How to correctly measure battery degradation

[@huboz0r]

Thanks for ramping up the 4k podcast format. One of the types i watch most, and also listen with screen off in the car. I like the experiments with new formats, the 0 mile test also gives a bunch of new insights.

[@go2ev]

Me also I was impress with last Model Y, that do 33km after 0% 0km

[@NO_OPEC_NO_PROBLEM]

@@go2evThat is impressive! Wonder how much you’d have after 4 years and 50k of miles. After Bjorn’s insights, I’m curious…

[@thegzak]

Totally agree about the start button - it’s an abomination in EVs. If you don’t intend to drive, then simply don’t put it in gear. Even a gas car turns on some auxiliary electronic systems before you turn the ignition, which is the equivalent of simply not putting an EV in gear after getting in.

[@NO_OPEC_NO_PROBLEM]

I suspect OEMs are pulling some familar functions from ICE to EVs to make consumers more comfortable.

[@xWris3]

Great talk! I don't know where you live but at 12:38 in France that's how you should take a roundabout. Only use inner-lane if you go more than half or U-turn. Straight is outside lane.

[@berthogendoorn2133]

Battery degradation can be linked to one or a few out of spec cells that cannot be fully charged and as such reduces the ability of the BMS to complete a 100% charge on the whole pack. I have seen Tesla Model S that had two defective 18650 in the pack and the technician simply cut the fusible links for the cells on the pack, (which removes the defective cells from the circuit) and that particular vehicle was able to recover a considerably, not back to original but certainly making the repair an economical fix rather than complete pack replacement.

[@volodumurkalunyak4651]

Having seen battery degradation on a laptop battery myself I can say battery degradation is whenever all of the cells hold less charge than before. Maybe one cell holds 50% (yes, laptops batteries are used even when that degraded) of originall capacity and outher one 51%, but all of the cells are relatievly similar. What you are writing about is failed cells - that also happens, but not that often. Degradation always happen, cell failture - rarely.

[@StevenYoungcaptual]

Oh yes-4K is wonderful on the 65” OLED TV!! Just beautiful with the 4K ! Great battery info !

[@benjamilindqvist912]

You are absolutely correct. As the battery ages, its internal resistance will go up. Therefore the charging losses get worse and worse over time. If you only measure how much energy you are getting from the wall, you are also measuring the energy lost due to the internal resistance of the battery. That is not a correct way to determine a battery's capacity. The only way to succesfully measure a single lithium cells capacity is to discharge it from 4,2 volts down to the point where the BMS would cut off the power. Around 3 volts. That is then the capacity the individual cell has. Same is true for a bigger battery. You just multiply the voltage by the amount of cells in series.

[@volodumurkalunyak4651]

Disassemble big EV battery just to measure degradation??? Yes, that will be the most exact way to measure, but not a practical way. Furthermore there will be huge labor cost: fresh battery disassembly/long test/reassembly and repeat once more after some time for second test.

[@baalinfinity2216]

I appreciate the long detailed discussion, it was interesting to hear your thoughts on how the companies could possibly mask initial degradation to keep the driving experience similar for the owner.

[@josemdbl4957]

Loved this podcast. Amazing how you can have all this stuff in your mind and explain it that good and nicely. Keep this format up!!

[@davidwatson22]

Agreed with you on degradation, but those mountain's look spectacular in 4k ,miss that in the live streams.

[@albinlabelle]

Thanks for this podcast. Nice landscape + weather there ! It's rather complicated indeed, if not impossible actually ! Long story short (my take away, FWIW) : ○ Initial 1- Measure how much energy is stored (or usable) in the battery going from 100% to ±0% with your new car (requires a dongle connected to the OBD) 2- Note %SOC BMS @100% SOC display ○ Periodically 3- Re-calibrate the battery 4- Then, perform new measure to evaluate battery degradation, on same trip, same season, same use of A/C or heating, way of driving… (ABC - Always Be Consistent !) § Note %SOC BMS @100% SOC display ○5 Add the evolution (between Initial and actual) of (%SOC BMS - %SOC Display)*theorical battery capacity to account for the top buffer. But even following such a strict protocol, I am unsure about the accuracy of this assessment. With rounding errors, and inability to fully be ABC, you probably can't expect to be precise at the 1% level. Would be interesting to perform two initial measurements, and see if you reach similar figures. Have you done that ?

[@JohnDoe-xr8dz]

I might be weird or something, but my EV is sort of a 'closet' too and I open the door often with no driving purpose at all. I like the start button.

[@phonehoppy]

Thank you Bjørn, great video, on a +1 nerd level. Two more thoughts I wish to add: 1. In Model 3 and Y (maybe S and X, too, but I don't know) the BMS can get decalibrated if you don't allow the car to go to sleep for an extended period of time. The BMS needs to check the open circuit voltage of the battery from time to time and over some hours, and it is doing that only if the circuit is really open, i.e. when the car is asleep. If you always keep on sentry mode or if you are using apps or websites that wake up the car frequently by remote access, the BMS will never get into that situation and will decalibrate over time. It will seem that you are losing range at a rapid pace and may think the battery is degrading, but that's not actually what is happening. The BMS is just getting more conservative and show you less range just to be sure, because it can't do those measurements. Just try and let the car sleep, for example by turning off sentry at home or extending the poll interval on apps or websites which regularly pull data from the car. You will get your range back after a couple of days... 2. As Bjørn said, you will get more heat loss when you hammer it and thus you mess up your measurements. But it gets even worse if you hammer it AT LOW SOC. Because the voltage of the battery cells drops significantly at low SoC, pulling the same power requires higher current (amperage), which in turn heats up the cells, which in turn increases heat loss, which in turn makes the car pull more current to keep up the power, and so on. This is kind of a snowball effect which makes your SoC drop much faster than expected, and because the BMS sometimes isn't fast enough to detect this situation early enough and set power limits to prevent it, you may run into a situation where, even at still positive SoC, you may suddenly run out of juice and will get stranded. So: When the SoC is really low, take it easy, even if the car doesn't yet show a power limit. I've seen a video of a Model S driver which ended up pushing his car the last few meters to the Supercharger, and maybe Bjørn's problem with Optimus Prime getting stranded with still +14 km of range also had something to do with that - pulling trailers takes a lot of power...

[@Steror]

I love Bjorn's ABC rule, it changes according to situation! Always Be Charging, Always Be Consistent, Always Be Chilling - I might steal that, haha

[@scottmcinnes4516]

Super interesting. Thanks Bjørn. I’ve seen a weird phenomenon for about a year now on my 2019 model 3: I would charge the car to 60%, go back home with say 59%, but a few hours later I would very often see 3% less (ie 56% - with nothing working on the background: no sentry mode, etc). But on occasion, 2 or 3% more (ie 61 or 62%). Probably the issue you mentioned of BMS needed calibration? Tesla service centre suggested I do a 100% to 3% run, two or three times, in order to fix the issue. Haven’t done it yet

[@DiogoFilipeR]

Maybe after charging it does some cell balancing and figured it has more or less than it was counting before

[@lovethytuber4770]

I'd definitely measure initial deg, it's deg after all. Moreover it gives you additional information about how the battery behaves within this initial range. It could show that you have to 'break in' the battery a certain way. As far as buffers are concerned, you kinda have to charge all cars to actual 100% to be able to compare them anyway. Bottom line is, you have to fully charge and discharge the batteries a defined number of times over a defined time periode, ideally under the same conditions. Sidenote: Damn right, don't ever call us german! :)

[@Vipauer]

Greatings from Portugal 🇵🇹

[@xiziz]

I do both discharge and charge when I test, 100%-2%-100%. I've done it once a year for three years during a dry summer day, charging back up at 14A at home. The degradation is the same on both charge and discharge for me. But I agree, discharge is the relevant number, how much capacity is left for me to use. (~9% measured degradation on a 4y(from manufacture date) ioniq 28 with >80k km.)

[@austin2planks]

Just found this videos. Ive been collecting BMS State of charge at Fully Charged for multiple e-Niros. So far best is 94.5% and worst 97%. One had dropped SoH but still had significant top buffer. Research continues!

[@MR-vj8dn]

This is very interesting information, about correct measurement of battery degradation. I've been asking myself if Dekras Battery test is enough. It is done in under 15 minutes.

[@James_Ryan]

Complicated indeed - thank goodness for Aviloo! :)

[@polytech90]

excellent podcast about the battery degradation. I would like you to podcast one day about the importance to have a good trip planner built-in in the car. some ev manufacturers like Hyundai-Kia-Genesis which manufacture excellent electric vehicle but the lack of a good trip planner make the road trip a little cumbersome. Tesla navigation system or even Google automotive is a good sample how ev manufacturers can improve the navigation system.

[@fjgaston]

One way to measure, instead testing from 100% to 2%, if you can read infos with OBD would be to measure based on cell voltage, for example from 4.10V to 3.10V then no buffer can fool you as high and low cell voltage is pretty reliable and consistent. I guess cell voltage difference at low SOC is also a good information about the degradation ?

[@steaksaretasty]

Good point about BMS calibration. Example: we have a 2020 model X long range plus with 25k miles (100 kwh pack). Usable capacity is showing in Scan my Tesla as only 86 kwh (91 kwh Nominal). Car usually is charged between 30 and 80%. In fact it has not seen anything less than 6% SOC in its life. It is mostly charged at home at 240V. Has it degraded that much or simply out of calibration? New 100 kwh pack should give about 92 kwh usable.

[@thegzak]

Well this is super relevant for me since my warranty is about to go up!

[@marcelvankeulen6223]

Interesting! Did ever test an electric motorcycle like the energica’s(fastcharging) or Zero’s? Thanks

[@bjornnyland]

No

[@fineartz99]

(at end). What? Speed-bumps at highway speeds?

[@martonzo-5802]

Liked this video a lot!

[@diamp1]

Yo Bjorn... I just bought a 2019 Audi Etron Quatro 55. Its only traveled 17k miles in 5 years. I charged it to 100% and only got 143 miles on a full charge. The weather in London today is 13 degrees Celsius so not very cold. The EPA range for this car is 225. miles . That is over 30% degradation. Do I need to take the car back to Audi to check battery health?

[@davidjohnson7633]

I love your deep dive into battery health and charging! Have you done any testing on charging losses? In other words, the difference between charging rate and actual battery intake. I’ve heard that the slower the charging rate, the greater the energy loss, with Level 1 charging resulting in a shocking 30% charging loss. Also, does Level 2 charging degrade the battery?

[@bjornnyland]

Yes

[@evdabbler]

On the point around how the car measures kWh, at least on Korean cars it's easy to reproduce, every second there is a reading of Amps drawn and voltage. Power = voltage * intensity. So every second you get a reading of instant power in kW drawn from the battery. The energy consumed in kWh over an hour is the sum of these kW values divide 3600 seconds. As intensity is negative when regenerating, that value is net of regen.

[@matthiasmuller5173]

I made for me and my car the simple version of measuring. Charging to 100%, driving to 0% :) and than consumption mulitplied with distance. This is my reference. Acutal, after 35.000km I see 4% less capacity to the netto capacity in the specs.

[@go2ev]

Many thankss, really interesting blog subject :)

[@baalinfinity2216]

I heard someone say the new Volvo C40 doesn't have a start button, if you have the fob in your pocket you just get in the driver seat and press the pedal. Do you know if this is true?

[@decimal1815]

Agree about 12 bars SOH on Leaf 1 - they are usually too optimistic ;) But the RIGHT side of the car is the RIGHT side for the battery port, because that's the side civilised drivers sit. Or the front is fine too!

[@shivan6416]

Agree for start button but disagree with AC running when openning the car. AC should be on when you set drive mode. Running the AC compressor when you just want to take something in the car (but not go) is useless.

44:23 next time take detour to left, to se a big meteor crater!

[@timberthewolf733]

My 2013 Chevy Volt, could deliver 10.3 kWh usable, now you still can get 10.3 .... I was confused until I looked it up and it has a 16.5 kWh pack. Ahhh Chevy is hiding it in the top buffer.

[@edoz8939]

Björn, if there is a technical error, like the car is continuing to accelerate for no reason because of a defect can you stop the car using the start button? Or if the driver is getting sick and you sit next to the driver it you want to stop the car.. then a start/stop button could be useful maybe?

[@kdyring2311]

Tesla has an emergency brake functionality for this unlikely case. Just hold the right stalk button in.

[@berthogendoorn2133]

The way you measure at 100% charge and at medium speed 90km/hr to very low state of charge is really real world measurement, which can be trusted!

[@noelvliegenthart7858]

You should upload this to Spotify so we could listen to it with our screens off

[@Cold-1]

As far as I know, Tesla has a second "hard" bottom buffer to prevent the battery dying from low discharge. And this buffer would not be usable for driving. Is that correct?

[@bjornnyland]

All EVs have it.

[@CheddarKungPao]

This is a really interesting topic. Our Leaf is from 2014 and I usually tell people it has no degradation, even though I have never done a thorough test and rationally I know there must be some form of degradation. But in reality, I don't experience any. The GOM still shows the same range. It still always goes as far as I ever drove it before. So if there is any degradation but I never experience it, does it really exist?

[@basedw]

Maybe the leaf has (had) a buffer bellow zero. Which is now lower/not there anymore. Tesla does this for example

[@CheddarKungPao]

@@basedw yep, could be. 🤷‍♂️ i dunno. But after 8 years it still behaves like it did when we got it.

[@richardgoldsmith7278]

On the leaf bars … some unscrupulous second hand dealers found out how to rewrite the original capacity so the capacity guage shows 12 bars again for resale. Buyer beware!

[@markeaton6734]

I'm forever going into the car because I forgot something, however I still prefer how my Tesla just comes awake ready to be useful.

[@Bodzio1982]

Most of the time I try to charge using slow chargers like 7 - 11 kWh. I top up my battery usually from 50% to 80%

[@sandmehlig]

Yup, if someone has kids, a "start engine" button is as useless as a key-code. There should always be a reliable authentication that the someone sitting in the drivers' seat is able and allowed to drive and applies pedals/steering appropriately to the current situation.

[@JW-mx3qg]

For Tesla’s cars, aren’t their batteries made and usable with a 10-20% reserve? In essence, they made them (battery pack)bigger with the assumption that people would go 100-0% charge/discharge, and therefore prevent premature degradation from such “abuse”?

[@samusaran7317]

Doubt it

[@Morpheusz89]

I like the start button in my E-tron :D

[@michalvaner3167]

Hello About the measurement with or without buffer and hiding it. It kind of depends on why you measure it. If the goal is to impress your neighbors about how great care you take of your car, you of course measure it with the degradation hidden and claim pure zero, let them burst with envy. If you want to fill in the „Battery degradation“ field in ABRP profile, then again, you let the car hide all the degradation it can, because it's how far it'll let you drive on one charge. Until ABRP learns how to utilize the real degradation to adjust charging speed estimates. If you're buying a used car, you want to see how much of that hiding/safety buffer is already eaten up. Because eventually it'll run out and the degradation will start showing up and you want to know how soon that'll be. Which brings me to other things around battery degradation. It's not only the range you lose when the battery degrade. But nobody really talks about how the car shows the tortoise sooner with degraded battery (because higher internal resistance it won't be able to provide as much power with higher charge level), how the car charges slower (because higher internal resistance will produce more heat that needs to be cooled away and might overheat). Is it then degrading faster because the buffer is eaten up and it'll charge to higher real percentage? Are these things only theoretical, or are there not enough old EVs around yet? Recently, I've bought a Kona with the 39kWh battery, and it's great so far, but I would like to know what to expect when it'll be maybe 15 years old or so 😇. I mean, if it has 30% smaller range, that would still be a useful car for some use cases, but what if the tortoise pops up with 20% of charge?

[@richardgoldsmith7278]

Coulomb counting is the only accurate measure of capacity, but almost impossible to measure.

[@eunu6928]

My Leaf 2017 , when I charge Fast drive less then I charge slow, or better say discharge faster with that 100% charged in 30minutes

[@cg986]

Why is Singapore lagging behind so much? The island is perfect for EV's... People are rich.

[@robertklasson5456]

I checked a few dozen Aviloo test results a car dealership put up online. Tesla averaged over 11% degradation. The lowest I found was a 2020 with 22000 km with 6.9% degradation. All other brands I checked were less than 3% degradation for 2019 models or newer. Are legacy auto better at hiding degradation, or does Aviloo have the wrong initial capacity for Teslas?

[@volodumurkalunyak4651]

Car dealership doesn't like you bying a Tesla as they don't have their cut in that transaction. They might (or might not, I cannot really know) use hand-picked part of the whole data. Tesla had also put out an update to hide some capacity as a below zero buffer. That might or might not got into Avilo measurements. Maybe that really should be measured as a degradation or "Tesla tax", it is for you to decide.

[@olam4u]

Always great videos Thanks

[@richardgoldsmith7278]

Tesla does calibration readings whenever the car is static and sleeping for a number of hours (5 or 6 in the Model 3) and those readings are then used by the BMS. I take the opportunity to fill in the in-between readings after I have driven close to zero SOC. 1st charge to about 25 - 30 % because that needs to be fairly soon after reaching zero, then rest for 5-6 hours before setting 50% limit for next night. Then 60% subsequent night then 70% and so on. I don’t drive every day so this plan is easy. Never gone below 0% and only go to 100% 4 or 5 times a year.

[@austin2planks]

You say 10% after 7 years is not alot. With Niro top buffer and long term high SoH numbers id really love you to test an old one and find out how good that Kia BMS really is. I mean there has to be some benefit to dog slow charging right? 😂

[@piscario75]

Yes I did a slow drive recently from 100 to 91% and travelled 48km which would have given our 38 Ioniq a range of 530km lol.

[@bjornnyland]

Lol

[@LiiMuRi]

I guess the most accurate way to measure degradation would be to remove the battery and run it through a standardized charge-discharge test cycle. Do this when the battery is new and old and you should have the most "correct" answer. It's just not very convenient...

[@valium20008]

Hi Bjorn. I've been watching your videos for quite some time, I agree with you most of the time. However I disagree with consumption, meaning that if I go from point A to point B, I need to know whats was my average consumption including everything (AC, heating battery, radio, etc), because some cars consume more accesories than other. I want to know out of my 77 kwh how much I've drained (250 Wh/km from 200 km trip means I have left 27 khw). I think this is more relevant to compare all the car consumers

[@bjornnyland]

You misunderstood. All cars I have tested does include everything it consumes during the drive (AC, heater, lights, USB, etc). But some cars count while stationary, which is incorrect. Re-watch that part again and you will understand what I mean.

[@LoneWolf-wp9dn]

Engine and motor mean the same thing... the machine that makes you move... its just that in the early days engine got associated with steam machines more etc etc... also propulsor is the exact same thing... machine that makes you go forward

[@bjornnyland]

Incorrect. There's no such thing as an electric engine.

[@LoneWolf-wp9dn]

@@bjornnyland its not incorrect linguistically... it means the same thing... etymologically... its just people got used to using them a certain way

[@erwingiger9735]

According to wiki: An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.

[@roygardiner4002]

@@erwingiger9735 Which is exactly what an EV motor does !

[@OrikkO78]

@@roygardiner4002 But hopefully not as soon as you press the button...

[@FullSpecO]

Battery degradation can also be seen as pretty simple. The batteries we have today accumulates minimal damage if the battery is at 50% - and is not used at all. Every hour the battery is not at 50% - it takes more damage. Any use - i.e. charging/discharging away from 50% - both over and under damages the battery more. And the further away from 50% the bigger the damage. In addition any quick charging/discharging damages the batteries even more than slow charging/discharging.

[@kjelle5350]

Depressing info

[@andys31337]

@@kjelle5350 everything around us constantly degrades, if we are honest

[@aviationboy8]

@@kjelle5350 yeah but it’s microscopic damage. So small you won’t even notice.

[@samusaran7317]

@@aviationboy8 That largely depends on charging curves and can be very noticeable or very minute. Look up battery chemistry

[@OrikkO78]

👍

[@roygardiner4002]

The obvious way to measure degradation is to compare the current range at 100% charge to the inital max range as delivered new. Express the difference as a percentage of the original range. Our 8 year old S85 at 85k miles has lost 7% using that simple method (in less than an hour).

[@bjornnyland]

Not accurate

[@aviationboy8]

@@bjornnyland I agree, but what about the model 3 with the range display enabled instead of %? Many owners report this drops 1-2% within months of ownership. Some sort of crude measurement, limited by the accuracy of the BMS? Of course as you mentioned, any buffers would hide the true degradation anyway.

[@Bud_Terence]

Hopefully this whole "science" is soon obsolete, with newer batterytech ... Degradation as slow as possible, at high chargingspeed and the battery lasts longer than 20 yrs at over 80%.... Dreams and wishes😂

[@kompost1]

Any new tech will still be bound to inefficiencies of one kind or another ref Ohms law, unless the tech works outside of Newtoon's law (ie. near 0Kelvin) Eventually, capacity increase, charge speed or range expectation won't be an issue. Ppl forget that consumption, range, speed or fatalities wasn't an issue for early adopters of ICE.

[@aviationboy8]

In a way it already exists in LFP form. 3000+ cycles and the ability to charge to 100% often, degradation is almost irrelevant.

[@lithosh007]

NIO cars doesn’t have battery degradation issue 😃

[@dragonfencing5147]

Second

[@aburahat_11]

First

[@gregchristie2763]

iM3NY protect Imperium 3 & Magnis Technology Aus.. batteries being produced today in New York with 2 million miles range with 3% degradation when fast charged so battery deg will be a thing of the past