Level 3 Charging Updates - SAE Meetings

The Society of Automotive Engineers' Hybrid J1772 Task Force met on June 22nd to review progress on electric and plug-in hybrid charging and electric vehicle supply equipment (EVSE).

Attendees included at least reps from the SAE, TEPCO, Tesla, BMW, LS Cable, Plug Smart, CCI, GM, Ford, Chrysler, and the Electric Power Research Institute (EPRI).

An important point: The J1772 Surface Vehicle Recommended Practice includes alternating current (AC) Level 1 (L1) and 2 (L2) provisions, as well as direct current (DC) Level 3 (L3) charging. The task force has completed the L1 and L2 recommended practice and connectors and equipment are on the streets.

The focus now includes fast-tracking the L3 portion of the specification. The L3 implementation being defined by the J1772 Task Force is not the CHAdeMO/TEPCO L3 connection currently used in Japan and with which the Leaf is fitted.

L1/L2:

- The J1772 recommended practice includes a provision for locking the connector into the vehicle during charging. This is to deter charge cable theft and also parking lot cable hijacking. The decision to implement a locking provision is up to the auto manufacturer. [At least one manufacturer rep was happy to learn about the existence of the provision...]

- By the 27th of July, the EPRI should have the J1772 EVSE test documents finalized. [The test procedures have procedures for testing both EVSE with continuous current adjustment capability, as well as EVSE devices that have 'discrete' charge levels and/or settings.]

L3:

- The timeline for the 'L3 add-on' has slipped at least a few months. The target to finish the DC portion of the J1772 standard is December 2010. The task force team is very aware that vehicles will be 'on the streets' in the US in December...

[note: Considering that vehicles will be shipping with CHAdeMO connectors around the time the DC portion of J1772 is being ratified, and considering the momentum behind the Japanese L3 standard, it appears that J1772 L3 is not going to be a factor in the first generation EVs. Will this create a VHS/Beta decision for the industry later?]

- One critical part of L3 charging is communication between the car and battery charger. A number of methods are being evaluated, including signaling over the DC power lines to the car, and signaling 'on top of' the L1/L2 pilot signal. Nissan is working on the required L3 communications messages.

- The DC L3 standard is defining the duty cycle for the connector as 20 minutes 'on' and 10 minutes off. [note: It wasn't clear if this was the duty cycle repeated for a single vehicle, or if it was based on a 20 minute charge for a single vehicle followed by 10 minutes to disconnect, move, and connect the next vehicle to the charger.]

The next meeting was originally scheduled for July 27th, but will be rescheduled as many of the Task Force members will be attending the Plug-In 2010 conference. <- link...

This document from Feb '10 gives an overview of L1 and L2, as well as a comparison of the J1772 DC plan and the JARI/TEPCO/CHAdeMO L3 interface. http://grouper.ieee.org/groups/earthobservationsSCC/IEEE_SAE_J1772_Update_10_02_08_Gery_Kissel.pdf

Here's a link to the SAE works in progress page for plug-in vehicle standards: http://www.sae.org/servlets/works/documentHome.do?comtID=TEVHYB&inputPage=wIpS

Glacial progress.

Thanks for the update

It seems evident that J1772 L3 charging will use the J1772 connector (which has always been their plan) and it's quite possible nobody will ever implement it.

Bicster said:

It seems evident that J1772 L3 charging will use the J1772 connector (which has always been their plan) and it's quite possible nobody will ever implement it.

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Yes - though it makes sense that we have just one port for all types of charging ...

A max of 20 minutes continuous charge is not acceptable.

garygid said:

A max of 20 minutes continuous charge is not acceptable.

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Yes. I wonder how the market will evolve. They need to get people moving - so as to serve maximum # of cars - yet allow us to do our work as we charge ...

garygid said:

A max of 20 minutes continuous charge is not acceptable.

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Can you please explain what you think the 20 minutes means? How much current for that 20 minutes? What type of batteries? What's the state of charge going in and then after the 20 minutes? What's the pack temperature?

AndyH said:

garygid said:

A max of 20 minutes continuous charge is not acceptable.

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Can you please explain what you think the 20 minutes means? How much current for that 20 minutes? What type of batteries? What's the state of charge going in and then after the 20 minutes? What's the pack temperature?

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I think that is cigarette lighter fast charging. Clearly limited for safety

Assuming it takes 30 minutes to get an 80% charge, then 20 minutes gives me only a 53% charge!

So, at 60 freeway miles per full charge, this 20-minute Quick-Charge would only get me 30 miles further, ... sad!

I guess one would like to get enough e-fuel to get to the next Quick-Charger.

Driving for 30 minutes, charging for 20, possibly waiting for 10 to 30 (or more) minutes. Still, the L3 charging will occsionally be a great help.

I'm not an EE so that might be the limiting factor, but I cannot tell anyone their end state of charge without knowing the starting SoC, charge rate, and time.

Help me out, please?

Assuming min SOC - it takes 27 minutes to fill Leaf to 80%.

Anyway, we don't know what that 20/10 cycle means at all. Any limitation as to how much time a vehicle can charge should be set by the charger provider rather than SAE - so, I don't think SAE will worry about that. May be they are saying - since fast charge generates a lot of heat - a charger should be capable of 20 minutes heating, 10 minutes cooling cycles ?

evnow said:

Assuming min SOC - it takes 27 minutes to fill Leaf to 80%.

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At what charge rate?

evnow said:

Anyway, we don't know what that 20/10 cycle means at all. Any limitation as to how much time a vehicle can charge should be set by the charger provider rather than SAE - so, I don't think SAE will worry about that. May be they are saying - since fast charge generates a lot of heat - a charger should be capable of 20 minutes heating, 10 minutes cooling cycles ?

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Exactly. I'm certainly not going to strain anything jumping to conclusions. :lol:

AndyH said:

evnow said:

Assuming min SOC - it takes 27 minutes to fill Leaf to 80%.

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At what charge rate?

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That is what Leaf says about fast charging.

isnt fast charging available in CA NOW? what is their experience charging? i was under the impression that the L3 charger will FULLY charge the car.

all charging systems brady down the current (cellphone car chargers excluded!!) as the SOC increases to prevent overcharging.

correct me; L3 charger runs at full speed until car hits 80% SOC then current ramps down as SOC approaches 100%. in all battery charging scenarios the "topping off" time is usually equal to the time it takes to get to 80-90% SOC.

the 27 minute parameter discussed is simply the point at which it "maximizes" the time of the user.

charging; 0-80% 27 minutes. 81%-100% 27 mins (this would actually probably be longer) = ~ 54 mins total

this is what is exhibited in my Zenn. i use KilloWatt meter to track power in. it starts at around 15 amps and the current drops as the SOC on my battery pack goes up. for what i do, its about 150 minutes to recharge to 100%, but i get back to probably 90-95% in 80-100 minutes (been doing this for 3 years and results are pretty consistent)

In the Level 3 charging, the current (charge rate) is still controlled by the car (up to the max current that the external "DC power supply" can provide).

Fast charge rates up to some point, then slower rates until some cells are "full".

DaveinOlyWA said:

charging; 0-80% 27 minutes. 81%-100% 27 mins (this would actually probably be longer) = ~ 54 mins total

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True. I just ignored the topping off at constant voltage. 0-80% is at constant current and fast.

I'm sure in a commercial situation, if someone else is waiting, the landlord would like you to move out at 80% point ... also in legislation PSRC is considering, they have the option of putting a time limit for charging a car.

And to add a new wrinkle. JFE claims level 3 charging that can complete in just 3 minutes @ 500-600 amps. Of course it's not CHAdeMO compatible, so not applicable to our Leafs as they are being built right now. But maybe someday.....:

http://green.autoblog.com/2010/06/24/jfe-to-conduct-field-trials-of-super-rapid-charger-by-years-end/

well we have to look at L3 charging and the needs it addresses. this is when you are in a hurry. would be for charging perhaps on an extended bathroom break (27 minutes not all that extended. with kids, our stops easily go 15-20 minutes). Valet service or some sort of message sent to user cellphone when say 90% is reached which would allow them to move car and let someone else in. in a business venture; the charger would automatically cut off someone off at a predetermined level to maximize profitability

if not in a hurry, like hotels, etc. then L2 would serve the needs. i think in some areas of higher EV penetration, issues of long lines at L3 stations may require a time limit for charging which not be based on the resulting SOC.

what if multiple cars are charging at once? would the total current be split up amongst the connected cars or would each get their own dedicated supply?

garygid said:

In the Level 3 charging, the current (charge rate) is still controlled by the car (up to the max current that the external "DC power supply" can provide).

Fast charge rates up to some point, then slower rates until some cells are "full".

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Guys, we're severely mixing up 'Leaf facts', generic 'battery facts' and L3 guesses. Gary - I asked you a couple of specific questions for a reason. Since we have absolutely no idea yet how the Leaf's systems handle the charge, how can you suggest you know what it's doing during charge?

Dave's assessment matches my bench-top lithium battery experience and my lithium road experience.

For the Leaf: We know that their L3 charge time number is defined as the time it takes to bring an 'empty' pack to 80% state of charge. We don't know what the car's battery management system does or how it throttles the charge to keep the pack happy. We don't know exactly how much battery capacity we have, and don't know yet what 'empty' means in terms of Amp-hours.

For the L3 charger: We don't know how much power the CHAdeMO/TEPCO charger delivers, we don't know if the charge is delivered linearly or if it's pulsed or if it varies. We don't know if CHAdeMO/TEPCO's unit has the same 20 minutes on/10 minutes off that the folks from SAE discussed for the J1772 DC input.

As for fast charging lithium - yes! The batteries on the market today are capable of 6 minute charges. The 10Ah cylindrical LiFePO4 cells I work with have a 10C continuous output rating (100A) and a 4C charge (40A) (15 minutes). The cells stay cool until the last portion of the charge. The charge is primarily limited by heat. The cells can handle a faster charge rate to 80% because that's the zone of lowest rate of heating.

Bottom line for me - we have a charge number from Nissan's sales department but don't have any idea yet what it means or if the engineering staff agrees. Time will tell, I guess.

Andy

AndyH said:

Bottom line for me - we have a charge number from Nissan's sales department but don't have any idea yet what it means or if the engineering staff agrees.

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I don't think it is as bad as that. From the day Leaf was announced they have been talking about 26 minute quick charge to 80%. That has to come from real engineering - not just sales talk.

http://wheels.blogs.nytimes.com/2009/08/03/nissan-unveils-leaf-electric-car/

evnow said:

AndyH said:

Bottom line for me - we have a charge number from Nissan's sales department but don't have any idea yet what it means or if the engineering staff agrees.

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I don't think it is as bad as that. From the day Leaf was announced they have been talking about 25 minute quick charge to 80%. That has to come from real engineering - not just sales talk.

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Sorry, evnow - I agree with you 100% and expect the car will perform as well or better than advertised. I'm really excited about getting one into my garage!

I wanted to make a clear distinction between what we know (or think we know) about the Leaf, and what the folks in the J1772 Task Force are doing, that's all.

Andy