V/8 amps compared to 240V/30 amps) when it is hot outside. Or maybe it would be better to temporarily disable the 'Priority Charging' setting so that the car wouldn't charge at all in those few, rare cases when your car's battery is <40% and it is really hot outside??? (But that would mean that when you want to take the car somewhere, you would have a very low drivability range.) Every morning you *should* start the day with a 90/100% charge (it just charged all night on your 40 Amp EVSE). So this would be an issue only those times that you drove the car for 130 miles or so during the day and then went home to palm springs (or anywhere it was 110 degrees) and wanted to drive 100 or more miles before it cooled down.

At any rate, whenever you mess with the charging parameters, it would be a good idea to keep a close eye on your charge every night (i.e., when you plug in) and every morning (say, when you get up) to make sure you don't get surprised by low (or no) charge when you want to go somewhere. Remember that there is a one-time override ("charge right NOW!!") you can activate by unpluging the charge cord from the car and immediately plugging it back in (within five seconds).

My Spark EV lived in the extreme heat of Palm Springs for 3 summers and 45,000 miles

Always plugged in as soon as I parked in my garage, always charged to 100% overnight, DCFC'd it probably 100 times over the period of the lease. Frequently run down to < 20 miles of range, sometimes as little as 5 miles.

I saw minimal battery degradation over that entire time. If it was even 10% I'd be surprised.

Maybe you should be concerned if you are buying, if you are leasing my philosophy is don't spend any time fretting over your battery. Use it, enjoy it and trust GM. I like the no hassle part of EV ownership, plug it in, walk away. Only if you have a time of day electric rate would I bother to worry about what time of day it was charging.

sparkyps said:

My Spark EV lived in the extreme heat of Palm Springs for 3 summers and 45,000 miles

Always plugged in as soon as I parked in my garage, always charged to 100% overnight, DCFC'd it probably 100 times over the period of the lease. Frequently run down to < 20 miles of range, sometimes as little as 5 miles.

I saw minimal battery degradation over that entire time. If it was even 10% I'd be surprised.

Maybe you should be concerned if you are buying, if you are leasing my philosophy is don't spend any time fretting over your battery. Use it, enjoy it and trust GM. I like the no hassle part of EV ownership, plug it in, walk away. Only if you have a time of day electric rate would I bother to worry about what time of day it was charging.

Click to expand...

The Bolt is the first time I've leased a car because I wanted to hedge against technology and concerns over our high temperatures. I have solar and am not on a TOU plan. Prior to the temperatures climbing up, I had the Bolt on immediate charging and plugged it in whenever it was in the garage. I now set it to 'Hilltop Reserve" because of advice to not keep it a state of fully charging in high temperatures. I've also set it up to charge overnight. The mystery is whether it will draw power from the 240V Juicebox charge station if it is set up for a delayed charge but still plugged in?

I'd call Chevy, but the last time I did that, all they did was read to me from the manual, something I've done several times about this already.

It's good to hear that you were fine with your Spark in our area. Though the car is leased, it's what I use for my weekly commute to Carlsbad, so that is the source of concern.

Unfortunately, when I don't fully understand the science behind something like this, I start to see a Bugs Bunny cartoon, where there are little gremlins syphoning off electrons and chewing on my batteries. LOL :lol:

Most of the concerns over battery degradation in the heat come from NIssan's debacle with the Leaf in hot climates like Phoenix and the California desert.

GM did the Spark EV right and I believe they did the Bolt EV right. You use barely half your range to get to Carlsbad, you simple are not going to ever have a problem over the 3 years of your lease due to battery degradation. I remember something in the Spark EV manual telling me to leave it plugged in when hot and not to partially charge it.

Leave it plugged in, the battery conditioning will run, the car will be fine. Leaving the car plugged in is what Tesla recommends as well.

GM understands the battery chemistry and controls the maximum voltage of the batteries to provide a good trade-off between battery life and range. They lose a lot of money if they get it wrong and they have to start replacing battery packs under warranty or owners complain about degradation. My philosophy is I bought a 238 mile range car and it would be foolish to treat it like a 200 mile range car in the hopes that at the end of 3 years it only degrades 5% instead of 10%.

There is only speculation and not even anecdotal evidence that babying your EV battery by substantially reducing the range you use will provide any noticable benefit over the period of the lease. Even the Spark is barely 3 years old, there just isn't any data regarding long term battery life vs usage patterns.

But, as I said, if you bought the car you might want to treat it more gingerly. I'm like you, I lease EVs because they are dirt cheap to lease and very expensive to purchase and the depreciation has far exceeded the residuals, at least for the non-Teslas. I'll let someone else experiment with the long term reliability of the batteries.

iankh said:

Unfortunately, when I don't fully understand the science behind something like this, I start to see a Bugs Bunny cartoon, where there are little gremlins syphoning off electrons and chewing on my batteries. LOL :lol:

Click to expand...

The little gremlins are syphoning off electrons, and chewing on your batteries but you won't have the car long enough to notice it. Drive more, worry less.