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Charging - 80% or 100%?

54K views 71 replies 35 participants last post by  hwneighbor 
#1 ·
I am a new Kona EV owner - had the car almost 3 weeks now. I know this is a topic that has been discussed but I can never find a black and white answer. I even emailed Hyundai and got some sort of canned email response about contacting my local dealership. The dealership was nice and all but when it came to this Kona EV they really didn't seem to much about the EV version. I knew way more than they knew. I would love to charge to 100% and I did it the 1st couple of Level 2 charges. Then got spooked and set the limit for 80%. I read a couple places (other forums - nothing from Hyundai) that Hyundai created a safety limit and when our cars say 100% that is actually 80% to protect the battery. If that is the case I'd love to charge to 100%. Does anyone actually know?
 
#2 ·
Your guess is as good as mine. Like you I researched as much as I could find on this subject, with no clear answers for the Kona EV. I do know that the Kona EV TMS is more robust (coolant, etc) than previous Hyundai (and other) EV vehicles. And the manual does not specifically say avoid or minimize charging to 100%

However, despite all that, I have decided for the time being to avoid charging to 100% except when going on a trip, or will be soon after using up that extra charge. Just charging to 80% on the Kona gives me more than enough range for normal around town, and short trip driving.
 
#4 ·
I too have wandered the web looking for a definitive statement but even though electric cars have been around a few years there is no simple explanation or plan. If you need only 80% then it would be better to only charge to that amount because they say the sweet spot for battery longevity is between 20-80% but if you need 100% because of a longer trip then what I have read is go to 100% but do not leave it sitting for longer than 8hrs fully charged.

I wait till I am down around 20% then charge to 80%. If I am going a fair distance the next day I often Level 2 charge to 80% two days before then top it off to 100% using Level 1 the night before I leave - I am lucky I have both Level 1 and 2. If I don't drive a longer distance I still charge to 100% once a month but make sure I do not leave it at 100% - check out the Battery University online or this article is not bad, https://pushevs.com/2018/04/27/battery-charging-full-versus-partial/

BTW some people charge to 100% every night and have no concerns!

Not exactly a black and white answer but most of the above appears in a fair number of places.
 
#37 ·
I too have wandered the web looking for a definitive statement but even though electric cars have been around a few years there is no simple explanation or plan. If you need only 80% then it would be better to only charge to that amount because they say the sweet spot for battery longevity is between 20-80% but if you need 100% because of a longer trip then what I have read is go to 100% but do not leave it sitting for longer than 8hrs fully charged.

I wait till I am down around 20% then charge to 80%. If I am going a fair distance the next day I often Level 2 charge to 80% two days before then top it off to 100% using Level 1 the night before I leave - I am lucky I have both Level 1 and 2. If I don't drive a longer distance I still charge to 100% once a month but make sure I do not leave it at 100% - check out the Battery University online or this article is not bad, Battery charging: Full versus Partial - 🔋PushEVs

BTW some people charge to 100% every night and have no concerns!

Not exactly a black and white answer but most of the above appears in a fair number of places.
...that loks like:
  • Cycling from 80 to 20 % we get 3.500 cycles
= 3500*7/365 ...if I charge it every week I will have 67 years of life-time (before EOL 70%)?!
😵
 
#5 ·
Yes, that appears about right. Charge to 80% most of time. Charge to 100% just before a long trip. Kona EV has a 67.1 kWh battery but only uses 64.0, so retains 3 kWh as safety reserve. But this reserve will get used up over time as you charge, more quickly if you charge to higher levels.

If you’re not concerned about distance you can charge to 100% every time. But that means after 5-8 years your max range will likely be 300 km rather than 400 due to battery deterioration.

The problem (well one of the problems) for Li batteries is being left on high charge levels for any period of time. I notice that, while not the exact same battery, Apple are updating their software in September to charge their Li batteries to 80% when first plugged in overnight, with a trickle charge for about an hour before you get up (Yes, the iPhone is now going to monitor your sleeping patterns).

This will extend battery life & how long batteries retain charge, but if you don’t care about that then you can still charge to 100%.

And discharging to very low levels can be really nasty because it physically damages the battery.
 
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#6 ·
Hyundai may have built in a buffer, on some other forums people have calculated it at ~5%
I am planning on getting a Kona EV sometime in the future, and I personally would charge it to ~80% for normal operation.
Just general care for Lithium Batteries.

Even apple know it's an issue and let you limit charge of the iPhone now!
 
#7 ·
 
#8 ·
Email I just received from Hyundai... no help what so ever.

"Based on the information provided, we have reviewed our records and show that it would be up to your own discretion; as the owner of the Kona EV, on whether or not to charge your vehicle up to 100% on Level 2 charger.

For any additional inquiries regarding the operation and features of your Kona EV it is advised speaking with your local Hyundai dealership."
 
#9 ·
My understanding, as an electronic technician, is that the life of lithium-ion batteries, such as used in the Hyundai Kona Electric, is good for the warranty period when operated to a maximum capacity of 80% of the actual capacity of the battery. The charging system of the car is set to only charge the battery to this level. So when the charge indicator on the dashboard indicates a 100% charge the actual battery is only charged to 80% of its capacity. The charging system is designed to cut off above the 100% indicated on the dashboard. That safeguards the battery and provides for the long life specified in the warranty.

Never discharging below 20% indication on the dashboard will extend the battery life a bit longer as will consistently keeping the the maximum charge below 81% as indicated on the dashboard.

In the case of my new Kona Electric I intend to charge to 80% for most of the time while extending that to 100% in the case where I need to drive long stretches between charging stations.

The Kona Electric charger limits DC - Level-3 charging to 80% as shown on the dashboard to prevent battery degradation, at such high charge rates, above that 80% indication. One can then safely charge to 100% (on the dashboard) using Level-2, or Level-1 charging following the DC charging. My intention is to avoid using DC - Level-3 charging unless it is essential for long trips between charging stations.
 
#10 ·
My understanding, as an electronic technician, is that the life of lithium-ion batteries, such as used in the Hyundai Kona Electric, is good for the warranty period when operated to a maximum capacity of 80% of the actual capacity of the battery. The charging system of the car is set to only charge the battery to this level. So when the charge indicator on the dashboard indicates a 100% charge the actual battery is only charged to 80% of its capacity. The charging system is designed to cut off above the 100% indicated on the dashboard. That safeguards the battery and provides for the long life specified in the warranty.
If you can confirm those capacities I’d be very grateful. I can’t find anything from Hyundai or independent research that clearly states how their batteries work ?

In relation to warranty it’s a bit different in Australia. Hyundai guarantee that max charge available from battery will not decrease below 80% in next 8 years. So max available capacity is currently 64 kWh, and they warrant it will not drop below 51kWh. Or in distance terms, current range is 450 km and they warrant range in 8 years time will be at least 360 km.

That said a lot has been written about Li battery deterioration, & your charging strategies are pretty much exactly what is recommended to maximise battery life (& range) ?
 
#11 ·
I charge mine 100% every time!

I'm not sure about other countries but here in US, Hyundai has Lifetime Battery Warranty. I called the Hyundai customer service, they told me that the battery warranty is "up to the dealers" to determine if it can be covered under warranty. I called the local dealer, they said it depends on the situation, they need to test the battery to find out.... blah blah blah....

Too many things to think about, so I just made it simple. I charge 100%. so far I have no issues I've had my car for 5 months now. I figured that if the battery fails, i just have the dealer replace it. :whistle:
 
#12 ·
If you’re happy with that, that’s fine. Although from my readings “lifetime” in USA is not defined, and can be as little as 4 months for some products. But what concerns me is the deterioration, rather than absolute failure, of the battery. I only picked up my Kona MY2020 last week, but have been driving a (Mitsubishi) PHEV for some years & that has made me more cautious with traction batteries.

The Hyundai warranty on traction batteries, at least in Aus, is that they will retain 80% charge after 8 years. Mitsubishi has a similar warranty. That sounds about where I was heading with my PHEV that I generally charged to 100% each time. A 100% charge when new gave me about 50km range in summer & 40km in winter. After 5 years this had reduced to (about) 40km in summer & 30km in winter.

There was no sign that the batteries would fail entirely, so there were no grounds for a claim against the 8 year Mitsubishi battery warranty. But the distance I could get on an icy morning was getting to the point that I couldn’t make the 23km round trip to work without using the ICE.

From my research, the remedy for this loss of charge/range in Li batteries is to exercise some care in charging. Doesn’t have to be onerous though. Simply keeping battery charge between 20 & 80% most of the time as suggested here should mean the car will keep its range a lot longer. As the Kona has a big battery this should rarely affect driving.

While we still don’t know the cause of fires in Teslas (& one Kona in Canada) I note that Tesla is reducing max charge in their older models X & S to 80% as a precaution. While that caution may prove unnecessary it gives me another incentive to minimise charging to 100%. Likewise Apple iPhone software (currently in beta for release in next update) will introduce rapid charging to 80%.

Everyone is different in their demands on cars & if you want to charge to 100% every time that’s fine. If you’re only doing short trips there should be no noticeable problems. But I want to do some trips that will challenge the kona’s range over coming years & want to retain the ability to do this.
 
#15 ·
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I'm still 100% charging after 10,000 miles still gets 307 mile range. I'm keeping a log so i can hope to share it to you guys later someday....

I heard Tesla has some studies showing battery degradation that is around 5% after driving 100K+ miles which is really insignificant in my opinion. Our battery might be on the same level if not better.

One caveat tho is that i NEVER fast charge my car or at least haven't fast charge it yet only charged in level 2 wall charger. maybe that the one that will degrade your battery faster....
 
#17 ·
I've never seen any evidence that the Kona's battery is larger than 64.08 kWh. That's what Hyundai says it is, 356V at 180Ah. One site, Norwegian I think, quotes a higher number but when I queried them by email they told me it was only a guess! The only buffer I can see is that the BMS avoids the last 3 to 6% below an actual 100%, that's visible with Torque Pro, as is cell voltage which tells you exactly where you are in the Li-ion charge envelope, if you care to look. I can only assume that this 3-6% is LG Chem's "buffer" to ensure that they, as a parts supplier, can meet and warranty Hyundai's specified life for a "64 kWh battery".

As for charge SoC, I keep my centered around 60%. So, if I need 40% for my range, I would charge to 80% and discharge to 40%, and so on. Most days I use only 10% but that's probably unusual compared to most owners here.
 
#18 ·
We just turned 44,000 kms on our 2019. Got it delivered feb 2019.

we drive approx 170 kms round trip to work 5 days a week.

we charge to 100% each day when we come home plug it in.

we have no issues with battery last charge showed 467 kms full charge.

it’s warrantied in Canada for 8 years or 160 kms.
 
#19 ·
I suspect if anyone does know, they aren't saying. I've had my Kona EV for about six weeks now and have the same issues you do with vague info. What I have found out is that there is apparently a "buffer" built into the battery system. Hyundai claims 64.1 kwh of useable power. Apparently there is a total of 71-odd kwh available in the batteries and users can't access that last 7 kwh. This protects the system from being totally discharged which apparently is not a good thing.

In light of this I've decided to go with 100% charges. My normal recharge routine is to visit a DC Level 3 charger not far from my house. I like that one because -- for now at least -- it offers free charges. (Yeah, I know; that ain't gonna' last...). There I get the usual 80% charge. Then I come home and plug into my own Level 2 charger which takes about 2 hours to top off to an indicated 100%. So even when the car is supposedly fully charged, I should still have about 10% leeway.

Of course no one at Hyundai will endorse this protocol, but they won't say I shouldn't do it, either. It seems reasonable to me, so I'm going to continue with it until someone can give me a good reason to stop...
 
#20 ·
You may be right but I haven’t seen evidence of a 71 kWh battery, nor that Hyundai have a 10% leeway. And seems impossible to get details, as you have found out. But depends on how much you need - in my case an 80% charge will last me a few days before it gets below 30%. Charging every few days is convenient, so unless I actually need that extra charge (or see actual evidence) I think I’ll keep to an indicated max of 80%.

Last time I saw calculation of the Kona battery capacity a researcher deduced a theoretical max of 67.1 kWh, although Hyundai only claim 64. I had always presumed, as Kiwi notes about warranty above, the difference was allowance for fact that no matter how careful you are in battery construction/installation batteries will rarely (if ever) reach their theoretical capacity due to impurities and damage incurred in manufacture, transportation & installation, etc.
 
#22 ·
The advice I hear is:
1) rapid dc charging is not good for the battery. It is meant only for times when you are on a tight schedule, and should not be done regularly.

2) It is not good for the battery to spend a lot of time fully charged. It is better to only charge it to 80% ( maybe 90%) so it spends less time in fully charged state.
This is supposed to be a technique that is supposed to help preserving your battery longevity. If you actually need the extra range, top it up to 100% before you need it.
This, again is to minimize the time while the car is sitting these fully charged. The recent battery fire related recall instructions explicitly prompt us do do this.
 
#25 ·
I just picked up my Kona last week, I texted my salesperson and she said its fine to charge to 100% regularly? In fact she said "Its better to keep at 100% charge."

I still think ill cap it at 80% unless I need the full range...
In my personal experience, as well intentioned as they may be, most Hyundai dealer staff don't seem to know much about EVs. And Hyundai HQ is bafflingly stingy with information. No idea why. Here's what I've managed to dig up off the internet on the subject of charging:

1) Every site related to battery charging that I've visited says that consistent 100% charges can lead to premature battery degrading. That is said to apply to all EV's, not just Konas.

2) Don't try to charge over 80% at a fast (DC) charger. Charging speed drops a lot above 80% and DC chargers (Level III's) in general are said to degrade batteries faster than Level II's (AC chargers). Can't swear if that is true or not, but intuitively I'd suspect it is. Level II units charge at a leisurely 7.2 -- 7.4 Kwh. Level III's slam the charge rate up to 30 -- 50 Kwh.

3) When using an AC (Level II, or home style) charger, limit to 80 -- 90% charge. If you are travelling a distance -- such as out of town -- it's OK to charge to 100%, but only do it on a Level II (AC) charger. One site suggested that for speedier 100% charges, do the first 80% on a Level III (DC) charger and then top off to 100% on a Level II. Sounded reasonable.

4) Another site I visited recommended running batteries down to 30 -- 50% before recharging. It seems reasonable too. As I've installed a Level II charger at home, that is another charging protocol I've adopted for my Kona EV. So far it seems to be working fine.

5) Just as a FYI...where I live electricity is hydro generated and costs about 10.5 cents per Kwh. Depending on driving conditions, that translates to between 1.5 -- 2.0 cents per kilometre. The VW Golf I had before my EV was pretty economical as internal combustion vehicles go. But at the present price for gasoline where I live ($1.22/litre) it would cost around 10.5 cents per kilometre to drive the VW, or at least five times as much as the EV. One more reason to love your electric car...
 
#24 ·
Salespeople do not necessarily know the product they sell. You cant go wrong being conservative in this case. If a sales person asserts something that you feel is controversial, you could ask for the source of this information. "what are you basing this recommendation on?" . I would be curious to hear what he says.
 
#26 · (Edited)
I'm a mechanic at Hyundai and also working with the kona ev. If the HV battery is charged at 100% this is at 4.2v per cell. This is the maximum capacity for this type of battery (Lithium-ion polymer). 4.2v is 100%. not 80% charge.
Handwriting Font Writing Paper product Paper


Like a cellphone battery charging to 100% all the time would shorten the lifespan of the battery pack to 300/500 charging cycles, but due to better temperature regulation this can be longer, in the link below it is explained.
Source: How to Prolong Lithium-based Batteries - Battery University
 
#27 ·
I'm a mechanic at Hyundai and also working with the kona ev. If the HV battery is charged at 100% this is at 4.2v per cell. This is the maximum capacity for this type of battery (Lithium-ion polymer). 4.2v is 100%. not 80% charge.
View attachment 5030

Like a cellphone battery charging to 100% all the time would shorten the lifespan of the battery pack to 300/500 charging cycles, but due to better temperature regulation this can be longer, in the link below it is explained.
Source: How to Prolong Lithium-based Batteries - Battery University
I just picked up my brand new 2020 Kona EV yesterday and as it is my first EV I'm trying to discover all the nuances as quickly as I can (and will get my baptism by fire next week as I am taking a 1200 mile trip to Florida!)

I see a lot about the 80%-max-except-when-doing-long-distance-between-stops rule and plan on keeping to this rule as best I can. I see a little discussion about the low limit but not as much. Not that I want to get to this point, but what are the downsides to going below say 20%, and how low can you go without doing real damage?

Thanks for all of the above information.
 
#30 ·
There is information in the manual from Hyundai that recommends charging settings. If I did not live on the top of a hill, I would charge to 100% every 3 or 4 days. Instead I set at 90% for my home level 2 charging so that I gain a couple of miles of range on the way down the hill.
 
#31 ·
Instead I set at 90% for my home level 2 charging so that I gain a couple of miles of range on the way down the hill.
I did some testing with the local free Clipper Creek AC charger in town yesterday. 2020 Kona EV rated at 7.2 kWh max on AC charging.

I normally get 7.4 kWh as indicated on the console and charge to 80%.

Yesterday i set max AC charge to 90% and watched the "gauge." As the SOC went past 82%, the ROC dropped from 7.4 kWh to 1.0 kWh.
 
#34 · (Edited)
From the horse’s mouth: Hyundai advice on how to maximise battery life.
1. Do not discharge battery to low levels (if you have to, recharge ASAP)
2. Charge more frequently (like every day)
3. Avoid frequent heavy acceleration (occasionally shouldn’t hurt too much)
4. Park in the shade (like in summer when it’s hot)
5. Set maximum charge to 80-90% (unless you really need it)
 
#38 · (Edited)
There is a lot of confusion about charging when there doesn't need to be. The 2021 Kona takes care of safe charging and will warm or cool the battery as needed. It also limits current at high states of charge.
Batteries only charge with DC, so if you use a Level 1 or 2 AC charger, the car converts the current to DC. The only real difference in the 3 types of chargers is the maximum current they provide.
Using a 100 kW charger, the car will automatically reduce the rate of charge from 75 kW to under 50 at 60% SoC and much less at 80%. By 90%, the current is similar to a Level 1 charge.

I just completed a BC to Ontario round trip without issues, except many broken chargers on the prairies.

It's a fantastic car,
Rick
 
#39 ·
Hi All,this is a great forum.Im basically in the same boat with a lot of you lot out there.
I'm a owner of a brand new Hyundai Kona Electric 2021 64/150 Khw here in the UK.
For the time being I've only charged my car from the home socket and only from 30% to -80%
It is a very slow charge.
I'm planning to have a charging point fitted at home soon.
Here in the UK the temperature gone down to 2Celsius
I've set up the battery protection winter mode in the settings in my Hyundai Kona Electric , however this takes a bit from the driving range.
My question to you guys is ,what are the numbers you are getting in terms of Kilowatt per mile in your Hyundai Kona please?
I've attached my energy consumption picture for my car, please feel free to comment on it.
I'd like also to mention that I've just switched to electric from a petrol car not long ago,this is my first electric car.
Please let me know your thoughts on this and please feel free to add some free advice for my car,it will be highly appreciated.
Thank you.
 

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#47 ·
2 Celsius is cold. My Kona has gone from averaging 5.2 kWh to 4.3 since the weather has changed. I was wondering if your car has a heat pump? Mine does not since it's an early 2020 and I'm in the U.S. If you have one that should help with the cold weather mileage. I have not as yet tried "winter mode" but I read it comes on automatically at a certain temperature. - Susanne
 
#40 ·
Your home charging setup should be based on what range you expect out of how many hours of charging overnight. As a rule of thumb I get (64kWh Kona) about 9 km (5.6 miles) or 2.5% for every hour at 8 amps 230VAC. Chargers delivering 16 or 32 amps will multiply that linearly, so 11 and 22 miles or 5 and 10%, respectively.

The cool weather doesn't affect charging at 8 amps (up to about 14) but it will certainly reduce your driving efficiency. Charging over roughly 14 amps may cause the battery heater to kick in when the pack is under 15°C, significantly slowing charge rate for maybe the first 1/4 hour or so.

You wouldn't intentionally let the car go down to 30% before charging. If the car is used daily, always charge while at home even if it means a smaller spread of percent, say 50 to 70%, which is what I normally use.
 
#41 ·
Good morning

Thank you very much for your insight and advice.
So what do you get from your battery when you driving your Kona in terms of kilowatt per mile please?
I'm only getting 4.3 kilowat per ,mile on mine now and it's set for the economy mode with the highest regen settings, so I don't drive it in sport or normal mode but only in eco mode if you look at my numbers in the screen shot picture, is this normal please?.
I look forward to you reply.
Thank you for your help, much appreciated.
 
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