# 800 volt ev conversion



## mitchhodge (Oct 1, 2021)

I'm new at this, so be gentle.
I"m seeing 800 volt cars on the market. Has anyone completed an ev conversion with an 800v system?
I'm doing my homework on the details of configuring a battery pack at 800v.


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## mitchhodge (Oct 1, 2021)

I'm also considering this since charging times are much quicker.


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## remy_martian (Feb 4, 2019)

Everything, including HV cables, contactors, inverters, traction motor choices, are a big step to less available (more expensive). Many public chargers are only good to 500V, though that may change.

Pioneers are the ones who get arrows in their backs, as the saying goes....while it sounds wonderful on paper, it's early days, imo.


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## mitchhodge (Oct 1, 2021)

Thanks for the reply. Emrax is helping source the components. I will be outsourcing the high voltage connections. As I understand, public chargers will still work on 800v systems, correct?
Also, I'm aware that this is dangerous work that should be left to professionals and I will be hiring someone to handle these. My big question is...Can existing batteries be configured to an 800v pack?


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## brian_ (Feb 7, 2017)

mitchhodge said:


> As I understand, public chargers will still work on 800v systems, correct?


Not directly. If the charger is, like the vast majority of public charging stations, only capable of 500 volts, it can't charge your 800 V battery at all. How would a 500 volt source overcome almost 800 volts of battery voltage to push more charge in?

There are two solutions currently used in production vehicles:
*Reconfiguration*
GM's Ultium system (just going into production for the GMC Hummer EV) arranges the battery modules into two equal banks, connecting them in parallel to charge from common charging stations (at up to 400 volts), and connecting them in series to charge from 800 V DC chargers. It's not clear in the reports that I found which configuration is used to operate the vehicle.

*Conversion*
Porsche's Taycan carries the usual onboard AC-to-DC charger (but producing up to 800 V DC) plus an additional onboard charging converter to charge the battery at up to 800 volts using up to 400 volts DC from a charging station.


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## brian_ (Feb 7, 2017)

mitchhodge said:


> My big question is...Can existing batteries be configured to an 800v pack?


If you're asking whether existing modules can be connected in series to reach almost 800 volts... yes, likely, as long as there isn't an isolation issue somewhere that is okay at 400 volts and not at 800 volts. The cells themselves don't care about the pack voltage.

By the way, "800 volts" would likely be the highest charging voltage, just as 400 volts is the highest charging voltage of a typical current EV pack, which most commonly has 96 cell groups in series for a nominal voltage around 360 V.


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## 57Chevy (Jan 31, 2020)

What sort of motor/inverter will you use? Nothing readily available wrecked/OEM except maybe Porsche uses 800V so you'll be up for custom inverters and motors.

Silicon typically has 600V, 1200V, 1700V rating categories and a Tesla at 400V using 600V transistors is about the right ratio for overhead margin. You can run 600V devices up to 500V ok but the closer you get to the device rating, the more chance you'll booff the lot with a stray voltage fluctuation. A *lot of effort and engineering goes into ensuring the voltages stay within the device rating so just upping the voltage isn't a sensible option. For 800V you will have to start out with at least 1200V rated devices as well as capacitors, wire insulation and so on. 

I'm looking at around 800V for my rig... have your credit card handy.


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## brian_ (Feb 7, 2017)

The BorgWarner (formerly Remy) HVH motors are rated up to 800 volts and controllers intended for them often cover this range... but yes, OEM equipment is generally not intended for this voltage.


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## remy_martian (Feb 4, 2019)

BW's packaged cartridge motor is max nameplated at 700V, but some projects, like the eCOPO Camaro, seem to run them at 800V.

The Emrax is rated at 800V...there seem to be some subtle ads being posted for them and their capability/interests on this forum lately.

I believe the Rimac is 800V (hence Porsche, which uses their drives & power electronics).


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## brian_ (Feb 7, 2017)

<deleted>


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## 57Chevy (Jan 31, 2020)

remy_martian said:


> The Emrax is rated at 800V..


I don't understand the desire for axial flux motors. They are harder to mount, heavier, slower and less efficient than a well designed regular motor. I'm sure they have niche applications but the hype and the reality don't seem to line up very well. A regular motor can do more than 40kW/kg steady-state when designed properly, but it does that by spinning very, very quickly. Axial flux is around 2kW/kg steady state.


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## mitchhodge (Oct 1, 2021)

First off, thanks to all those for responding.
I'm slow walking this and don't mind being my own gineu pig. It seems that 800v will become more mainstream as it allows for substantially quicker charge time. I just bought a BMW I3 and love it. However, the 30plus minute rapid charging time makes road trips a bit of a chore. I don't mind waiting alone, but I don't want to put others through this.

I'm looking at the Emrax 228 motor...228 (109kW | 230Nm) - EMRAX . It's 720v. They have sent links for an inverter and bms to handle 800v so I believe the components are covered.
As far as charging goes, as long as I have the onboard charger, I can plug in anywhere, correct? I have a BMW I3 and I can plug it into 110, 220, rapid charge station, etc... 
Again, I'm learning, so tell me if I'm looking at this wrong. If anyone knows of an in person class, I would appreciate it if you send info.


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## mitchhodge (Oct 1, 2021)

The voltage for the Emrax is 680max.


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## cricketo (Oct 4, 2018)

mitchhodge said:


> It seems that 800v will become more mainstream as it allows for substantially quicker charge time. I just bought a BMW I3 and love it. However, the 30plus minute rapid charging time makes road trips a bit of a chore. I don't mind waiting alone, but I don't want to put others through this.


Not a voltage problem.


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## brian_ (Feb 7, 2017)

mitchhodge said:


> As far as charging goes, as long as I have the onboard charger, I can plug in anywhere, correct? I have a BMW I3 and I can plug it into 110, 220, rapid charge station, etc...


The onboard charger converts AC at 120 V or 240 V to the DC voltage required by the battery, so regardless of the battery voltage you can plug into charging stations (or even ordinary outlets) for AC charging - not DC charging. "Rapid charging" isn't a standard term, but presumably means DC fast charging; if your battery voltage is over 500 V you can't DC charge at most charging stations without an onboard voltage converter or a battery re-configuration system.

Perhaps some understanding of how the types of charging work is needed... 

In AC charging, the charging station is just an outlet that turns on when requested and supplies a constant voltage; the car's onboard charger converts that to the voltage which is needed.
In DC charging, the car tells the charging station what is needed, and the charging station delivers it; however, a typical DC charging station can only deliver up to 500 volts, so it is unable to charge a battery that needs more than that.
ChargeHub and PlugShare don't even have filters to display 800 volt stations, because they and the vehicles that use them are so rare that they haven't bothered; I assume that if you buy something that can only DC charge from 800 volts it comes with some sort of guide. The only available "800" volt EV that I can think of is the Porsche Taycan; Porsche's map only filters by power level, and the car comes with a voltage converter onboard. It must be really disappointing to pay for the Taycan, select a 150 kW capable charging station, and find that the car can only charge at 50 kW (just like the cheapest DC fast-charge capable EVs) because that's the power limit for the onboard converter.


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## remy_martian (Feb 4, 2019)

Most people take trips once or twice a year. Sizing your car for a once or twice a year vacation, and carrying all that baggage (weight, cost, etc) in a dailycommute is ridiculous, imo. Just as it is driving a Ford Excursion 4x4 daily in SF Bay traffic because you go to Tahoe twice a year with the extender fam.....rent a car/bus.

My charge time on the Bolt EV is ZERO. I get home, I plug in. It charges while I sleep. The only reason I went Level 2 charging after a year on a 110V EVSE was I volunteered to participate & provide feedback in a peak charge control pilot program with my utility. Fast charging is a necessity for those who have no place to plug in nightly - frankly I'd rather own a house than a $130,000 EV and live in a closet.

500V is ubiquitous for a number of reasons, of which some have already been cited...800V may come, but there's no hurry for _commercial_ reasons, which are also grounded in basic semiconductor physics and in the power supplies servers use.... yup, your Google & iTunes.

The only reason to go higher voltage in my book is to extract maximum HP out of your motor, if you have one that needs 700V, etc. Beyond 500V, everything gets to be a complete pain in the ass - contactors, wires, even the lowly fuse. Even splitting the battery for 500V charging means devices rated beyond 500/600V everywhere.

For what it's worth, the Emrax website site has 800V motors in case people get the idea there has been a correction to that posted here. Overspec'ing an inverter that's already overspec'd is throwing money down a rathole. Using a motor in an 800V battery system that's below the battery voltage is also a dubious choice, imo. Why?

The choice of 800V is questionable, especially for someone allegedly taking a lot of trips with their planned project - remember that NOBODY will repair your homebrew contraption on the road but you, so my general rule, based on several hotrodding ICE projects that broke down during the "trial period" (which can last decades, lol), is don't drive any further than you're willing to pay for a tow _home_ (not to the nearest mechanic). Even there, good luck finding a towing company that will do anything but put an EV on a flatbed (rollback),

Your project, your money, your decisions.


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## cricketo (Oct 4, 2018)

remy_martian said:


> The only reason to go higher voltage in my book is to extract maximum HP out of your motor, if you have one that needs 700V, etc.


For battery packs over say 200kWh it could make sense to go to higher voltages for the purposes of charging. We may soon start seeing vehicles with larger batteries like that especially in commercial vehicles.


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## mitchhodge (Oct 1, 2021)

this is all good feedback. As I understand the Emrax is 680v max. I'm connecting directly to a 3.89 differential. I need the voltage to get the max power out of the motor.

The faster charging will be a bonus when the stations are upgraded. Now I understand the rapid dc charging stations won't accommodate me but that's fine. 
Yes, I heed your warnings....I don't mind being my own ginea pig.


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## mitchhodge (Oct 1, 2021)

Emrax has been excellent with answering my questions. I'm depending on them to recommend the additional components.


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## cricketo (Oct 4, 2018)

mitchhodge said:


> The faster charging will be a bonus when the stations are upgraded.


Dude, one more time - you are not getting faster charging by upping the voltage. You're maxed out at the battery pack, not at the power delivery. If you had a gigantic battery pack like Tesla Semi, then upping the voltage will be relevant.


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## mitchhodge (Oct 1, 2021)

I understand that now. I still need the high voltage to get the most power from the motor.


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## remy_martian (Feb 4, 2019)

mitchhodge said:


> this is all good feedback. As I understand the Emrax is 680v max. I'm connecting directly to a 3.89 differential. I need the voltage to get the max power out of the motor.


With a direct connection to a 3.89 diff, you'll see around 2400 RPM at the pinion/motor-shaft.

Higher voltage does NOTHING for you for a motor rated at 4500RPM (I'm generalizing based on a prior glance at the 800V Emrax).

So, running at half speed, like you are, may be a complete waste beyond 400V-500V at legal highway speeds.


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## mitchhodge (Oct 1, 2021)

I'll turn at 3500 rpm at 70 mph (from the rpm calculator). My truck has the aerodynamics of a shoe box so I'm taking that into consideration. 2400 rpm puts me at 48 mph...not great for the interstate.
Check me on this. With the motor rated at 4500 rpm (800v), a 400v battery would allow only 2400 rpm. Am I thinking this correctly?
...yes, as you can see I'm electrically challenged. I will hire out this portion once I get the drivetrain set up.


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## brian_ (Feb 7, 2017)

mitchhodge said:


> As I understand the Emrax is 680v max. I'm connecting directly to a 3.89 differential. I need the voltage to get the max power out of the motor.


Or you could choose the medium-voltage (500 VDC) or even low-voltage (160 VDC) version of the same motor (228), which can produce the same power using less voltage and more current than the high-voltage (680 VDC) version. I would encourage anyone seriously considering the Emrax motor line to read the manual which is linked to the product pages.



mitchhodge said:


> Emrax has been excellent with answering my questions. I'm depending on them to recommend the additional components.


Have you asked them whether the medium-voltage version of the same motor would be more suitable, or at least as capable?


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## brian_ (Feb 7, 2017)

mitchhodge said:


> Check me on this. With the motor rated at 4500 rpm (800v), a 400v battery would allow only 2400 rpm. Am I thinking this correctly?


It's not that simple, because the motor is not running under no load; the direct proportionality of speed to voltage for a given motor is only for the unloaded (zero torque) condition.


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## mitchhodge (Oct 1, 2021)

I've been communicating with Emrax regularly. They recommended the high voltage. A larger motor with less voltage was also recommended but that motor is twice the cost.
They have a worksheet and this configuration is ideal for getting rolling and maintaining a highway speed.
I've been reading the manual....getting my head around it slowly.


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## remy_martian (Feb 4, 2019)

You missed the part about going over 500V being very expensive. 

If you can get the power output you need at lower voltage, either go for it or find another solution. 

It seems to me that your direct drive constraint is driving a lot of not so great decisions, systemwide...including public chargers.


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## brian_ (Feb 7, 2017)

mitchhodge said:


> I've been communicating with Emrax regularly. They recommended the high voltage. A larger motor with less voltage was also recommended but that motor is twice the cost.


Why a larger motor? A medium-voltage (500 V max) Emrax 228 has the same output at the same speeds as a high-voltage (680 V max) Emrax 228... just with less voltage and more current.

This graph, from the technical specs and the manual, shows the 228 motor output... *regardless of voltage* version ("HV", "MV", or "LV").









There is no need to go to the larger Emrax 268 to get the power of the high-voltage 228 at more reasonable voltage.


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## mitchhodge (Oct 1, 2021)

This is helpful...so I can stick with a 400v system? Does this limit the max rpm of the motor?
They are telling me that the high voltage will get the most out of the motor.
Forgive my mental block on current and voltage.


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## remy_martian (Feb 4, 2019)

Yes, you will get more out, as will the salesperson.

You don't care about a percent or two better efficacy because of lower copper losses. You're not in a solar race across Australia.


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## ishiwgao (May 5, 2011)

57Chevy said:


> I don't understand the desire for axial flux motors. They are harder to mount, heavier, slower and less efficient than a well designed regular motor. I'm sure they have niche applications but the hype and the reality don't seem to line up very well. A regular motor can do more than 40kW/kg steady-state when designed properly, but it does that by spinning very, very quickly. Axial flux is around 2kW/kg steady state.


Which "regular motor" suitable for automotive applications (at least >50kW of power) has a 40kW/kg steady state performance? 

I only know small motors rated <1kW spinning at 200,000rpm that are capable of such high kW/kg, whereas the 2kW/kg axial flux you're talking about is for motors with >200kW. Would you prefer to use and configure 200x 1kW regular motors or 1x 200kW axial flux?

You're not comparing apples to apples in terms of application capability.


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## 57Chevy (Jan 31, 2020)

ishiwgao said:


> Which "regular motor" suitable for automotive applications


They are designed and used by an OEM so not available to buy unfortunately. Steady-state and peak power are 50kW, nominal speed is 40k. The point of the comparison is "when designed properly" which means optimising the cooling model so thermal inertia isn't part of the equation. The potential to have high power density from a regular design is there once the designers get the cooling sorted out; not so much with axial due to the rpm limitation. [my background is high power-density motor design].



ishiwgao said:


> the 2kW/kg axial flux you're talking about is for motors with >200kW


That figure is right off their datasheet. 41kg and 85kW steady-state, although yes, their low voltage version appears to do better at 5kW/kg. Even if the cooling was optimised and we took the peak power as steady-state, it only goes up to 9kW/kg.


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## mitchhodge (Oct 1, 2021)

Hi all,
thanks again for all the input. I'm learning more and moving forward with the 400v


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## jonescg (Nov 3, 2010)

Hi Mitch,
When I built Voltron-Evo, the electric race bike, I too had trouble deciding on the right voltage. Because the motor came in two winds relevant to me - 3 turn and 4 turn, one had a higher kV, that is, the voltage at which a particular torque is applied to the rotating shaft. My problem was the options for inverters - at the time, there were two inverter options with maximum top voltages of 400 V and 720 V. The 400 V DC option coupled to the 3-turn motor was only capable of spinning the Evo motor up to a base speed of 2000 rpm or so, and would rely heavily on field weakening to get it to top speed at the expense of torque. The 720 V max option would spin the 4-turn motor to a bas speed of 3800 rpm before employing field weakening, so it was the more powerful combination, but it called for a 700 V fully charged pack. I built a 168-series battery which worked well and safely. However, it called for a LOT of BMS and hassle, and now that inverters are better placed to manage power at the ~360 V range, I would prefer to drop the operating voltage by half. It's certainly possible, but rarely worth the effort.


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## Frank (Dec 6, 2008)

I think OEM's choose the 400V nominal rating as it's a good compromise between limiting current (hence, wire size) and finding "standard" rated components. As someone mentioned above, it's a lot easier to find wire, fuses, etc. for 400V than 800V.

What kind of conversion are you considering i.e. which vehicle and for what purpose?


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## mons2b (Nov 17, 2015)

800v in a diy car sounds suicidal.


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## 57Chevy (Jan 31, 2020)

mons2b said:


> 800v in a diy car sounds suicidal.


Why? You'll die just as quickly licking 400V. More likely to die from crashing the car than the voltage.

Benefit is big power output, penalty is cost mostly. Standard hotrodding (voltrodding) stuff really.


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## remy_martian (Feb 4, 2019)

You should consider 400V equally lethal to 800V unless you use 650V wiring & passive devices on an 800V system because "it's close enough". If you don't have that respect, stick to 96V.


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## onegreenev (May 18, 2012)

mitchhodge said:


> I'm new at this, so be gentle.
> I"m seeing 800 volt cars on the market. Has anyone completed an ev conversion with an 800v system?
> I'm doing my homework on the details of configuring a battery pack at 800v.


I use low voltage 144 volts for the electric Porsche 914 and if I use my Synkromotive controller as a charger I can take 48 volts and bump it up to 144 with no problem using inductors. It works quite well and I used it once to charge my 156 volt pack. Just wanted to try. I can charge up to 192 volts with the controller and I can connect directly to my solar panels and charge directly from the panels. As long as the input DC voltage is less than the lowest voltage of the pack the controller will charge to that properly up to a nominal 192 volts. If it can be done with low voltage it can be done with high voltage. So an input of 400 volts can if the vehicle is equipped with the proper charger and inductors charge the 800v pack.


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## remy_martian (Feb 4, 2019)

Yes, you can do all that. The point of doing an EV is efficiency. 

Some may not care (like if you're on solar), but you'll get banned pretty quickly from a public charger network if you're whacking current spikes from it in an effort to boost the charge voltage. Especially if you're doing a 50kW charge rate...


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## brian_ (Feb 7, 2017)

mons2b said:


> 800v in a diy car sounds suicidal.


I'm sure that a few years ago lots of people thought that 400 volts in a DIY car sounded suicidal.

But the project has moved on from the 800 volt idea, so this "how much voltage is too much" debate is no longer relevant.


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## remy_martian (Feb 4, 2019)

It still does, and is very unforgiving. Still are lots of 96V conversions here, though at least Pb batteries have moved on.


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## brian_ (Feb 7, 2017)

onegreenev said:


> ... So an input of 400 volts can if the vehicle is equipped with the proper charger and inductors charge the 800v pack.


Yes, with proper hardware... a Porsche Taycan needs up to 800 volts to charge and is designed for 800 V DC charging stations, but has an onboard voltage converter (not just inductors) to charge from 400 V DC if that's the only DC charging available.

But this project no longer needs any of that.


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## jonescg (Nov 3, 2010)

Yeah voltage is just a number. If done properly, any voltage is safe to work around. Just make sure you do it properly.


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## remy_martian (Feb 4, 2019)

wow...just a number. 

Risk is just a number. 

People killed annually by arc flash and electrocution is just a number.


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## jonescg (Nov 3, 2010)

Well, just a number with a V after it


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## remy_martian (Feb 4, 2019)

That's better 😂


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