Why should you not charge to 100% permanently?

[Activ8]

Mrs asked me? Hmmm, good question!
We talked about the battery conditioning and looking after the longevity etc, BUT she says ...
We like to change our cars every 3 years or so, does it affect the battery warranty? Will they produce a log showing the battery status, an energy account and a coloured bar chart that scores us as poorly educated owners, graphing proof not allowing us to continue EV ownership that concludes with a short listing in a Worldwide banned group?

Our laptops are always hooked into the mains, 100% charged unless we wander around the house and garden.

Have we covertly signed something honouring the 20%-80% guidance? Should we be looking after the second and third EV owners?

Any 100 percenters on here?

[ricky10]

Current crop of EV don’t have battery health information. But it is obviously easy to see a cars range drop significantly due to battery degradation.

I think at some point EU will mandate new EVs to have clear battery health information much like iPhone or Android phone battery health. So that it makes it clear to consumer who are buying second hand products what they are purchasing.

This is the reason why I don’t like buying second hand EV especially the ones coming off lease deal. Drove a lease car from enterprise while our Enyaq was being repaired, that Mokka’s battery degradation was shocking. 12month old car, battery drop from 100% to 89% in a few miles. But it does stabilise after that.

[Skku]

Mrs asked me? Hmmm, good question!
We talked about the battery conditioning and looking after the longevity etc, BUT she says ...
We like to change our cars every 3 years or so, does it affect the battery warranty? Will they produce a log showing the battery status, an energy account and a coloured bar chart that scores us as poorly educated owners, graphing proof not allowing us to continue EV ownership that concludes with a short listing in a Worldwide banned group?

Our laptops are always hooked into the mains, 100% charged unless we wander around the house and garden.

Have we covertly signed something honouring the 20%-80% guidance? Should we be looking after the second and third EV owners?

Any 100 percenters on here?

Well ... If you want the battery in your car OR computer to have the best chance of lasting as long as possible...then you don't charge them to 100 % unless when you need to...

[Activ8]

Well ... If you want the battery in your car OR computer to have the best chance of lasting as long as possible...then you don't charge them to 100 % unless when you need to...
[/quote]

Very true..... or is it?
I've been recycling li-ion cells for nearly 25 years, mainly from "dead" laptop 6-8 18650 cell packs. Split out and tested in my experience its just a single cell failing, the remaining cells test fine and get repurposed to my other projects. Most bin the laptop packs or used to, not so much now. Phone packs too, can be built up and recycled.

The 288 cells (96S3P format) in our 82kW/210kWh EV pack uses only 77kW (about 94%) if I've understood this correctly? The same pack in the vRS outputs 250kWh under the same battery warranty and guarantees 70% charge upto 160k km. We didn't buy the car for the 2nd or 3rd owner or specced it for resale etc - so, why should I be concerned about the battery during my ownership. Its warrantied - end of.

Happy to be educated though.
Wouldn't mind knowing more about the EV's battery.

[ricky10]

You shouldn’t be concerned about battery deg during 3yr period of your ownership because a) the deg will be at best 10% -15% and b) you not gonna see the fall out of the issue.

The thing to note is that if you ACTIVELY encourage battery deg, as you seem to be suggesting as you don’t care about looking after it. Then you basically throwing money away every time you charge to 100%.

In my example of the lease car you are basically losing 10% of the charge after 12months every time you charge it to full. So that was about £1/£2 depend on your tariff. If you don’t care about loosing £2 every week on a charge assuming you are getting a full charge every week ie £100 a year then don’t worry about it. Let someone else care about that after your ownership.

The fact you asking the question is kinda rhetorical I feel

[ricky10]

Also to add, if you really want to damage the battery, you can potentially wear it out before the warranty period. If thats an experiment you intend to carry out, it would be good to know what the result is as all the long term battery tests are about preserving longevity and never one done to show how quickly the battery can be worn

[Activ8]

Appreciate the replies.

So whats a full 100% charge 82kW or 77kW?
How are the battery and individual cells being managed by the car?

[ricky10]

Full charge would be between 75-80kwh depend on what you charge with ie DC or AC. DC charge is close to 99% efficiency where AC charge loose efficiency due to conversion. Max battery capacity varies depend on condition at the time of charge.

Battery management is usually a close guarded thing. The BMS is a closed system so there is nothing you can do to alter that physically other than the 85 has a manual battery conditioning function.

[Activ8]

Full charge would be between 75-80kwh depend on what you charge with ie DC or AC. DC charge is close to 99% efficiency where AC charge loose efficiency due to conversion. Max battery capacity varies depend on condition at the time of charge.

Battery management is usually a close guarded thing. The BMS is a closed system so there is nothing you can do to alter that physically other than the 85 has a manual battery conditioning function.

Thanks.
Im confused by the terminology regarding charging efficiency?
So the conversion from AC output to DC input can vary? Likewise DC out to DC in?
Plus the relationship between the vehicles % and kWh conversion also the chargers meter being used?
The temp and status of the ev battery could also play with the charging % and it registering its capacity?
So the useable 77kW and 6% is an allowance for these factors?

Apologies for all questions!

[CrowSysE243]

Full charge would be between 75-80kwh depend on what you charge with ie DC or AC. DC charge is close to 99% efficiency where AC charge loose efficiency due to conversion. Max battery capacity varies depend on condition at the time of charge.

Battery management is usually a close guarded thing. The BMS is a closed system so there is nothing you can do to alter that physically other than the 85 has a manual battery conditioning function.

Thanks.
Im confused by the terminology regarding charging efficiency?
So the conversion from AC output to DC input can vary? Likewise DC out to DC in?
Plus the relationship between the vehicles % and kWh conversion also the chargers meter being used?
The temp and status of the ev battery could also play with the charging % and it registering its capacity?
So the useable 77kW and 6% is an allowance for these factors?

Apologies for all questions!

Charging efficiency is the ratio of the added energy that gets stored in the battery to the energy that was drawn from the charger.

When AC charging the nominal 230V AC supply has to be converted to approximately 400V DC, so it has to be rectified and smoothed to get DC and the voltage has to be stepped up to the required value. This is carried out in the car and the converter(charger) is specified to have a minimum efficiency of 95% and a maximum power of 11kW. It is likely that the conversion efficiency will reduce if the charging rate is lower as the losses in the charger will be essentially constant, however the charger is typically a bit more efficient than the specification. There will also be some losses in the cables to the car. Typically I get about 95% efficiency at home from our 7kW nominal PodPoint with a 10m cable. For example I have recorded using 37.4kWh (PodPoint and my AC demand monitoring system give virtually the same result) charging from 20% to 70% with the battery management system (BMS) showing an increase in stored charge of 35.6kWh giving a charging efficiency of 95.1%. Under other circumstances I have recorded overall efficiency as low as 87%, typically when charging from a mode 2 (granny) charger at 6A.

When DC charging the car receives the required voltage directly from the external charger so the charging efficiency within the car is close to 100%, however the charger is carrying out voltage coversion, including AC to DC converion if powered direct from grid supplies, and the current in the cables is much higher. The cost of the losses in the charging system still have to be covered, either by increasing the price per delivered kWh or by measuring the power at the input. When DC charging I have recorded charging efficiencies (ratio of BMS reported addedcharge to charger reported energy used) from 90% to 100%.

The car reported consumption rate is based on the output from the battery so does not take into account the losses in the charging process. My car is reporting an overall average of 4.3 miles per kWh for 16000 miles in just under a year but the input figure is between approximately 3.9 and 4 miles per kWh on the data I have processed so far.

The percentage charge displayed by the car and the percentage that the BMS thinks that it has are different. When my car displays 100% the BMS percentage is about 96%. 80% displayed is about 78% BMS. 50% display is about 51.2% BMS. 20% display is about 24% BMS. 10% display is about 15% BMS. The nominal 77kWh capacity is nominally from 0% to 100% display, however the actual capacity depends on factors such as temperature and the condition of the battery. In the winter it is generally lower than in the summer. For my car the BMS has reported its estimate of the maximum capacity of the battery between 75.2kWh in the winter to 78.7kWh in the summer. It is currently just below 77kWh with the trend increasing.

These charging efficiency estimates are all subject to the uncertainty in the measuring devices, which will vary with the charger being used! The algorithms used by the BMS are unknown. The most reliable measures are the cost of charging, the distance driven and the range achieved.