[jmacneil]

This was in my "news feed" but it's at least the second report of this research that has crossed my path in the last day or two.

Should we file this under "bad research" and think no more of it, given the evidence that there are many reports of Teslas (and even Leafs) that have been rapid charged daily for years without destroying their batteries or catching fire?

Fast Charging Stations Damage Tesla Car Batteries After Just 25 Charging Cycles

A new paper shows that a selling feature of electric cars, fast-charging stations along highways, actually subject batteries to high temperatures and high resistance that can cause them to crack, leak, and lose their storage capacity.

www.science20.com

 

[cah197]

Well obviously they don’t crack and explode after 60 rapid charges.

Looks like this was a standalone year without battery cooling.

 

[cah197]

Just read the paper.

From what I can see they let the batteries exceed 60 degrees Celsius.

Now in an actively cooled pack they’re normally kept well below that.

A good argument for active thermal cooling in EVs.

 

[Peter Devon]

What is true is that you don't want to leave your EV parked in the hot desert sun all day with the car turned off. Then batteries will overheat and degrade.
Buy an EV with active heating and cooling, with a heat pump, and park in the shade.

 

[tom66]

Seems like a really badly implemented study. A Tesla battery isn't down to 80% capacity after 25 cycles because it is liquid cooled during the peak of charging power dissipation. If the cells exceed 60'C they fail. Who would have guessed? Perhaps vehicle manufacturers know this, that's why they have battery cooling?

 

[80698]

When I was living in Florida I had a 24kWh LEAF which I watched lose 3 capacity bars in the space of a year. It was only rapid charged twice by me. And the previous owner from new had only done 4 or 5 DC charges themselves from memory. It was parked out in the open 24/7 and was charging at work in direct sunlight. The constant heat of the warmer climate seemed to be doing far more damage when compared to my UK 30kWh LEAF which was just short of 1000 Rapid charge sessions when I got rid of it and still had all 12 capacity bars showing.

The rapid charging sometimes had the temperature gauge right up in the red when I was constantly charging and driving non stop but would then drop most of the way back down overnight. In the US I don't remember seeing the battery temperature gauge ever being especially high, but simply remaining consistently warm seemed to be the killer.

I'd also argue about how they say by the time the battery reaches 80% it no longer has useful life. In most EVs the degradation tends to slow down after the initial drop. And especially as batteries are getting bigger and bigger an 80% drop isn't going to make modern EVs useless. Take the 64kWh Kona as an example. At 80% that's still over 50kWh, which is more than enough to drive the average 30 miles that people drive per day.

There are plenty of us here who have probably rapid charged more than 60 times in their EVs lifetime, and I don't think many of us have died in cracked battery explosions that just happen because you charged it more than 25x

 

[DBMandrake]

Just read the paper.

From what I can see they let the batteries exceed 60 degrees Celsius.

Now in an actively cooled pack they’re normally kept well below that.

A good argument for active thermal cooling in EVs.

60 degrees ? That's practically cooking the battery alive...

Yes, these temperatures will cause rapid degradation if they're sustained for long periods of time, and this is probably the primary degradation mechanism for a car like a Leaf with no battery cooling system in a hot climate. (And to a lesser degree a moderate climate) I certainly would not buy a Leaf in Florida or Texas...

So build EV's with a proper active battery thermal management system that can keep the cell temperatures at a comfy 20-30C including when charging, job done.

To further improve the situation add a user controllable charge limiter so that owners can by default charge to less than 100% and only use 100% when setting out on a long trip. Heat related degradation occurs mostly at a high SoC so keeping the SoC a bit lower is also effective in reducing heat related degradation.

Hang on a minute, don't some EV's already have both these features ? Maybe we should buy those ones...

 

[DBMandrake]

I'd also argue about how they say by the time the battery reaches 80% it no longer has useful life. In most EVs the degradation tends to slow down after the initial drop. And especially as batteries are getting bigger and bigger an 80% drop isn't going to make modern EVs useless. Take the 64kWh Kona as an example. At 80% that's still over 50kWh, which is more than enough to drive the average 30 miles that people drive per day.

I'm not so sure that's true. From what I've seen there are actually three phases of degradation rate with cells, not two.

The first is the initial degradation from brand new - which as you say is a bit steeper over the first few percent, then levels out for most of the life of the battery at a slower rate.

However once the cells near their cycle life, degradation rate increases dramatically again. This may depend a bit on the type of cell but I've experienced this first hand.

 

[Orrery]

Maybe the headline should have read:
"We're trying to sell a better charging algorithm and in trying to find a way of publicising it we managed to do this to a cell, though we're not quite sure how, but it still looks good in the picture."

 

[Orrery]

Duplicated post

 

[pbceng]

i read through this article and it appears they tried two charging strategies on single cells. This is a completely different situation to the same cell integrated into the car as has been pointed out above. Firstly the pack is water cooled and secondly the BMS adapts the charge profile to keep the charge current within quite tight limits depending on the temperature and resistance of the cells.

Taking my car (a Tesla Model S 90D) as an example 100% indicated equated to approx 75kWh when the car was nearly new (~1,000 miles). Since then a change in my job role resulted in me using approx 50% rapid charging for around 3.5 years and 111,000 miles - somewhere between 350-450 events. I have tried not to let the indicated SOC drop below 20% for very long and if charging to 100% depart shortly after top of charge. Normal charge limit was 90% for this period. Due to health issues my car has done very little mileage in the last six months and has been home charged to a normal level of 80% every few days rather than daily as before, but 100% SOC now seems to equate to 73-74.5kWh as reported by the BMS. This doesn't necessarily indicate little degradation because the indicated SOC range will probably have adjusted relative to actual, but it certainly isn't anywhere near the magnitude this article states - my car would have lasted a few weeks if it was correct! In practise I am also not seeing any real difference in ranage. A recent trip of 170 miles in total with four separate drives (2 at motorway speeds, 2 low speed) spread over a day used up 50kWh for an indicated 75% SOC used. Given we used the facility to heat up the car before getting in, and the rest periods this would seem consistent with a usable capacity somewhere in the BMS reported range.

 

[jmacneil]

The whole thing looked like a poor study design to me - especially if they want to mention Tesla in their publicity, given the issues around cell cooling, etc.

But it's the sort of thing that "the average member of the public" might see pushed in their news feed and use to justify their continuing purchase and use of ICE because "EVs have a short battery life" and other similar nonsense.

 

[cah197]

The whole thing looked like a poor study design to me - especially of they want to mention Tesla in their publicity, given the issues around cell cooling, etc.

That’s not how it works. They deliberately mention Tesla so they get publicity for their studies and hence further funding.

 

[Orrery]

But it's the sort of thing that "the average member of the public" might see pushed in their news feed and use to justify their continuing purchase and use of ICE because "EVs have a short battery life" and other similar nonsense.

Yes, I've already had it pointed at me by a petrol head on another forum before it arrived on here.

Maybe it is just another plant from the oil industry? This sort of story could well be part of the well tried and tested technique of sowing doubt, which was used to such good effect by tobacco companies to undermine solid scientific evidence. The same technique has been used, and still is, by creationists, mainly in the US and Oz, where it is called "Teach the Controversy". The pretence is that there is still some sort of debate going on about evolution, and demanding 'fairness' and equal time in the media to push their bogosity - used extensively by Climate Change deniers until recently.

There is a complete industry in pushing bogus stories, with funding hidden behind multiple layers of publicity agents and 'scientific' think tanks or 'institutes'. I really wouldn't be surprised if this turned out to be one.

 

[donald]

Apparently if you charge a 400V battery pack up with 1500V, pour sulphuric acid over it before submerging it in the sea for a month, throw it off a cliff face, drag it back up, and run it over with a 40 tonne truck ... all of which often happens on a commute out of Milton Keynes according to the Union of Dumbfek Petrolheadaholes, then scientists found battery packs becomes damaged and do not last more than 5 years.

 

[cah197]

Apparently if you charge a 400V battery pack up with 1500V, pour sulphuric acid over it before submerging it in the sea for a month, throw it off a cliff face, drag it back up, and run it over with a 40 tonne truck ... all of which often happens on a commute out of Milton Keynes according to the Union of Dumbfek Petrolheadaholes, then scientists found battery packs becomes damaged and do not last more than 5 years.

As an EV driver of over 5 years, I rented a car recently.

It wouldn’t go over 40 mph, no matter how hard I pressed on the go pedal. Also, when I brought it back to the rental company the motor was smoking.

The rental company told me that this car had ‘gears’ and I was meant to select the appropriate one for the speed. I asked if they had some sort of look-up table for this.

I also heard from a friend with a Porch (I think that’s how you spell it), that if you do more than 50 0-60 runs back to back the clutch will burn up and that’s £5k at least.

ICE will never catch on.