Tips To Keep Your Electric Car’s Battery Healthy In The Record-Breaking Heat Wave

By · July 01, 2013

EVs vs Heat

When the mercury rises, avoid parking your EV in direct sunlight.

Yesterday, temperatures across Arizona, Nevada, Utah, Colorado and California reached record-breaking highs, making even the most normal of everyday activities unbearable for all but the most hardened of heat-loving Americans.

Like humans, electric car battery packs prefer moderate temperates rather than extreme tropical ones, but with the heat wave set to increase its intensity and widen into northwestern states like Oregon, Washington, Idaho and Montana, what can you do to keep your car’s battery pack happy in unbearable weather?

Avoid Extremes of Use

Just like any other battery pack, passing current in and out of your car’s battery pack will warm it up. The higher the current passing through the battery pack -- either in or out -- the quicker the pack warms up.

It’s worth noting too that as the battery pack reaches 20 percent full or less, its cell voltages start to drop dramatically. Since electrical power equals voltage times current, the current drain on the battery pack will increase as the pack voltage drops to maintain the power levels demanded by the car. This will in turn heat your car’s battery pack up—not exactly what you want when it’s already triple digits outside.

To keep your battery pack as healthy as possible and as cool as possible, it’s best to avoid heavy acceleration and running your car down to a low state of charge.

Charge Smart

As we’ve just explained, passing high currents through your car’s battery pack will cause it to heat up far more quickly than passing low currents through it.

Since the CHAdeMO quick charge and Tesla Supercharger stations rely on extremely high current flows to quickly replenish the battery packs on cars like the Nissan LEAF or Tesla Model S to 80 percent full in under 30 minutes, think twice before using them when the mercury is reaching for the sky.

The same is true for 100 percent or ‘range’ charges in hot weather. As a battery pack reaches a full state of charge and its internal resistance rises, it becomes harder and harder to push electrons into the battery. In turn, this puts additional stress on the battery pack and increases the rate at which it heats up.

Consequentially, if you know you only need an 80 percent charge to reach your destination, setting your car to stop charging at 80 percent will put less strain on it and help it stay healthy in hot weather.

Park Smart

With the sidewalks in some cities hot enough to give pedestrians second degree burns, you need to make sure that your car gets just as much shade as you do.

Where possible, park in the shade out of direct sunlight, as this should help your car’s battery pack stay cooler than it otherwise would. In addition, you’ll find your car far more pleasant to return to.

Keep Your Car Plugged in

While some cars like the Nissan LEAF and Mitsubishi i rely on passive forced air cooling to keep them cool in hot weather, others—like the Tesla Model S, Chevrolet Volt and BMW ActiveE—use sophisticated thermal management systems with liquid coolant.

By closely monitoring the pack temperature, these fully-automated systems work by pumping refrigerant around the battery pack to keep them operating at peak efficiency. If your car is not plugged in, they will use some battery power to keep the pack cool. If your car is plugged in, they will generally run from mains power.

If your car uses an active thermal management system, it’s a good idea to keep it plugged in whenever possible in hot weather, to maximize range and keep the battery pack as cool as you can.


· · 4 years ago

Fast charging a Tesla Model S in hot weather is no different than fast charging in cool weather. The liquid cooling system goes into overdrive during a fast charge.

· · 4 years ago

A more subtle suggestion for those with Leafs in hot climates - try to park on cool pavement, such as that which has been in the shade. From discussions on, it seems that the heat radiated directly onto the bottom of the car is often more effective at raising the pack's temperature than the heat from the sun hitting the car.

In other words, say you are returning from your lunch break, about midday. It may be better to park in a spot that was shaded all morning but sunny all afternoon than one that was in the sun all morning and shaded in the afternoon.

· · 4 years ago

Is any of this necessary with the Tesla Model S, or Chevy Volt? Both have refrigerant based battery cooling systems. It's basically climate control for your batteries.

· · 4 years ago


Can't remember where I've read it, but in very extreme temperatures the volt is required to be plugged in, either extremely hot or extremely cold. If this is impossible, than the allowable temperature range is narrowed. Temporary excursions outside this zone while not plugged in are allowable, since the battery is semiprotected from the elements.

The Tesla Roadster is actually quite a bit better at temperature extremes than the Model S, especially on the cold end of things. When very very cold, the car will spend around a minute warming up the battery prior to allowing operation. When very hot, the airconditioner will start immediately to cool the battery once the 'ignition' is turned on. Again, since the Roadster battery is protected from the elements far better than the model S, there is much, much less of an issue if the Roadster must remain unplugged during extreme temperature temporary excursions.

· · 4 years ago

The fact that we have to talk about it is a sign that some of the "BEVs" aren't ready for the wide range of climate... I really mean the Leaf.

I believe this is a perfect test to see if those so called "improved" 2013 Leaf can really handle the heat or NOT. Plugin America do another survey by this November to see if any of the 2013 Leaf degraded or NOT.

Another tip, don't take your Leaf to Las Vegas or Death Valley, your car/battery can't handle it...

· · 4 years ago

Here is some data from my Blink charger for June 29, 2013. Following is data for outside temperatures. The temperature sensor for my weather station, on the west side of the house and close to where my Volt is parked, said it reached 119. But the official high was a mere 112. The time on the Blink data (from the Blink website) does not appear to adjust for no Daylight Savings Time in Arizona. There seems to be a pretty good fit between peak temperatures and the Volt battery thermal management system (BTMS) power draws – which I am assuming are the last two rows of the first table.

Interestingly - and maybe because I haven't known exactly what I should be looking for - this seems to be the first clear-cut evidence of the Volt's BTMS when the car has been plugged in. We had a couple of days last winter when the temperatures reached the mid-20s.

Plugin Events
Port Start End
0 2013-06-29 11:15:31 MST 2013-06-29 16:24:34 MST

Charge Events
(kWh) Start End
2.526 11:15 16:24

Power Events
Start End Energy (kWh)
11:15 12:08 2.108
14:04 14:21 0.307
16:15 16:24 0.111

Tucson, AZ
06.29.2013 11:30 107.8
06.29.2013 12:00 109.6
06.29.2013 12:30 110.2
06.29.2013 13:00 112.3
06.29.2013 13:30 113.9
06.29.2013 14:00 116.6
06.29.2013 14:30 117.5
06.29.2013 15:00 117.2
06.29.2013 15:30 119
06.29.2013 16:00 115.6
06.29.2013 16:30 115.6

· · 4 years ago

The so-called urban heat island effect is what Brian has described. Below is a link to an article prepared by the town of Gilbert, Arizona (it's part of the metro Phoenix complex,) that describes how the design of pavements and building rooftops can help reduce it . . .

Obviously, these are long term plans, as it's going to take many years before all the streets and flat building rooftops in any give community can be "replaced." Other locales that witness excessive summer heat but with different requirements (Chicago, for instance, where there is far greater year-round humidity, more rain and far colder winters) address the problem with their indigenous techniques.

And, yes, as with MMF, I'm interested to see how well the cells do in the 2013 Nissan Leaf by the end of the summer. I'm sure lots of people are watching.

Liquid thermal management for the batteries is less effective when the car isn't plugged in during long term parking situations at temperature extremes. This is probably true regardless of brand. Remember, also, that cooling systems in ICE cars are not infallible. Radiators crack at temperature extremes, hoses have to be replaced periodically and fluids can boil off and/or have their effectiveness compromised if the proper chemical balance isn't maintained. While these systems are better engineered than ones of previous decades, catastrophic failure is still a possibility.

One next generation battery thermal management system that interests me is shown here . . .

In essence, it's a block of some sort of proprietary wax-graphite compound that surrounds the battery cells and will melt to a semi-liquid in extreme heat situations. It is purported to work well enough to isolate a single cell experiencing thermal runaway and protecting adjacent ones. It doesn't require liquids being pumped into radiators for cooling and recirculating. Hence, it's a mechanically passive solution . . . and one that is already on the market.

Meanwhile, newer cell technologies that address the problem of limited temerature operating parameters are also on the horizon. A123 (which, I guess, now calls themselves B456) announced late last year their EXT refinement for their popular LiFePO4 cells designed to address this . . .

And the latest buzz appears to be around solid electrolyte lithium sulfur cells . . .

. . . which, in addition to being more robust in temperature extremes, feature far greater energy density than anything we have in current EVs.

· · 4 years ago


Thanks for sharing those links. From my various travels to your state, I have experienced this heat island effect to a far greater degree than I have in my own state. Now that I drive a Leaf, I do pay a little more attention to it. Like MMF said, the Leaf isn't really ready for all climates. That doesn't really surprise me for a first-generation semi-rushed-to-market product. It does mean that those of us who jumped on them will have to take a few more precautions to protect our investments. I too will be waiting for November to see the results of Plug-In America's next survey.

That phase-change material is almost too obvious for use as a simple short-term temperature control. If this could last for 24 hours and melted at a reasonable temperature, it could solve most (but not all) of the current issues. You do need to add a means to re-freeze the material when you plug in, though. Otherwise, it's all for naught.

· · 4 years ago

From what I gather, Brian, the AllCell phase change material has to get pretty hot (maybe 125+°?) before it reaches a semi-liquid state. There's also nothing to indicate that it has to completely re-harden if a hot ambient temperature battery charging sequence has to commence. If anything. it's probably going to be gentler on the cells than doing that same hot temp charging scenario with the Leaf's current passive air cooled pack.

When I borrowed my friend's Leaf last summer it was typically 105+° most days. As I normally would with the old Saturn, I parked about a mile from my U of A workplace, walked the final leg (on-campus parking is hideously expensive) and chose a spot on the street with afternoon shade. All my charging was done at night, when temperatures got back into the 80° range and, being that I don't have my own Level 2 EVSE, I did it with 120V house current, which is gentler on the batteries, underneath a shaded carport (minimal heat island effect.)

Do read through the article on lithium sulfur cells, though. The below quotes from it makes me think that Li-S cells are going just what every Death Valley (Tucson, Phoenix, Yuma, Las Vegas, Barstow ) EV-driving resident has been asking for . . .

". . . shorter recharging times for a full-scale EV pack could be achieved if one heats the Li-S battery to 100 deg C (212° F.) This is counterintuitive to present Li-ion designs, but conductivity goes up with heat for solid state Li-S."

"This heating could be accomplished by a built-in TMS (thermal management system) to heat the battery. The battery also heats itself during its operation, so this too could be contemplated by engineers."

"A Li-ion battery with liquid electrolyte cannot be allowed to get too hot. Present Li-ion electric car batteries are usually engineered with a liquid cooling TMS to prevent excessive vapor pressures, the electrolyte from evaporating, and in worst-case, fire" . . . "solid-state Li-S chemistry works much differently."

Wake me up when it actually gets hot. We all went up to Phoenix last Saturday night to put my son on a plane bound for New York. Most of the flights out of there earlier that day got delayed because 118° is the high temp threshold for takeoffs. There might not be enough lift to get the plane in the air before the end of the runway. Nobody has been "brave" enough to test the theory with a fully loaded airliner. The kid's flight was running a couple of hours behind schedule when it left at about 1:30AM. It was still above 100° in Phoenix even at that hour! It eventually dropped to 91° there later that night and was a "chilly" 85° or so when we got back to Tucson at around 3:00AM.

· · 4 years ago

@Ben, Brian

Too bad someone doesn't use ice, at least for the cold weather end. The Sensible heat change of water is 1 degree fahrenheit per pound for 1 btu, but the latent capacity of ice is 144 btu per pound. So, not many pounds of water could supply quite a bit of heat to a battery pack in very cold weather for quite a while

Sticking with water, even though the temperature is beyond the current range of cells, perhaps in the future when batteries can withstand 212 degrees, then the latent heat of water vaporization is 970 btu/pound. Of course, kept at a partial vacuum the water will boil at lower temps.

So the trick with phase-change materials is to find a material that will have a high solid to liquid latent heat. As far as sensible specific heat , ammonia is interesting in that, in liquid state, its specific heat varies from 1.1 btu/lb @ 32 degrees to 1.61 btu/lb @ 248 degrees fahrenheit, whereas distilled water stays at 1. These are all at above atmospheric presures. It is known as a 'hot' liquid. Interestingly in view of the foregoing, the hotter it gets the 'hotter' it gets.

· · 4 years ago

I think I'm following you, Bill. I'm not sure about all this ice, water and ammonia btu stuff, but it appears that AllCell has a workable commercial product already. It's out of the lab and into the hands of retailers, who are already selling ebike packs built around their phase change material . . .

Lithium ion packs on these ebikes typically have not had any thermal management and this product seems to provides it. The company is in negotiations with automotive OEMs as we speak. My thoughts are that AllCell is perfectly poised in a few years to manufacture replacement packs for today's Leaf. Maybe they can convince J.C Whitney's to retail 'em.


Here's a link to an article in Charged magazine regarding AllCell's phase change material, which seems to go into a bit more detail and outlines it a bit more clearly than what's shown on the company's web site . . .

One thing I gleamed from this article was that the material gets semi-soft at far higher temperatures than I initially thought. It's still basically a solid up to around 300° C (572° F)!

As for batteries that can withstand 212° (ie: the solid electrolyte lithium sulfurs, which is really a different subject but buried within the same above post,) this appears to be an optimum temperature for high speed charging in this chemistry and not a safety threshold . . . which leads me to believe that these next generation cells could be comfortably operating at temperatures that would fry one of today's.

· · 4 years ago

Just wondering if using my A/C while plugged in increases the battery temperature? May sound obvious to some, but I am unschooled in the science of electrons, and this seems to be the case with my I-MiEV. I had been getting 85+ miles per battery in the warm(but not hot) weather. When we had an uptick in the humidity I decided to pre-cool the car in my detached garage. I started the car up and noted the temperature sensor read 91 degrees. The outside temperature was only about 72 degrees. The car's range reduced dramatically, although I was also using the A/C while on my commute.

· · 4 years ago

@Benjamin Nead

Interesting article. Nice to see people are pursuing better batteries... Now me, I'm much more interested in larger capacity than faster charging ability. As a for instance, when I made a field trip to Brian Schwerdt's house near Cicero, NY, If I had a 400 mile range it would have been much easier.. Then I could just charge when I sleep and not worry about it. The new EV2 article here on PIC shows he's building it with a 71.5 kwh battery... HEAR HEAR, hehe.

· · 4 years ago

I would say yes, JKDLOU. You're attempting to charge while simultaneously putting a load on the battery by running the A/C. The battery will heat up while charging - even without an extra load - and also be hot immediately after driving. Running the air conditioning while operating the vehicle is also going to cut into your potential range.

On seriously hot days, park the car in the shade and let it sit for an hour or so before charging (the Leaf's owners manual recommends this and I'll guess it's also something advised for the iMiEV.)

Try to do your charging at night, when it's coolest outside. This is a good time to vent your garage , if possible, and also partially roll down the window on your car. Seal your garage early morning (to help keep the cooler nighttime air inside that enclosure) and stop charging then (give the battery a chance to equalize it's temperature somewhat before immediately driving off) but leave your car windows partially open.

Then, during the first few minutes of driving, keep the car windows ajar. Finally, roll the windows up and then turn the air conditioning on. Your car interior will cool down quicker and your A/C won't be working as hard . . . hence, not cutting down your range as severely.

All in all. this is the sort of thing that owners of older ICE cars have to do, if their cars don't have the greatest of A/C units and there's a chance that running it hard is going overheat the engine's cooling system.

· · 4 years ago

Longer range, Bill? Again . . . check out that Li-S battery article. Factoring that the voltage (power) is lower per single cell (about 2.5V from what I understand, compared to about 3.6V on most single lithium ion cells,) you are rewarded, in turn, with something like a four fold increase in energy density. A 300 mile Leaf with the same sized/weight pack that's in there today? It sounds like we'll see this in a few years.

· · 4 years ago


I got a chance to read through that article on Li-S battery technology, it's pretty cool stuff. One thing I'll point out is that it has the same volumetric energy density as Li-Ion. A 300 mile Leaf with such a battery would be the same weight, but 4x the size. Not a show stopper, but worth noting. The real metric most care about is price per kWh. Price is the main reason most automakers are shying away from huge batteries.

I find it interesting that the hybridcars article is claiming that Tesla's 3rd generation EV is going to use Li-Ion, and not Li-S. I'm not sure why the delay of 3-4 years, and what Tesla expects/hopes will happen in that time, but now I'm doubly curious.

Another point is that a GM exec hinted that there are prototype cars on the road today that have 3x the energy density of the Volt. It doesn't sound like that particular cut of Li-S technology is mature enough to have that kind of a prototype. I wonder what they are using.

· · 4 years ago

I run my VOLT very hard, its a commuter that was running 70miles RT per day now im pushing 90. with 1 to 1 1/2 charges per day. I know the SOC is never 0% with the software GM uses to protect the battery and health, the car already has 11,700 miles on it. Im really eager to see the battery life in another year or 2. From what I have researched we (VOLT Owners) have alot less to worry about in the battery heath world due to the great active battery management. Possibly the Tesla's will have as equal of a success with their active thermal management as well.

I have a parking garage at work and home so this helps from direct sunlight/heat during the day.

Any others on here who drive hard like me?

· · 4 years ago

I disagree strongly with the opinion that hot weather effects "prove" the LEAF to be unready for prime time. Most of my driving is in the San Fernando Valley, & has been for many years & 5 cars, most recently my 2011 LEAF. I have had no trouble with my batteries. This contrasts vividly with my ICE cars in the summer heat: the number of blown head gaskets, & the many times I had to pull over to let the engine cool. Would these critics say that ICEs are likewise not ready for prime time?

· · 4 years ago

@Frondeo - Define 'hot weather'. Nevertheless, you raise an interesting question. I leased a LEAF for a little over a year and drove it through two Tucson AZ summers before turning it in. I really liked the car and had every intention of keeping / buying it at the end of the lease. But after two summers of deep-cycling to get to the top of Tucson's aptly named summer escape, Summerhaven, it became clear the LEAF would soon not be able to make the trip, at least to the top of the Catalina Mountain Range.

So what killed the battery (actually just down 1 bar, apparently about 15%)? Was it the heat or the repeated deep cycling required to make the weekly 30 mile, 6,000 foot climbs? Or the combination?

· · 4 years ago

True, Brian, that 4X energy density Li-S will not directly translate into a battery that's going to automatically give 4X the range. But there are other details in that sidebar worth noting. The cells are probably not going to require a liquid TMS (they actually like to run hot, apparently) and, thus can be packed more densely into the enclosure. It's been discussed here before, when estimating battery energy density, that it's important to factor in the total weight of the pack (TMS, enclosure, etc.) when calculating measurements such as Watts per kilogram. Even if we can get an improved Li-S version the current sized Leaf battery to do, say, 125 miles per charge and weight less, this is significant progress.

As for cost, sulfur is incredibly cheap when compared to cobalt and manganese. In fact, it's a waste material left over from refining tar sand oil. There are currently mountains of the stuff and a problem as to what to do with all of it. So, one other promise of Li-S is a lower cost cell. I guess all we can see how it all plays out.

What GM got up their sleeve? I know they've got millions sunk into Envia, which is company developing a promising next generation Lithium Ion cell. I'm going to guess they'll become a real player before Li-S. The crystal ball is a little cloudy on this one as well.


While I agree with you, Frondeo, that EVs are ready for prime time, there are still legitimate concerns with how well current iterations (the Leaf, in particular, with it's passive air cooled pack) perform the hottest of climates.

The San Fernando Valley (Los Angeles area) is far more temperate than the Mojave and Sonoran Deserts, where most of these sizable reductions in battery capacity occurred last summer. The verdict is still out as to how well the 2013 pack (presumably different cell chemistry) will do. I also think the Leaf is a marvelous car on so many different levels. But a more heat resistant battery would make it a more universally adaptable vehicle.

There was a time when a pack mule was a better choice of transportation through Death Valley than a Model T Ford. We probably won't have to wait 100 years for an EV with better batteries to make just about any current ICE vehicle you can think of look anachronistic for the same mission.

· · 4 years ago

Having had experience with mules, & 1 or 2 with a Model T, I would say that the mule is still the better choice in Death Valley. (The mule also is more reliable than VW Bugs- been stranded in Mojave a few times in those!)
Seriously, though I have had to make some changes in driving habits, not only am I driving more safely & intelligently, it's all worth it to be refueling at home, off my solar panels. I don't even know what gas costs anymore.

· · 4 years ago

Interesting that you brought up the VW Bug, Frondeo. The WWII military variant, the Kubelwagen, was able to operate as effectively in the Sahara Desert (no radiator to boil over) as it did on the Russian Front (no radiator to freeze.)

That flat 4 air-cooled VW engine really was a brilliant and adaptable design. One of the weak links of the stock iteration, though, was the undersized oil cooler that protruded from the top of the crankcase and was buried inside the fan shroud. The stock oil cooler obscured airflow to the number 3 cylinder exhaust valve and this was typically the valve that would fail from heat stress.

By the early 1970s we began to see any number of aftermarket oversized externally-mounted oil coolers and oil pumps with improved flow capacity to match them. This, in turn, allowed the engine to be hot rodded more reliably and make it particularly adaptable for things like dune buggy duties and Baja racing.

If we can get next generation EV batteries to operate comfortably in the same temperature zone as the old VW air-cooled engine (solid state Li-S chemistry appears to promise this,) we should be in pretty good shape in regards to being able to driving through Death Valley electrically on a hot summer day.

· · 4 years ago

Yes, Benjamin, some of my friends did Baja oil coolers with amazing effectiveness. Cooling is an interesting problem. My '60's MGB-GT did much better than my friends' Detroit cars, because of a good, well-positioned oil cooler ( right behind the grill). I did use desert bags out to Ridgecrest & places.
I have no covered parking for my LEAF, so I hose down the blacktop where it sits, to "barefoot" temp. Seems to help...

· · 4 years ago


By using your garden hose you are lowering the temperature from the dry bulb to the wet bulb, and in arizona's dryness it is probably 60 degrees difference, and more like 100 if the blacktop has been in the afternoon sun.

No one in the humid Great Lakes states knows what a "Swamp Cooler" is, but I bet every Arizona child does. Unless Air Conditioning is ubiquitous now. But I'll bet almost all commercial buildings have evaporative condensers, since in dry hot weather they'll cut the electric use by a 1/3 at least.

· · 4 years ago

You're right, Bill. Swamp or evaporative coolers are (or were) ubiquitous in Arizona.
It's still a viable way to cool down the interior of a dwelling and they even make portable units for car interiors . . .

Unfortunately, they lose their effectiveness very quickly in humid conditions, which is why you only see them being used in desert climates. Even here in southern Arizona, after the summer monsoons arrive between July and September, they are rendered almost useless.

The other main reason that air conditioning has supplanted evaporative cooling in recent years is that water (which a good sized swamp box will use a lot of) is now considered a scarcer resource that electricity in these parts. Larger commercial buildings here are almost never swamp cooled any more. Many residential dwelling have both swamp and A/C, so the home owner can switch between the two depending on outdoor humidity.

You can't really call yourself an Arizonan, though, if you haven't rebuilt a swamp box at least once. There is also a particularly pleasant smell associated with aspen wood fibers, which the better swamp cooler pads are made from . . .

· · 4 years ago

Several years ago we installed a 20 SEER Trane heat pump. I seem to remember being told the thing was so efficient it used about the same amount of electricity as our old swamp cooler. We subsequently removed the swamp cooler and, with the PV we have installed, were running on a break-even basis with the local electric grid (until I started driving EVs - a deficit that should be corrected next month).

Anyhow, it is an academic question because I don't think we will ever go back to evaporative cooling again. But was I sold a bill of goods?

· · 4 years ago

No, Steven, that heat pump is the way to go nowadays in the desert. It's also a heater in the winter (although that part of the equation isn't so critical in our climate, save for those couple of nights when it gets below 32° F) Adding the PV solar completes the package.

New to EVs? Start here

  1. Seven Things To Know About Buying a Plug-In Car
    A few simple tips before you visit the dealership.
  2. Incentives for Plug-in Hybrids and Electric Cars
    Take advantage of credits and rebates to reduce EV costs.
  3. Buying Your First Home EV Charger
    You'll want a home charger. Here's how to buy the right one.