Pros and Cons of 800 V Charging

[Olle]

Hi all,
What are the pros and cons of the new 800 V charging regimen compared to 350 to 400 V that we charge our Teslas with? As an electrical engineering student I would be very interested to find out. I have been searching the inter webs high and low for this topic and never found any relevant answers. It would be fun to discuss! Here is a start. If other forum members who are interested would like to chime in and add their opinions to the pros and cons list I think we could get an interesting little discussion going.

800V pros and cons (as compared to 400V) It is also assumed that the inverter motor combo runs 800 V but this may be wrong. Please correct me if this is the case.

Pros	Cons
Lower weight of conductors (as a function of lower current).	Lower power density in the motors due to larger insulation surface (function of thinner winding) and insulation thickness (function of voltage).
Lower cooling requirements, for inverters and conductors as a function of lower current.	Lower inverter efficiency and rpm band due to trade offs in high voltage MOSFETs.
Lower inverter mass due to fewer or alternatively lower current inverter components.	Higher cost and weight of insulation for all HV conductors inside and the car and in the chargers.
	Increased risk of injury in the event of shut off and /or insulation failure.

 

[Olle]

Hi all,
What are the pros and cons of the new 800 V charging regimen compared to 350 to 400 V that we charge our Teslas with? As an electrical engineering student I would be very interested to find out. I have been searching the inter webs high and low for this topic and never found any relevant answers. It would be fun to discuss! Here is a start. If other forum members who are interested would like to chime in and add their opinions to the pros and cons list I think we could get an interesting little discussion going.

800V pros and cons (as compared to 400V) It is also assumed that the inverter motor combo runs 800 V but this may be wrong. Please correct me if this is the case.

Pros	Cons
Lower weight of conductors (as a function of lower current).	Lower power density in the motors due to larger insulation surface (function of thinner winding) and insulation thickness (function of voltage).
Lower cooling requirements, for inverters and conductors as a function of lower current.	Lower inverter efficiency and rpm band due to trade offs in high voltage MOSFETs.
Lower inverter mass due to fewer or alternatively lower current inverter components.	Higher cost and weight of insulation for all HV conductors inside and the car and in the chargers.
	Increased risk of injury in the event of shut off and /or insulation failure.

Also, I wanted to add: charging power is equal in the comparison.

 

[nwdiver]

Also, I wanted to add: charging power is equal in the comparison.

Is it? Some DC chargers are current limited. Francis Energy just installed some here that are 60kW with a 75A limit so if you have a 800v pack you get ~60kW but if you have a 400v pack you only get ~30kW.

 

[Big Earl]

Is it? Some DC chargers are current limited. Francis Energy just installed some here that are 60kW with a 75A limit so if you have a 800v pack you get ~60kW but if you have a 400v pack you only get ~30kW.

Yikes. Sounds like Francis Energy just wasted a bunch of money.

800V charging doesn’t offer much, if any, practical benefit to the owner. I’ve seen videos where it’s actually a hindrance in a Taycan due to so many charging stations only supporting up to 500 volts. Porsche offers a couple of optional on-board transformers to make things compatible, but the fast (high amperage) one is rather expensive.

 

[nwdiver]

Yikes. Sounds like Francis Energy just wasted a bunch of money.

800V charging doesn’t offer much, if any, practical benefit to the owner. I’ve seen videos where it’s actually a hindrance in a Taycan due to so many charging stations only supporting up to 500 volts. Porsche offers a couple of optional on-board transformers to make things compatible, but the fast (high amperage) one is rather expensive.

I read somewhere that the Taycan can basically reconfigure its 800v pack with internal switches into parallel 400v packs for charging.

Hmmm... maybe not...

'An important note is that at 400V chargers, Porsche Taycan can go up to 150 kW when equipped with the Optional On-Board DC Charger package ($460). Without this DC/DC converter, it will not be able to charge so fast, as the battery system is about 800V nominal.'

 

[Olle]

Is it? Some DC chargers are current limited. Francis Energy just installed some here that are 60kW with a 75A limit so if you have a 800v pack you get ~60kW but if you have a 400v pack you only get ~30kW.

You are right, power doesn't have to be equal and I recognize that not all charging systems will provide equal power for both voltages. What I meant is; if we set the power to equal in a theoretical comparison, we also reduce the number of variables and thereby make it easier to theoretically compare the two. If we instead had made a comparison where say 800V had twice the power of 400V, we introduce too many unknowns, one of the obvious being the charge power limits of the battery cells. There is a lot of hand waving in the media about the benefits of the two systems but I have never seen anything substantial. I though we could look at a more fact based comparison.

 

[Olle]

I read somewhere that the Taycan can basically reconfigure its 800v pack with internal switches into parallel 400v packs for charging.

Hmmm... maybe not...

'An important note is that at 400V chargers, Porsche Taycan can go up to 150 kW when equipped with the Optional On-Board DC Charger package ($460). Without this DC/DC converter, it will not be able to charge so fast, as the battery system is about 800V nominal.'

Yes of course. Otherwise it would have a massively expensive and heavy boost converter. This is why I asked in the beginning of the thread if its motor inverter combo is running 800. It could theoretically run 400 since the contractors for the 400 circuit are already in the pack.

 

[Big Earl]

Yes of course. Otherwise it would have a massively expensive and heavy boost converter. This is why I asked in the beginning of the thread if its motor inverter combo is running 800. It could theoretically run 400 since the contractors for the 400 circuit are already in the pack.

As mentioned in the link in that post, the Porsche has a DC-DC converter to make the voltage change from 400 to 800. The whole car is 800 volt architecture. The optional upgraded converter allows up to 150 kW charging from 400 volt charging stations, which isn’t spectacular.

 

[Olle]

Yikes. Sounds like Francis Energy just wasted a bunch of money.

800V charging doesn’t offer much, if any, practical benefit to the owner. I’ve seen videos where it’s actually a hindrance in a Taycan due to so many charging stations only supporting up to 500 volts. Porsche offers a couple of optional on-board transformers to make things compatible, but the fast (high amperage) one is rather expensive.

Exactly. 800V doesn't offer much as things stand today. But let's say there was an 800V system that was designed correctly? I.e. if Tesla had an 800V Supercharger, with cars to match.

 

[Olle]

As mentioned in the link in that post, the Porsche has a DC-DC converter to make the voltage change from 400 to 800. The whole car is 800 volt architecture. The optional upgraded converter allows up to 150 kW charging from 400 volt charging stations, which isn’t spectacular.

Yes, it says that you can buy a DC charge package for 400 but it doesn't say there is DC-DC converter. You wouldn't get that for $400, maybe $40,000 Picture your average big and heavy Tesla converter from 120 to 400V at 13 kW which sits under your backseat already... multiply that by a weight and cost of 20. Would be very surprising if Taycan has that, it must be a 400V circuit. What you get for the extra money for the "DC Charging Package" is probably a couple of contractors or perhaps just a software unlock.

 

[Big Earl]

Yes, it says that you can buy a DC charge package for 400 but it doesn't say there is DC-DC converter. You wouldn't get that for $400, maybe $40,000 Picture your average big and heavy Tesla converter from 120 to 400V at 13 kW which sits under your backseat already... multiply that by a weight and cost of 20. Would be very surprising if Taycan has that, it must be a 400V circuit. What you get for the extra money for the "DC Charging Package" is probably a couple of contractors or perhaps just a software unlock.

Aah. That certainly makes sense.

 

[Olle]

Hi all,
What are the pros and cons of the new 800 V charging regimen compared to 350 to 400 V that we charge our Teslas with? As an electrical engineering student I would be very interested to find out. I have been searching the inter webs high and low for this topic and never found any relevant answers. It would be fun to discuss! Here is a start. If other forum members who are interested would like to chime in and add their opinions to the pros and cons list I think we could get an interesting little discussion going.

800V pros and cons (as compared to 400V) It is also assumed that the inverter motor combo runs 800 V but this may be wrong. Please correct me if this is the case.

Pros	Cons
Lower weight of conductors (as a function of lower current).	Lower power density in the motors due to larger insulation surface (function of thinner winding) and insulation thickness (function of voltage).
Lower cooling requirements, for inverters and conductors as a function of lower current.	Lower inverter efficiency and rpm band due to trade offs in high voltage MOSFETs.
Lower inverter mass due to fewer or alternatively lower current inverter components.	Higher cost and weight of insulation for all HV conductors inside and the car and in the chargers.
	Increased risk of injury in the event of shut off and /or insulation failure.

Just realized another con is AC charging complexity and possibly energy loss. You either need a battery pack divider circuit to get closer to the AC input or run the boost converters all the way to 800V, or put a transformer before the rectifier. No matter which one of these, you will add weight and or lose efficiency. The average 3 phase AC voltage in the world seems to be around 400 V. List of Voltages & Frequencies (Hz) by Country - Electric Power Around the Globe
Perhaps that's why EVs up until today run 400V? That way we have minimum amount of conversion loss at least at level 2 when you would typically run 3 phase. America runs 2 phase commercial or home split one phase for level two so you get 208 to 277 V but rest of world seems to use 3 phase which brings you to just around 400V

 

[Candleflame]

Just realized another con is AC charging complexity and possibly energy loss. You either need a battery pack divider circuit to get closer to the AC input or run the boost converters all the way to 800V, or put a transformer before the rectifier. No matter which one of these, you will add weight and or lose efficiency. The average 3 phase AC voltage in the world seems to be around 400 V. List of Voltages & Frequencies (Hz) by Country - Electric Power Around the Globe
Perhaps that's why EVs up until today run 400V? That way we have minimum amount of conversion loss at least at level 2 when you would typically run 3 phase. America runs 2 phase commercial or home split one phase for level two so you get 208 to 277 V but rest of world seems to use 3 phase which brings you to just around 400V

3 phase AC voltage is 220-240V. The convention of 400V just comes because if you measure the voltage differential between phases you get 400V which is however only relevant when a 3 phase motor is being supplied by 3 phase electricity. For the purposes of charging you have 3 inlets all being fueled by i.e. 240V x3 phases (as you measure between neutral and any given phase)

 

[Olle]

3 phase AC voltage is 220-240V. The convention of 400V just comes because if you measure the voltage differential between phases you get 400V which is however only relevant when a 3 phase motor is being supplied by 3 phase electricity. For the purposes of charging you have 3 inlets all being fueled by i.e. 240V x3 phases (as you measure between neutral and any given phase)

Interesting. Here in America our 1 and 2 phase Tesla connectors actually don't use the neutral wire at all when you connect to a two phase outlet and you get the full voltage between phases i.e for American 120V line to neutral you get √3*120=208V. Are you saying in Australia a Tesla charger is not taking advantage of full L-L voltage? Do you know why?

 

[Olle]

Elon finally adressed the 800 V charging yesterday at the earnings call. He said it would reduce the cost of the 3/Y series with $100 per car, so not worth disrupting the production and charging infrastructure just for this, not by a long shot. To summarize the 800 V idea he said "delete, delete, delete"
But, Drew said for bigger vehicles like Semi it might be worth it.

 

[boulder.dude]

Looks like 800V enables better charging curves?

Kia EV6 crowned the best charging EV in the latest P3 Charge Index

P3 has announced results of its third annual Charge Index, 21 cars took part in research looking for the king of charging speed and efficiency.

www.arenaev.com

 

[Candleflame]

Interesting. Here in America our 1 and 2 phase Tesla connectors actually don't use the neutral wire at all when you connect to a two phase outlet and you get the full voltage between phases i.e for American 120V line to neutral you get √3*120=208V. Are you saying in Australia a Tesla charger is not taking advantage of full L-L voltage? Do you know why?

it is taking advantage of the full voltage which is 240 or 230V in Australia. It just depends how you measure.
Better to think less of electricity and more of water (as they are pretty much the same).

The water flows via 3 hoses into the car with a individual pressure of 240V and a speed of 12A. For a total of 36A at 240V.

However, if you would like to supply a three phase motor you connect the 3 hoses to the 3 ends and again send 240V of pressure and 12A flowrate into the 3 seperate directions. Because the direction of flow is into different directions around the motor they push each other forward (or one wire may even suck some water away from the others) so you end up with 418V of pressure/potential when you take the entire system into account.

American 2 phase power is not really 2 phase, its actually like a 0.5 phase or split phase power you create by installing a neutral wire halfway into your circuit and then seperate half of the mass/amount of individual wirestrands (or something like that im not an electrical engineer). That means you have one 120V and one -120V rail going into the home.

So to get access to the original 240V single phase coming from the USA grid you disconnect the neutral wire and then you dont half your voltage anymore.
For the home 240V you dont bypass neutral in the USA you use a special kind of circuit breaker which connects both circuits together (and uses up two breaker slots) i think...

 

[Olle]

American 2 phase power is not really 2 phase, its actually like a 0.5 phase or split phase power you create by installing a neutral wire halfway into your circuit and then seperate half of the mass/amount of individual wirestrands (or something like that im not an electrical engineer). That means you have one 120V and one -120V rail going into the home.

No.
Two phase really is two phase. This is why you see 208 V at most American public AC chargers. Most of them are installed at commercial properties that don't have access to split one phase. Instead they use 2 out of 3 phases, which is like I wrote above √3*120=208V

208 vs 240

My new condo has a breaker wired for 208 50 A for EV charging. The electrician is going to include the NEMA 14-50 outlet. Right now, it's just a blank plate covering the box. From what I have read, it will still work on 208 except it will be slightly slower. Is this correct? Model 3 Long...

teslamotorsclub.com

So to get access to the original 240V single phase coming from the USA grid you disconnect the neutral wire and then you dont half your voltage anymore.
For the home 240V you dont bypass neutral in the USA you use a special kind of circuit breaker which connects both circuits together (and uses up two breaker slots) i think...

Yes, for residential circuits this is correct. This is what most of us use for Tesla-charging at home.

 

[Candleflame]

No.
Two phase really is two phase. This is why you see 208 V at most American public AC chargers. Most of them are installed at commercial properties that don't have access to split one phase. Instead they use 2 out of 3 phases, which is like I wrote above √3*120=208V

208 vs 240

My new condo has a breaker wired for 208 50 A for EV charging. The electrician is going to include the NEMA 14-50 outlet. Right now, it's just a blank plate covering the box. From what I have read, it will still work on 208 except it will be slightly slower. Is this correct? Model 3 Long...

teslamotorsclub.com

Yes, for residential circuits this is correct. This is what most of us use for Tesla-charging at home.

teslas dont support more than 1 phase in the usa. the us electrical grid runs at 240V.

 

[Olle]

teslas dont support more than 1 phase in the usa. the us electrical grid runs at 240V.

Does it?
Luckily our Teslas aren't aware of your statement. Otherwise Level 2 Tesla charging would be a luxury available to single family dwellers only.

• The US grid runs 120/208V three-phase and 277/480V three-phase. This is why the Tesla onboard chargers are rated for 277V.
• Residential single family typically has 120V single-phase, split into two 120V lines 180 degrees out of phase with each other, giving 240V between them.
• Residential multi family housing is typically 120/208V three-phase and commercial properties have a choice of 120/208 three-phase and 277/480 three-phase.
• Level two charging outside of private residences utilizes 208V two-phase charging without neutral, meaning that a Tesla onboard charger sees the difference between when two phases, which is the green curve shown in this diagram: