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Discussion Starter · #41 ·
Budgeting time!

I was originally hoping that I could complete this cut-away project for under $12,000. . . I'm now seeing that this is wishful thinking! Let me break my estimates down. . .

Main Salvage Leaf - $9,000
Secondary Leaf for just the battery pack - $5,000 (after selling off other components on eBay)
Fabrication and mounting work: $4,000

I'm not even listing an "extraneous" column and I'm already at $18k. . . way over budget.

This is the most cost-effective route I can think of to achieve this LeSharo EV conversion. . . I have been brain storming everything I can think of, including building from scratch components with god-forsaken lead-acid batteries, and this Leaf-Sharo still seems to be the best route for both functionality and cost. Therefore, I am thinking I may have to slow this project down. . . probably not complete it by this Winter :(, and just watch and learn the Salvage market better and keep an eye out for smokin' Leaf deals. . .

Any other thoughts about this?

I've been using Copart salvage auctions. I was appalled when I realized how much their members fees are! After fees and taxes a bid that ends at $7,500 ends up costing $9,500 to pick-up from the lot. And that's if it doesn't need to be shipped!

Anyone have any recommendations for better (or just more?) places to find salvaged Leafs?

Can anyone give me hope!?
 

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Can anyone give me hope!?
I'm no Obi-Wan, but, I'll give it a try.

I was originally hoping that I could complete this cut-away project for under $12,000.
You can generally get forklift DC motors for free/scrap which would be, oh, $250 or so.

You could use two of those in series. $500.

Boom, motor's done.

Spend $10,000 on batteries, save $1500 for controller and other necessary bits.

There are Volt packs available for $1000 for the whole car's worth. Not sure where you are, but, that's how I'd go. I wouldn't rip the car apart myself unless I thought it was interesting or fun or I was extremely thrifty.

I have been brain storming everything I can think of, including building from scratch components with god-forsaken lead-acid batteries
There is no equilibrium where lead-acids make sense. They are universally worse and more expensive. It's not a shortcut, it's not a "Well I'm cheap and I'll accept lower performance", even if you want to cut corners and accept lower performance, just go with fewer lithiums, it's still better. It's better in every way.
 

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Discussion Starter · #43 ·
You could use two of those in series. $500.

Ok, I'm gonna have to play with this!

https://www.youtube.com/watch?v=tJqN9qADajM


Any resources/suggestions where I can learn more about running two DC motors in series?



There are Volt packs available for $1000 for the whole car's worth. Not sure where you are, but, that's how I'd go. I wouldn't rip the car apart myself unless I thought it was interesting or fun or I was extremely thrifty.
I'm located in MN. Not a ton of EV popularity up here. People seem to think they wouldn't work well in the cold, but the few local owners I've talked to say they work just fine~


Where are you finding a whole 380V 24kWh pack for $1000??? Pricing it out on eBay, I usually see a single cell (7.6V, 64AH) for about $100, which comes out to your $10k for 2 complete Leaf batteries for my project. But are you really finding them for $1k each, for a whole pack?? That price would definitely make my project a go ;)


There is no equilibrium where lead-acids make sense. They are universally worse and more expensive. It's not a shortcut, it's not a "Well I'm cheap and I'll accept lower performance", even if you want to cut corners and accept lower performance, just go with fewer lithiums, it's still better. It's better in every way.

Sage advice. Worthy of Obi-Wan.
 

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Where are you finding a whole 380V 24kWh pack for $1000???
The Chevy Volt pack is 16-18kWh depending on model year. A quick look on ebay has one for $2340 in VA (here) but has been on sale since early March and is overpriced.

The cheapest way to obtain the parts is buying a wrecked EV. With patience you should be able to buy a decent Leaf for well under $5K and a Volt a lot cheaper than that.

If you don't want to buy a wreck then you just need to invest time searching online adds... Damien purchased a Volt pack for ~$700 and that's in Ireland where very few Volts were sold.
 

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Any resources/suggestions where I can learn more about running two DC motors in series?
Have a look at Damiens 1,000 Euro EV Build thread (here). It's not dual motor but will give you a feel for the simplicity of DC.

I would also suggest you watch his new series that starts in a couple of weeks time. He will document a 7 day EV conversion using a very low cost AC motor with direct drive :cool:
 

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Any resources/suggestions where I can learn more about running two DC motors in series?
Err, I don't know why I said series.

What I meant was, head-to-tail. So they're both turning the same shaft.

I'm just worried about power requirements as you climb hills. For acceleration you'd be fine with one big motor, but, climbing hills with that extra weight might be more than a single motor can handle.

You can also do them side-by-side with a chain link, but, ick.

Electrically you'd probably hook them up in parallel, kinda just, run them blind to each other.

Where are you finding a whole 380V 24kWh pack for $1000???
http://www.car-parts.com

Find a junker near you that's selling them off. Bit annoying as you have to pick make/model/year but $700-2000 seem to be the going price. That's for someone else doing the disassembly for you.

For a DC series motor, 380v is way overspec unless you're Duncan :p. The motors are spec'd for 48v usually, so you can give them 3-4x that but, I'm not sure how happy the insulation is above that. There's the world's biggest thread about repurposing forklift motors here.
 

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Where are you finding a whole 380V 24kWh pack for $1000??? Pricing it out on eBay, I usually see a single cell (7.6V, 64AH) for about $100, which comes out to your $10k for 2 complete Leaf batteries for my project.
That's a module, containing a 2s2p combination of four cells (each cell 32 Ah @ 3.8 V), not just a single cell. There are 48 modules in a Leaf pack, so yes, two packs or 96 modules would be about $10K at $100 per module.

If the individual module price is high this may reflect the labour of disassembly and/or selection of only good modules.
 

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Err, I don't know why I said series.

What I meant was, head-to-tail. So they're both turning the same shaft.
That's in series, mechanically. :) If you want an electrical analogy, the torque of the motors add (like voltages of cells in series) and the rotational speed is the same (like the current through cells in series).

The electrical power supply to the motors would presumably be in parallel.

You could describe the mechanical configuration as "in tandem" if you want.
 

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This brings up another point I've been wondering about. The Leaf Motor (EM61) operates at 380V. What happens if I power this motor with a lower voltage battery? Say I used 12s Tesla packs and ended up with about 270 Volts? What if I got really crazy and went to 150V?

The Motor would have less power?
The Motor would get hotter?
The stock wiring would not be capable of handling the current?
The available battery voltage limits the voltage which can be supplied to the motor. At low speed the motor is current-limited, so up to some point the lower battery voltage is not a limitation. As speed rises more voltage is needed to push the current, and most production EV motors are limited to a constant power (so as voltage rises with speed, current drops in inverse proportion to the voltage), until the limit of available voltage is reached. Reducing the available voltage should just cut off the top speed end of the operating curve.

So yes, the peak power available would be less, but when operating within the available voltage and power and stock gearing there should be no change in efficiency (or heat generation, or current). You can't trade off between current and voltage by just using a lower-voltage battery.

If you change gearing to operate at a different motor speed for a given road speed, you shift to a different point in the operating curve, which may be more or less efficient. Certainly if you use taller (less reduction) gearing so the motor runs more slowly it will need to be producing more torque (for a given road speed and power output), and so will be using more current (at a lower voltage). That only means hotter if it doesn't cool as well at lower rotational speed or is less efficient at the new operating point.

This makes me wonder more crazy things. What if I used a lower power EV motor, (or wired the EM61 at a lower voltage?) and included a voltage ramper to give shorter bursts of higher power. I know there are a lot of circuits/products available out there to change voltage up or down pretty easily. I know these components get hot. Would it be possible to use one of these to provide a temporary "boost" by ramping up battery voltage for a short time?
While not a common technique, Toyota has used a voltage doubler incorporated into the inverter of some of their hybrids to run the motor at up to twice the battery voltage.
 

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Discussion Starter · #51 ·
Jack at EVTV has a couple of dual motor setups on his website (here) :cool:
That is a wild picture! I have often wondered about this. . . running two motors in a mechanical series. . . I am not certain I understand exactly what is going on in this photo, but I am wanting to understand more!

Feeling so much support from this forum! So many good comments ~ I'm deeply appreciating the help spreading this knowledge~

As I have mentioned, we have a habit of off-roading with our RV, and I have oft-wondered about turning it into a 4WD. This video was inspiring to me:
https://www.youtube.com/watch?v=3ZHCrXu3vus

He's proposing that wiring DC motors in electrical series might be an effective solution for a sort-of built-in traction control in a 4WD application. He states P = V * R^2. If one wheel suddenly lost traction, it's resistance would drop dramatically, and then the other wheels would take-up all that extra ampereage/power. Any thoughts on if this principle might work?

I got all excited imagining a set-up with 4 small DC motors, one on each wheel . . . . then I realized it would be a steering and suspension nightmare :D.

Might it be remotely sane to consider having two forklift motors as you have mentioned, one in place of the old petrol motor, driving the front wheels, and the second driving the back axle. Imagining differential issues in the rear wheels might prevent this from being practical for most road driving? Maybe one motor in the front and two in the back, one for each wheel?

I will look more deeply into running the motors in mechanical series.

I'm watching the salvage auctions. Made a few bids today, but didn't win. 2011 International eStar, and also a 2017 Bolt. (Anyone have word about these 60kWh Chevy batteries being decent or not?)

I'm sure this is a common question but. . . is it easy enough to implement regenerative breaking with a forklift motor? I really like the idea of having the car handle like the Tesla's do . . . where as soon as you let off the accelerator, it starts heavily regen-breaking. Does it just depend on how I configure my speed controller, as Mr. Damien Maguire would have me build from near scratch? :p
 

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Drive configurations

I got all excited imagining a set-up with 4 small DC motors, one on each wheel . . . . then I realized it would be a steering and suspension nightmare :D.
Agreed - for road vehicles, hub-mounted motors are undesirable.

Might it be remotely sane to consider having two forklift motors as you have mentioned, one in place of the old petrol motor, driving the front wheels, and the second driving the back axle. Imagining differential issues in the rear wheels might prevent this from being practical for most road driving? Maybe one motor in the front and two in the back, one for each wheel?
A differential - or separate motors per wheel - is required for any axle unless it is always on a loose surface, so front and rear are the same in this respect. At the front the LeSharo's Renault chassis comes with a transaxle containing a differential; you would need to provide a differential at the rear if using a single motor for the rear axle.

The LeSharo was designed for a front-wheel-drive chassis. Is the room to change out the rear suspension and fit in a motor (or motors) and a driven axle?
 

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Regenerative braking

I'm sure this is a common question but. . . is it easy enough to implement regenerative breaking with a forklift motor?
...
Does it just depend on how I configure my speed controller, as Mr. Damien Maguire would have me build from near scratch? :p
No. "Forklift" motors have the field winding in series with the rotor winding, so the current is the same through both windings. For rational regenerative braking in a brushed DC motor you want separate control of the field current (or "excitation"), so a shunt-wound (or separately excited, a.k.a. "SepEx") motor configuration would be more suitable. Of course SepEx controllers are twice as complex (with separate rotor and field winding control), and uncommon.

I really like the idea of having the car handle like the Tesla's do . . . where as soon as you let off the accelerator, it starts heavily regen-breaking.
Why do people think that Tesla is the only builder of electric cars? Every production EV does regenerative braking when the brake pedal is pushed; likely all of them (including Tesla, but also Nissan, GM, etc) do some regenerative braking when the accelerator pedal is fully released. Tesla does less of this than others, perhaps because the base versions of their cars are rear-wheel-drive, and strong rear-only braking is unstable.
 

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As I have mentioned, we have a habit of off-roading with our RV, and I have oft-wondered about turning it into a 4WD. This video was inspiring to me:
https://www.youtube.com/watch?v=3ZHCrXu3vus

He's proposing that wiring DC motors in electrical series might be an effective solution for a sort-of built-in traction control in a 4WD application. He states P = V * R^2. If one wheel suddenly lost traction, it's resistance would drop dramatically, and then the other wheels would take-up all that extra ampereage/power. Any thoughts on if this principle might work?
I didn't listen to the audio to go with the fuzzy video, but I'm pretty certain that you should just ignore this guy.

No, power is not the product of voltage and resistance squared. It is the product of voltage squared divided by resistance (because P=VI and I=V/R, so P=V^2/R)... and even then, only for a resistor. A motor is mostly an inductor, not a resistor.

It is not obvious to me that a DC motor under less mechanical load would have lower electrical resistance. Thinking of this another way: torque depends on current, so with series wiring forcing both motors to flow the same current (one can't "take up extra amperage" from the other), they will produce the same torque; if one is freely spinning wouldn't it speed up, taking more of the voltage and taking over the available power?
 

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Discussion Starter · #55 ·
No. "Forklift" motors have the field winding in series with the rotor winding, so the current is the same through both windings. For rational regenerative braking in a brushed DC motor you want separate control of the field current (or "excitation"), so a shunt-wound (or separately excited, a.k.a. "SepEx") motor configuration would be more suitable. Of course SepEx controllers are twice as complex (with separate rotor and field winding control), and uncommon.
This all sounds incredibly complicated to me. . . Probably not wanting to look for an uncommon and complex situation. I am feeling a bit torn about the direction to proceed with this project. . . I really like the idea of the ultra-cheap DC motor approach, keep-it-simple style. But I am also totally in love with regen breaking ~ it just warms my heart every time it's happening! I don't completely mind the space-ship whir of a brushed motor. . . but I'd really greatly prefer a nearly-silent AC motor ~ such peacefulness! I am so completely turned off by all the CAN and ID codes and sensor malfunctions, etc of using a complete commercial system. Watching that video about the "bare-bones" leaf drive-train on the table made me want to just about throw-up. . . All these components that have to match just right, and if something goes wrong, I'm beholden to Nissan to somehow bail me out? I'm largely doing this because I want a car that will run reliably for years to come, and that I understand (more or less) how it works and how to fix it.



Are there any decent stand-alone AC motor/controller options? Looking at the AC-51 for about $2k seems potentially doable. . . but then it looks like a controller for it is another $2.5k, and it's starting to kill my budget again. . . I know AC motors are more expensive. But is there anything out there that might work for my project? I've been doing some power requirement calculations and it seems like a 60kW motor might be acceptable for my project? (~5k lbs, desired top-speed ~50mph on flat).

Tesla does less of this than others, perhaps because the base versions of their cars are rear-wheel-drive, and strong rear-only braking is unstable.
That is an interesting point! I did not think about the rear-wheel regen in Tesla's~ I'm not a Tesla enthusiast, but I did drive one once, and I really liked the way the throttle responded by a dramatic regenerative slow-down simply upon releasing the throttle.


I didn't listen to the audio to go with the fuzzy video, but I'm pretty certain that you should just ignore this guy.

No, power is not the product of voltage and resistance squared. It is the product of voltage squared divided by resistance (because P=VI and I=V/R, so P=V^2/R)... and even then, only for a resistor. A motor is mostly an inductor, not a resistor.

It is not obvious to me that a DC motor under less mechanical load would have lower electrical resistance. Thinking of this another way: torque depends on current, so with series wiring forcing both motors to flow the same current (one can't "take up extra amperage" from the other), they will produce the same torque; if one is freely spinning wouldn't it speed up, taking more of the voltage and taking over the available power?

Thank you for your clarifications brian. I should probably stop listening to fuzzy videos with un-confident sounding people :p I think your explanation of the run-away wheel drawing more voltage makes much more sense.


Agreed - for road vehicles, hub-mounted motors are undesirable.


A differential - or separate motors per wheel - is required for any axle unless it is always on a loose surface, so front and rear are the same in this respect. At the front the LeSharo's Renault chassis comes with a transaxle containing a differential; you would need to provide a differential at the rear if using a single motor for the rear axle.

The LeSharo was designed for a front-wheel-drive chassis. Is the room to change out the rear suspension and fit in a motor (or motors) and a driven axle?

I don't think I would be confident adding an additional differential in the back. . . I might just have to be polite and stick with the FWD :cool:


Watched several videos about running two DC motors in mechanical series, and that does seem quite approachable. I'm assuming these motors would have to be more-or-less identical? (at least make/model being the same?) This is making me think I will have to look towards eBay to find this rather than look for a local salvage forklift. Do all/most of these series wound DC motors have the shaft accessible on both ends to facilitate this configuration?



https://www.youtube.com/watch?v=Ie7qvo-aC5k
 

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I am also totally in love with regen breaking ~ it just warms my heart every time it's happening!
If budget is any constraint... it should be the first thing on the chopping block.

How much extra would you pay for 5% improvement?

You can get the brake-saving part of regen really cheaply and easily, just not the energy recovery part.

I'm assuming these motors would have to be more-or-less identical? (at least make/model being the same?)
I can think of ways it would matter and ways that it wouldn't. I'm not sure what would dominate.

DC series motors have no defined speed. Without a load they accelerate off into orbit. With a load, they bog down and slow down. To me that seems helpful to your situation.

Suppose you have two motors, each trying to accelerate infinitely. And suppose some mismatch means one ends up trying to do all the work. Will it? It will hit a max speed, the other will continue trying to reach infinite speed, but they're on the same shaft. So, the smaller one will end up being loaded until such a point that the bigger one starts to pick up the slack again. They should roughly share the load according to their capabilities.

Even if only one hogs all the power until it needs it, and the second one functionally coasts... when you need it the big one will bog down and the small one will start to do something. If the big one was fine 90% of the time on its own, it's no big deal if it actually is or not.

If the motors are in electrical series, they need to be matched for winding wire cross section, since electrical series means that the same current will flow through both of them (it only has one path). If you had one with skinny wire and one thick, the amps would be limited to whatever the thinner one could handle.

You probably won't do that, you'll probably wire them in electrical parallel. So I don't think it makes much difference.

I think I've seen a EV Corvette that was using Warp9 and an Impulse9 mated to each other in mechanical series, just because that was the max length they had available in the engine bay.

This is making me think I will have to look towards eBay to find this rather than look for a local salvage forklift. Do all/most of these series wound DC motors have the shaft accessible on both ends to facilitate this configuration?
Nope. Most won't. No need for it most of the time. Sometimes a fan gets mounted there.

However, you only need one of them to be double-sided, the end one doesn't need it.
 

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Discussion Starter · #57 ·
If budget is any constraint... it should be the first thing on the chopping block.

How much extra would you pay for 5% improvement?
I can totally see your point, but I'm not sure I'm convinced about only a 5% improvement. According to this:

https://electrek.co/2018/04/24/regenerative-braking-how-it-works/

There are Tesla owners who have calculated and claim they are getting up to 30% effective improvement from their regen braking. Also, because my LeSharo will be significantly heavier than many EV conversions, it will have a lot more inertia, and thus more energy required (and potentially stored) from the deceleration process.

When I was driving a Honda Insight Hybrid over "the hill" (Hwy 17) in California, I remember I would drive in lower gears, thus utilizing more of the electric assist while going up the hill and time it just right so I would use up all of the hybrid battery by the time I got to the top of the hill . . . . then by the time I got back down to the bottom of the other side, the battery would be completely charged again. This is obviously a vastly different situation being a hybrid car ~ but the daily experience of this still rings in my memory.

While AC motors are obviously not for scrupulous budget builds in the $1k - $2k range ~ I may have a little wiggle room since my budget is up to $12k for this project. I am hoping for a 60kWh battery to start with, and if I could find that for $4k-$6k (somewhat optimistic, I know), then I would still have $6k to dedicate towards motor, controller, etc~ Thus putting AC motors back in my budget options.

I am still hoping to receive any suggestions from folks who might know of some good stand-alone AC motors that would work for this project.

I am also wondering. . . is there any possibility of using a Leaf motor, without all the Leaf-other-stuff? Could I potentially use a commercial EV motor, but pair it with a stand-alone controller in order to avoid all the crazy peripherals, CAN, sensors, OBDII, etc and keep the project simple? I've been down the track of seeing why it makes sense to use the entire drive-train from a commercial EV. . .. but is it really absolutely necessary?

DC series motors have no defined speed. Without a load they accelerate off into orbit. With a load, they bog down and slow down. To me that seems helpful to your situation.

Suppose you have two motors, each trying to accelerate infinitely. And suppose some mismatch means one ends up trying to do all the work. Will it? It will hit a max speed, the other will continue trying to reach infinite speed, but they're on the same shaft. So, the smaller one will end up being loaded until such a point that the bigger one starts to pick up the slack again. They should roughly share the load according to their capabilities.

Even if only one hogs all the power until it needs it, and the second one functionally coasts... when you need it the big one will bog down and the small one will start to do something. If the big one was fine 90% of the time on its own, it's no big deal if it actually is or not.

You'll probably wire them in electrical parallel. So I don't think it makes much difference.

I think I've seen a EV Corvette that was using Warp9 and an Impulse9 mated to each other in mechanical series, just because that was the max length they had available in the engine bay.

However, you only need one of them to be double-sided, the end one doesn't need it.
This is awesome! I would not have thought about it this way initially, but this does make sense and gives a lot more flexibility if I choose to go the DC route.
 

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Re - Regen

A taxi driver in a big city will be the benefits from re-gen - although even then 30% is a wee bit of a stretch
But that is a LOT of stop start traffic and a situation where time is important

Using regen on hills is a bad idea - it's a lot less efficient than simply letting your speed change as you go up and down the hills

For country driving in a sensible manner you get almost no advantage

Around here I use my brakes twice on a two hour drive - ZERO advantage from re-gen
 

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Discussion Starter · #59 ·
Re - Regen

A taxi driver in a big city will be the benefits from re-gen - although even then 30% is a wee bit of a stretch
But that is a LOT of stop start traffic and a situation where time is important

Using regen on hills is a bad idea - it's a lot less efficient than simply letting your speed change as you go up and down the hills

For country driving in a sensible manner you get almost no advantage

Around here I use my brakes twice on a two hour drive - ZERO advantage from re-gen

The experience I had where regen seemed so effective was on a long hill at higher speeds where a lot of active breaking to maintain safe speeds was required. I think this type of road condition would make regen even more effective than the taxi-driver scenario. This may not be an all too often scenario, but indeed there are quite a few of these types of hills in the town I live in (Duluth ~ the San Francisco of the midwest.)

I can totally agree that in the rolling hills of the country it would be less effective to use regen and maintain speed, than it would be to maintain motor-power and let the speed of the vehicle vary a little bit.

Probably on a road-trip, I would not find many ideal scenarios to really utilize the regenerative braking (especially in Oklahoma :p). But because I intend to utilize my RV as a daily (or more likely ~ weekly) driver in my hometown, where it seems to me regen would be most effective with a larger vehicle, I am starting to really lean towards A/C motors.

On a related note. I had a great experience purchasing NiFe batteries through Ali-Baba. I got a 12V 400Ah battery to power my small off-grid home for a 1/3 of the price that it would have cost to purchase this item from within the US (including shipping). Is there anyone that has ordered an EV motor direct from a company in China who might want to share their experience?
 

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Regen can only improve range if it is used to harvest energy that would have been wasted anyway, like heat from friction brakes. If it is used at other times, it will be like trying to use alternators on your wheels to improve efficiency. Generalizing range gains of regen does not make much sense unless you know exactly how and why it will be configured, since regen can actually decrease range if it is not configured correctly.
 
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