Twin Chargers: Why?

[eledille]

If so, the regen can be more effecient if a 20 kw charger is onboard - potentially giving a longer range....I don't know, maybe others know how roadster handle this

Neither the roadster nor Model S uses the regen to charge from the grid, so additional chargers will have no effect on the regen.

It can be done, though, the regen is essentially a three phase battery charger. Renault has built one (75 A, 400 V, 52 kW).

bolosky: Perfectly right, the Roadster has a three phase charger handing regen which is twice as powerful as the single phase charger used for recharging. As dpeilow says, continuous charging would require more cooling, which might be a problem in the air-cooled Roadster. If the regen is liquid cooled, this should not be too hard to do. A small ICE produces more heat when idling than a 50 kW three phase charger does at full power.

 

[TEG]

I am guessing that the regen is handled by the inverter electronics inside the motor / transaxle housing, and the separate charger(s) (under the rear seats) only handle grid charging, and not coupled to regen at all. I am also guessing that the inverter / regen circuit is totally Telsa custom / proprietary, but the charger(s) may be more "off the shelf". Anyone know if Tesla has designed the charger(s) themselves from scratch?

 

[dhrivnak]

Could it mean that there are two separate chargers and plugs on board so one could plug into two J1772 plugs? Most public chargers have multiple plugs and as long as a second EV is not next to you one could use both to charge faster.

 

[WhiteKnight]

Tesla restricting access to super chargers probably has to with the warranty. traveling and fast charging a 160 mile battery puts a lot more cycles on it than a 300 mile pack (traveling the same distance). Ex: I have a 300 mile pack, I travel NYC->Boston. A 160 mile pack would have to charge 1-2 times. while a 300 mile pack would have to charge 0-1 time. The longer the trip the number of super charges become multiplicative. Boston->DC 300 mile pack super charges 1-2 times while 160 super charges 3-4 times. The super charging really adds up for the 160 and that's what Tesla wants to avoid. Li-ion battery packs have a cycle life. So to provide a warranty of 8 years would require them to sacrifice the super charging.

This sounds right to me. You should not buy the 40 kWh pack if you want to take a road trip - won't work.
Highway Range Ignorance

 

[WhiteKnight]

Could it mean that there are two separate chargers and plugs on board so one could plug into two J1772 plugs? Most public chargers have multiple plugs and as long as a second EV is not next to you one could use both to charge faster.

I would love to know the answer to this question. I would like to hope you could use two plugs but wouldn't that require two charging doors?

 

[Mycroft]

The chargers are mounted under the rear passenger seat. There is room for one or two chargers. They're linked together to the single charge port.

The second charger is ONLY beneficial (to the best of my knowledge) if you want to be able to charge from a power source greater than 50amps. i.e. the HPC 2.0.

I'm sure more information will be forthcoming.

 

[TEG]

Could it mean that there are two separate chargers and plugs on board so one could plug into two J1772 plugs? Most public chargers have multiple plugs and as long as a second EV is not next to you one could use both to charge faster.

I suggested that as an idea a while back. But there is no sign whatsoever from Tesla that they intend to do that.
Rather, as-stated, I think the intention is for them to be linked, and just pull from the one plug at higher current rates.

A socket on each side to "double dip" would also make sense in that the Model S is so wide it might span two parking spaces!

(Compact parking spaces? Sure - I'll take two! All your charge spots R belong to us! )

 

[ljbad4life]

This sounds right to me. You should not buy the 40 kWh pack if you want to take a road trip - won't work.
Highway Range Ignorance

Well from a time stand point anything less than 200 mile doesn't make sense for road trips. drive 2 hours to wait 30-40 minutes? rinse and repeat. The longer the trip the more tedious traveling this way. More than 1/3rd of your time is spent charging. I wouldn't call that ignorance, Tesla gives a FAR more comprehensive and FAR more accurate estimate of Range than any other EV manufacturer. Nissan Leaf is rated for 100 miles at an avg speed of 20 mph same thing goes for the Mitzubishi iMeiv. So Tesla rating of range at 55 mph is good enough for me.

 

[dsm363]

The second charger is ONLY beneficial (to the best of my knowledge) if you want to be able to charge from a power source greater than 50amps. i.e. the HPC 2.0.

You're correct in that it's a 50A outlet which means you can pull 40A. The HPC will allow you with the second charger to go to 80A.

 

[Eberhard]

I want not only two but three charger - could connect each charger to a different phase for 3-phase charging.

 

[Mycroft]

I hope you get it Eberhard. They could mount the third charger in the Frunk or possibly the jumpseat footwell, (without the jumpseats of course.

 

[Robert.Boston]

Or, more to the point, simply have a single 3-phase charger in the place where the two 1-phase chargers fit. The problem lies not with the charger, I believe, but rather with the pin design of the charging port, which clearly cannot handle 3-phase power.

 

[cinergi]

I am guessing that the regen is handled by the inverter electronics inside the motor / transaxle housing, and the separate charger(s) (under the rear seats) only handle grid charging, and not coupled to regen at all.

This is what I was told at the Model S Beta event. The PEM in the Roadster does both regen and charging, but that's been separated to separate components in the Model S. The "Drive Inverter" is NOT responsible for grid charging in the Model S.

 

[Larry Chanin]

Am I missing the advantage(s) of the Twin Chargers option? I don't see any:

20KW means something like 90amp delivery, which means over 100amp circuit breaker. You're not going to find those on the road, so it's only for home, where you've probably got enough time to charge at the usual 40/45 amps.

For Supercharging, we apparently don't need the Twin Chargers, just the 85kWh battery. That's what we'd target for long road trips.


So, why get the Twin Chargers? This is reason alone for me to not upgrade to a Signature model (don't want to pay for options I won't ever use).

Hi,

I think in the vast majority of cases early adopters will find very little utility in purchasing dual on-board chargers for at least a number of years and perhaps never.

We obviously don't need this when charging at home, at work or during hotel stays. The main utility would be along major highway routes, just like Superchargers. Whereas I would be interested in hearing more details about how widespread the HPC network is, I'm inclined to believe it is still insufficient in most areas of the country. Likewise, I don't think that there are many, if any Tesla stores located along highways to constitute a useful high amperage network.

However, there may be certain conditions where using dual on-board chargers in conjunction with high amperage roadside sources may be preferable to Supercharging. Please refer to the following posting for one possible example.

So I spoke to Tesla customer rep and they confirmed the 40Kwh will never have a QC option. The fastest it can charge is ~2 hours if you buy the twin charger. If not it'll take ~4hours.

Also they only expect the 60Kwh and 80Kwh owners to quick charge ONLY in emergencies. The y expect supercharging for those battery packs to only happen 2% of the time during the entire life cycle of the battery. So don't be planning on supercharging everyday.

This is because supercharging regularly will actually kill the battery and they obviously don't want that. The Nissan Leaf has a smaller battery pack and different chemistry so it can quick charge more often than the Tesla battery packs.

So if someone makes frequent long roadtrips it might be better if they used high amperage AC charging using the dual on-board chargers rather than DC Supercharging to avoid undue degradation of the battery pack. The problem is that currently there is not much in the way of high amperage sources located along strategic highway routes.

As I see it the only high amperage AC sources are located at RV parks, at Tesla stores and at the HPC network sites. I am not familiar with how widespread the HPC network is, but I'm pretty sure that most RV parks and Tesla stores are not along strategic highway routes. So to make use of these sources in most cases we would have to detour off of a direct highway route. Such a detour probably wouldn't save much time versus a 30 amp source along a highway.

So from my perspective it would be better to defer the purchase of the second on-board charger until there is a clearer picture of whether or not there is widespread adoption of high amperage sources, particularly along strategic highway routes. Well, you may ask do you have any reason to believe that retrofitting a second charger is feasible? Please refer to an excerpt from this posting.

I wrote to the customer service dept. about some of the questions/issues we have been speculating upon and got some definitive answers.


Hi there Evan,

Let me go through each of your questions below and see if I can answer them for you. If at the end you have further questions, please feel free to follow up with me, I would be glad to try and clarify further!

...

2)Will it be possible to upgrade to dual chargers at a later date for a reasonable cost, or is that something that needs to be done at the time of build and original ordering?
· We have engineered Model S to allow customers with the 10kW charger option to upgrade to the Twin Charger setup at a later date. The business case and terms of use have not yet been determined and therefore are not an option at this time. We advise customers to choose a Model S charger setup that meets their present as well as future needs.

...

Please feel free to contact us again if you have further questions!


Kind regards,

Stephen Smith | Customer Advocate
3500 Deer Creek Rd. | Palo Alto, Ca 94304
p 650.681.5051 | e [email protected]

So we have a legitimate reason to believe that retrofitting in the future may be possible even though Tesla currently recommends purchasing the second charger in advance of the establishment of a widespread high amperage source network.

Larry

 

[TEG]

...As I see it the only high amperage AC sources are located at RV parks, at Tesla stores and at the HPC network sites. I am not familiar with how widespread the HPC network is, but I'm pretty sure that most RV parks and Tesla stores are not along strategic highway routes. So to make use of these sources in most cases we would have to detour off of a direct highway route. Such a detour probably wouldn't save much time versus a 30 amp source along a highway...

Actually I think it would be unusual to find an RV park or campground outlet that provides more than 10kW.
Typically an HPC type connector is "hard wired" and not run through a plug/socket. So primarily at high end homes (with 200amp+ service), or at dedicated HPC sites of which there aren't a whole lot outside of California or parts of Europe.

 

[Larry Chanin]

Actually I think it would be unusual to find an RV park or campground outlet that provides more than 10kW.
Typically an HPC type connector is "hard wired" and not run through a plug/socket. So primarily at high end homes (with 200amp+ service), or at dedicated HPC sites of which there aren't a whole lot outside of California or parts of Europe.

Hi TEG,

Thanks for the information.

I guess that further strengthens my argument about the limited utility of dual on-board chargers for early adopters.

Larry

 

[TEG]

Yes, and helps explain why Tesla has decided to make 10kW standard, and 20kW optional.

 

[Larry Chanin]

Yes, and helps explain why Tesla has decided to make 10kW standard, and 20kW optional.

Hi TEG,

Yes, but only on the standard models, not the Signatures. :biggrin:

Larry

 

[jkirkebo]

Hi TEG,

Thanks for the information.

I guess that further strengthens my argument about the limited utility of dual on-board chargers for early adopters.

Larry

It would be much less limited utility if they would allow the second charger to be powered from a separate source. Imagine a second charge port on the other side of the car. You could get 19.2kW from dual 14-50 outlets! Us europeans could get 7.4kW from dual 16A 230V outlets or 14.7kW from a three-phase 32A outlet with a breakout cable. That would make me definately order the second charger.

Which charge port powers what is easy to control. First port connected gets the first charger *and* the second if the pilot exceeds 42A or so. Second charge port gets the second charger if it's still available.

Bonus is you now have a charge port on either side of the car for convenience.

 

[Larry Chanin]

It would be much less limited utility if they would allow the second charger to be powered from a separate source. Imagine a second charge port on the other side of the car. You could get 19.2kW from dual 14-50 outlets! Us europeans could get 7.4kW from dual 16A 230V outlets or 14.7kW from a three-phase 32A outlet with a breakout cable. That would make me definately order the second charger.

Which charge port powers what is easy to control. First port connected gets the first charger *and* the second if the pilot exceeds 42A or so. Second charge port gets the second charger if it's still available.

Bonus is you now have a charge port on either side of the car for convenience.

Hi,

From my layman's perspective that sounds like a very reasonable option. Have you forwarded it to Tesla for consideration? I know that so far they've been rather reluntant to pursue alternative charging approaches, particularly three-phase. Nevertheless, I still think it couldn't hurt to send them a request for future consideration.

Larry