# Direct connect PM motor question



## TheSGC (Nov 15, 2007)

Usually a PM motor isn't great for a car/suv, but since you are trying to make a semi-hybird it may be ok. If you got a controller with Regen built it I do no see any problem with the motor spinning all the time. It should either power/assist, freewheel or regen so it should be fine. The trick would be getting the controller to drive the motor at the proper RPMs to it is insync with the ICE. But it should be very doable, and make sure you design it to keep the AMPs are low as possible because high amps/heat kills PM motors extremely easily


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## Xringer (Oct 12, 2008)

Thanks for the input. I was looking at the Mars ME-0708 which is rated for 8HP with 15 Peak and a Kelly 36-48V 300A or maybe 500A regen controller. 

My plan was to get up to speed with the ICE and then apply EV motor power
until I could see some Amps being used. 
Then try to ration the power for a reasonable amount of miles or time.

The idea is to get my CRV doing 40 or 50 MPG for 20 or 30 miles..
(Short trips around town).

I'm getting about 30 MPG right now, so a few extra HP might just do it..?.


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## ElectriCar (Jun 15, 2008)

It should work fine as long as you have control over the motor and an amp reading. You'll sense when it starts to overtake the ICE as well. I don't think there's any chance of damage if you overpower and use it to take over as primary power. The ICE would behave just as if you let off the accelerator on a down hill run. 

If I read your info right, there's no differential between your new input shaft and the ICE. If there were, you could use all electric around town as long as it had sufficient power. 

RE the permanent magnet thing, it will regen but not sure about heat being a problem. I've worked with DC motors for years and I'm not aware of problems with them anymore than other types. As far as heat tolerance, look at the data plate for "Insulation Type" Click http://www.reliance.com/prodserv/motgen/b9652new/b9652.htm to see what your motor type is rated. You'll be surprised at how hot electric motors can operate continuously with no problems. The minimum temp is 110C for a DC motor and goes up to 195C.


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## Xringer (Oct 12, 2008)

If you clicked on the video URL (above), you can see the transfer case connection plate spinning around as I push the car out and back into the garage.

Of course the car is in neutral, so the tranny & ICE not involved directly with the transfer case output.


You're right, there will not be much of an EV-only mode. However,
there might be some limited EV mode. 

I'm thinking that a_* coast or glide *_(while in neutral or clutch depressed)
on flat or downhill road might be extended a bit by adding some E-motor power while the ICE is resting.. 



After reading about the EMIS on the netgain site, I'm wondering if I could program a controller to automatically control the current as the load varied.?. http://www.go-ev.com/

If not, perhaps build a Cruise Control type circuit that would read the driver input control, then only apply a pre-set amount of Amps to the motor. And staying at that setting even if the car was heading up hill..

If it had a 100 AH 48V pack, and I wanted 20 minutes of ICE assist,
it would limit at ~200 amps..?.

Humm, I wonder if a 200 Amp controller has a built-in 200Amp limiter?


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## jeromio (Oct 8, 2008)

I don't know anything about the configuration of the Honda CRV awd drivetrain. However, in general, I would presume this would be a "bad idea (tm)". The gear train is not meant to be driven. It might work, with the caveat that you will be putting strain on drivetrain for which it was not intended. I presume there is a way to lock the T-case but have it effectively be in neutral w/ regard to the transmission? In otherwords, the only way I can see this being feasible is if the rear wheels can be locked to the front wheels while also allowing the transfer case to be divorced from the transmission. It would still sort of work without that last bit, but you'd be turning transmission unecessarily - and if it's an auto, spinning the torque converter. Typically these FWD->AWD vehicles have a viscous coupling to the rear and you'd be running this in reverse. So you'd be heating up the fluid until it locked and started spinning the front half of the drivetrain. It all just seems less than good.

How much does the rear diff and half shafts weigh? I would presume that the weight there would be the only reason not to simply drive the rear wheels with the electric motor. This would be far simpler and more reliable. Also, the correlation between the ICE and this drivetrain will be much simpler - you could apply power to both with little or no ill effect - you'd have AWD.


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## TX_Dj (Jul 25, 2008)

Xringer said:


> I _think _the prop shaft turns at about 2200 RPMs at 60 MPH. (Not confirmed yet).


Easy enough to figure out. If you can get me your tire size and confirm your gear ratios, I can tell you for certain.



> *Is it possible to spin up the motor to 2000-3000 RPM (with the controller off or disconnected) without harming the motor or loading down the ICE?*


*

Yes... so long as that speed is not in excess of what the motor can sustain. However, being a PM motor, it will impart some drag to the system when unpowered, because it will always try to be a generator when it's being turned my mechanical force. The amount of drag should be insignificant for the ICE.*


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## Xringer (Oct 12, 2008)

Here you go jeromio. It's a detailed explanation of the rear diff.. 

http://www.hobby-rc.com/rtawd.pdf


I read this pdf years ago.. But IIRC, it seems like connecting a motor directly *into *the rear diff would work fine. Just get the E-motor RPMs up so that the diff is tricked into thinking the front wheels are spinning and the little clutch will engage and send power to the rear wheels. 

There are a few drawbacks:

1. You are right about the weight. The rear diff and rear half shafts are pretty heavy. The long propeller is hollow and is lighter than it looks.

2. When you are not using the e-motor, the half shafts still turn the pump
and load down the rear wheels. Increased rolling resistance.

3. When the e-motor is on, it has to drive a pump, extra load on the motor, wasting power.

4. If you had the rear wheels being driven with 2 HP and stepped on the ICE throttle to pass a car, your rear drive might suddenly disengage.

5. When coasting down a hill, the rear half shafts will be disengaged from the E-motor.. So, there is no possibility of re-gen braking.. 


Edit:

Here's a simpler explanation of RTAWD (Last post. #10).

http://townhall-talk.edmunds.com/direct/view/.ef229e9/0


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## jeromio (Oct 8, 2008)

Ah - so the viscous coupling is attached to the diff, rather than being inside the T-case/diff/transmission. Okay, so you moved up a step in feasibility .

Do you know if that output shaft is driven by the front diff? It'd be ideal if there was simply a pinion on the ring. Driving power back thru would mean the gears would be meshing wrong, but that's not a show-stopper.

I still think the ideal would be to drive (directly, not with a viscous clutch in between) a rear diff for a siamese hybrid....


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## Xringer (Oct 12, 2008)

TX_Dj said:


> Easy enough to figure out. If you can get me your tire size and confirm your gear ratios, I can tell you for certain.
> 
> 
> 
> Yes... so long as that speed is not in excess of what the motor can sustain. However, being a PM motor, it will impart some drag to the system when unpowered, because it will always try to be a generator when it's being turned my mechanical force. The amount of drag should be insignificant for the ICE.



Okay, the tires are Mich Hydrothread 205/70R15 (95T) and all I could find on the 'gears' was this.. (My CRV is a 5 speed manual).


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## Xringer (Oct 12, 2008)

jeromio said:


> Ah - so the viscous coupling is attached to the diff, rather than being inside the T-case/diff/transmission. Okay, so you moved up a step in feasibility .
> 
> Do you know if that output shaft is driven by the front diff? It'd be ideal if there was simply a pinion on the ring. Driving power back thru would mean the gears would be meshing wrong, but that's not a show-stopper.
> 
> I still think the ideal would be to drive (directly, not with a viscous clutch in between) a rear diff for a siamese hybrid....


The output shaft (or PTO?) turns when the front wheels turn.. 
(*See video above*). I don't know how they are coupled.

I do know that the ICE does not effect the front wheels or PTO until
the transmission is put into gear and the clutch released.


I'm not too worried about gears meshing wrong, since the propeller shaft (and rear diff) 
is made to be driven in both CCW and CW (for forward & reverse modes).


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## jeromio (Oct 8, 2008)

Xringer said:


> The output shaft (or PTO?) turns when the front wheels turn..
> (*See video above*). I don't know how they are coupled.


You did mention that and it does suggest that the output is linked to the front diff.


> I do know that the ICE does not effect the front wheels or PTO until
> the transmission is put into gear and the clutch released.
> 
> 
> ...


Reverse is always a light-duty operation. There are never syncros for reverse and typically you have straight cut gears for reverse (hence the whine you hear when backing up). But you're talking about applying torque and power thru this part of the drivetrain for extended periods of time, at higher rates of power. The physical analogy would be a downshift - engine braking. But that is a pretty minor load compared to moving the mass of the vehicle (esp in this app since there's a fluid clutch in between). Helical R&P's are are designed to mesh in one direction. 

In many (most?) 4x4 trucks, the mfg simply uses a rear diff in the front. In this case, the front diff is always running "backwards". So the life of this unit is expected to be lower. But this is an acceptable trade b/c these trucks are only operated in 4x4 mode a small (<10%) percent. In heavy duty apps, a reverse cut R&P is used.

To clarify, I'm not saying this is a deal breaker, it's just sub-optimal.


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## Xringer (Oct 12, 2008)

jeromio said:


> You did mention that and it does suggest that the output is linked to the front diff.
> *Reverse is always a light-duty operation. There are never syncros for reverse and typically you have straight cut gears for reverse (hence the whine you hear when backing up). *But you're talking about applying torque and power thru this part of the drivetrain for extended periods of time, at higher rates of power. The physical analogy would be a downshift - engine braking. But that is a pretty minor load compared to moving the mass of the vehicle (esp in this app since there's a fluid clutch in between). Helical R&P's are are designed to mesh in one direction.
> 
> In many (most?) 4x4 trucks, the mfg simply uses a rear diff in the front. In this case, the front diff is always running "backwards". So the life of this unit is expected to be lower. But this is an acceptable trade b/c these trucks are only operated in 4x4 mode a small (<10%) percent. In heavy duty apps, a reverse cut R&P is used.
> ...



I'm not sure I'll even want to use reverse in EV mode. 
The reason I mentioned it, is because the gear(s) in the _transfer case_ are likely (or should be) designed for full power in both CCW & CW. 
Those 4wheeler guys like to get stuck in the mud and back out of it at 5000 RPM.. 

The whining syncros, shifting gears & etc are in the transmission (right?) and not in the transfer case.?. 

I'm not sure what's really driving the transfer case, but it sure seems like
it turns when the front wheels turn. 

Found a pic.. The input gear to the TC does have slanted teeth..









Turn this 90deg to the right and that's how it plugs into the tranny.
Those bolts go in from the left side. (drivers side)..

Also found these semi related pics:


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## Xringer (Oct 12, 2008)

TX_Dj said:


> However, being a PM motor, it will impart some drag to the system when unpowered, because _*it will always try to be a generator *_when it's being turned my mechanical force. The amount of drag should be insignificant for the ICE.



I've been wondering about that drag. If I'm not doing any re-gen battery charging, while driving 55 MPH, 
there will likely be 40 to 90? volts coming off the motor. 

But, *since I'm not taking any current off it, what causes the loading effect?*

In any event, I've been thinking maybe I should not even use a free-wheeling mode at all. Just have two modes, forward and regen. 


So, when I'm heading down the road using the ICE only, the regen will
be tapping 1 Amp off the PM-motor, putting back a little juice.
(It's got over-charge protection). One amp should not effect the MPG
very much and just might keep the pack warmed up on cool days.

When I'm going down a steep hill or coming up to a stop sign,
I can pull back the stick for some extra regen-braking..

For long highway trips, I kinda like the idea of regen charging on the fly.
If I'm going 100 miles with lots of down-hill roads, it might be nice to have some juice available when I get there..

Yeah, anytime the Scangauge is showing 45 MPG, add in some regen to pull it down to 40 MPG.. 

UNLESS, there is a free socket at my destination..


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## TX_Dj (Jul 25, 2008)

Xringer said:


> I've been wondering about that drag. If I'm not doing any re-gen battery charging, while driving 55 MPH,
> there will likely be 40 to 90? volts coming off the motor.
> 
> But, *since I'm not taking any current off it, what causes the loading effect?*


Magnets.

Even without a load, there is quite a bit of drag on a PM motor.

Here's another concern I'd have for your design- the exhaust runs right past all the spots you could mount the rear motor... which is going to make the motor quite hot. Not a good thing, probably.


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## Xringer (Oct 12, 2008)

TX_Dj said:


> Magnets.
> 
> Even without a load, there is quite a bit of drag on a PM motor.
> 
> Here's another concern I'd have for your design- the exhaust runs right past all the spots you could mount the rear motor... which is going to make the motor quite hot. Not a good thing, probably.



Magnets eh.. I was thinking maybe it might have been due to the internal resistance of the copper wire windings. If there is any resistance at all, it's going to heat up the wire a tad as it draws current and as the current flows, there might be some inductive reactance.. 


That 'semi-related' exhaust picture above is off the web, I just used it to illustrate the Honda style prop drive system with the transfercase. 
I don't think that's even a CRV. And the pipe is pretty modified.. 

My rust bucket looks like this:
The bad angle is because my wife won't let me buy a lift..


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## Xringer (Oct 12, 2008)

TX_Dj said:


> Easy enough to figure out. If you can get me your tire size and confirm your gear ratios, I can tell you for certain.
> 
> 
> 
> Yes... so long as that speed is not in excess of what the motor can sustain. However, being a PM motor, it will impart some drag to the system when unpowered, because it will always try to be a generator when it's being turned my mechanical force. The amount of drag should be insignificant for the ICE.



Did you get enough info from my post? http://www.diyelectriccar.com/forums/showpost.php?p=77558&postcount=10


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