Charging slows down as the battery SOC increases, i.e. it will take longer to charge the closer the battery gets to 100%. Charging consumes the same amount of power (11.5kW in this case) but you get less range per minute added for each minute you charge. The same thing can be observed when you charge your phone. It is fast to charge when you first start charging but charging slows down as your phone's battery approaches 100%.
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Charging at 48A?
- Thread starter Gellie
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TomServo
Active Member
My old CC and now HPWC running at 40 amps/36 mph holds that rate until about 96% then it starts to taper. Now SuperChargers start to taper at around 40%.
Good point. My car does hold full rate charging pretty long though. Depending how far my BMS is out of calibration, I've seen the charge rate stay at 45 MPH from around 97% full and to as high as 100% full. Seen below, the last time I charged to 100%, it was still full speed at 97%. I think that charge didn't slow down until 99%. Several minutes after it hits 100%, it'll drop to ~24 amps and taper down for ~30 more minutes. During this taper, it records no additional kWh or mile increase.
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dhrivnak
Active Member
Looks like Voltage is on the low side as I typically charge at 245 volts. It could be you area at the end of a line or lose connection or a small or long wire.
That's because the voltage of the battery goes up, so the conversion is lower amps going into the battery. This page talks a whole lot about battery charging.
Tesla Battery Longevity
As a Tesla owner, you have probably done the simple math of dividing the current Rated range of your car by the battery percentage to…
maadotaa.medium.com
But the main thing here is the voltage curve of the battery cell. It's assinine they did the % backwards, but whatever, you can see how much the voltage jumps from about 90 to 100%
If you charge the Tesla vehicle using a Level 2 charging station at 32A the Tesla charging screen will show ~240V and 32A. The charging amperage will ramp up during the first 30 seconds of charging and ramp down at the very end of the charging cycle but for the duration of the charging session, i.e. from 50% to 75% the amperage will not vary (at least according to the Tesla charging screen.) If you time the charging session from 50% to 70% and then again from 70% to 90% it will show that it takes significantly longer to charge from 70% to 90%. For Level 2 charging the voltage and amperage do not reduce as when using a Supercharger and the charging session will start to taper the charging rate at ~40% SOC.
Early in the charging session there are many spaces on the battery cell anode for ions (in this case lithium ions) to attach to the anode. As the battery charge increases the number of available locations on the anode where the ions can go are filled up, it takes longer for the ions to move and attach to the anode.
Early in the charging session there are many spaces on the battery cell anode for ions (in this case lithium ions) to attach to the anode. As the battery charge increases the number of available locations on the anode where the ions can go are filled up, it takes longer for the ions to move and attach to the anode.
I'm not sure why, but my experience is different than yours. My charging rate on a L2 charger is a constant value for any SoC below ~97%.
From below, you can see the linear charge increase from ~20% to just below 100%. 70% to 90% took no longer than 50% to 70%.
I see people talking about charging slowing down as it gets more full, but it's being misunderstood/misstated a bit here. The charging tapering curve is always in effect, but it's just that the home charging power in kW is so low that people hardly ever charge high enough for the curve to reach it to have to reduce that power.
This home charging is like 11 kW or 7 kW. When people talk about tapering at Superchargers, they are talking about 60, 50, 40 kW and that still WAY above home charging rates. People won't see this 11 or 7 kW home charging get reduced until around 96% or so, as @TomServo was mentioning. So that is never what is going on with people's home charging if they are only going up to 80% or 90%. It would still be capable of about 20 or 30 kW at that point.
This home charging is like 11 kW or 7 kW. When people talk about tapering at Superchargers, they are talking about 60, 50, 40 kW and that still WAY above home charging rates. People won't see this 11 or 7 kW home charging get reduced until around 96% or so, as @TomServo was mentioning. So that is never what is going on with people's home charging if they are only going up to 80% or 90%. It would still be capable of about 20 or 30 kW at that point.
Just to double check, I just charged on the L2 (30A) ChargePoint charger at my work. 71% to 95%, no slowdown.
Actually, I don't. My post #23 above shows 97% with no slowdown. The full 45 MPH at 97%. It will slow down, but sometimes not until 99%, or even 100% when my BMS is off.
I just happened to have charged to 100% yesterday morning, and I can confirm the input current drops near the end. I'm not sure of the behavior of charging near the limit of the new-chemistry cells, though.
Seems like my Model Y performance charges around 39-42 miles depending volts on 48a but my Model Y Long range charges at 45-48 miles depending on volts on 48a charging HPWC at home and hotels I've gone and have seen , performance model are a little slower but not a big deal when using Level 2 charging
ucmndd
Well-Known Member
They charge at precisely the same rate, the long range can just go farther on the same amount of energy vs. the performance.
iamnid
Active Member
The "miles per hour" metric isn't really helpful. It's the kilowatts that's really important. "Miles per hour" is an imprecise estimate based on a few variables. It could be that the battery size is different between your 2 model Ys (they slightly increased it some time last year). Additionally, because the range on the Model Y Performance is different than the LR, the "miles per hour" won't be exactly the same because the Performance gets less "miles" per kwh of the battery.
Look at the kilowatts that are going into the car. They'll be the same despite what the "miles per hour" says.
It's an easy calculation too -- voltage X amps = kilowatts.
ucmndd
Well-Known Member
Technically voltage x amps = watts, so divide by 1,000 if you want kilowatts.
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