Why shouldn't I charge my 64 kWh Kona EV to 100% every day?

100 Fahrenheit is 38C, not 50C.. I'm in steamy Central Florida and we just went through a couple of days with 97 to 99 F and even while fast charging, the battery never got above 101 F.. Battery cooling kicked in and kept the maximum temperature around 100.4F..

 

It's great just how little heat the more efficient EVs give off compared to ICE engines.

 

Pretty much all individual sub-system efficiencies throughout the Kona and other EVs are ballpark 90% or higher. The AC charger is 91% (quoted from Hyundai), the battery charge or discharge are each around 98% (my measurements), while the motor could be 92 to 96% based on other EVs. The inverter powering the motor might be around 88-93%.
The result of all that is that 'system' (combined) efficiencies while driving or charging are highly favorable compared with the primitive heat engine that to this day is still the current state of the art in ICE, which can be anywhere from zero to maybe 30% at best efficient. Improving on that is low-hanging fruit for the better hybrid designs which is why the Toyota HSD (in the Prius and others) has been so very effective for a run of some 22 years so far.

 

Only for 2019 and earlier Kona EVs. Starting in 2020 it's 10 years / 100,000 miles.

As to whether battery capacity degradation is covered under warranty or not, I read the 2020 U.S. warranty booklet and still don't know the answer for sure because it says both things (though I suspect it is covered). See the warranty booklet page here.

The high voltage pack is used periodically - roughly daily after the current BMS reprogramming service campaign - to keep the 12v battery charged so it can power the standby systems that run even when the car is "off". This happens whether or not the car is plugged in. I suspect they recommend the 100% charge for storage because they know it will be drawn down slowly and want to extend the length of time this can be done.

 

Yes, recommending anything less just increases risk for themselves with no upside. It's up to owners to recognise the trade-off of potentially increased battery life for being for more proactive and attentive in the case where long term storage is needed, ideally using the charge % limiter and left plugged in.
Disconnecting the 12V battery is another option as then nothing can draw down the traction battery other than natural losses.

 

My Volts recommended that for longer than a month, IIRC, with the high voltage battery at 50%. But to reach it to reconnect you needed to open the rear hatch manually, or leave it blocked slightly open.

But the Volt had an unadvertised Easter egg "Transportation Mode" that turned off most of the functions that drew on the 12v battery. Using just that mode, I was able to leave the car for as long as 6 weeks with a loss of about .05v.

 

It is no wonder owners get confused by all this stuff - the manuals are dreadful, including inconsistencies between jurisdictions.
The OP @JSU first posted April last year, so I assume was quoting from his 2019 US manual. My Kona was manufactured in Feb last year for the AU/NZ market, and my relevant paragraph reads as follows:
“If the vehicle will not be in use for an extended period of time, charge the high voltage battery every three months to prevent it from discharging. Also, if the charge amount is not enough, immediately charge to full and store the vehicle.”
Followed by:
“If the high voltage battery charge amount is below 20%, you can keep the high voltage battery performance in optimal condition if you charge the high voltage battery to 100%. (Once a month or more is recommended.)
Only in this 2nd paragraph do you get any sense of what Hyundai considers to be “not enough” in the 1st paragraph, though for usage rather than storage...

 

I must say the Kona owner's manual is pretty dreadful all around.

 

Nevermind the two or more vague mentions about DC charging being best avoided where possible. No doubt it's a difficult balance between giving practical, memorable advice and making it too complicated. Not to mention that many owners and drivers would not even bother to familiarise themselves with the manual contents. Too much information can be detrimental and be glad we don't really know SoH and subsequently continually obsess over it like Leaf owners do.
A local acquaintance who administers a small Kona and Ioniq EV fleet for business use mentioned to me that some drivers are unaware that the car must be occasionally charged and end up needing a flatbed tow. This is where a "quick start" guide might be helpful.

I read the second paragraph as meaning that if you are running it under 20%, charge to 100% once a month rather than after every incident, which of course we presume to understand is for cell balancing. I never go that low and rarely to 100% with the result that it's taken 20 months to get one "cell" to deviate 0.02 V, fixed with a single charge to 100%.
The first paragraph is absurdly non-specific for a relatively-predictable situation. It could just say to expect the battery to lose X% a week and ensure that it never drops below Y%.

 

There is a LOT of pure-D BS being spewed all up and down the internet about EV battery charging and most of it is by people who don't even own one, but sit and pontificate based on what they read.
From the perspect of an actual Kona EV owner for 16 months and 24,000 miles, including low and high temps, and 80 mile per day commutes I have a few real observations. The Kona EV is far more robust than is presented by the arm-chair experts. I've been charging mine primarily on a 240V 50A home charger, and since I have a healthy commute I don't really have the luxury of babying the car. I can make three full trips to and from work without a charge - that's 240 miles. I've experimented with driving as economically as possible and achieved over 6 mi/kWh in town driving and average 4.0-4.2 on the highway when operating in warm weather with some restraint. At the same time I've driven at a solid 75-80 mph on the freeway with surprisingly little consumption of additional range...around 95 miles "used" for 80 miles driven at high, steady-state speeds. I've also discovered that in stoplight driving it's better to accelerate quickly to just above the target speed, then let off with 0 regen and coast all the way to the next light with the mi/kWh pegged to the right, then add regen in stages to slow down. It's easy to stay in the mid-5 mi/kWh using this technique. Since the car has a high performance mode I finally decided I should enjoy the use of it since it's a total blast to launch away from a traffic stop like being fired from a carrier, leaving all the ICE cars far behind, and because Sport mode unleashes the car's full power, I suspect driving "economically" in Sport mode may be more efficient than in ECO. There are so many ways to change-up how the car is driven to try and unlock more range, but for sure I have not been disappointed in the Kona's range.
As for charging, I've used the DCFC a few times just to see how it worked and of course the reason to limit charge to 80% has NOTHING to do with the battery per se, and everything to do with the cost of charging! All batteries charge faster when empty and slow as they near full due to the nature of flowing electrons. To charge from 80-100% on a DCFC takes as long as it does to charge from 0-80%, and at .27-.30/minute, do the math. It's simply not cost, nor time-efficient to squeeze in that last 20% unless absolutely needed.
On my home charger I generally plug in every day simply because it's convenient to do and why not. I also generally charge to 90% and seldom go below 35% before charging. As of my last charge, with my eclectic style of driving, range is listed at 258 miles at 90% and this has proven to be reliable. It's summer now so of course the battery has greater electric potential. I DO however charge to 100% when the mood strikes me, because, why not...my last 100% charge on a 16 month old, 24K mile battery showed 297 miles range available which is pretty respectable. Granted, living in the center of Hell demands full use of AC in the hot summer which cuts into range, but thanks to the amazing efficiency of the Kona's regen, even with all this, my miles driven usually end up correlating very closely with what the range estimated started out showing.

In every conversation I have with people who don't own an electric car they throw out the cost of replacing batteries as if it's required every few months, YET it's about time for people to start looking around at the ever growing number of Teslas that are pushing 10 years old and still have ample battery capacity. Talking about changing batteries in a EV is akin to replacing the engine and transmission in an ICE car and is that cheap? Nope. Do you need to do it every few years? Nope. Same thing for electric cars. I'm not going to try and "preserve" my battery because I didn't buy an EV to baby, but to drive everyday and so far it's been solid across the board.

Sadly for EV adoption, the price of gasoline has plummeted which is what has REALLY driven EV sales down.

 

I do think that unless you drive long distances regularly in places with minimal charging infrastructure, much concern about range anxiety and battery replacement is overblown. Overall, an EV will save you lots of money on maintenance because it has so much less stuff to go wrong, get out of adjustment, etc. And EVs come with a convenience no ICE car has: The ability to "fill up the tank" overnight while you're sleeping. But yeah, cheap gas is an obstacle to people switching to something unfamiliar.

 

I find EV owners in NZ are well aware of why they might stop fast charging at around 80%, most having Leafs they know it's for efficient use of the charger. Furthermore my local DCFC only charges by kWh used.

 

Cell deviation is not a constant and will increase as the SOC decreases. Balancing isn't going to fix that.

You may want to rethink the above argument. Many of those original Model S Teslas have gone through drive unit (basically motor and grearbox) replacements (often more than once), battery replacements, etc. They were less reliable than a modern day ICE. I suggest visiting an owner forum once in a while.

Even if we ignore Tesla, the Kona has had many owners who needed motor replacements as well. I would love to see Hyundai report how many ICE Kona engines they replaced compared to EV Kona motors. Then divide those stats by number sold of each variant. That would prove or disprove the urban legend that EVs are more reliable when everything else in the car except powertrain is the same.

 

I think using Hyundai as an ICE reliability example might not be the best considering they had recalled more than 1.2 million Sonatas and Santa Fe Sports in 2015 and 2017 to replace engines in 2011-2014 Sonatas and 2013-2014 Santa Fe Sports, plus the thousands of Elantra engine failures not the mention the 400,000 Elantras recalled because their engines propensity to catch fire. That said I completely agree with you and I don't believe that EV drive trains are inherently more reliable than ICE... yet. The big problem I see with the EV situation is that they continue to insist on making drive units and gear boxes as closed non serviceable units. The failure points even in teslas seem to be potentially relatively easily replaceable bearings. I just don't understand the mentality of throwing in a $5K replacement motor to deal with a failed $10 bearing, surely you didn't save nearly $5000 in labor to do so.

 

Well, this is my first Hyundai, and sorry to say, I expected better. I have never had a motor (engine) or gear drive (transmission) changed in any past vehicle. And some of them (my past Subaru's) went to very high mileage with no major problems of any kind. I too, thought that going electric should entail more reliability. Not so sure about that now.

 

First of all you can't compare Tesla to Kona ev is mistake Not the same Battery and Software !!!

 

Jeff Dahn's video is general, not Tesla specific (other than mentioning his relationship with Tesla). There is no comparison going on. I recall that AEVA folk were providing similar advice on Li-Ion batteries to members before Tesla Motor Corp existed. They observed that the degradation could be slowed by not charging to 100% all the time. If you want to extend the life of your phone or laptop battery, do the same thing.

 

Works great with my phone. I almost never charge it to 100%. Only if I forgot to unplug, which luckily only happened a few times in the last year.

I always keep my phone between 80-20%.

 

It's good advice for all battery tech. I use an Oral-B rechargeable toothbrush, which uses a Nicad or NiMH battery. I'm on my second. The first one I left on its charger, switched on, all the time. Rated when new for 14 days, 2x2-min cleans a day, after 4.5 years it would just about die during 1 clean.
My 2nd is only charged when it stops, so averages a 50% charge. After 4.5 years it still lasts 9 days, 2 charges a day...