# Locost EV conversion log



## Zieg (10 mo ago)

Hi everyone,

I am still in the early planning stages here, but I thought I may as well start a thread to document some of what I'm working on/planning, both for information and feedback.

The car:
-Lotus 7 replica (AKA 'Locost'), built by myself to original book dimensions.
-Currently powered by a 2004 Yamaha R1 motorcycle engine.
-Current weight is about 1200 lbs without driver and half a tank of gas
-Primary use is Autocross, though it is street legal

Goals:
-Safe and well-built EV conversion
-Torque at low speeds but still possible to cruise on the freeway
-Keep reasonably close to the same weight
-Range isn't a huge concern but 30 miles or so would be nice
-Keep costs under $10k CAD?

Here's a photo from last season:










So the car is obviously a front engine RWD layout (I guess, technically the engine is 'mid' since no part of it is forward of the front axle). The rear axle is a narrowed Ford 7.5" out of a Ranger. From what I can tell, it looks like I can get up to a 4.56 gearset for it. It is currently geared to 3.45, which means the engine is running at 6-7000 rpm on the highway (not good) and still doesn't have as much low end torque as I would like. Also, due to the open intake and limited space for a muffler, I am constantly within a decibel or so of going over the noise limit when I get near redline at WOT. The car will do over 60 MPH in first gear, so I rarely even hit second on the courses we typically run here.

Since I will be left without a transmission after the bike engine is out, and to keep weight down, I am planning to go directly from motor to axle with a two-piece driveshaft. I thought long and hard about a DC motor, but decided against it due to a few reasons, including choice of controllers and availability of suitable motors locally.

So I am looking at either a Leaf motor or a Hyper 9. It would be nice to use a Leaf motor for the lower cost, and bonus if I can get the charger to work with whatever batteries I choose. Right now I can't seem to find much info on using the charger, and even less info on using it with a different battery voltage.

And speaking of batteries, I'm leaning towards second gen Chevy Volt. It looks like I could fit four modules in the car - two under the hood and two in the back where the gas tank is now. The Volt battery comes with three 16s modules and four 12s modules, so I can think of two possibilities:
1. Use two of each module size to get 28s2p (actually 4p since each module is internally 2p) (Good for Hyper 9)
2. Use all three 16s modules plus one 12s in series for 60s (Leaf motor would need at least this much voltage)

Since I designed all the suspension and everything except for the basic layout of the 'book chassis', I already had a CAD model to start with. Here's what it looks like with the Hyper 9 and a Spicer PTO u-joint adapter:









And finally, some of my comparisons. I had to go and wrap my head around how synchronous motors work, so hopefully this is right. *I would really appreciate some feedback on this!* To get the Leaf numbers, I first took the commonly available graph for the 80kW motor and scaled it up to 110kW at the same RPM. I then scaled the RPM for a given torque value, based on going from 360v to 240v.









If I did that all correct, it looks like the Leaf motor would give me better torque up to about 40 mph and then the Hyper 9 takes over. The MPH line assumes 4.56 gears. On one hand, I like the added low end power, but on the other hand, power is only useful if you can put it to the ground. Maybe as a next step, I should make another graph that compares wheel torque instead of driveshaft torque, and play around with different combinations of motors and rear end gears.

And that's about where I am at now. Any input is appreciated. My timeline for buying parts is basically most of the summer, then once this season is over I plan to tear the car down and start the conversion as a winter project.

Cheers!


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## floydr (Jun 21, 2021)

Zieg said:


> So I am looking at either a Leaf motor or a Hyper 9. It would be nice to use a Leaf motor for the lower cost, and bonus if I can get the charger to work with whatever batteries I choose. Right now I can't seem to find much info on using the charger, and even less info on using it with a different battery voltage.


Is it a level 2 J1722 charging station? all it does is provide both L1/L2 of a split phase system to your charger OBC which charges to Your Voltage. You are in Canada?
level 2 j1722 with the appropriate interface for the J1722 socket such as this one J1772 Active Vehicle Control Module AVC2 - For Public Charge Stations
later floyd


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## remy_martian (Feb 4, 2019)

Hey Mr Excel graphs,

Now do a plot of curves for tire force (assume infinite coeff friction), motor torque, and acceleration (a = F/m) vs vehicle speed. From there a second graph of distance vs speed from a standing start.

Seems geared too tall to me by about 2:1, though it is low mass...or was.

Zero to 100 Kanadian miles /hour in 6 seconds?


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## Zieg (10 mo ago)

Floyd, actually I meant the onboard charger (and whatever controls it). I'm not actually sure at this point where the charger gets its control from. If it's onboard programming or if it just gets CAN messages (which I suspect is the case). I don't need anything fancy though, that's for sure.

Remy, well the tire force graph would look just like the torque curves if assuming infinite traction. 1345 lbs for the Leaf motor and 834 for the Hyper 9 at the peak. Not really an excel wizard but what I came up with is this:


They both have flat curves up to 30 mph, so assuming infinite traction, no losses etc, the 0-30 is 1.5s Leaf and 2.5s Hyper 9 (ha, yeah right!).
30-60 is trickier but if I average the acceleration of the Leaf motor through speed range, I get 2.2s Leaf and 2.5s again for the H9 since it's still in constant torque.
Total times for both would be 3.7s for the Leaf and 5.0s for the H9.

Where it gets more interesting is 60-80. Using the same averaging of acceleration method, 7.8s for the Leaf and only 5.7s on the H9. Therefore 0-80 is 11.5s Leaf and 10.7s Hyper 9.

Thanks for the idea, that tells a very interesting story! And you're right, the H9 would be better if geared lower..


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## Duncan (Dec 8, 2008)

If it was mine I would cut the back out and put the entire Leaf unit in there - 
making up a rear suspension setup would be relatively easy and it should be better than a live axle 
I have a subaru rear diff with MacPherson struts - easy to make and works well
That would also give you the entire front engine bay AND the old transmission tunnel area for batteries

Your acceleration times are a bit slow - I'm doing 95 mph in just under 8 seconds


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## remy_martian (Feb 4, 2019)

What's your final drive ratio?


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## brian_ (Feb 7, 2017)

Zieg said:


> So the car is obviously a front engine RWD layout (I guess, technically the engine is 'mid' since no part of it is forward of the front axle).


Yes, "front-mid engine"; Nissan even named one of its platforms FMR in recognition of this configuration.



Zieg said:


> Since I designed all the suspension and everything except for the basic layout of the 'book chassis', I already had a CAD model to start with. Here's what it looks like with the Hyper 9 and a Spicer PTO u-joint adapter:
> View attachment 128742


The motor appears to be in roughly the stock engine location. Can it go further back, in location of a Lotus 7 or Locost (but not this motorcycle-powered) transmission? That would help with space for battery in the front.


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## Zieg (10 mo ago)

Duncan said:


> If it was mine I would cut the back out and put the entire Leaf unit in there -
> making up a rear suspension setup would be relatively easy and it should be better than a live axle
> I have a subaru rear diff with MacPherson struts - easy to make and works well
> That would also give you the entire front engine bay AND the old transmission tunnel area for batteries
> ...


Yeah, I have been thinking about that. Will continue to keep the idea in mind, but there would also come a point where I decide to build a whole new car a few years down the road. Maybe even something with a Bolt (or Tesla?) motor...

As for the acceleration, I guess it's really coming down to motor kW and gearing.. Though I have been reading about people extracting more power out of the Leaf motors. One option might be to use 4.10 gears instead of 4.56 and plan on upping the current coming out of the inverter a bit. 



remy_martian said:


> What's your final drive ratio?


The math above was done assuming a direct coupling to the diff, and 4.56 gears in the diff (though see above for my second thoughts on that).



brian_ said:


> Yes, "front-mid engine"; Nissan even named one of its platforms FMR in recognition of this configuration.
> 
> 
> The motor appears to be in roughly the stock engine location. Can it go further back, in location of a Lotus 7 or Locost (but not this motorcycle-powered) transmission? That would help with space for battery in the front.


Sadly, no. Due to the bike engine layout, I did not build much of a widening into the tunnel - partly to allow myself some more room at the pedal box. The tunnel is very narrow through the middle of the car, widening to the passenger side near the front to accommodate the offset output shaft of the engine. What you see the driveshaft connecting to at the bottom of the screen is the reverse box (necessary to make the car street legal). What I would want to do is mount the center carrier bearing of the new driveshaft to the same place as the reverse box. If it makes sense to do so, I could then offset the motor to the passenger side a couple of inches for better balance, depending on battery arrangement.

Speaking of batteries, are there any other options I should be looking at, other than the Volt? They seem pretty well favored but I'm always open to other possibilities. The brand new 1.6kWh batteries that EV West sells look amazing, but way over my budget sadly.


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## brian_ (Feb 7, 2017)

Zieg said:


> ... Due to the bike engine layout, I did not build much of a widening into the tunnel - partly to allow myself some more room at the pedal box. The tunnel is very narrow through the middle of the car, widening to the passenger side near the front to accommodate the offset output shaft of the engine.


That makes sense, but it's unfortunate for this conversion. It is, perhaps, an argument for going for the new build now, whether that has an independent rear suspension and rear-mounted drive unit or the current suspension and a tunnel-mounted motor.


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## blackterminal (Oct 14, 2021)

Duncan said:


> If it was mine I would cut the back out and put the entire Leaf unit in there -
> making up a rear suspension setup would be relatively easy and it should be better than a live axle
> I have a subaru rear diff with MacPherson struts - easy to make and works well
> That would also give you the entire front engine bay AND the old transmission tunnel area for batteries
> ...


It looks a bit like your car Duncan.


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## Duncan (Dec 8, 2008)

If going for a new car I would make one comment
Battery space is limited - the space between the wheels on each side is completely wasted on a 7
I would be going for a car without that wasted space
You could either put batteries down each "sill" - or move the driver and passenger further apart and put batteries down the middle 

Something like this


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## Zieg (10 mo ago)

Yeah, the new car path would most likely be a full body, and hopefully more aerodynamic. Not sure how much I would want to be climbing over a huge sill, so I'd probably prefer batteries down the center. 

After some more thought, I'm going to go ahead with a front engine conversion for the time being, and make the new build be a future goal. For the next couple years I would prefer not to start a whole new build due to other life factors, but I can at least start designing something new, completely from the ground up. 

Meantime, I phoned a nearby salvage yard and asked about both a Leaf motor and Volt battery they had. Waiting to hear back on whether they can include some of the extra wiring I asked for.


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## Duncan (Dec 8, 2008)

Zieg said:


> Yeah, the new car path would most likely be a full body, and hopefully more aerodynamic. Not sure how much I would want to be climbing over a huge sill, so I'd probably prefer batteries down the center.
> 
> After some more thought, I'm going to go ahead with a front engine conversion for the time being, and make the new build be a future goal. For the next couple years I would prefer not to start a whole new build due to other life factors, but I can at least start designing something new, completely from the ground up.
> 
> Meantime, I phoned a nearby salvage yard and asked about both a Leaf motor and Volt battery they had. Waiting to hear back on whether they can include some of the extra wiring I asked for.


With the motor in the front you will not have anywhere near enough room for the batteries
My motor is situated where the gearbox should be - and I managed to fit only 14 kWh of the 16 kWh Volt battery in the engine bay
That is with the battery on the floor - which gives a wonderfully low C of G 
You could probably fit a 9 inch diameter motor in your "tunnel" - remember you can lose the clutch pedal so you can afford to move the tubes over a bit


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## Zieg (10 mo ago)

Hmm, yeah it does look like I could offset the tubes but it would be pretty extensive. The inside dimension of the tunnel is 4" now do I guess I'd have to do 2.5" per side if I wanted to keep it centered. 

Unfortunately the Leaf motor looks to be a good bit wider, but on the bright side it's also shorter than the Hyper 9. I'm not planning to use all of the cells from the Volt, but it looks like I could put two 16s modules right up front, one 12s beside the motor, and one each of 16s and 12s modules in the back, for a total of 72s without having to mod the tunnel. That arrangement would leave me with about 30 pounds added behind the rear axle compared with a full tank of gas. If I really had to I could move a 12s or a 16s to the back as well, but that would be a last resort.

As far as frame mods go, I did have to offset the motor to the right, so I'll have to model up a driveshaft and see what the u-joint angles look like. Probably going to have to mod the steering rack mounts, definitely relocate the 12v battery, etc. But I think it looks promising?


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## Duncan (Dec 8, 2008)

Zieg said:


> Hmm, yeah it does look like I could offset the tubes but it would be pretty extensive. The inside dimension of the tunnel is 4" now do I guess I'd have to do 2.5" per side if I wanted to keep it centered.
> 
> Unfortunately the Leaf motor looks to be a good bit wider, but on the bright side it's also shorter than the Hyper 9. I'm not planning to use all of the cells from the Volt, but it looks like I could put two 16s modules right up front, one 12s beside the motor, and one each of 16s and 12s modules in the back, for a total of 72s without having to mod the tunnel. That arrangement would leave me with about 30 pounds added behind the rear axle compared with a full tank of gas. If I really had to I could move a 12s or a 16s to the back as well, but that would be a last resort.
> 
> ...


The trouble is the Leaf motor is a high revving low torque unit - it really wants about an 8:1 final drive

The advantage of the DC forklift motors is that they are low revving high torque units 

Your two tubes are at floor level - right?
So the motor is above that level - at floor level the motor is effectively zero thickness

The tubes on my car are too close together to lower the motor into place - so I have to drop the motor into the passengers footwell and then shift it sideways into place

On my car the floor is completely flat with the batteries and motor as low as I can get them
This means that I'm running with soft springs (70 lb/in front 100 lb/in rear) and no roll bars at all and it still only just rolls a tiny amount


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## Zieg (10 mo ago)

Duncan said:


> The trouble is the Leaf motor is a high revving low torque unit - it really wants about an 8:1 final drive
> 
> The advantage of the DC forklift motors is that they are low revving high torque units


Hmm, maybe part of my problem is that I'm not understanding how to estimate power outputs of a DC motor and/or underestimating how much current I can draw from these Volt batteries in short bursts. Looking at the Warp 9 specs they say 100 ft lbs at 500 amps, so I guess I'd be looking for peaks around 1500 amps? And to do that, would I need 3 battery modules in parallel?

I guess the other thing I should look into is how to scale these graphs. A 16s+12s module arrangement would get me like 112v so I think that would be enough, but I don't know how to calculate how much torque I would end up with at a given RPM.

This is the one I'm looking at for reference:








All this is wrong, but I'm leaving it crossed out so people know what not to do!
Edit: Alright, I think I have my head wrapped around it now. All my reading about AC motors threw me for a bit of a loop but it looks like DC is a lot simpler. It looks like if you want more torque at a given RPM, just increase the voltage proportionately. I'm going to go play with more spreadsheets now..


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## Zieg (10 mo ago)

Edit: This is all wrong too, same as above, leaving it here but crossed out.

Alright, gonna need this checked please. I had to sift through a bunch of information that sometimes contradicted other posts, but I think what I figured out was that for a given rpm, if you increase the voltage by a factor of x, the amperage will also increase by x, and the torque produced at that same rpm will increase by a factor of x^2. That last bit, I am least confident in, though, since it was hard to find info about how to compare power levels at the same speed. I whipped up a spreadsheet based on that assumption and checked the power in vs power out and it did seem to follow. I also found updated motor specs from Go-EV (motors made in 2010 or newer) so I plugged it all in and whooooo doggy that paints a very different picture! If this is all correct, then I guess it looks like a no-brainer. I even changed the rear end ratio in the calcs back to the 3.45 it's currently sitting at.


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## remy_martian (Feb 4, 2019)

Zieg said:


> Hmm, maybe part of my problem is that I'm not understanding how to estimate power outputs of a DC motor and/or underestimating how much current I can draw from these Volt batteries in short bursts. Looking at the Warp 9 specs they say 100 ft lbs at 500 amps, so I guess I'd be looking for peaks around 1500 amps? And to do that, would I need 3 battery modules in parallel?
> 
> I guess the other thing I should look into is how to scale these graphs. A 16s+12s module arrangement would get me like 112v so I think that would be enough, but I don't know how to calculate how much torque I would end up with at a given RPM.
> 
> ...


Um...not really.

Voltage is proportional to speed in a DC and Current is proportional to torque.

Back EMF cuts back max current, which is why you increase voltage.

The square law you're seeing is horsepower, not torque.


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## Zieg (10 mo ago)

remy_martian said:


> Um...not really.
> 
> Voltage is proportional to speed in a DC and Current is proportional to torque.
> 
> ...


dangit just when I thought I was getting somewhere.

Ok, so torque in ft-lbs = HP x 5252 / RPM, right? So let's say we are making 100 hp at 1000 rpm, I plug that in and get 525.2 ft-lbs.

If I double the voltage and double the amps I quadrouple the horsepower? So now we are making 400 hp at 1000 rpm? Plugging that number in gets me 2100.8 ft-lbs, or quadrouple the torque. What did I miss this time? If RPM isn't constant in that squared law, how would you calculate the new expected torque at a given rpm?
_Looks like what I missed was that it still follows a constant torque line while hooked up to a typical controller, and just like with an AC motor, the point at which the flat line starts to decay just gets pushed further out when you add voltage._


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## remy_martian (Feb 4, 2019)

Finite Element Analysis to capture the back EMF contribution, if you must calculate.

Easier to bench test.


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## Duncan (Dec 8, 2008)

Hi Zeig
The relationship is simple 
Torque is proportional to Current 
So lets took at your Warp 9 - 500 amps = 100 ft lbs - with a 4:1 final drive that gives 400 ft lbs at the back wheels - 
Your wheel will be about 2 ft in diameter - so - 400 ft lbs will give you 400 lbs of push
Is not enough for blistering acceleration
My car is 900 kg (with me in it) and has 55% on the rear = 495 kg - 1089 lbs
So 1200 amps would give - 960 lbs
But my 11 inch motor gives me more torque per amp - So I am getting more "push" than that

Your car is almost certainly going to be lighter so maybe 1000 amps would be enough

You need more Volts to drive the torque as the revs rise
The dreaded back EMF
The Motor diagrams are not much use as they have a controller in the circuit - 
they feed say 72v to the controller and the controller reduces that voltage to the voltage that the motor needs to to get the desired current

The way I got the "numbers" for my motor was that I used too low a battery voltage 
At 120 volt I accelerated to 100 kph and 200 amps and stayed there - the controller had maxed out and the battery was only supplying enough volts for 200 amps

So knew that 120 volts and 200 amps and 3600 rpm was one of the points on the graph
Back EMF is proportional to current and to rpm
It takes about 10 volt per 1000 amps to overcome the resistive loads in the motor
And the battery sags a bit

So I ended up with about 100 volts Back EMF = 200 amps x 3600 rpm

With my current setup - nominally 340 volt - call it 320 volt
I start off with 1200 amps
At about 1900 rpm (55 kph) my controller is maxed out
By 3800 rpm (110 kph) - I am down to 600 amps
By 5700 rpm (160 kph) - I am down to 400 amps

That is for my 11 inch Hitachi motor
Your 9 inch motor will almost certainly give LESS back EMF per rpm/amp


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## Zieg (10 mo ago)

Ah, okay, very interesting! Thank you all for all the help by the way, it's been hugely helpful. 

I think on Monday I'm going to phone around to some motor rebuilders in town and see if anyone has anything that might be promising. I know there's one place that does pretty extensive testing, so they might even be able to provide me with a graph at my actual desired voltage. That would make me feel a lot better, anyway. Seems like DC controllers are getting harder to find, but I had also been looking for 2000A options. Maybe I'll open the search to 1000A models too..


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## remy_martian (Feb 4, 2019)

2000A is a crazy amount of heat being produced (proportional to square of current) in both motor and controller, not to mention the weight of the pack needed to produce that much current.

You also have to be very careful about spec'ing a drag racing car vs a car running sustained levels on a track. Night and day what you can put into a motor continuously for the race period.


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## Zieg (10 mo ago)

Yeah, absolutely. 

I think I finally have my head wrapped around all this. For anyone else who finds this in a search, this thread really helped clear things up for me too: torque of 9" dc with 144v pack?

So basically, yes, amps will have a direct proportional effect on torque. The volts side of the equation seems to just influence the max speed at which constant torque will still be made. If I go for a 1000 amp controller and a warp 9 (or, hopefully, a forklift motor with characteristics very much like a warp 9) then I should be making constant torque pretty much right up to 60 mph on 3.45 gears. I'd have 912 lb-ft of wheel torque which sounds pretty dang good. Assuming infinite traction, no losses and all that other fun stuff, 0-60 in 4.3 seconds. 

Now I need to decide how to arrange batteries for that. If I buy a complete Chevy Volt gen 2 battery it will come with 3 x 16s modules and 4 x 12s modules. A 16s with two 12s would get me to 40s (or 160v at 4v/cell), but I would only have enough cells to do 2 in parallel. I don't know if it's safe to pull 500 amps through each module, need to look into that next.


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## brian_ (Feb 7, 2017)

Zieg said:


> ... but I think what I figured out was that for a given rpm, if you increase the voltage by a factor of x, the amperage will also increase by x...


No, because while there is resistance in motor windings, the motor is not simply a resistor. Voltage is needed to overcome back EMF which is proportional to both speed and current.


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## Zieg (10 mo ago)

Yeah I was just editing all that, haha. Think I got it now.

Also found out that the stock fuse in a 2018 Volt is apparently rated for 350 amps. I'm trying to verify this but it SEEMS like it can pass 200% of its rated current for a period of time. If that means Chevy thinks the cells could support that much current for short periods, I may be okay running just two in parallel. Around here our autox courses are about 60-70 seconds. Probably around 15 minutes between runs.


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## remy_martian (Feb 4, 2019)

No - it says the wiring can support 350A without incinerating the car.


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## Duncan (Dec 8, 2008)

Zieg said:


> Yeah I was just editing all that, haha. Think I got it now.
> 
> Also found out that the stock fuse in a 2018 Volt is apparently rated for 350 amps. I'm trying to verify this but it SEEMS like it can pass 200% of its rated current for a period of time. If that means Chevy thinks the cells could support that much current for short periods, I may be okay running just two in parallel. Around here our autox courses are about 60-70 seconds. Probably around 15 minutes between runs.


I'm using the early Volt modules in series - AND the std Vollt fuse - 

The cells appear to sag by 20% with 1200 amps - the fuse has not blown!!!
(My thread has me testing this at a drag race a couple of years ago)

To Brian's point about track use verses drag racing - I use my car for both

Yesterday was a triple event - 3 1/4 mile runs - Autokhana on grass - Autocross on tarmac - I was down near empty after the third Autocross run

The drag runs were for a much shorter time - but at constant max power - the track runs were for longer but at lower power levels


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## piotrsko (Dec 9, 2007)

Fuses are IR2T devices where an important function is time by how much watts to melt the fuse material. Lots of watts takes little time. 
I suspect the fuse will absorb 1200 amps, but not for long. I don't think the batteries can push more than 1000 amps on a short, but in my case that's 262 hp which will melt the KOSTOV since motors can be fuses, too. I cant get to that current because of voltage sag and cabling resistance. I can get to 600 amps for a moment, 450 amps for 4 minutes on my 196v split duplex pack


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## Bratitude (Jan 23, 2020)

the full charger and dcdc converter stack is all controllable via can. zombieverter vcu can run the full stack, motor, charger, etc. leaf bms is very easy to talk to. leafspy works great. But volt modules are a good choice. Cheap and power dense. 

ether pick up the 160kw inverter or a open-inverter replacement board to push the 80kw inverter to 140kw.


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## dcdebolt (Feb 21, 2009)

I'm planning a similar build with a 1972 Datsun 1200 and 4.56 gears. I had really wanted to do a Nissan Leaf motor with a Chevy Volt battery, but realized it would be much heavier than a Hyper 9 setup when all was said and done. Your locost may be better off with a Hyper 9 and Tesla modules. 5 to 7 tesla modules (120v) and a direct drive Hyper 9 in the transmission tunnel. 250lb or so for 26kwh battery vs over 400lbs for a 18kwh Chevy Volt pack - the Tesla modules are much lighter for what you get. The motor is lighter too it seems. And a yoke for a driveshaft can be bought from evwest for the Hyper 9 shaft. You can't easily do that on a Leaf motor. Vibrations are more likely spinning at that high an rpm anyway. So you'd need to couple to a transmission or torquebox if mounting longitudinally...

Check out the miata zeroev built with a direct-drive hyper 9 on YouTube. It has a torquebox (1.6:1 i think) to a 4.1 rear end but its also got bigger diameter tires (at least bigger than the 13s on my 1200) and more weight. They don't say how well it accelerates though!


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## Bratitude (Jan 23, 2020)

dcdebolt said:


> I'm planning a similar build with a 1972 Datsun 1200 and 4.56 gears. I had really wanted to do a Nissan Leaf motor with a Chevy Volt battery, but realized it would be much heavier it would be than a Hyper 9 setup when all was said and done. Your locost would be better off with a Hyper 9 and Tesla modules. 5 to 7 tesla modules (120v) and a direct drive Hyper 9 in the transmission tunnel. 250lb or so for 26kwh battery vs over 400lbs for a 18kwh Chevy Volt pack - the Tesla modules are much lighter for what you get. The motor is lighter too it seems. And a yoke for a driveshaft can be bought from evwest for the Hyper 9 shaft. You can't easily do that on a Leaf motor. Vibrations are more likely spinning at that high an rpm anyway. So you'd need to add a transmission …


leaf motor is near the 200kw class.
volt batteries leaf motors are cheap.

locost
Or hicost?


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## Duncan (Dec 8, 2008)

dcdebolt said:


> I'm planning a similar build with a 1972 Datsun 1200 and 4.56 gears. I had really wanted to do a Nissan Leaf motor with a Chevy Volt battery, but realized it would be much heavier than a Hyper 9 setup when all was said and done. Your locost may be better off with a Hyper 9 and Tesla modules. 5 to 7 tesla modules (120v) and a direct drive Hyper 9 in the transmission tunnel. 250lb or so for 26kwh battery vs over 400lbs for a 18kwh Chevy Volt pack - the Tesla modules are much lighter for what you get. The motor is lighter too it seems. And a yoke for a driveshaft can be bought from evwest for the Hyper 9 shaft. You can't easily do that on a Leaf motor. Vibrations are more likely spinning at that high an rpm anyway. So you'd need to couple to a transmission or torquebox if mounting longitudinally...
> 
> Check out the miata zeroev built with a direct-drive hyper 9 on YouTube. It has a torquebox (1.6:1 i think) to a 4.1 rear end but its also got bigger diameter tires (at least bigger than the 13s on my 1200) and more weight. They don't say how well it accelerates though!


That would give you a very low voltage setup - and Volt batteries are not that heavy when you throw away the junk - about 160 kg


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## Zieg (10 mo ago)

Okay, battery has arrived! I measured the cell voltage at 3.5v, and I think their optimal storage voltage is something like 3.85v. I have a hobby lipo charger for my airplane/drone batteries that can charge up to 6s @ 5 amps. Thinking about disconnecting the BMS and everything, then using the charger to bring the cells up to storage voltage. Any issued with doing that?

I also posted in my other thread about the Leaf transmission conversion, going to be pulling the bearings off the jackshaft as soon as I can get my hands on a suitable puller, then start CADDing up a new housing.


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## Duncan (Dec 8, 2008)

Zieg said:


> Okay, battery has arrived! I measured the cell voltage at 3.5v, and I think their optimal storage voltage is something like 3.85v. I have a hobby lipo charger for my airplane/drone batteries that can charge up to 6s @ 5 amps. Thinking about disconnecting the BMS and everything, then using the charger to bring the cells up to storage voltage. Any issued with doing that?
> 
> I also posted in my other thread about the Leaf transmission conversion, going to be pulling the bearings off the jackshaft as soon as I can get my hands on a suitable puller, then start CADDing up a new housing.
> View attachment 129466


Yes that is exactly what I would do
First remove all of the bolt on interconnects - which gets you down to the modules 
Take the covers off (one at a time) and measure every cell (every pair? of cells in parallel)
Then charge them up to your "storage voltage"
If its like he two Volt batteries I have worked on they will all be within about 12 millivolts


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## remy_martian (Feb 4, 2019)

At 3.5V, I'd say it's "close enough", if they were mine - I would not futz with them.


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## Duncan (Dec 8, 2008)

remy_martian said:


> At 3.5V, I'd say it's "close enough", if they were mine - I would not futz with them.


3.5 V is about the lower limit as far as I'm concerned - but I would definately check every cell make sure they are all the same


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## remy_martian (Feb 4, 2019)

For storage? 

Why?


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## Duncan (Dec 8, 2008)

remy_martian said:


> For storage?
> 
> Why?


This is your reference point for these cells - 
you should measure and write down the voltage of each cell so that you can compare that to the numbers that you will get when you re-check in X months when you get around to finally using them
From my experience they will not have changed - but its good to know that for your actual battery


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## remy_martian (Feb 4, 2019)

So, buy a Sharpie, number the cells, measure each, put them away.

I don't understand why the risk and complexity of charging is needed at this point when all he plans to do is hoard a Volt battery 😉


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## remy_martian (Feb 4, 2019)

While I am thinking of it, DO NOT use a cheap multimeter to measure cell voltages. 

I used a Harbor Fright freebie meter (was handy in the toolbox, too lazy to grab the HP out of the house) and got dozens of millivolts of variation among the Model X modules I had harvested. 

A couple of days later I walked out of the house with the HP and decided for some reason to remeasure...they were all almost perfectly matched. I have no explanation why the HF meter would vary so much, but it did.


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## Duncan (Dec 8, 2008)

remy_martian said:


> So, buy a Sharpie, number the cells, measure each, put them away.
> 
> I don't understand why the risk and complexity of charging is needed at this point when all he plans to do is hoard a Volt battery 😉


Its exactly what I did when I got my second battery (its not mine its for a maniac who wants to build a drag bike)

I checked the voltages - decided that they were too close to the 3.5 volts that I use as a minimum and charged them up to 3.9 volts

I feel much happier about that battery being stored with a middle ish charge

I did have a power supply with a large enough voltage that I could simply charge each module individually


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## Zieg (10 mo ago)

Admittedly, most of my experience comes from RC car/plane batteries, but with those it's always recommended that you store them at a certain voltage. Otherwise they can degrade faster.

I pulled up the 2018 Volt owners manual and it says to run the battery down to 2-3 bars SOC on the dash if the vehicle is going to be stored for between 4 weeks and a year. It looks like there are 10 bars, so I'm tempted to assume that means 20-30% soc, but so far I can't correlate that to a specific voltage.


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## piotrsko (Dec 9, 2007)

Hey Duncan: why do you consider 3.9 to be middle charge? I must be missing something. My middle for storage is 3.6, about a volt over my calculated low warning under heavy operation.


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## brian_ (Feb 7, 2017)

dcdebolt said:


> Check out the miata zeroev built with a direct-drive hyper 9 on YouTube. It has a torquebox (1.6:1 i think) to a 4.1 rear end ...


It has a reduction gearbox, so it's not direct-drive, although it is fixed-ratio (or single-speed).

Zero EV built their own reduction gearbox for this car, and were testing it in preparation for putting it into production... but it has never appeared as a product on their website. Zero EV's own YouTube videos provide much more detail than _The Late Brake Show_.


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## brian_ (Feb 7, 2017)

Duncan said:


> I checked the voltages - decided that they were too close to the 3.5 volts that I use as a minimum and charged them up to 3.9 volts
> 
> I feel much happier about that battery being stored with a middle ish charge


While at mid-point charge would be to the nominal cell voltage (3.75V in this case), recommended storage state of charge is usually significantly more than 50%, and 3.9 V/cell seems generally reasonable.


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## Duncan (Dec 8, 2008)

piotrsko said:


> Hey Duncan: why do you consider 3.9 to be middle charge? I must be missing something. My middle for storage is 3.6, about a volt over my calculated low warning under heavy operation.


Hi Piotrsko
I don't have a "low under load" number - I always back off before looking at the voltage 
Just had a look at my videos of the 1/8th mile drags - the peak "sag" was about 20% which would give me a voltage under full load of 3.1 volts 

With the cells just sitting I am treating 3.5 volts as empty and 4.1 volts as full - 
Yabert provided the actual curve I'm using 
Somewhere in the middle of this thread








2012 Chevy Volt Battery:


Paid $2000 + $150 shipping from a junkyard. It is a work of art. I'll be sad to tear it apart for the cells, but that's life. I'm getting 373 vdc for the battery, and 3.88 vdc per cell. IF there are 288 cells. Already things aren't making sense. I count 72 modules about 1" thick...




www.diyelectriccar.com


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## piotrsko (Dec 9, 2007)

Thanks. Hmm I can get to 2.5 like I said, but that is winter voltage sag under 15C temps. Since they pop back up to what I guesstimate original values, and lacking any firm expertise, that's my storage target. It's below the 4.2 I use for max charge. Am I killing cells? Can't tell, but may have lost some capacity and I don't do my old go to work and back max range test.


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## Zieg (10 mo ago)

Okay, been a bit busy with other life stuff but I have the battery all torn apart and charged up to 3.65v. Each cell took 10 Ah just to go from 3.5v to 3.65v. Wow.

I was hoping to use as many parts out of the battery module as possible, but sadly I don't think I will get much.

The current sensor is a Lem DHAB S/51. Looks like it is rated for up to 350A according to the datasheet. Unfortunately it is not listed as compatible with the Thuderstruck MCU that I'm hoping to use.

The BMS/BECM is also probably not usable to me, because it doesn't seem like anyone has managed to interface with it, or use it in a configuration with fewer cells. If anyone knows differently, please let me know!

The HV contactors are an interesting one. Panasonic AEVS760122. Not a lot of hits when I googled the number, but I did find a datasheet for the AEVS series. If this is the correct datasheet, it's rated at 60A continuous, 180A for 1 minute. A bit disappointing, I was hoping they would have been rated a little higher. It has spade connectors that are approximately 5/8" wide. I can't tell if it has an economizer but at 12v it was drawing about 0.4A, which is pretty close to the datasheet. If I do reuse these, I may have to drill holes through the spades so I can bolt an eyelet, and that sounds pretty janky. What do you guys think?

















As for the pre-charge contactor, it is labelled AEC11012 M11. I honestly haven't really looked into these. I found a datasheet for an AEC_N_11012 that says they are good for 5A. The same sheet says the coil current is 0.117A but I haven't verified that yet. There are actually two of these relays included, I believe the other is for charging. I do plan to re-use these.

The resistor has 50W printed on it and measured 69.0 Ohms on my Fluke. I'll re-use this too.

I've also ordered my Openinverter kit and it should be arriving any day now.


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## Duncan (Dec 8, 2008)

I tried to use the large contactors from the battery - but my "abuse" made them stick shut !! - so I bought a pair of big contactors

I'm still using one of the large contactors for my pre-charge circuit

Pre-charge resister --- I use an old kettle element


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## remy_martian (Feb 4, 2019)

You know you're ready to put it in drive when there's a good strong tea brewed by your precharge resistor 😂


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## piotrsko (Dec 9, 2007)

Gen 1 packs had 400 amp hydrogen quenched panasonic main relays good for 600 volts. Good for gen1 volts and odd switching where you never get over 200 amps. They will operate once at 400 amps but thats all you get.


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## Zieg (10 mo ago)

Well, the pile is growing. What we're looking at here is a gigantic EVSE, Thunderstruck MCU, 4x Dilithium BMS satellites, Dilithium touchscreen display, current sensor, LEV200 contactor. Not shown: The Openinverter board already installed in the inverter, second contactor on my bench for testing, 30ft of 2/0, Gen 1 Volt DC-DC converter, and the charger which is coming in a separate box.









I'm working on designing an enclosure to cover the exposed DC input connections on the inverter. Already made a protective cover for storage.









I'm also working on a RC economizer for the contactors. I put 12v to one for about an hour and it drew 1.2A initially, tapering to 1A as it heated up. But I wasn't entirely comfortable with how hot it got:









So I think this circuit should do the trick. I'm going to try to get fancy and print a custom PCB to hold the resistor/capacitor and a smaller relay to switch the current to the coil. I think this should work decently enough. Should draw about 5w after 200ms.










I'm also still working on the Leaf transmission modification, will post an update in that thread shortly.


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## Zieg (10 mo ago)

PCB design is a bit of a learning curve, but I am making progress. Here's what I'm looking at for an economizer circuit for my two main contactors: 









Software is called KiCad if anyone is interested, and there are some GREAT tutorials here:


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## remy_martian (Feb 4, 2019)

Oshpark.com is good for fabbing a small qty of boards. I use them all the time.

Fast, excellent quality, US made.


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## remy_martian (Feb 4, 2019)

Turn your relays 180 degrees for a nicer layout


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## Zieg (10 mo ago)

Okay, ordered the boards from Oshpark. Their pricing model is you pay by the square inch, but you get three copies. Figured I'd cut the cost in half by redoing the board for a single economizer circuit since I'm getting three anyway. Feeling pretty good about that!


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## remy_martian (Feb 4, 2019)

My hand calcs on your circuit are 15.4W with the cap dead short (t0) and 8W when the cap is fully charged (open DC) assuming a 13V battery/DC-DC.

I'm wondering where the 5W came from, unless it was estimating coil power vs coil plus resistor power?


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## Zieg (10 mo ago)

Ah, good catch. I was playing around with the circuit and decided I wasn't comfortable going as low as 5w, so I dropped R1 down to 10 ohm. I'll be testing it once the components show up, and I was careful to select components that could be easily changed if I see something I don't like.


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## Zieg (10 mo ago)

Okay, time for another update. I've been trying to push multiple fronts simultaneously so I can hop from one task to another when I get stuck or tired of working on any one thing.

The economizer board I designed seems to work great. Apparently I picked the wrong footprint for the resistor, but thankfully it wasn't off by much and I was able to make it work by bending the leads a bit. The contactors stay nice and cool now!










I've been revisiting the placement of the motor and in light of the projected cost of building a custom reducer box, plus having another driveshaft made, I thought I should try harder to see if I could fit the motor in the back with an IRS setup. It's taken quite a few iterations but I think it is possible. I had to go back to the textbooks I bought on suspension design and make sure the geometry would work out (both on its own right and relative to the front suspension geometry). I think I have it in a pretty good place now. The motor is offset to the passenger side a bit, which is fine because it will help offset my own weight. I still need to add some tubes for bracing and to support the coilover, but so far so good. Losing the solid axle will save me 135 lbs plus whatever the driveshaft weighs (probably 50 lbs?), while adding back the weight of the CV axles, uprights, wheel bearings and wishbones. Lower wishbones est weight is about 3 lbs, uprights would be 2.5 if made from 6061. Not sure about the other components, but certainly the difference in unsprung weight would be huge. It would also free up space in the tunnel to run the power and coolant lines, as well as maybe some electronics (dc/dc converter?).




















For cooling, I found an electric water pump out of a Prius, which seems to be a common choice. I don't think I want to try splitting the flow between the motor/inverter and batteries, so I'm looking at connecting them in series on one big loop. The BMS will be reading battery temp directly and I think I can get motor/inverter temp through CANBUS, but I think it would also be wise to install a flow switch or something, so if the pump fails or there's a blockage I will know about it right away. I also need to figure out a way to control the electric rad fan. A simple fan switch in the coolant would be awesome, but I can't seem to find one with a suitably low 'on' temperature. Being made for ICE engines they are all 160*F or more. Even the digital adjustable controllers don't seem to adjust low enough, and the ones that do use a radiator probe that you shove into the fins, and I don't think I'm a fan of that. Any suggestions would be appreciated.










I got my hands on a used GE Wattstation EVSE, my goodness this thing is huge! I thought it was interesting that the control board has an ethernet port and multiple serial ports.. Apparently they were made to be expandable so you could connect card readers and bill people for usage if you mount it in a public space. It's only rated for around 7kW but that's still way more than I need.










I also got my MCU talking to my laptop and the Dilithium touchscreen. It can't really do much until it's connected to a few more things, but it was still encouraging to see. I also started on an overall wiring diagram and it's getting very complicated. Lots of details to work out there.









And finally, while playing with the Leaf reducer housings I 'did a stupid' and tried to reinstall the jackshaft without first removing the grounding brush. Result: broken grounding brush. Looks like a replacement from Nissan is >$125 which seems like utter insanity to me. After searching around on my own I wasn't able to find any similar brushes. Thankfully, I eventually found a local brush supplier (carbonbrushes.ca). I had a great conversation with the owner Dan, and he found me something that should be a direct fit. I had no idea brush selection could be so complicated, but there are apparently many different materials and characteristics, so I'm glad I was able to talk through the application with him and make sure the replacement brush would live up to its task.









I think that's all for now. I have decided not to race the car for the rest of the season, so as soon as I can clear space in my garage, I will be pulling the car in and removing the ICE components. Currently my side of the garage is full of the vinyl plank flooring I am using to replace the carpet on the top floor of the house, and all that has to be done before the baby comes in October. I'm about halfway done at the moment (two rooms and the stairs done, two rooms and a hallway left). Busy busy!


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## remy_martian (Feb 4, 2019)

What, no Flir pic of the economizer board and contactor???? Science demands it...
🤓


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## Zieg (10 mo ago)

remy_martian said:


> What, no Flir pic of the economizer board and contactor???? Science demands it...
> 🤓



Haha, fair enough. I never looked at or touched the economizer last time, but this time I noticed the resistor was way hotter than I am comfortable with. The whole system was drawing 0.65A according to the power supply, and the voltage drop across the resistor was 5.85V, meaning the resistor was dissipating about 4 watts.. That matches the math, and since the resistor is rated for 10 watts I thought nothing more of it. However, the FLIR (and my fingertips!) tells a different story... I just tried turning the voltage down on the power supply and the contactor will close with as low as 7.4 volts running through the system. I'll have to do a few back calcs (and test it without the economizer board) and then I should be able to select a higher ohm resistor that I'd still feel comfortable using.










At least the contactor is running much cooler as expected (despite the temperature in the room being higher than it was during my first test).


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## remy_martian (Feb 4, 2019)

Two of those boards in your car will cost you 170 feet of range due to resistor losses...
🤓


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## Duncan (Dec 8, 2008)

I am a maverick about suspension design - as far as I am concerned the "roll centers" are complete bollocks

What you need to look for is the angle recovery so that if the car rolls 5 degrees the tyres are still vertical to the road

Saying that my car with the battery on the floor simply does not roll much at all

When you know the final corner weights then you can calculate the required spring rates - I'm using 70 lb/in on the front and 100 lb/in on the back
and I expect your car to be considerably lighter


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## Zieg (10 mo ago)

Heh, yeah, it seems like a pretty polarizing topic - whether they matter, and if so, how to calculate them and what to aim for. I kind of split the difference and made sure it looked okay, but didn't go to any great lengths to optimize for it. 

And on that note, the above numbers are with 0.5 deg static negative camber. From what I gathered from my textbooks, a slight bit of positive camber on the outside wheel should be okay. I don't want to add any more static camber or camber gain in bump, for fear of having traction issues. 

As for springs, yeah, I'm going to have to revisit the front and rear. I tried hard to mount the rear coilovers directly to the uprights instead of the wishbones, but there just wasn't enough clearance. Now that they are on the wishbones the motion ratio is different, meaning I have more travel than I want, and a much lower wheel rate for the same springs. Thankfully, I do have some stiffer springs that should get me back to a similar wheel rate, so I'll use that as my baseline before ordering new springs all around. I don't think the extra droop travel will be a problem but I will need to machine some bump stops so I don't put a wheel through the top of the fenders...


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