80% vs 100% charge

[Babyrocko1908]

Why would this be a concern? When the charge limit you selected is hit, the car switches off any draw from the cable. It's really no different than leaving your TV and toaster plugged in when they're off.

The upside of staying plugged in is that when the battery management system kicks in to keep the pack in its optimal temperature range, it will draw power from the line instead of from the batteries, thereby reducing the charge/discharge cycles the batteries accumulate (and which are a source of degradation). There is a reason that EV makers recommend keeping the car plugged in between use whenever possible.

It was a concern because I didn't understand fully how the battery management system worked. I will begin plugging in the car every night tonight. Great explanation for this EV newbie!!

 

[hmp10]

It was a concern because I didn't understand fully how the battery management system worked. I will begin plugging in the car every night tonight. Great explanation for this EV newbie!!

I do recommend keeping the car plugged in, but don't get worried about not having done so thus far. It would take a long time (as in years) for the relatively minor accumulation of charge/discharge cycles from not plugging in the car to become significant.

I get a lot more freaked out about dendrite formation from letting the car sit at 100% charge for long, and I've done that twice when I forgot to lower the charge limit back down to 80% after a road trip. As soon as I realized what happened, I jumped in the car to drive it down to 80% charge . . . and it took a lot of hard driving to do it due to the Lucid's damnably long range.

 

[idiot900]

Why would this be a concern? When the charge limit you selected is hit, the car switches off any draw from the cable. It's really no different than leaving your TV and toaster plugged in when they're off.

The upside of staying plugged in is that when the battery management system kicks in to keep the pack in its optimal temperature range, it will draw power from the line instead of from the batteries, thereby reducing the charge/discharge cycles the batteries accumulate (and which are a source of degradation). There is a reason that EV makers recommend keeping the car plugged in between use whenever possible.

Indeed, even though I set the charge limit to 80%, it's usually 79% when I actually get in the car in the morning. I view this as a feature - no reason to continually cycle the battery by tiny amounts to keep it strictly at 80%.

I wonder how precise the displayed percentage is? I assume it's just taking values from a predetermined voltage curve calculated for the battery chemistry and size.

 

[HariK]

I do recommend keeping the car plugged in, but don't get worried about not having done so thus far. It would take a long time (as in years) for the relatively minor accumulation of charge/discharge cycles from not plugging in the car to become significant.

I get a lot more freaked out about dendrite formation from letting the car sit at 100% charge for long, and I've done that twice when I forgot to lower the charge limit back down to 80% after a road trip. As soon as I realized what happened, I jumped in the car to drive it down to 80% charge . . . and it took a lot of hard driving to do it due to the Lucid's damnably long range.

I have 1 240V 60A breaker feeding a NEMA 15-40 outlet right now but I plan to get a 2nd EV. So, leaving both cars connected every night is not an option unless I get a specific charger with 2 ccs outputs like this. https://evadept.com/best-dual-ev-charger-for-two-cars/
I will just charge one car at a time when it hits 50% and charge to 80% to keep it simple. I put in a 60A breaker in case I hard wire and draw 48A in future for 11kW instead of 9kW. For now all I used was the Lucid mobile charger which came with Lucid.

 

[hmp10]

Indeed, even though I set the charge limit to 80%, it's usually 79% when I actually get in the car in the morning. I view this as a feature - no reason to continually cycle the battery by tiny amounts to keep it strictly at 80%.

I wonder how precise the displayed percentage is? I assume it's just taking values from a predetermined voltage curve calculated for the battery chemistry and size.

I wonder, too, about the precision. Also, the slider bar for setting the charge limit is very difficult to land exactly on any specific charge level.

Without having touched the slider setting, my car will variously show anything from 78% to 80% when I get in the car for the first time each day. I, too, assume that the car is programmed to allow a bit of phantom drain before starting the charge cycle.

 

[hmp10]

I have 1 240V 60A breaker feeding a NEMA 15-40 outlet right now but I plan to get a 2nd EV. So, leaving both cars connected every night is not an option unless I get a specific charger with 2 ccs outputs like this. https://evadept.com/best-dual-ev-charger-for-two-cars/
I will just charge one car at a time when it hits 50% and charge to 80% to keep it simple. I put in a 60A breaker in case I hard wire and draw 48A in future for 11kW instead of 9kW. For now all I used was the Lucid mobile charger which came with Lucid.

When I designed our new house, I wired the garage for up to three EVs. We have two at the moment, and I think putting in a second line if your panel can accommodate it would be worth the cost.

We keep both our Model S Plaid and our Lucid plugged in whenever they're in the garage. I have noticed that the Lucid's battery management system seems to come on a lot more often than the Tesla's, which is parked right next to the Air. I don't know why that is, but if I had to choose which to keep plugged in, it would be the Air for this reason.

 

[HariK]

When I designed our new house, I wired the garage for up to three EVs. We have two at the moment, and I think putting in a second line if your panel can accommodate it would be worth the cost.

We keep both our Model S Plaid and our Lucid plugged in whenever they're in the garage. I have noticed that the Lucid's battery management system seems to come on a lot more often than the Tesla's, which is parked right next to the Air. I don't know why that is, but if I had to choose which to keep plugged in, it would be the Air for this reason.

I will consider that when Lucid offers the bi-directional output and a cut off switch to power the home using Lucid. To complicate matters, another EV I ordered also supports V2H, V2G and V2V. Not sure which one I want to use to power the home.

 

[ksn]

Does this mean we have to turn off scheduled charging in order to pull energy from the charger for BMS at all times ? If it’s connected and scheduled charging is on the BMS will pull energy from the battery if it’s running during the off charging hours .

 

[joec]

This reminds me of when people come up with all sorts of voodoo for charging their phones. Only x times per week. Only after it drains down to x percent. Unplugging after it reaches 100% so it doesn't "overcharge." And on and on. So much misinformation out there that leads to people getting paranoid. And then coming up with all sorts of tricks that are basically nonsense.

At the end of the day, the folks who made my phone and programmed its charging system know a heck of a lot more about this stuff than I do. So I plug in whenever possible and don't think about it otherwise. And I've never had an issue.

If anything, a car's battery is even more over engineered in this regard. Think of it this way; Lucid have personally guaranteed the battery will still get at least 70% charge in 8 years. Otherwise, they owe you a new battery, which is like $50k. Believe me, they design these things such that it would take quite a bit to actually harm it. The programmers of the charging system have even more at stake in keeping your battery healthy than you do. So don't worry about it.

Just follow the general advice: Keep it between 20 and 80 most of the time. Plug in and top it to 80% as often as you can.

 

[hmp10]

Does this mean we have to turn off scheduled charging in order to pull energy from the charger for BMS at all times ? If it’s connected and scheduled charging is on the BMS will pull energy from the battery if it’s running during the off charging hours .

It's just a guess, but I have a feeling that Lucid anticipated this and will allow the car to draw line power for the BMS even when outside scheduled charging hours.

 

[hmp10]

Some time ago I wondered on this forum whether the difference in the 112-kWh LG Chem battery pack in the GT and the 118-kWh Samsung battery pack in the DE derived in part from using smaller buffers in the Samsung pack. I wondered this because Lucid had noted that the Samsungs were developed especially to tolerate fast charging but made no such claim when discussing the LG Chem batteries.

Then yesterday, while digging to find something else about the batteries, I came across this language about Lucid's 118-kWh pack:

"Tesla’s Model S Long Range has the smallest battery capacity of the three, at 100 kWh, from which it extracts 405 miles of combined EPA-rated range. The Mercedes-Benz EQS 580 4Matic has a bigger battery, at 120 kWh (108 kWh usable), but less range: 340 miles. The Air’s battery capacity is 118 kWh—both gross and usable, Lucid says. How does that work? 'Lucid has the hardware and software expertise to use the full energy of the battery while preserving battery life and fast charging performance in hot and cold climates.' In other words: 'We’re not saying.'"

(https://chargedevs.com/features/202...-first-500-mile-ev-should-be-taken-seriously/)

This is the first support I've found for my speculation that Lucid may use a smaller buffer -- or even none at all -- in the Samsung battery pack. If true, that reflects either great confidence in the robustness of the Samsung cells or such a desire to hit an extreme EPA range rating that they dispensed with the caution that most other EV makers take by putting buffers on the top and bottom ends of their packs' charge capacities.

 

[xponents]

Some time ago I wondered on this forum whether the difference in the 112-kWh LG Chem battery pack in the GT and the 118-kWh Samsung battery pack in the DE derived in part from using smaller buffers in the Samsung pack. I wondered this because Lucid had noted that the Samsungs were developed especially to tolerate fast charging but made no such claim when discussing the LG Chem batteries.

Then yesterday, while digging to find something else about the batteries, I came across this language about Lucid's 118-kWh pack:

"Tesla’s Model S Long Range has the smallest battery capacity of the three, at 100 kWh, from which it extracts 405 miles of combined EPA-rated range. The Mercedes-Benz EQS 580 4Matic has a bigger battery, at 120 kWh (108 kWh usable), but less range: 340 miles. The Air’s battery capacity is 118 kWh—both gross and usable, Lucid says. How does that work? 'Lucid has the hardware and software expertise to use the full energy of the battery while preserving battery life and fast charging performance in hot and cold climates.' In other words: 'We’re not saying.'"

(https://chargedevs.com/features/202...-first-500-mile-ev-should-be-taken-seriously/)

This is the first support I've found for my speculation that Lucid may use a smaller buffer -- or even none at all -- in the Samsung battery pack. If true, that reflects either great confidence in the robustness of the Samsung cells or such a desire to hit an extreme EPA range rating that they dispensed with the caution that most other EV makers take by putting buffers on the top and bottom ends of their packs' charge capacities.

Does the 112 go all the way?

 

[Adnillien]

It's just a guess, but I have a feeling that Lucid anticipated this and will allow the car to draw line power for the BMS even when outside scheduled charging hours.

Interesting discussion. Yesterday afternoon I charged up to the 80% limit that I had set and the car had stopped charging and had gone back to sleep. I decided to pre-cool the interior so I woke up the car, it charged for a 30 seconds or so like it normally does when plugged in and waking up. The car stopped charging again before I set the remote climate. I then set the remote climate, the car started to cool but the energy for the cooling was coming from the battery, not the EVSE even though I was still plugged in. I lost 2% SOC during the pre-cooling and the car did not initiate charging again.

 

[hmp10]

Interesting discussion. Yesterday afternoon I charged up to the 80% limit that I had set and the car had stopped charging and had gone back to sleep. I decided to pre-cool the interior so I woke up the car, it charged for a 30 seconds or so like it normally does when plugged in and waking up. The car stopped charging again before I set the remote climate. I then set the remote climate, the car started to cool but the energy for the cooling was coming from the battery, not the EVSE even though I was still plugged in. I lost 2% SOC during the pre-cooling and the car did not initiate charging again.

So maybe the charge scheduling takes priority over drawing line power for BMS and other usages?

 

[Adnillien]

So maybe the charge scheduling takes priority over drawing line power for BMS and other usages?

These are the things that I would love to know or be able to get answers from the engineering team.

 

[hmp10]

Does the 112 go all the way?

Don't know. Not even sure about the 118-kWh pack, as that one paragraph I quoted is the only source I've ever found, and I've done some digging.

Another source says that "all" EV manufacturers use buffers, with a limited exception being Tesla that defaults to a 90% charge as the full charge but allows a driver to override the upper buffer and go all the way to a true 100% charge when needed. (I haven't actually looked to see if there is such a feature in our 2021 Model S Plaid.)

How long will an electric vehicle battery last?

You probably get this question asked all the time as a Tesla owner — how long does the battery last? It turns out that lithium-ion batteries are well-suited for use in electric vehicles for the same reason they’re well-suited to portable electronics like cell phones and laptops...

evannex.com

I've learned a long time ago that you can both prove and disprove any given assertion with an internet search, so knowing the quality of the original source of the information is critical.

 

[Sandvinsd]

It's just a guess, but I have a feeling that Lucid anticipated this and will allow the car to draw line power for the BMS even when outside scheduled charging hours.

Well, that is a good reason to leave the car unplugged.

 

[hmp10]

Well, that is a good reason to leave the car unplugged.

But isn't the whole point of scheduled charging about the convenience of leaving the car plugged in without having to worry about when you have to plug and unplug it to avoid peak rates?

I doubt that the little bit of electricity the BMS system might use during peak hours is going to make much difference to an electric bill.

 

[Sandvinsd]

But isn't the whole point of scheduled charging about the convenience of leaving the car plugged in without having to worry about when you have to plug and unplug it to avoid peak rates?

Yea, it is. And the fact that the car will pull power during on-peak times defeats the purpose of scheduled charging. I’ll only plug It in on the days I need to charge and not plug in when I don’t. I just avoid paying close to 70 cents per kWh (on-peak) for any power that I don’t have to. It adds up.

 

[hmp10]

Yea, it is. And the fact that the car will pull power during on-peak times defeats the purpose of scheduled charging. I just avoid paying close to 70 cents per kWh (on-peak) for any power that I don’t have to. It adds up.

Wow . . . that's a very high rate. We've just hit 17 cents (no off-peak rates here), and people are grousing.

Even so, I wouldn't go so far as saying that pulling BMS power off the line during peak rates defeats the purpose of scheduled charging. It takes far more power to charge up the car than to operate the BMS system intermittently for short periods.

In any case, Adnillien's post suggests the BMS might not pull line power outside of scheduled charging hours. Maybe your concern is why Lucid would have programmed it that way.