Impact of high amp charging on Model 3 battery life

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Mike

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#22
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......
 

JWardell

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#23
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.
 

arnis

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#24
Model 3 UMC likely will be cheaper (compared to S/X UMC). And people like cheaper.
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.

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
 
Last edited:

arnis

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#25
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.
 

roflwaffle

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#26
• 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.
 

arnis

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#27
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.
 

Rusty

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#28
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.
 

arnis

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#32
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.
 

Sandy

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#33
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.
 

AdamHolmes

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#35
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
 

voip-ninja

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#36
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.