20/80 Li Ion Charging

[moeali]

I thought 4680 battery architectue is dry chemistry and is not governed by the same 80/20 rule. Is that not the case?

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[JBee]

I wish that graph also came with an explanation of what a cycle is. Because I read that a cycle is charging from 0-100% and Tesla batteries were rated for over 10,000 cycles.

The same thing said that if you charge from 20-80% that is a half cycle so you could charge twice from 20-80 and have the same wear on the battery as if you had charged once from 0-100. So if that's the case then 45-75 might be like a quarter cycle or maybe even an eighth cycle in which case you would probably get more miles per cycle.

Otherwise the graph isn't normalized and should have a number of miles driven at different degradation milestones. This way we could see "at 100k miles driven you will have 93% battery vs 83% battery capacity" or whatever it is.

On that graph is does say the range of SOC that the test is cycled in between. But without the lifetime energy for each that graph is hard to translate visually into lifetime cell range.

Cycling also varies with chemistry, lifepo4 looks much better in cycles:

Note this graph also give a bit of information on different C rates.

Then I'd just need temperature and age etc overlayed to make something like this to see what the best range is for my goal:

 

[BayouCityBob]

I would just guide folks that the primary enemy (excepting LFP) is holding at high states of charge and time/heat. FWIW Rivian are guiding to hold at 70% SOC on a daily basis. Battery U is super helpful.

BTW, the intuition on this is bolstered by PHEVs. The number of cycles on a PHEV will often run 350+ a year. OTOH, the number of full cycles on an EV will rarely exceed 75 a year. But we do not see big failure rates in early Volts, for example. Reason is that the battery is only allowed to operate in the 20-80% range and - of course - a 20% loss in range is not that detectable when you only have 40 miles to begin with.

 

[HaulingAss]

My research over the years has found that Li Ion batteries charged to 80% maximum and discharged to no more than 20% have an ‘indefinite’ lifespan. I understand there are many other factors but that this is a fundamental of this battery chemistry.
Will CT (or do any Teslas) allow programming for an 80/20 regimen?
If so… and this is recommended to maintain battery pack life, the a 500 mile range CT would be reduced to a functional range of 60% of that or 300 miles. And a 300 mile range CT would be reduced to 180 miles if these ship with Li Ion packs.
Im having a hard time with this functionality against hybrid tech.
Thoughts?

It sounds like you have never owned a Tesla.

Most people don't need to use the top or bottom 20% of the battery except perhaps a few times a year. It's there for when you need it. I can top off in my carport from 80% to 100% in a little over an hour. If I wake up and decide to go out of state, I just charge it to 100% while I'm showering and getting my stuff together.

 

[cvalue13]

. Even with all that, my battery health after 6K miles has dropped to 98%.

where/how you check that?

 

[cvalue13]

So, if you live in Minnesota (cold) you’re screwed on range, and if you live in Texas (hot) you’re screwed on battery life?

At home I only charge with 110 trickle, maybe that helps

But truck is stored outdoors (in Texas) so maybe that hurts

 

[JBee]

I would just guide folks that the primary enemy (excepting LFP) is holding at high states of charge and time/heat. FWIW Rivian are guiding to hold at 70% SOC on a daily basis. Battery U is super helpful.

BTW, the intuition on this is bolstered by PHEVs. The number of cycles on a PHEV will often run 350+ a year. OTOH, the number of full cycles on an EV will rarely exceed 75 a year. But we do not see big failure rates in early Volts, for example. Reason is that the battery is only allowed to operate in the 20-80% range and - of course - a 20% loss in range is not that detectable when you only have 40 miles to begin with.

meh but guidance isn't details...an Ozzie fella wants to know, you know?

I'll keep on digging I suppose, when the sun comes back up.

 

[Diehard]

Most people don't need to use the top or bottom 20% of the battery except perhaps a few times -er year. It's there for when you need it. I can top off in my carport from 80% to 100% in a little over an hour. If I wake up and decide to go out of state, I just charge it to 100% while I'm showering and getting my stuff together.

I do the same with my truck even when I know the next day I will be traveling. I charge to 80% overnight and top off in the morning before leaving. That way the pack is warm when I leave and the time spent at high SOC is minimized. If people find this inconvenient most BEVs these days can be programmed to start charging anytime you want or they could be given target departure time. Unless someone needs the whole pack everyday, there is no reason to worry about the unused part of the pack. OP needs to see how he is using his current ICE and be realistic about how much of the problem is really a problem.

 

[Diehard]

where/how you check that?

Through OBD2 with a blue tooth reader. There are other owners over 10K still at 100%. I have no idea what Ford means by health.

Edit: I am guessing, cell voltage variation from the average may have something to do with it.

 

[JBee]

So, if you live in Minnesota (cold) you’re screwed on range, and if you live in Texas (hot) you’re screwed on battery life?

At home I only charge with 110 trickle, maybe that helps

But truck is stored outdoors (in Texas) so maybe that hurts

Yeah that sounds about right.

Have to chalk that one up to the pros of making it garageable, and having a garage to put it in.

The lower the C rate for charge/discharge the better from what I know, unless I find another limit on C somewhere in there to prove me wrong. I don't think charging from 120V could be worse than from 230V though. SC definitely is.

 

[HaulingAss]

Yeah that sounds about right.

Have to chalk that one up to the pros of making it garageable, and having a garage to put it in.

The lower the C rate for charge/discharge the better from what I know, unless I find another limit on C somewhere in there to prove me wrong. I don't think charging from 120V could be worse than from 230V though. SC definitely is.

Charging on 120V wall outlet is definitely worse than a more powerful 240V circuit in cold weather and causes increased degradation. In the US the standard 120V outlet is 15 amps and this means the car will not pull more than 1,400 watts (or a bit less). That's not enough to warm a large battery pack (75kWh-100kWh) up in a reasonable amount of time and charging a very cold battery, even at a slow rate, causes accelerated degradation. A higher C-rate will warm the battery even without active warming by the BMS.

If the EVSE tells the BMS it has 240V and 50 amps to work with, it will be much happier because it has plenty of power to rapidly bring the battery to the optimum temperature and to charge it in a reasonable amount of time.

The battery degradation caused by high C-rate charging is largely due to the heat created within the cell not being able to dissipate quickly enough from the localized point of origin, inside the cell. And that's even true, to a lesser degree, when the pack is actively cooled by coolant circulating through the pack (because the coolant cannot cool at the source of heat generation except via conduction). However, even charging at the maximum rate enabled by the on-board charging is nowhere near fast enough to cause battery degradation by high C-rate charging, the C-levels are too low to build damaging heat.

For example, a 75 kWh (useable) battery might have a capacity of 80 kWh. Charging on a 60-amp circuit at 48 amps is 10.5 kW or a C-rate of 0.13, meaning it would take over 7 hours to charge from 0%-100%.

A 7-hour charge is trickle charging and is likely close to an ideal charge rate for keeping battery degradation to a minimum.

 

[PilotPete]

When consumers are empowered to swap their own batteries, most of them end up in the landfill.

When Apple replaces my phone battery, 100% of them are recycled.

It’s the law of unintended consequences.

 

[Crissa]

when apple replaces the batteries a lot more phones (with their batteries) end up in landfill.

Edit: I for one kept the phones I could replace the batteries for myself a lot longer. Any extra cost or effort to replace the battery pushed me to junk the whole thing and buy a new unit. I doubt I am the only one operating this way. And I doubt manufacturers don’t know that.

Apple literally pays you for the old phone.

-Crissa

 

[Crissa]

Charging on 120V wall outlet is definitely worse than a more powerful 240V circuit in cold weather and ...

No, that's junk.

The voltage the charger uses only affects the charger, not the battery.

That said, I use 240v because it means my charger runs more efficiently.

-Crissa

 

[HaulingAss]

No, that's junk.

The voltage the charger uses only affects the charger, not the battery.

That said, I use 240v because it means my charger runs more efficiently.

-Crissa

Please, 120V charging is worse because, like I said, in the US common outlets are only 120V at 15 amps.

It's not the voltage that makes it worse, it's the low wattage available from common 120V outlets (I literally said it was worse than a more powerful 240V outlet.).

Your objection is worse than pedantic.

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