# Impact of high amp charging on Model 3 battery life



## voip-ninja

In the FAQ Tech Talk thread an interesting point came up with someone indicating that they choose to charge their Tesla below the full 40 amp charge rate possible on their home outlet, instead choosing to throttle the charging speed to 15 amps since they can still get the charge level they need and *hope or expect that this will have a positive affect on long term performance of the battery.
*
I think that this is a subject worthy of further discussion in order to better understand two issues;

1. Does voluntary reduction of charge rate in home charging scenarios prolong battery life?
2. Does capping charge to a below max range value prolong battery life?

This is what I believe we know about this at this time. When time permits I will start quoting and linking sources.

1. Elon Musk when pressed on the question of what charge level home owners should charge to for daily driving in order to get maximum longterm life of the battery is quoted as saying "around 80%". I believe this was something he posted to Twitter.


__ https://twitter.com/i/web/status/448466037441179649
2. Tesla have published information that indicates that owners that charge frequently at high charge rates at super charger stations can expect a small amount of battery wear to result. Super charging though has no impact on warranty which has a maximum allowable battery reduction of something like 1-2% per year.

3. Initial survey information from Model 3 owners does not appear to show any correlation between battery degradation and type of charging done.

http://www.pluginamerica.org/surveys/batteries/model-s/faq.php

4. Private Model S/X rental/taxi operator in the Southern California area that rents a large fleet of Model S/X cars charge exclusively on super chargers (taking advantage of the bundled "free" supercharger access) and some of their vehicles have over 100,000 miles on them with no observed extra wear on battery life.

http://www.greencarreports.com/news...0k-and-300k-miles-still-humming-along-happily



> The most significant news is the battery degradation figure.
> 
> After 250,000 miles, the Model S registers just 7 percent degradation and still charges to 230 miles.
> That's only 20 miles fewer than its original 250-mile range rating.
> Better yet, a second Model S has reached the 300,000-mile mark-in just two years-due to its service in the Tesloop ride-sharing service in California, according to _Electrek._


It is worth noting that the operator did have one Model S that had its battery completely replaced under warranty during the unlimited mile 8 year battery warranty, it would no longer take a charge. It's hard to say what would happen if a regular owner ran into this problem after 8 years since their battery was basically dead and would have cost $20,000 to replace out of pocket.


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## garsh

Charging at low rates is less efficient. There is some amount of fixed overhead involved with charging. So keep that in mind as well. It will cost you slightly more to charge at lower rates.


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## voip-ninja

garsh said:


> Charging at low rates is less efficient. There is some amount of fixed overhead involved with charging. So keep that in mind as well. It will cost you slightly more to charge at lower rates.


Thanks, that's definitely a valid point worth mentioning. The "overhead" of charging at 10/15/20 amps is noticeably higher than doing faster charging at 30-40 amps.


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## Model34mePlease

Is there any reason to believe that AC charging is any worse for the battery than SC (DC) charging at equivalent power-to-the-battery rates. If not, then I would predict that AC charging has inconsequential effect on degrading the battery since the AC charge rate is vastly lower than SC rates.


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## Tom Bodera

garsh said:


> Charging at low rates is less efficient. There is some amount of fixed overhead involved with charging. So keep that in mind as well. It will cost you slightly more to charge at lower rates.


I agree that overhead(Phantom Drains) and DC conversion efficiency (Which is better above 15 amps) is better at higher rates. However as you approach the higher rates or max rating on the AC cable (80% of max Safety factored), the cable should in theory begin to heat which would decrease efficiency. So if you have a 40 Amp charger on a 50 amp rated wiring, would not charging at 30 Amps be most efficient?


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## Rusty

voip-ninja said:


> The only reason to not charge at the maximum rate is if it is demonstrated to impact the lifespan of the battery. To date I haven't seen any evidence of a hit to the battery longevity by charging at 40 amps vs 15 amps with the amount of data that has been released on battery life of early Model S vehicles.


The charge will be slightly more efficient with lower amps. This won't add up to much for one charge, but over the life of the car can add up to several bucks.


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## voip-ninja

Rusty said:


> The charge will be slightly more efficient with lower amps. This won't add up to much for one charge, but over the life of the car can add up to several bucks.


In the thread I created for this specific discussion it was pointed out that charging is actually more efficient at higher amps on a 220V line, not less efficient. Maybe we could discuss it further there.


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## Rick59

voip-ninja said:


> In the thread I created for this specific discussion it was pointed out that charging is actually more efficient at higher amps on a 220V line, not less efficient. Maybe we could discuss it further there.


For the lazy people (like me), what's the name of the thread?


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## voip-ninja

Rick59 said:


> For the lazy people (like me), what's the name of the thread?


It has the obscure name of "impact of high amp charging on model 3".



https://teslaownersonline.com/threads/impact-of-high-amp-charging-on-model-3.5002/


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## Frank99

Tom Bodera said:


> So if you have a 40 Amp charger on a 50 amp rated wiring, would not charging at 30 Amps be most efficient?


Perhaps you'd have lower resistive losses because the wire is cooler, but you'd have to charge 25% longer, meaning that the electronics are taking power while controlling the charging for 25% longer. Is that worse for efficiency than resistive losses in the wire? One can't make a blanket statement here; you'd have to measure the two different situations and see.


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## EvanLin

Frank99 said:


> Perhaps you'd have lower resistive losses because the wire is cooler, but you'd have to charge 25% longer, meaning that the electronics are taking power while controlling the charging for 25% longer. Is that worse for efficiency than resistive losses in the wire?


I think electronics use much less power than charging, just like "turn off screen/headlight" vs. "driving 10mph slower" to save energy.


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## Guest

Overhead at speeds below 3kW charge rate is too high for long term use (below 230V 16A). Though all EVs support at least that speed.
Cooling draw (overhead) at speeds above ~30kW also starts to increase in some cases (very warm pack with thermal management).

Degradation speed hardly varies at AC charging (3-22kW). Maximum charging speed of Model 3 batteries vary according to pack size.
We can expect 100kW and 75kW respectively to be the upper ends for Model 3 battery packs. Charging those with onboard charger that is rated up to 10kW is far far away from maximum charging speed potential.

General guidance should be to charge fast. In case of local energy production or storage, no faster than these can cope.
Daily rapid charger usage will speed up degradation process (slightly), even with actively cooled packs.
In terms of long term savings, EV's should always be charged with cheapest electricity possible. Local is the best,
cheapest night tariff is next.

PS. It appears Tesla has smaller onboard charger for standard range Model 3. Cheaper to produce and also makes
maximum charging rate (C value) between two packs very similar.


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## garsh

I wasn't able to find numbers for a Tesla, but I found several reports about the charging overheads for the Nissan Leaf.

Level 1 (120v, 12 amps): 78% efficient
Level 2 (240v, 16 amps): 91% efficient
Level 2 (208v, 30 amps): 91% efficient
CHAdeMO (500v DC, ~100 amps): 93% efficient

So it looks like there may be some minimum level of charge rate required to overcome the majority of overhead losses, then other factors become more important in calculating charging losses. Hopefully we can dig up similar reports for a Tesla.

Sources:
http://www.mynissanleaf.com/viewtopic.php?t=8583
https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf
http://www.mdpi.com/2032-6653/7/4/570/pdf


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## Brokedoc

garsh said:


> I wasn't able to find numbers for a Tesla, but I found several reports about the charging overheads for the Nissan Leaf.
> 
> Level 1 (120v, 12 amps): 78% efficient
> Level 2 (240v, 16 amps): 91% efficient
> Level 2 (208v, 30 amps): 91% efficient
> CHAdeMO (500v DC, ~100 amps): 93% efficient
> 
> So it looks like there may be some minimum level of charge rate required to overcome the majority of overhead losses, then other factors become more important in calculating charging losses. Hopefully we can dig up similar reports for a Tesla.
> 
> Sources:
> http://www.mynissanleaf.com/viewtopic.php?t=8583
> https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf
> https://www.researchgate.net/profil...ency-of-quick-DC-vehicle-battery-charging.pdf


This is VERY useful. I didn't read the full articles but presumably the same efficiency for Level 2 16amps and 30 amps does not account for heat loss. @PTFI has already noticed significant heat of the charging cable @ 36 amps to the point that he makes sure the cable is not coiled and can dissipate heat faster.

Another user had commented about length of charge as a factor contributing to degradation of battery chemistry but, if true, this must be a minor factor because Tesla recommends daily charging even for people who drive very little and leaving the charging cable plugged in when on extended periods of inactivity.


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## garsh

Brokedoc said:


> Another user had commented about length of charge as a factor contributing to degradation of battery chemistry but, if true, this must be a minor factor because Tesla recommends daily charging even for people who drive very little and leaving the charging cable plugged in when on extended periods of inactivity.


You might be confusing "length of charge" with "being plugged in". Being plugged in without charging will have no effect.


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## Brokedoc

garsh said:


> You might be confusing "length of charge" with "being plugged in". Being plugged in without charging will have no effect.


Yes. The terms used are not precise. Based on my X, I would say that leaving the car plugged in results in intermittent charging due to phantom loss about every 6-12 hrs because my app sends me notifications that charging is complete. Therefore leaving the car plugged in does increase the time of charging.

Also, is length of charging that deteriorates battery chemistry purely a function of time or is it the typical measurement of amp-hours which is a clearly known issue that all rechargeable batteries have a limited lifespan in terms of charge cycles. Li-Ion batteries have the advantage that the charge cycle can be fractional when calculating battery lifespan (i.e 10 charges of 20%=2 charge cycles) whereas older chemistries such as Ni-Cad were not (10 charges of 20%=10 charge cycles)

Battery deterioration is unavoidable and multifactorial. I love these scientific discussions and I would love to see experiments showing the effect of each variable. Time charging, age of batteries, Current, Heat, charge cycles. Also, I suspect the cold winter weather in NY may be preservative for battery life but reduce battery capacity during the colder months (I remember somewhere storing unused alkaline batteries in the fridge prolongs shelf life). There must be some sweet spot where we can balance our charge rate to overcome efficiency losses, not generate too much wasted heat, and maximize battery lifespan. This sweet spot will vary for everyone based on their charge capacity at home and the distance of their typical commute and the amount of time they have at home to charge (or the hours that their utility drops the rate).


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## JWardell

Folks, the generalization of higher charge rates being more efficient is not necessarily true. It all depends on the efficiency and design of the AC to DC converter, in this case the chargers built into the car just above the battery.
Most AC to DC converters are most efficient at their maximum current rating. And the 3 is getting two different ones depending on model. The standard will charge most efficiently at 32A while the long range will charge most efficiently at 40A, but less efficiently at 32A than the standard battery charger.
Of course if your wires and connections are not oversized to handle the higher current, then resistance will turn larger currents into heat in the wiring and drop the efficiency, adding another variable to the equation.
And of course DC charging through superchargers and Chademo bypasses the AC to DC battery chargers in the car, and therefore depend on the efficiency of the huge transformers at the site.


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## Model34mePlease

garsh said:


> I wasn't able to find numbers for a Tesla, but I found several reports about the charging overheads for the Nissan Leaf.
> 
> Level 1 (120v, 12 amps): 78% efficient
> Level 2 (240v, 16 amps): 91% efficient
> Level 2 (208v, 30 amps): 91% efficient
> CHAdeMO (500v DC, ~100 amps): 93% efficient
> 
> So it looks like there may be some minimum level of charge rate required to overcome the majority of overhead losses, then other factors become more important in calculating charging losses. Hopefully we can dig up similar reports for a Tesla.
> 
> Sources:
> http://www.mynissanleaf.com/viewtopic.php?t=8583
> https://avt.inl.gov/sites/default/files/pdf/fsev/SteadyStateLoadCharacterization2015Leaf.pdf
> https://www.researchgate.net/profil...ency-of-quick-DC-vehicle-battery-charging.pdf


Am I misunderstanding these numbers or does AC to DC conversion really only lose a maximum of 2% efficiency?


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## Model34mePlease

JWardell said:


> the 3 is getting two different ones depending on model. The standard will charge most efficiently at 32A while the long range will charge most efficiently at 40A, but less efficiently at 32A than the standard battery charger.


That is an interesting observation given that the new UMC will only charge at a maximum of 32A


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## voip-ninja

Model34mePlease said:


> That is an interesting observation given that the new UMC will only charge at a maximum of 32A


Well, it could also be a play to try to improve sales of the wall charger by artificially lowering the max charge rate achievable via 50 amp circuit and 40 amp wall outlet. Hopefully though they had a less nefarious reason.


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## Model34mePlease

voip-ninja said:


> Well, it could also be a play to try to improve sales of the wall charger by artificially lowering the max charge rate achievable via 50 amp circuit and 40 amp wall outlet. Hopefully though they had a less nefarious reason.


You could also purchase the the Model S/X UMC.


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## Mike

voip-ninja said:


> Well, it could also be a play to try to improve sales of the wall charger by artificially lowering the max charge rate achievable via 50 amp circuit and 40 amp wall outlet. Hopefully though they had a less nefarious reason.


Let's hope this is still early days and the higher rate UMC ships with the long range optioned car......


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## JWardell

Model34mePlease said:


> That is an interesting observation given that the new UMC will only charge at a maximum of 32A


That's right, so peak efficiency 40A charging in a LR car is achieved when plugged into a wall adapter or J1772 with high enough current.
And technically you will charge with slightly higher efficiency in the short range battery car when plugged in to 32A and lower.


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## Guest

Model 3 UMC likely will be cheaper (compared to S/X UMC). And people like cheaper.


Model34mePlease said:


> Am I misunderstanding these numbers or does AC to DC conversion really only lose a maximum of 2% efficiency?


AFAIK DC charging is more efficient. If I remember correctly, I had something above 95%. But maybe data comes from more degraded battery with higher internal resistance. AC-DC conversation is less efficient. Around 5% is lost. Also DC-station losses are never mentioned by DC-station itself. Current meter is at DC side. This is why DC-stations have lots of cooling.. losses.



garsh said:


> So it looks like there may be some minimum level of charge rate required to overcome the majority of overhead losses, then other factors become more important in calculating charging losses. Hopefully we can dig up similar reports for a Tesla.


Well, charging losses are almost constant. There is around 200-400W parasitic load (depending on EV and ambient temp) while charging. Some goes to contactors, some goes to coolant pump (if it is active, not always), and there is loss when converting HV to 13V (likely with minimum overhead, aka even if there is no load at 12V system, having DC-DC converter activated has some loss). And there is some wiring losses, and some chemical losses. Last one does change with charging speed, but difference between 1/20C and 1/6C is not great (per kWh charged, not time !)
AND DUE TO THAT,
charging at Level 1 (which is 115V*12A=~1,4kW) means lots of waste. As 1.4kW enters the vehicle, 0,4kW is overhead, 1,0kW charges the chemistry. Therefore far from efficient. 400 units wasted, 1000 units charged. (theoretical 71% efficiency)
European trickle charge 230V*10A=2,3kW, same overhead. We get 400 units wasted, 1900 units charged (theoretical 83% efficiency)
And recommended* minimum (230V*16A=3,6kW, same overhead. We get 400 units wasted, 3200 units charged (theoretical 89% efficiency).
And first Tesla limit 230V*32A=7,3kW, same overhead, 400 units wasted, 6900 units charged (theoretical 94% efficiency).

And there are actual losses between power meter and the plug. These depend on temperature of the wires, their length, terminal torques and contact area cleanliness (aka quality of the whole wiring), relay and breaker efficiency and what is the load compared to nominal load per wire cross section (less than recommended or as much as is recommended/allowed). My wiring is actually pretty bad. I found out that one of my house main breakers has a noticeable voltage loss (must replace that). Also the 20m cable buried has some loss (around 50W).

*by me


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## Guest

PS. If I have spare time, I will measure Leaf's constant parasitic load while charging.
I will use amp-clamp at EVSE and wait until Leaf is 99% charged. About half an hour before
dropping the charge session it has 2-4 cycles when charger pauses the charging session
(current to the battery drops to 0 amps). It waits for BMS to discharge the most charged cellpair,
so that voltage could drop slightly so it could push a little more.
But that method will battery losses and possible some AC-DC conversion losses.


PS2: Charging speed drops dramatically at almost full. This also means extremely bad efficiency.
One more reason not to charge to full daily.


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## roflwaffle

> • Main factors controlling battery lifetime
> o Time at high T & SOC (weak coupling with DOD & C-rate)
> o Cycling at high DOD & C-rate; Low/high T & SOC


https://www.nrel.gov/docs/fy14osti/62813.pdf

Keeping average SOC down could reduce degradation, but Tesla's BMS should do a good job keeping temperatures down to minimize those differences, and will also minimize issues with large temperature swings, but someone who consistently uses most of their pack/range and supercharges a lot could see more degradation.


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## Guest

Tesla S/X hardly does anything to cool down the pack while not supercharging.
Tesla S/X thermal system can not chill the battery without running compressor. 
It actually can't cool at all while stationary (it doesn't even have a fan on glycol loop).
AFAIK, it doesn't run AC while charging at home in non extreme temperatures (50*C).
S/X battery pack cools slowly according to ambient temperature.
Therefore what Tesla does is it minimizes differences in the pack. And of course,
Tesla chose the right chemistry. One that isn't afraid of 35*C / 95*F in long term.

Model 3 will be different. It will have single (dual) fan that can also pull through glycol loop.
Though I suspect it will not while having regular charging session, like S/X.
Other EV's also don't do that.


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## Rusty

arnis said:


> Model 3 UMC likely will be cheaper (compared to S/X UMC). And people like cheaper.
> 
> AFAIK DC charging is more efficient. If I remember correctly, I had something above 95%. But maybe data comes from more degraded battery with higher internal resistance. AC-DC conversation is less efficient. Around 5% is lost. Also DC-station losses are never mentioned by DC-station itself. Current meter is at DC side. This is why DC-stations have lots of cooling.. losses.
> 
> Well, charging losses are almost constant. There is around 200-400W parasitic load (depending on EV and ambient temp) while charging. Some goes to contactors, some goes to coolant pump (if it is active, not always), and there is loss when converting HV to 13V (likely with minimum overhead, aka even if there is no load at 12V system, having DC-DC converter activated has some loss). And there is some wiring losses, and some chemical losses. Last one does change with charging speed, but difference between 1/20C and 1/6C is not great (per kWh charged, not time !)
> AND DUE TO THAT,
> charging at Level 1 (which is 115V*12A=~1,4kW) means lots of waste. As 1.4kW enters the vehicle, 0,4kW is overhead, 1,0kW charges the chemistry. Therefore far from efficient. 400 units wasted, 1000 units charged. (theoretical 71% efficiency)
> European trickle charge 230V*10A=2,3kW, same overhead. We get 400 units wasted, 1900 units charged (theoretical 83% efficiency)
> And recommended* minimum (230V*16A=3,6kW, same overhead. We get 400 units wasted, 3200 units charged (theoretical 89% efficiency).
> And first Tesla limit 230V*32A=7,3kW, same overhead, 400 units wasted, 6900 units charged (theoretical 94% efficiency).
> 
> And there are actual losses between power meter and the plug. These depend on temperature of the wires, their length, terminal torques and contact area cleanliness (aka quality of the whole wiring), relay and breaker efficiency and what is the load compared to nominal load per wire cross section (less than recommended or as much as is recommended/allowed). My wiring is actually pretty bad. I found out that one of my house main breakers has a noticeable voltage loss (must replace that). Also the 20m cable buried has some loss (around 50W).
> 
> *by me


I agree with most of your numbers. I don't agree with your constant 400 units overhead. A 32A charge will create more heat and thus more overhead losses vs. a 16A charge.


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## EValuatED

Great discussion! @TrevP did you not glean (and did we also see from either @PTFI or @RiggerJon) that the max was 48A for the LR?


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## TrevP

EValuatED said:


> Great discussion! @TrevP did you not glean (and did we also see from either @PTFI or @RiggerJon) that the max was 48A for the LR?


Nothing definitive yet but I suspect the car's onboard charger can indeed handle 48amps.


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## RiggerJon

TrevP said:


> Nothing definitive yet but I suspect the car's onboard charger can indeed handle 48amps.


I'm almost sure I read the LR model supports 48 amps. I'm testing it out this afternoon on a TWC - will report back.


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## Guest

Rusty said:


> I don't agree with your constant 400 units overhead. A 32A charge will create more heat and thus more overhead losses vs. a 16A charge.


Yes, there will be more watts of heat generated per hour, but amount of watt-hours of heat generated during the charge will be almost the same.
I didn't take chemical loss into account (I said xxx watts will charge the chemistry and then failed with English when I said xxx will be charged:fearscream
To find out how many watts are stored we should multiply charge current with efficiency, something like 0.97.
Also 400W might be too much. Let's assume 200-300W of losses elsewhere.


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## Sandy

TrevP said:


> Nothing definitive yet but I suspect the car's onboard charger can indeed handle 48amps.


I agree with this for the LR. Hopefully one of our new owner friends can confirm this on preferably on a Tesla wall connector set at 60amps or above.


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## RiggerJon

Sandy said:


> I agree with this for the LR. Hopefully one of our new owner friends can confirm this on preferably on a Tesla wall connector set at 60amps or above.


Onboard is 48 amps.


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## AdamHolmes

RiggerJon said:


> Onboard is 48 amps.


 Finally confirmation, thanks!

I know everyone has suggested just go for the nema 14-50 over the wall charger and I really don't need the extra bit, my commute is less than 20 miles, but I really want to wc for convenience and aesthetics.

I'll feel a bit better about spending 500 dollars knowing at least ill be getting a bit more than eye candy


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## voip-ninja

AdamHolmes said:


> Finally confirmation, thanks!
> 
> I know everyone has suggested just go for the nema 14-50 over the wall charger and I really don't need the extra bit, my commute is less than 20 miles, but I really want to wc for convenience and aesthetics.
> 
> I'll feel a bit better about spending 500 dollars knowing at least ill be getting a bit more than eye candy


What's the minimum circuit though you can pull a full 48 amps through to the WC? 60 amps?

50 amp circuit can only deliver 40 to the WC.


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## RiggerJon

voip-ninja said:


> What's the minimum circuit though you can pull a full 48 amps through to the WC? 60 amps?
> 
> 50 amp circuit can only deliver 40 to the WC.


Yes, I believe 60 amps is required to pull 48.


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## Frank99

80% of the circuit rating - 60A * 0.8 = 48 amps.


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## garsh

I wired up my NEMA 14-50 outlets using 6 gauge wire. That should let me upgrade to a 60 amp breaker and a wall connector later if I decide I want to.


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## MelindaV

RiggerJon said:


> Onboard is 48 amps.


so is the charge rate at the 48a consistent as you were seeing with the UMCs, and pretty equal 1mile:1amp, so about 48miles/hour of charge rate?


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## d0cdave

Here's a Model X 75D charging on my HPWC.


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## d0cdave

And here's a Model X P90DL at 72A. Same HPWC.


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## MelindaV

d0cdave said:


> View attachment 3600
> 
> 
> And here's a Model X P90DL at 72A. Same HPWC.


the rate on the X isn't really relevant. it's a different onboard charger and the 3 itself has a different range per kWh than the S or X.


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## d0cdave

MelindaV said:


> the rate on the X isn't really relevant. it's a different onboard charger and the 3 itself has a different range per kWh than the S or X.


Gotcha... didn't think of that. Not sure that the charger in the 3 is that much different, but rate of charge would definitely be different. Curious if we can get a definitive miles-per-hour charge screen shot.


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## RiggerJon

MelindaV said:


> so is the charge rate at the 48a consistent as you were seeing with the UMCs, and pretty equal 1mile:1amp, so about 48miles/hour of charge rate?


I'm going back through the pics I've taken and I think I might've misstated the 40 amp charge rate somewhere along the way. I'll try to locate & correct.

When I'm at home with a 50 amp circuit & old UMC, the 40 amp pull charges at about 30 miles/hr. The TWC I used yesterday pulled 48 amps & was around 36 miles/hr. The install of the TWC had a pretty long run from the main panel, so I suspect that 36 figure is a little less than what it's capable of in an ideal setting.


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## Russell

RiggerJon, besides Homelink and mirrors angling down on reverse, what have they enabled with the latest ota? Is EAP still disabled?


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## RiggerJon

d0cdave said:


> Gotcha... didn't think of that. Not sure that the charger in the 3 is that much different, but rate of charge would definitely be different. Curious if we can get a definitive miles-per-hour charge screen shot.


The charger(s) setup on the X are different. To compare across models you really need to evaluate it by kW. I charge at 10kW at home with a 40 amp pull via the old UMC, and yesterday the TWC at 48 amps was 12kW. Perhaps an S or X owner can weigh in on theirs.


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## jmmdownhil

Great info about charging options. I haven't seen anything about "surge protection". Is that built in on the Tesla battery/charger/cable systems or is it necessary to add this to the 40/50 amp line?


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## Brokedoc

RiggerJon said:


> The charger(s) setup on the X are different. To compare across models you really need to evaluate it by kW. I charge at 10kW at home with a 40 amp pull via the old UMC, and yesterday the TWC at 48 amps was 12kW. Perhaps an S or X owner can weigh in on theirs.


The battery management system is VERY complex. The kW fluctuates based on battery existing charge level (and on the SC based on if other cars are plugged into the second channel). Then the MPH charge rate also fluctuates based on the vehicle's energy usage. Sitting in the car while charging and using A/C and blasting music or if the battery cooler pump is active will give less MPH for the same kW. It's really hard to compare screenshots without controlling for the other variables. Generally the current readings equalize after being plugged in for a minute or so and we should try to turn off excess power sources to get an idea of steady state charge rate while plugged in and car is off.


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## Brokedoc

jmmdownhil said:


> Great info about charging options. I haven't seen anything about "surge protection". Is that built in on the Tesla battery/charger/cable systems or is it necessary to add this to the 40/50 amp line?


Great question! I have no idea about surge protection built into the Tesla but when I had my service redone for my house, I bought a "whole house" surge protector that's not as expensive as you would think. Below I have a link to one for under $200. Only a little more complicated than putting in a breaker switch but you may need to rearrange some circuits in you box to put the surge protector as close to the service as possible for maximal protection. I still have extra surge protectors for my TVs and computers but it's a small price to pay for all the expensive things we have plugged in...

Leviton 1 panel surge protector


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## JWardell

I have no doubt Tesla has some excellent surge protection built into the car's chargers, but if you are in an area prone to lightning or surges, it wouldn't hurt to add extra like the Leviton linked above to better protect your $50,000 plug-in electrical device.


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## voip-ninja

JWardell said:


> I have no doubt Tesla has some excellent surge protection built into the car's chargers, but if you are in an area prone to lightning or surges, it wouldn't hurt to add extra like the Leviton linked above to better protect your $50,000 plug-in electrical device.


Are there any documented cases of a grid surge causing a Tesla battery or electrical system to become damaged? Seems like it would really, really be in Tesla's best interest to handle this on their end of things.


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## Guest

JWardell said:


> I have no doubt Tesla has some excellent surge protection built into the car's chargers,


Highly doubt it. Powerful surge protectors must be replaceable. Not mentioned anywhere.
Though adding surge protection at mains box is doable with good grounding.

Here in Estonia, two weeks ago first EV, Nissan Leaf, got an indirect hit from the grid while charging.
Onboard charger died. Insurance paid for damage as it was "force majeure" (like flooding, tree, fire etc).
Some time ago vehicle got a direct hit (though not EV). Slight paint defect. Also insurance covered.

PS: how do you guys call these two different insurances:
a) insurance that is mandatory (covers the cost if you are guilty to properties of other parties and occupants)
b) insurance that is not mandatory (except leased vehicles), covers the cost of your own property damage (with small deductible) - excludes any costs due to bad behaviour (drunk, rally etc)


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## mishakim

arnis said:


> Highly doubt it. Powerful surge protectors must be replaceable. Not mentioned anywhere.
> Though adding surge protection at mains box is doable with good grounding.
> 
> Here in Estonia, two weeks ago first EV, Nissan Leaf, got an indirect hit from the grid while charging.
> Onboard charger died. Insurance paid for damage as it was "force majeure" (like flooding, tree, fire etc).
> Some time ago vehicle got a direct hit (though not EV). Slight paint defect. Also insurance covered.
> 
> PS: how do you guys call these two different insurances:
> a) insurance that is mandatory (covers the cost if you are guilty to properties of other parties and occupants)
> b) insurance that is not mandatory (except leased vehicles), covers the cost of your own property damage (with small deductible) - excludes any costs due to bad behaviour (drunk, rally etc)


In the US, such things vary state-by-state, but in general:
a) is called Liability insurance
b) can have two parts, called Comprehensive and Collision (Collision is for damage to the car due to you crashing it or another car crashing into it, Comprehensive is any other type of damage)
There is also Uninsured Motorist coverage, required by some states, to cover the damage to your car or person if the other driver doesn't have any or enough Liability insurance


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## Guest

Which are mandatory by law? Or contract.


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## voip-ninja

arnis said:


> Which are mandatory by law? Or contract.


This is quite a tangent and I'd recommend moving this to a new topic. The short answer is that state law typically requires that you carry insurance for damage and bodily injury caused while you are driving. "full" comprehensive coverage that covers other cases is not typically required unless the vehicle is under a loan or lease, the bank will always require you have this coverage to underwrite your lease or loan.


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## JWardell

arnis said:


> Highly doubt it. Powerful surge protectors must be replaceable. Not mentioned anywhere.
> Though adding surge protection at mains box is doable with good grounding.
> 
> Here in Estonia, two weeks ago first EV, Nissan Leaf, got an indirect hit from the grid while charging.
> Onboard charger died. Insurance paid for damage as it was "force majeure" (like flooding, tree, fire etc).
> Some time ago vehicle got a direct hit (though not EV). Slight paint defect. Also insurance covered.
> 
> PS: how do you guys call these two different insurances:
> a) insurance that is mandatory (covers the cost if you are guilty to properties of other parties and occupants)
> b) insurance that is not mandatory (except leased vehicles), covers the cost of your own property damage (with small deductible) - excludes any costs due to bad behaviour (drunk, rally etc)


I disagree. There is no way Tesla would take chances saving a few pennies with poor surge protection and chance high numbers of failed chargers.
I can't think of ANY other home electronics with replaceable surge protection.
And actually, replacing a failed charger or battery pack is of course possible.
Are you saying that Tesla doesn't have well-designed chargers just because your Leaf doesn't? Don't even get me started on the differences between the Leaf and Tesla battery design and management.


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## Guest

Well, Tesla can't ignore laws of physics.
I have no examples of Tesla charger failure due to voltage spike at home.
But a supercharger (which is made out of the same chargers) did allow voltage spike to get onboard.
https://teslamotorsclub.com/tmc/thr...tning-at-the-grove-city-oh-supercharger.48083

One example is enough to prove that Tesla's chargers can not arrest all surges. Though tiny hits might be managed.


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## TheStig

I’ll make an attempt to get back on topic here....

Given what we know and how the Tesla battery managment behaves I think it is safe to say any AC based charge rate is not likely doing any meaningful harm to the pack. 32, 40, or 48 amps after the 10% or so loss converting that AC to DC to charge the cells is not going to stress a pack of the Model 3’s size.

Supercharging heavily seems different. It has to equal some increased stress on the battery especially if you supercharge to high states of charge. Like more than 80%. The rate tapering that is applied demonstrates that. The Chevy Bolt accepts 50kW but tapers off aggressively. Tesla’s take in more than double that rate and taper off much higher in the charge curve but with a larger pack. I’m sure this is all carefully calculated to protect the manufacturers from warranty claims on the battery packs which are very long for the automotive world and result in a big financial liability for the company’s until the cars age out of warranty.


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## Rusty

voip-ninja said:


> What's the minimum circuit though you can pull a full 48 amps through to the WC? 60 amps?
> 
> 50 amp circuit can only deliver 40 to the WC.


From my understanding of NEC, a 50 amp circuit can provide 50 amps.


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## garsh

Rusty said:


> From my understanding of NEC, a 50 amp circuit can provide 50 amps.


I believe the NEC says that _short duration_ loads (like compressor startup current) can go up to the limit, while _continuous_ loads should not exceed 80% of the breaker rating.


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## TheStig

Correct, an EVSE is a continuous load and you must de-rate by 20%. 40A breaker -20% 32A load, 50A breaker, -20% 40A load, 60A breaker -20% 48A load. This de-rate allows for the wire and breaker to dissipate the heat that will build up over the hours of charging.

Today I charge a Mercedes B Class Electric Drive (B250E) @ 40A off a 50A breaker and not only does the charge cord get warm, the 6 gauge wire from the panel to the outlet does as well. 6 gauge wire is rated for 60 or 65 amps (I forget which) but even at 40A of load over a 2-3 hour continuous charge it heats up. Not to a dangerous or concerning level but enough that you can clearly see why this de-rating is a MUST.


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## Frank99

For continuous loads (longer than 3 hours), the NEC requires that the circuit (wires, breaker) be sized at 125% of the load (or, alternatively, the load can be 80% of the circuit rating). 
*Article 100*: Continuous Load: A load where the maximum current is expected to continue for 3 hours or more.
*210.19(A)* ... Where a branch circuit supplies continuous loads...the minimum branch-circuit conductor size...shall have an allowable ampacity not less than...125 percent of the continuous load.
625.40 Rating. Electric vehicle supply equipment shall have sufficient rating to supply the load served. For the purposes of this article, electric vehicle charging loads shall be considered to be continuous loads.


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## Rusty

Frank99 said:


> For continuous loads (longer than 3 hours), the NEC requires that the circuit (wires, breaker) be sized at 125% of the load (or, alternatively, the load can be 80% of the circuit rating).
> *Article 100*: Continuous Load: A load where the maximum current is expected to continue for 3 hours or more.
> *210.19(A)* ... Where a branch circuit supplies continuous loads...the minimum branch-circuit conductor size...shall have an allowable ampacity not less than...125 percent of the continuous load.
> 625.40 Rating. Electric vehicle supply equipment shall have sufficient rating to supply the load served. For the purposes of this article, electric vehicle charging loads shall be considered to be continuous loads.


Thanks for the info. Is a 50 amp plug ok continuously?

For continuous loads (longer than 3 hours), the NEC requires that the circuit (*wires, breaker)*be sized at 125%ofthe load (or, alternatively, theload can be 80% of the circuit rating).


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## TheStig

You won’t find a EVSE (Tesla or other) that charges above 40A with a 14-50 plug on it. Anything above that is hardwired.


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## Frank99

A 50 amp outlet is fine to pull 50 amps from..as long as you do it for less than three hours.


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## Sandy

garsh said:


> I wired up my NEMA 14-50 outlets using 6 gauge wire. That should let me upgrade to a 60 amp breaker and a wall connector later if I decide I want to.


True. That's why in my recent install I used 6/3 wire. Good in Canada for 150' run on a 60 amp breaker. Anything longer requires an upgrade to 4/3. My run is 80'.


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## Insaneoctane

Did we ever get an answer about charging efficiency? I would like to charge my Model 3 using my HPWC at the most efficient current settings possible. It's wired up through a 60 amp breaker and set to 48 amps right now, but I could dial it down on the touchscreen. Question still remains, which setting is the most efficient?


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## Guest

Maximum charging speed is efficient. There are inefficiencies off-board the vehicle as well.
Depending on the wiring and connection quality between power meter and charger, YEMV (your efficiency may vary).
Thick conductors (not cable thickness) and excellent connections reduce inefficiencies that might increase with higher power. 
Also breakers that have never tripped, are more efficient. 
Charging at speeds at or above 3.3kW (16A) is recommended for minimal parasitic losses.
Also electrically, on board charger, as a device, should be operated at least on half-load (10kW charger at least at 5kW) for better results. Dual charger Tesla's might have exception here.
Li-ion battery coulombic efficiency is very high. Especially up to 90% state of charge. Keep it below that on daily basis anyway.
*For best results, keep charging between 32-48A. *
Verify that nowhere between power meter and the plug is there any meaningful warm/hot spots (Ir-camera or Ir-thermometer) during maximum charging speed.


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## Insaneoctane

My 6 gauge wire run from the HPWC to the panel installed 60A breaker is literally 30 inches. I will measure the temperature of the 1" conduit that houses the run, but how warm would you suggest is "meaningful"?


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## Guest

Don't worry about that last part (very short thick cable, meaningless voltage drop). 
How about cable before breaker and power meter? What about that cross section. Also think about other devices under that cable (things that will run when you charge EV)

The most easiest way to measure losses is to measure voltage drop (under consistent load, for example max 48A).
Also measuring voltage drop right when charging beings (first 10 seconds) and an hour later. Will give you rough estimation how much things warm up (warm cable means more resistance).
Literally taking multimeter, measuring voltage between right after power meter and voltage right before it enters HPWC (while vehicle charging at maximum). Though you must know how to handle a 10$ multimeter.

10 degrees (absolute, C or K) would be acceptable, 20 degrees above ambient would count as not good. 30 is not ok to continue (hot to touch). Likely places to find this is wire under screw terminal and breaker/relay.


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## Insaneoctane

arnis said:


> ... Though you must know how to handle a 10$ multimeter.... .


Thanks for the input.

FWIW- Anyone else considering doing this, I would caution that handling even a $10 multi meter could be dangerous when dealing with these voltages and your service panel.


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## voip-ninja

Insaneoctane said:


> Thanks for the input.
> 
> FWIW- Anyone else considering doing this, I would caution that handling even a $10 multi meter could be dangerous when dealing with these voltages and your service panel.


No kidding. 40-60 amps at 220V is absolutely not something to be trivialized like any idiot with a multimeter can do it safely.


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## Scuffers

Really?

I happily use my free credit card sized multi-meter on 415V 3 phase ccts.

(I draw the line at 13/27KV stuff mind....)


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## Idur

Scuffers said:


> Really?
> 
> I happily use my free credit card sized multi-meter on 415V 3 phase ccts.
> 
> (I draw the line at 13/27KV stuff mind....)


I still think having a multimeter and knowing how to use it safely are two different things. Be safe. Electrocution kills.

Safe voltages are 24 V AC or 30 V DC. 415 V AC or 400 V AC like we have on the continent can be lethal. I think 240 V (or even 110 V) in the US should only be tested by people who know how to do it safely.


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## Guest

Idur said:


> Safe voltages are 24 V AC or 30 V DC.


To be more exact, 30V AC and 60V DC are called safe limits though touching 100V DC is still damn safe if done with dry finger.
Up to 1000V is easy to learn/protect yourself with simple/cheap measures.
Multimeter itself is safe (if it is not cheap Chinese crap). Problems occurs near HV stuff. 
Death doesn't require a multimeter - ignorance - that will do it.

Crash course for stuff up to 1000V - if you are not absolutely sure what are you doing, get appropriate HV gloves - this way it's hard to kill yourself by touching something though you can still break the multimeter so don't get an expensive one


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## JWardell

The quote is "any idiot" and that sets a low bar, for all you know they might touch the metal part of the leads. Just as you say, below 60V is safe. 100V with a dry finger requires knowledge and is already above that bar.
I know electricians here who have no problem wiring circuits live, they say they just get used to the sensation. But again, they are careful to only use one dry hand, they have some knowledge to do something potentially stupid 
You and I of course have much more electrical knowledge than average and therefore are confident in working in situations up to 1000V, but you certainly can't expect everyone to be able to without knowledge.
The highest I've worked with is 277VAC and I am super careful...yet still had a spark and the brightness alone is enough to knock you off a ladder...spoken from experience


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## Scuffers

JWardell said:


> The quote is "any idiot" and that sets a low bar, for all you know they might touch the metal part of the leads.


And that's the bigger point, let 'any idiot' loose with just about any tool and you have a receipt for disaster!

None of this is rocket science, but boy are there some idiots about!


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