2022 Nissan Leaf. Supplied
Hi Bryce
I’d be most grateful if you could point me toward any commentary you or others have written around the question of EVs at highway driving speeds with elevated outside temperatures.
My wife and I recently took our 40 kWh ZE1Nissan Leaf to Sydney and back from Geelong – and discovered to our surprise that it overheated, asking us to “drive slowly” on a couple of occasions and greatly reduced the rate of DC charging.
In fact, we found it hard to keep the battery temperature gauge in the “happy” white zone when charging after driving for 1 to 2 hours at 100km/h at an ambient temperature 32 degrees, and even then at a 50kW DC charger it throttled charging back to around 15kW.
I know that the Nissan has no active cooling for the battery, but now that I’m looking I can’t seem to find much by way of specific details for any make of EV on its ability to dissipate heat.
Understandably extended highway speeds, repeated DC charges and summer temperatures that are often well above 32 degrees are all going to put an EV battery’s heat management to the test. All I can find so far are statements that range and recharge rates may be affected by elevated temperatures (and lots on low temperature performance), neither of which is very helpful!
Am I missing something here or is this a problem specific to the Leaf?
Cheers
Scott
Hi Scott: that’s an interesting ‘can of worms’ you raise! In general, extreme hot and cold conditions do affect EV battery performance if going outside its preferred operating range.
To reduce this possibility, most manufacturers include active, liquid based cooling (and sometimes heating) systems for their battery, as they all do for the drive electronics. So for most EVs, extreme heat and cold are something to be aware of when driving, but as a general rule these measures make it no more of an issue for an EV than for an internal combustion engine (ICE) car.
Cut-away view of Nissan Leaf ZE0 battery pack. Image: Nissan
The Nissan Leaf is however the exception – so whilst the problem you describe is rare for an EV, it’s not unique to you – although it is unique to the Leaf.
To put this into perspective, I’ll first go back to around 2012 when some of the early 24 kWh Leafs sold in the US went to the hot, desert climate of Arizona. It was found there that the desert heat used to age the batteries at two to three times Nissan’s ‘expected’ rate due to overheating.
As a result, Nissan copped a bad rap for poor battery life and the myth that all EV batteries have short lives like phone ones began. (This by the way is despite the evidence of 12 years plus of modern EV battery use that EV batteries lose range at quite low rates).
Anyway, the outcome then was that around 2014 Nissan altered their battery chemistry to better cope with heat and the problem appeared to go away.
In fact, it seemed that Nissan became paranoid after that and have worked hard to stop Leaf batteries getting too hot ever since … short of actually installing a battery cooling system. (Although they do have one for the drive system electronics).
This has been an ‘interesting’ decision, given all the other EV manufacturers include the aforementioned coolant based battery temperature control systems to ensure their batteries stay within the optimum operating temperature range in all but the worst conditions.
It later turned out though that the Leaf battery heating problem never really went away. With the upping of the Leaf battery to 40 kWh (in the same battery box sixe as the original 24k kWh), early ZE1 40 kWh Leafs had software in them to disable DC charging if it got too hot – although later ones only reduced the charge rate and a software fix implemented for the earlier 40kWh ones.
It seems you have been the ‘beneficiary’ of this change, so you can at least still DC charge, albeit at an even slower rate than the none-too-fast 40 kW normal DC charging maximum of the Leaf. (As a contrast, due to their battery cooling systems modern EVs now come with DC charging rates upwards of 100 kW to 250kW and beyond).
By the way, this DC throttling back issue probably only became noticed with the Leaf battery size increase to 40 kWh as this is effectively the minimum battery size for long trips needing multiple DC charging stops.
Unfortunately, a 40 kWh battery also means you need to stop more often for a DC charge as compared to say the 63 kWh Leaf e+ battery. This means that on long, high speed drives on hot days, the 40 kWh uncooled Leaf battery doesn’t get much of a chance to cool off between charges!
Summing up:
The short answer to your overheating issue is it applies to all Leafs when used in ‘extreme’ use cases due to Nissan never put a cooling system in the battery.
Instead, they implemented a few work-arounds that people bump into from time to time. (Although they did install a form of battery cooling/heating that works when DC charging for the e-NV200 van …. which uses the same EV mechanicals and battery as the Leaf).
Going forward:
Nissan now include a full liquid battery temperature control system in their latest EV (the Ariya), so it seems they are quietly admitting that EV batteries need cooling and are fixing it. Plus I know of at least one aftermarket replacement battery in development for the Leaf that does include a proper liquid cooling system.
However, this doesn’t solve your dilemma Scott. The 40 kWh Leaf is great for getting around even the biggest big city with the capacity to do the odd DC fast charge being handy.
Personally though, I don’t recommend Leafs for really long distance ‘commuter’ trips where you need to do multiple DC fast charges in one drive day – especially 40 kWh ones as they need to fast-charge more often.
(I am sure there are many 40 kWh Leaf owners who will attest to easy long distance drives: I am referring to wanting one for regular interstate etc ‘commuting’ runs where you need reliable short charging time turn-arounds when you want to do them, not when the Weather Gods are on your side).
Apologies, Scott, for not being a lot of help in dealing with your Leaf needs though. If doing that sort of trip is rare for you, it might just be worth planning the trips for cooler weather.
However, if you want to do lots more of that type of driving without worrying about the weather, a 40 kWh Leaf is probably not the right EV for you. More ‘permanent’ solutions are:
A: Upgrading to an aftermarket cooled battery when it becomes available (about 6 – 12 months for the ZE0 version is my best guess – and probably even later for the ZE1 you have).
That is an expensive option for what is after all a perfectly good car – perhaps just not one suited to your needs, so I would recommend option b below:
B: Selling your Leaf to someone whose use-case better fits the 40 kWh Leaf’s capacities (resale prices are very good at present!) and buying one with a cooled battery. (i.e. any EV other than a Leaf).
If looking at option B, the soon to arrive MG4 is looking a strong contender as the 2023 ‘bargain EV of the year’ for a budget priced EV with a good range, features and load capabilities.
If not quite so price-conscious, the Renault e-tech Megane due here later this year is likely to be the pick of 2023 for a medium-small EV with excellent features, efficiency, charging and load capabilities (including a reasonable tow rating).
Other options include the Hyundai Ioniq 5, Kia EV6, Polestar 2, Volvo C40 and XC40 recharge. Thankfully, if taking option b: 2023 is looking to be a good year for finally having EV options to choose from!
MG4. Image: MG
Hope that explains things a bit Scott? Sorry if I haven’t been a lot of help in solving your issue.
Kind regards
Bryce
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Keyword: Is there an issue with the Nissan Leaf battery overheating during highway driving?