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Discussion Starter · #1 ·
So I don't know where/how we could provide feedback to get this changed, but is anyone else really bothered by the whole 90% thing? I don't mean the act of charging to 90% of actual max capacity to save battery life. I mean that 90% and 100% both then get mussed up together and used for various things and you have to do extra (yes, easy) math any time you're considering things.

What I'd like to see is if you set the car to charge to 100%, that would actually charge to 90% of total capacity. An additional option would allow for "overcharging" or such and carry a disclaimer that repeated use of overcharger will lower battery capacity overtime. 100+ would be displayed until capacity gets down to 100 of normal (90 total). I'm sure the reason why car companies use the total capacity vs the recommended is for advertising purposes, but it is just goofy to live with 9/10ths forever. If you're only supposed to fill to a certain line, you measure based on the line, not the total.

Anyway, just an idea.
 

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I'm not bothered by it. It is what it is. You also shouldn't top off a gas tank, which could flood the carbon canister and screw up emissions controls.
Exactly though. If you fill a gas tank to the normal stopping point (without forced topping off), the fuel gauge shows full. Not 9/10ths. I can't imagine anyone designing a car that would only show full when you forcibly top it off.
 

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I'm sure the reason why car companies use the total capacity vs the recommended is for advertising purposes, but it is just goofy to live with 9/10ths forever. If you're only supposed to fill to a certain line, you measure based on the line, not the total.
There is nothing preventing you from charging to whatever level you choose. The recommendation from Volvo is to charge to 90% for normal daily driving, or to 100% for longer distance driving needs. Your battery warranty is not impacted in any way.
 

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I’m very confused by this question/post. You can charge to whatever you want, but manufacturers generally recommend 90% or less for daily driving. I charge my Tesla to 75% daily, but that’s my choice. I can, and do, charge to 100% for trips. When you charge above a certain percentage, regen braking is also severely limited, and the vehicle is not as efficient because of that until the battery percentage comes under a certain value. I do not want the car to show it’s at 100% when in reality it’s at 90% or 80% or whatever other value.
 

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I am not bothered, get the VW ID.4 or Audi Q4 and they will recommend 80%. They warranty battery for 8 years 100K miles, I am sure they assumed some people will go to 100%. That said if you lease set it to 100%, if you own see if 80% works as that will give the best live to the battery stay within 30-80%. If you need the range all the time then use 90% or 100%
 

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It's a bit fussy and old fashioned in the fast moving EV world, but if I was thinking of keeping it I would certainly pay more attention. Manufacturers have had various levels of caution - VW would void the warranty on early eGolfs if you rapid charged it more than 3 times in a row for example, and Volvo looks cautious to me in 2021.
My first EV was a Renault Zoe in 2015, there was certainly a buffer at the top (the XC40 is 75kWh usable out of 77kWh total), but they made no demands of the driver, in terms of how to drive or charge it. Difference being it was a 22kWh battery, and the battery itself was leased, with a guaranteed replacement if it degraded too much. Fast forward to 2021 and they don't lease batteries anymore (50kWh now!) because they don't need to - very few batteries had to be replaced.
I've been 'brought up' not having to nanny batteries so it's strange to me, but then the range is so vast that I can afford to now.
 

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but is anyone else really bothered by the whole 90% thing?
Yes, but the same way that I am bothered by the fact that the gas gauge in my ICE car goes well below E. There is a beauty in not being too exact in these things. I think that for most people it's not relevant most of the time. If one charges routinely at home then they really don't ever need to care about the percent except when 100% would be meaningful. This is different from ICE where you have to vary your routine periodically based on the remaining fuel. The normal becomes not caring about the charge state.
 

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I am not inconvenienced by the 90/100% approach but no one has explained why a rechargeable battery shouldn’t be fully charged most of the time. Is it an engineering thing intrinsic to batteries?
As lithium batteries become full they require more energy to charge. This extra energy is released as heat in the battery. This has been shown in studies to degrade batteries more quickly over time by changing the chemical composition in the battery.

There are several things that manufacturers do to prevent this degradation. One method is to slow charging as the battery becomes full, another is actively cooling the battery. Because of the slower charge rate and the extra energy required it can make more sense to routinely only charge to 80% unless you need the extra 10% or 20%.

https://www.nature.com/articles/srep12967 said:
Abstract
Temperature is known to have a significant impact on the performance, safety and cycle lifetime of lithium-ion batteries (LiB). However, the comprehensive effects of temperature on the cyclic aging rate of LiB have yet to be found. We use an electrochemistry-based model (ECBE) here to measure the effects on the aging behavior of cycled LiB operating within the temperature range of 25 °C to 55 °C. The increasing degradation rate of the maximum charge storage of LiB during cycling at elevated temperature is found to relate mainly to the degradations at the electrodes and that the degradation of LCO cathode is larger than graphite anode at elevated temperature. In particular, the formation and modification of the surface films on the electrodes as well as structural/phase changes of the LCO electrode, as reported in the literatures, are found to be the main contributors to the increasing degradation rate of the maximum charge storage of LiB with temperature for the specific operating temperature range. Larger increases in the Warburg elements and cell impedance are also found with cycling at higher temperature, but they do not seriously affect the state of health (SoH) of LiB as shown in this work.
 

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I am not inconvenienced by the 90/100% approach but no one has explained why a rechargeable battery shouldn’t be fully charged most of the time. Is it an engineering thing intrinsic to batteries?
One point is that if the battery is 100% then the regen system is basically not functioning because there is no where to put that energy that is being generated. That makes the system inefficient in that aspect.
 

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There are a few decent articles on the web that explain it as well as some stats from existing EVs based on the range they kept the battery within. Think about your cell phone, charging it to 100% every day and in 2-3 years your battery has degraded a considerable amount.


But there are many other good ones out there.
 

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As lithium batteries become full they require more energy to charge. This extra energy is released as heat in the battery. This has been shown in studies to degrade batteries more quickly over time by changing the chemical composition in the battery.

There are several things that manufacturers do to prevent this degradation. One method is to slow charging as the battery becomes full, another is actively cooling the battery. Because of the slower charge rate and the extra energy required it can make more sense to routinely only charge to 80% unless you need the extra 10% or 20%.
Thank you so much. Finally an engineering explanation. Would that Volvo has provided rationales for their various recommendations…don’t use one-pedal mode on the highway, etc.
 

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Thank you so much. Finally an engineering explanation. Would that Volvo has provided rationales for their various recommendations…don’t use one-pedal mode on the highway, etc.
I use one pedal on the high way …. Even when it’s a 14 hour driving day.

As to the original poster I love the fact Volvo clearly states 90 is the limited to lower wear on the battery. I rarely charge to 100 but occasionally you have to to get over charging infrastructure holes.

Rhuges. You are right charging to 100% dennies regenerative charging but only for as long as the system is at 100% unless you charge to 100% at the top of a mountain or start your journey down hill you are wasting almost nothing due to it being full.

That said if you are close to 100% is there a massive decrease in regenerative efficiency due to the physics of li batteries?
 

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Back to the OP question. It is interesting and could make it easier for the general population.

For example, visualize the existing SoC to be like the following. It is difficult for many people to understand charging to 90% as being full:
Drinkware Liquid Light Fluid Cylinder

But, perhaps if it were to look like the next illustration, it would be easier for people to grasp:
Liquid Drinkware Light Fluid Test tube

Showing 111% is a little disconcerting. But, it is akin to the saying, "turn it up to 11".
Font Circle Automotive wheel system Measuring instrument Auto part



Manufactures could still quote EPA over the entire range. I'm not sure how that would fly.
 

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I always charge mine to 100%. I drive a lot so I always let it fully charge. It gets to about 100% about 5 times a week. Not my problem if Volvo has to fix the battery over time.
Good logic but one slight flaw.

You charge to 100% because you want the extra range but by doing so will decrease the maximum range so after a while you range at 100% might be less than it would of been at 90 if you had always done 90.

What is the threshold for Volvo replacing the battery. If it is high enough then I am 100% wrong :)
 
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