mux
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Wed Mar 28, 2018 11:48 pm

Understanding how DCQC works without having a firm understanding of basic power electronics and switching power supplies will always get you a bunch of incongruities and confusion, as any simplified layman model of the components required for a DCQC+electric car system will have essential components removed for clarity. Add in more confusing concepts like requesting a voltage vs current and there will be no end to the discussion.

Charging any battery as quickly as possible is done through a constant-current-then-constant-voltage process, where the current into the battery is limited to some maximum amount until the per-cell voltage reaches - in the old Leaf - 4.08V, and then the charger will effectively become a constant voltage supply at that voltage, with the battery drawing whatever current it does at that particular voltage.

There is no such thing as a perfect current source or a perfect voltage source, and as such any power supply, including a DCQC station, will always be both in some way. Likewise, batteries are not just voltage sources - they have internal resistance and they heat up during use, so there are additional requirements to safely charging and discharging. The battery cannot willy nilly ask for any amount of current and receive it, nor can the DCQC just supply any amount of current without regard for voltage and temperature. These are parameters that must be communicated back and forth, and these are exactly the kinds of things you see running over the CHAdeMO CAN-bus.

Additionally, there are no voltage sense wires going over the CHAdeMO protocol, so the charger has no direct way of knowing what the actual battery voltage is, without the resistance of all the wires going to it. It's charging blindly on CAN-messages, essentially.

Taking all of this into account, pretty much the only way to ever design a DCQC station is to first let the station voltage-match to the battery, and then increase the supply voltage stepwise up to the point where either the maximum battery voltage (4.08V/cell, approx. 390V in the Leaf) is reached, or until the battery says it can't take any more. Anything else on the HV bus will simply be along for the ride at that point, drawing whatever current it draws at that amount of overvoltage. This is how the extender is charged, and how ANY car with CHAdeMO or CCS will be able to add in an extender and have it quick-charge effortlessly.

This is exactly what I see happening in my car. Near empty, I charged at a CHAdeMO station. The station supplied approx. 110A to the car, of which 80 was going into the extender and 30 into the main battery.

lorenfb
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Thu Mar 29, 2018 9:39 am

mux wrote:Understanding how DCQC works without having a firm understanding of basic power electronics and switching power supplies will always get you a bunch of incongruities and confusion, as any simplified layman model of the components required for a DCQC+electric car system will have essential components removed for clarity. Add in more confusing concepts like requesting a voltage vs current and there will be no end to the discussion.

Charging any battery as quickly as possible is done through a constant-current-then-constant-voltage process, where the current into the battery is limited to some maximum amount until the per-cell voltage reaches - in the old Leaf - 4.08V, and then the charger will effectively become a constant voltage supply at that voltage, with the battery drawing whatever current it does at that particular voltage.

There is no such thing as a perfect current source or a perfect voltage source, and as such any power supply, including a DCQC station, will always be both in some way. Likewise, batteries are not just voltage sources - they have internal resistance and they heat up during use, so there are additional requirements to safely charging and discharging. The battery cannot willy nilly ask for any amount of current and receive it, nor can the DCQC just supply any amount of current without regard for voltage and temperature. These are parameters that must be communicated back and forth, and these are exactly the kinds of things you see running over the CHAdeMO CAN-bus.

Additionally, there are no voltage sense wires going over the CHAdeMO protocol, so the charger has no direct way of knowing what the actual battery voltage is, without the resistance of all the wires going to it. It's charging blindly on CAN-messages, essentially.

Taking all of this into account, pretty much the only way to ever design a DCQC station is to first let the station voltage-match to the battery, and then increase the supply voltage stepwise up to the point where either the maximum battery voltage (4.08V/cell, approx. 390V in the Leaf) is reached, or until the battery says it can't take any more. Anything else on the HV bus will simply be along for the ride at that point, drawing whatever current it draws at that amount of overvoltage. This is how the extender is charged, and how ANY car with CHAdeMO or CCS will be able to add in an extender and have it quick-charge effortlessly.

This is exactly what I see happening in my car. Near empty, I charged at a CHAdeMO station. The station supplied approx. 110A to the car, of which 80 was going into the extender and 30 into the main battery.
Thanks for your primer on DCQC. Sorry to divert the thread. Please continue providing updates on your progress.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 4.5K miles, 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 20%, temp < 105F

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TonyWilliams
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 2:36 am

Many of you know that we (Quick Charge Power) build JdeMO, which is an aftermarket CHAdeMO fast charge kit for the 2012-2014 Toyota RAV4 EV, as well as the 2008-2011 Tesla Roadster. The kit for the 2014 - 2018 Mercedes B-Class ED / B250e is underway for the fall of 2018. All of these cars use a Tesla battery.

I’m not sure why the above poster doesn’t believe that there is a battery voltage measuring capability for the charger. It’s certainly in the spec. In addition, the max battery voltage is announced via CAN, as well as max amps.

Fundamentally, this battery voltage measuring happens at the moment that the contactors close on both the charger and vehicle (after the plug has locked, the only time it safe to do this measurement).

The charger must physically measure a CHAdeMO compatible voltage of 50 to 500 volts DC, before it will allow any power to be sent to the battery. The future spec will be 50-1000 volts.

The vehicle is sending one simple control message via CAN... how many amps in 100ms time increments. The zero amp message is a shutdown. At the moment both charger and vehicle High Voltage contactors close, the charger physically measures a CHAdeMO compatible 50-500 volts, and the vehicle begins sending its amp request at a ramp up rate of up to 20 amps per second.

The current maximum amp request from the vehicle is 400 amps. The 2011-2018 LEAF is 125 amps maximum, and the 2019 LEAF e+ with liquid cooled LG-Chem cells will be 200 amps maximum.

Previous to contactors closing, a series of analog enable messages are exchanged (0-12 volt DC), as well as basic digital CAN massages (max amps, max voltage).

The plug is locked to the vehicle when the this communication begins. The charger provides a 0-500 volt insulation / isolation test while still disconnected from vehicle battery, looking for any reason not to start a charge with deadly high voltage DC.

t0 ————- contactors close
t0 + 500ms - charger confirms 50-500 volts DC from vehicle
t0 + 1sec —- up to 20 amps requested by vehicle
t0 + 5sec —- 120 amps requested (assuming this is max for vehicle)
t0 + XX min - maximum battery voltage reached as determined by vehicle (395-400v in LEAF)
t0 + XX min - vehicle amp request lowered to not exceed max voltage
t0 + end —— vehicle determines charge complete, sends zero amp message, both contactors open
t0 + end+ —- charger measures zero voltage, unlocks plug

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TonyWilliams
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 2:57 am

lorenfb wrote:3. We are both attempting to determine how the DCQC might function with two batteries connected in parallel and where one battery is controlling the total charging current. Unless you can document that the DCQC is a current source, the charging method whether using
L1/L2 or DCQC is the same - using a voltage source input and pulse width modulating the input voltage to achieve a desired charging current.
Obviously the DCQC device becomes much more costly for the electric company providing the charging station and they're no longer providing a simple service as usual which is just supplying a simple voltage to its users.
It’s great to see that you are consistent in your cluelessness with electronics as you are about Tesla.

You quite literally don’t bother to know or understand anything; you just spew.

mux
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 5:20 am

TonyWilliams wrote:(...)

I’m not sure why the above poster doesn’t believe that there is a battery voltage measuring capability for the charger. It’s certainly in the spec. In addition, the max battery voltage is announced via CAN, as well as max amps.(...)
My comment is specifically about there not being a continuous battery voltage measurement. There are no sense wires, the only thing CHAdeMO does is measure the no-load voltage at the beginning of charge. It cannot do a continuous voltage measurement on the actual battery poles to do a proper CCCV. Any measurement under load will necessarily include the parasitic resistance across the wires, which is very significant at decent charging rates. This also limits the usefulness of DCQC at high SoC, as the charger is very conservative with its termination voltage. Most CHAdeMO stations don't even have sense wires in the end of the charging cable - they just limit the maximum voltage at the charger output in the 'box', not at the connector end and certainly not at the battery poles. This is at least true for the ABB CHAdeMO chargers that are ubiquitous in the Netherlands.

That's all. I'm currently reading up on the spec, as I'm currently designing a CHAdeMO charger to install at home, using a bunch of spare batteries as a high-power buffer.

lorenfb
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 6:05 am

mux wrote:
TonyWilliams wrote:(...)

I’m not sure why the above poster doesn’t believe that there is a battery voltage measuring capability for the charger. It’s certainly in the spec. In addition, the max battery voltage is announced via CAN, as well as max amps.(...)
My comment is specifically about there not being a continuous battery voltage measurement. There are no sense wires, the only thing CHAdeMO does is measure the no-load voltage at the beginning of charge. It cannot do a continuous voltage measurement on the actual battery poles to do a proper CCCV. Any measurement under load will necessarily include the parasitic resistance across the wires, which is very significant at decent charging rates. This also limits the usefulness of DCQC at high SoC, as the charger is very conservative with its termination voltage. Most CHAdeMO stations don't even have sense wires in the end of the charging cable - they just limit the maximum voltage at the charger output in the 'box', not at the connector end and certainly not at the battery poles. This is at least true for the ABB CHAdeMO chargers that are ubiquitous in the Netherlands.

That's all. I'm currently reading up on the spec, as I'm currently designing a CHAdeMO charger to install at home, using a bunch of spare batteries as a high-power buffer.
That poster always finds away to promote his products by attacking others on MNL, which resulted in being banned multiple times.
As a result of his being so personally obnoxious, I only attended the Leaf/EV meetings here in SoCal only twice when I first acquired
my Leaf in 2013. Just ignore him. He likes to take things out of context to imply a "superior knowledge" and to promote his products.
How coincidental was it that he presents a description of how the DCQC functions after a link; (http://mynissanleaf.com/viewtopic.php?f ... 10#p523066),
to a PDF was presented? As you point out, there're many very detailed aspects of the DCQC spec that many even with "expert" knowledge
lack and are learning over time.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 4.5K miles, 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 20%, temp < 105F

mux
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 7:28 am

Ah, right, I thought it was a bit out of left field to start calling people names out of nowhere and completely out of context. If there is any advice I can give Mr. Williams, it's: if you want to sell your products, don't be a dick.

Regardless, I don't have a beef with any of you and all I'm after is to either educate, be educated or contribute meaningfully to the highest possible utility of old Nissan Leafs. If you disregard the ad homs, this page has been a very good source of useful DCQC information and discussion. I'm not invested enough in this community to care much about the interpersonal stuff that comes with any community.

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TonyWilliams
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 8:33 am

mux wrote:Ah, right, I thought it was a bit out of left field to start calling people names out of nowhere and completely out of context. If there is any advice I can give Mr. Williams, it's: if you want to sell your products, don't be a dick.

Regardless, I don't have a beef with any of you and all I'm after is to either educate, be educated or contribute meaningfully to the highest possible utility of old Nissan Leafs. If you disregard the ad homs, this page has been a very good source of useful DCQC information and discussion. I'm not invested enough in this community to care much about the interpersonal stuff that comes with any community.
I’m not selling products here, as clearly NONE of those listed fit any Nissan vehicle. I’m also not sure why you are responding this way. Truly bizarre.

The poster who I did address is a complete buffoon, and is on my block list. Some others blocked are classics like Ed?? and OrientExpress, too. Bloviating wastes of time.

While I agree that this thread is great, I’ll also point out that I started it. Do I get a brownie point?

6.5 years ago... Extra Battery, How to Integrate with 24kWh Traction Battery?

Tue Oct 25, 2011 9:56 pm

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TonyWilliams
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 8:50 am

lorenfb wrote:That poster always finds away to promote his products by attacking others on MNL, which resulted in being banned multiple times.
As a result of his being so personally obnoxious, I only attended the Leaf/EV meetings here in SoCal only twice when I first acquired
my Leaf in 2013. Just ignore him. He likes to take things out of context to imply a "superior knowledge" and to promote his products.
How coincidental was it that he presents a description of how the DCQC functions after a link; (http://mynissanleaf.com/viewtopic.php?f ... 10#p523066),
to a PDF was presented? As you point out, there're many very detailed aspects of the DCQC spec that many even with "expert" knowledge
lack and are learning over time.
Yes, I quickly read that link, and became an “expert” in 5 minutes. How on God’s earth did we get that CHAdeMO stuff working and sold to hundreds of customers worldwide for the past several years? Maybe you’ll claim next that you were the brains behind it all? Must be “lorenb logic”, the same logic applied in your many flawed posts.

Listen, I doubt that I could pick you out of a line up of “angry old folks”, so even if you ever were at our group breakfast meetings, who would know? Not me, and not anybody that I know or respect. Maybe you’re paranoid?

I hope you are still losing your butt shorting TSLA, too. I’m smiling big knowing there are people like you out there.

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TonyWilliams
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Fri Mar 30, 2018 8:56 am

mux wrote:
TonyWilliams wrote:(...)

I’m not sure why the above poster doesn’t believe that there is a battery voltage measuring capability for the charger. It’s certainly in the spec. In addition, the max battery voltage is announced via CAN, as well as max amps.(...)
My comment is specifically about there not being a continuous battery voltage measurement. There are no sense wires, the only thing CHAdeMO does is measure the no-load voltage at the beginning of charge. It cannot do a continuous voltage measurement on the actual battery poles to do a proper CCCV. Any measurement under load will necessarily include the parasitic resistance across the wires, which is very significant at decent charging rates. This also limits the usefulness of DCQC at high SoC, as the charger is very conservative with its termination voltage. Most CHAdeMO stations don't even have sense wires in the end of the charging cable - they just limit the maximum voltage at the charger output in the 'box', not at the connector end and certainly not at the battery poles. This is at least true for the ABB CHAdeMO chargers that are ubiquitous in the Netherlands.

That's all. I'm currently reading up on the spec, as I'm currently designing a CHAdeMO charger to install at home, using a bunch of spare batteries as a high-power buffer.
But, there is a continuous measuring of both pack and cell pair voltages. It’s just done in the vehicle. The BMS is monitoring that, and sending that amp request every 100ms.

Sounds like a fun project that you have started. One thing to understand in any of the various DC fast charge standards is that the vehicle ALWAYS controls the charge rate. The charger is a dumb box, doing what it is told, within the programmed limits.

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