DIY Electric Car Forums banner
1 - 20 of 47 Posts

·
Premium Member
Joined
·
29 Posts
Discussion Starter · #1 ·
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.
 

·
Registered
Joined
·
2,984 Posts
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.
 

·
Premium Member
Joined
·
29 Posts
Discussion Starter · #4 ·
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?
 

·
Registered
Joined
·
7,950 Posts
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.
 

·
Registered
Joined
·
7,950 Posts
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.
 

·
Registered
Joined
·
221 Posts
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.
 

·
Registered
Joined
·
7,950 Posts
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.
 

·
Registered
Joined
·
2,984 Posts
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).
 

·
Registered
Joined
·
221 Posts
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.
 

·
Premium Member
Joined
·
29 Posts
Discussion Starter · #12 ·
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.
 

·
Registered
Joined
·
7,950 Posts
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.
 

·
Registered
Joined
·
2,984 Posts
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.
 

·
Registered
Joined
·
786 Posts
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.
 

·
Premium Member
Joined
·
29 Posts
Discussion Starter · #18 ·
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.
 
1 - 20 of 47 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top