# Tempted to scrap my transmission and go direct drive



## meanderingthemaze (Jan 25, 2010)

I had been convinced to keep the transmission, but now I'm starting to think that for my application, it might make sense to do direct drive, especially since it's a pickup with a differential. Just not sure if the gear ratio is right. I'm hearing that about a 1:7 ratio is what you want if you go direct drive.

Direct Drive Pros:
1. You lose the weight of the transmission
2. Potentially cheaper? not sure, but fabrication would be different
3. Simpler for others to drive
4. I can eat my lunch while driving 

Cons:
1. No control over RPM
2. Potentially less efficient range of RPM
3. No way to disengage tranny (ie: with clutch)

Am I leaving anything out?

If I did go direct drive, would I just connect the motor shaft to the drive shaft (1:1) and only use the differential gearing?


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## Anaerin (Feb 4, 2009)

meanderingthemaze said:


> I had been convinced to keep the transmission, but now I'm starting to think that for my application, it might make sense to do direct drive, especially since it's a pickup with a differential. Just not sure if the gear ratio is right. I'm hearing that about a 1:7 ratio is what you want if you go direct drive.


Well, 7:1 (Or there abouts), if you can find it (IIRC).


meanderingthemaze said:


> Direct Drive Pros:
> 1. You lose the weight of the transmission
> 2. Potentially cheaper? not sure, but fabrication would be different
> 3. Simpler for others to drive
> 4. I can eat my lunch while driving


5. Less drag caused by the gearbox


meanderingthemaze said:


> Cons:
> 1. No control over RPM
> 2. Potentially less efficient range of RPM
> 3. No way to disengage tranny (ie: with clutch)
> ...


Not that I can see offhand.


meanderingthemaze said:


> If I did go direct drive, would I just connect the motor shaft to the drive shaft (1:1) and only use the differential gearing?


Yes, exactly right. But why would you want to/need to disengage the motor? Electric motors have full torque all the way down to 0RPM, so there's no need for slipping the clutch. And if you want to reverse, get a set of reversing contactors. If you're using AC, it's even better, as you can use Regen braking to slow you down as well.

As for "No control of RPM", for this application RPM=Speed, and it's controlled exactly the same as it would be if you had the transmission in place, by the (formerly) loud pedal.

Essentially, if you get the correct ratio differential, then Direct Drive can be thought of as putting the gearbox in 2nd (or 3rd, depending on the ratio you get) and breaking off the stick. Given that most electric motors have a very wide power band, this should be no problem whatsoever. While it is true that the torque of electric motors tends to slope off a little at higher RPMs, it would mean you don't get quite such a hard acceleration when travelling at high speed. Not really much of an issue, and it tends to match the performance of an ICE anyway (Overtaking in 5th gear being the example here).

So, in conclusion, if you can get the correct ratio diff, then go for it.


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## Coulomb (Apr 22, 2009)

meanderingthemaze said:


> Am I leaving anything out?


The biggie to me is not having the gutter climbing torque of a high torque motor geared down with the equivalent of first gear.

And, if you do have a large enough ratio, can you get the speed you want at the high end? This is particularly a problem with DC motors, which tend to have a bit of a sharp cutoff at the top end. Permanent magnet motors (brushless or brushed) have more or less a brick wall at the top end: you run out of voltage, you get no more RPM. Even downhill, they will regen back to the "right" speed for your maximum voltage.

This is one of the reasons for the interest in series/parallel switching of two motors with contactors. That way, you get a sort of fixed 2:1 transmission without most of the weight and space, so you can get the high speed and the low end torque.


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## meanderingthemaze (Jan 25, 2010)

THANKS ANAERIN!

I'm not a gearhead, so please forgive the backward ratio, 7:1, got it.

Here's the proposed conversion:
1969 Datsun L521 Pickup
HPEVS' AC-50 Drive System w/ Curtis 1238-75
108V Pack Voltage (18x6V Lead-Acid)

The main concern for control over motor RPM is the drop in torque at high RPM, but as I don't have a lot of experience with driving different EV configurations in different conditions, I'm only able to project what I will need, or go off of the opinions of the smart people here at this forum. In the link above you can look at the torque curve. Unfortunately, it means nothing to me, as I'm not a gearhead as stated earlier. Perhaps you can help interpret it.

Another potential concern is that if you had a Toyota-esque "stuck throttle" problem, the clutch would allow you to get out of that dangerous situation very quickly. It's a hypothetical, sure. And I plan to have a master braker switch so I have a safety shut off anyway.

Anyway, thanks, that helps.


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## meanderingthemaze (Jan 25, 2010)

Coulomb,

we were posting at the same time. check my response. what you say makes sense. I do have to climb some good size hills, and I'm guessing that the final conversion curb weight will be around 3500lbs.

Will I have problems on hills with a 7:1 fixed ratio?


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## CPLTECH (Sep 14, 2007)

*Re: Tempted to scrap my transmission*

It is nice to have the torque of 1st gear when turning left from a dead stop. 2nd gets scary. 
It is nice to gear down when climbing hills/grades.
It is nice to keep the motor cool when allowed to keep in RPM range the motor likes. Low RPM’s at high amps equals lots of heat.

Speaking from the experiences of 8K EV miles in a 94 S Ten. 9" DC 120V


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## meanderingthemaze (Jan 25, 2010)

Duly noted CPLTECH.

Not sure if it makes a big difference between DC and AC though?!?!


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## EVfun (Mar 14, 2010)

meanderingthemaze said:


> Here's the proposed conversion:
> 1969 Datsun L521 Pickup
> HPEVS' AC-50 Drive System w/ Curtis 1238-75
> 108V Pack Voltage (18x6V Lead-Acid)


I do not believe that 50 horsepower with a maximum torque of 90 ft/lb. is going to be sufficient for a direct drive Pickup. It could work for a small pickup like yours if you wanted to limit the top speed to city speeds maximum (lower gearing.)

I wish I had just gone direct drive in my Datsun 411 wagon. I would have used 2, 6.7 inch ADC motors instead of one 8 inch ADC. That would have given me about 230 ft/lb. of torque (800 motor amps) to multiply 4.56 times in the low ratio rear axle that is available. That is about 1050 ft/lb. at the rear axles. 

As I built it (stock 4-speed, standard 4.11 rear end ratio) I will have about 100 ft/lb. of torque to save the clutch (about 600 motor amps.) With the 2.18 second gear ratio I will have about 900 ft/lb. of torque at the rear axles. My Beach Buggy has about 600 ft/lb. of torque at the rear axles and weighs only 1400 lb. It takes off pretty good but is no hot rod.


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## AmpEater (Mar 10, 2008)

meanderingthemaze said:


> THANKS ANAERIN!
> 
> 
> Here's the proposed conversion:
> ...


You're going to need more motor for direct drive. An 11" should be enough, or two 9". You're making up for a lack of a transmission with brute force, which means more heat to deal with. 

And generally the rule of thumb is direct drive needs higher voltage in order to maintain a decent top end. AC gets around this a little bit. A SepEx would also be a good candidate for this application, if paired with a suitable controller.


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## ngrimm (Oct 19, 2007)

After driving my Ninja for a little while with one speed at 4:1, I definitely want at least two speeds when I convert a small truck. The Ninja is heavy, 300+ pounds of batteries, has lots of power once you get rolling but it's a little soft from a stand still. I couldn't even get it to pull onto my little tilt bed trailer. Of course it was pretty steep since acid started running out of the batteries. I can just picture a pickup having one wheel in a hole and not being able to move. I noticed someone has a couple Ford Ranger electronic shifting transfer cases for sale. If you could just shift from low to high, I wonder how well that would work.


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## Anaerin (Feb 4, 2009)

Okay, dumping the values into my handy little calculator (http://evthoughts.blogspot.com/2009/05/testing-idea.html), we get:

Tyre Type: P235/65 R18
Wheel Rim Diameter (mm): 457
Tyre Depth (%): 65
Tyre Width (mm): 235
Total Diameter (mm): 763
Wheel Circumference (mm): 2397

Motor Max RPM: 6000
Gear Ratio: 1:1
Differential Ratio: 7:1
Final Drive Speed: 857

Top Speed (kph): 123
Top Speed (mph): 77

If you change the diff ratio to 5:1, you get:

Final Drive Speed: 1200
Top Speed (kph): 173
Top Speed (mph): 107

Which is a little better if you want speed, though that will sacrifice torque.


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## dtbaker (Jan 5, 2008)

I'll chime in w/ opinion that you will not have reasonable start torque AND top end without a transmission.


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## Coulomb (Apr 22, 2009)

meanderingthemaze said:


> Will I have problems on hills with a 7:1 fixed ratio?


It will still drive, it's a matter of whether or not you find the performance acceptable. I don't have a feel for how bad the performance would be with a given motor. However, as others have noted, it's clear that without a gearbox, you need a substantially larger motor, AC or DC.


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## DIGGER11 (Mar 16, 2010)

Coulomb said:


> It will still drive, it's a matter of whether or not you find the performance acceptable. I don't have a feel for how bad the performance would be with a given motor. However, as others have noted, it's clear that without a gearbox, you need a substantially larger motor, AC or DC.


I have been told that lots of volts and good amps will pretty much move anything with a 9" DC or equivalent AC motor.

If you race then you will need more, but for an occasional quick start or a long hill, then a 9" will even be o.k for a direct drive 3500lb.

A 1,000 amp controller and enough C power out of your batteries is a necessity.

I prefer the simplicity of the "Golf Cart" Approach i.e. Direct Drive. It's just that you need to size the components correctly to get it to work.


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## toddshotrods (Feb 10, 2009)

I'm building from scratch and decided to design my entire vehicle around my single 11", direct drive, powetrain. I was originally planning to run a transmission, but eventually decided to go direct drive. I am still building, so no performance/driving data to contribute yet, but I can add my thoughts on the subject.

If you're going to drive your vehicle in normal traffic, be that heavy, and want direct drive, you need a big motor. I would say 11" minimum, but I would probably choose a 13". You want a vehicle that does its daily routine without a lot of drama. Having a huge battery pack and constantly having to dump massive current into the motor is not a healthy prescription. Beside the wear and tear on your batteries and motor, it's just not going to be as nice to drive as a vehicle that has enough torque to effortlessly do its normal activities.

Most production vehicles have a lot more power than the average person will ever use. In use this makes them feel smooth and comfortable, like they're not breaking a sweat. It makes the drive more enjoyable than smashing you foot to the floor, chanting "come on baby!" 

For the record, I am an advocate of direct drive. I believe it is the way to go with EVs, but the whole vehicle needs to be designed and set up for it. Transmissions are a way to compensate for the fact that an ICE has to get spinning to get into its torque band. Why not start building vehicles that take advantage of one of the electric motor's biggest selling points - gobs of torque, right now!?


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## TheSGC (Nov 15, 2007)

I would say you need at least an 11" motor running at 156 volts for a transmission-less EV. I have a Civic with a 9" motor and a Zilla 1K-LV running at 96 volts and I have to start off in 1st (11.31:1) if I want to move anything close to traffic speeds. If I start in 2nd (6.38:1) my acceleration is 1/4 of starting in first and too slow for normal in town traffic acceleration. I also contend with hills and starting in 2nd is a No-No for me, but my EV has a 4 speeds auto so all I do is just step on the pedal zip away, but make sure I have 1st gear up to 15 MPH at the minimum, then 2nd up to 30 and 3rd for the rest. I have never needed my 4th gear and third should get me to 55 MPH without too much trouble but I haven't needed to try it.


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## AmpEater (Mar 10, 2008)

The "Max Recommended Vehicle Weight" for NetGain motors

Direct drive;

TransWarP 7" 1500
TransWarP 9" 1800
TransWarP 11" 2200

With transmission;

ImPulse 9" 3400
WarP 9" 3600
WarP 11" 4400
WarP 13" 7000


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## Woodsmith (Jun 5, 2008)

Do you know your existing axle and transmission ratios?

You could find the gear selection that gives closest to your desired 7:1 and then just leave it there. Drive around for a week or two in all your normal day to day driving and see if it works for you and your motor/controller set up.

Making allowances for the saving in transmission losses and weight you will get a good idea if direct drive will work for you with only one ratio.

I still think that a two speed will be better for most. Something along the lines of an old Laycock type overdrive but running a increasing instead of an reducing drive ratio so you have a direct 1:1 to the axle and a lower ratio, say 1.4:1 to the axle for hills and traffic.


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## dragster (Sep 3, 2008)

Way do you think the vehicle manufacturer made a transmission in the first place.
1. it would be fun to have one
2. you can hear it shift as you go faster
3. move a heavy vehicle with out using a lot of energy


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## AmpEater (Mar 10, 2008)

dragster said:


> Way do you think the vehicle manufacturer made a transmission in the first place.


1. Engine technology makes it impossible to start from 0rpm and much of the power is made within a specific RPM range?


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## Woodsmith (Jun 5, 2008)

dragster said:


> Way do you think the vehicle manufacturer made a transmission in the first place.
> 1. it would be fun to have one
> 2. you can hear it shift as you go faster
> 3. move a heavy vehicle with out using a lot of energy


To cope with the torque/power curve specific to the ICE fitted to the vehicle.

The transmission, as fitted to ICE vehicles, is mainly to allow for the ICE needing to be running at a significant RPM before there is sufficient torque to move the vehicle. Also different ICE have different torque curves and so transmission have different ratios to suit. This is why the transmission in a small car has different ratios compared with a large car and a truck. also why the same model of car will have different ratios depending on the ICE type and whether it is the shopping car, the estate car, the sporty version, etc.

Not all ICE vehicles have a transmission of selectable gears. Some just have a clutch of sorts. They just generally have a low ratio (high numbers) transmission and travel at slow speeds. Some small garden tractors for instance.

Changing from an ICE to electric doesn't mean a selectable transmission is necessary or redundant. It depends on the type of motor fitted and the use of the vehicle. However, blindly using the ICE transmission (or not), though easy, doesn't always give the best solution but it is a cost effective compromise.


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## dragster (Sep 3, 2008)

So if your at the bottom of a big hill with a 3500lb EV with no transmission the amp load is the same as on a flat road thank you for that insite, your bridge is on it's way.


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## toddshotrods (Feb 10, 2009)

That's my point - design a vehicle, not a powertrain conversion! Whether or not you need a transmission is a really open question. The important questions are what your needs are, and what you have to work with. You'll figure out whether or not to shift from that.

I wouldn't run the transmission just because it's there, and I wouldn't run direct just because it's possible. I would do the thing that will best serve my specific application.

The great thing about EVs is it is possible to run direct drive. You can develop a setup that will do everything you need it to do, with ultimate simplicity. Try hooking a typical V8 engine directly to the rear end!


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## toddshotrods (Feb 10, 2009)

dragster said:


> So if your at the bottom of a big hill with a 3500lb EV with no transmission the amp load is the same as on a flat road thank you for that insite, your bridge is on it's way.


You're shooting in the dark. How do you know he even has a big hill to climb? That's the whole point some of us are trying to make. If he has a flat, low-speed, commute 3600lbs could be of no consequence. Saying you must have a transmission, without considering the circumstances, is just as goofy as saying to heck with a transmission direct drive is much simpler, without considering the circumstances.

The point is not to prove a point but to offer viable help.


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## dtbaker (Jan 5, 2008)

toddshotrods said:


> I would do the thing that will best serve my specific application.


the point is that in MOST cases, if a person wants a highway speed vehicle, the minimum horsepower (least expensive) motor to give the required continuous power to maintain that speed at a reasonable grade will not be large enough to 'get up and go' from a stop without a transmission, nor is it likely to find a motor with a broad enough rpm and efficiency band to go all the way from 0 to highway (70mph?) without a transmission.


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## toddshotrods (Feb 10, 2009)

dtbaker said:


> the point is that in MOST cases, if a person wants a highway speed vehicle, the minimum horsepower (least expensive) motor to give the required continuous power to maintain that speed at a reasonable grade will not be large enough to 'get up and go' from a stop without a transmission, nor is it likely to find a motor with a broad enough rpm and efficiency band to go all the way from 0 to highway (70mph?) without a transmission.


I have no problem with that. I was just trying to counter the philosophy that because the ICE had one the EV must have one. You pointed out specific conditions in which he would need a tranmission. That is info that can be used to make an informed decision. Actually, the point of being at the bottom of a big hill is, but it wasn't presented in a purely factual basis. It was intended to sway the conversation and prove a point. That isn't helping the guy. Remember this thread was started by someone who is considering running direct and needed help making the decision. I like direct drive but wouldn't tell someone with a 3600lb vehicle running 144 volts/600amps, and planning on highway usage, to try it.

This subject always causes this huge debate over who's right or wrong rather than what will work best for the person who asked. When I was debating it I got the same thing, including the typical it won't work warnings - even though White Zombie was on video proving it would for my application.

How are you going to use your vehicle? Will you ever have hills to climb or highways to travel. How big of a motor is practical or affordable for you? How big of a controller and battery pack can you afford? Is a lithium based battery pack in the picture?

Start with the facts and let them answer the question.


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## Coley (Jul 26, 2007)

*Re: Tempted to scrap my transmission*



CPLTECH said:


> It is nice to have the torque of 1st gear when turning left from a dead stop. 2nd gets scary.
> It is nice to gear down when climbing hills/grades.
> It is nice to keep the motor cool when allowed to keep in RPM range the motor likes. Low RPM’s at high amps equals lots of heat.
> 
> ...


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## meanderingthemaze (Jan 25, 2010)

Ok, so thanks to everyone for the MANY replies. I can't respond to each one, but here's the rundown again in case it will help anyone give me useful hypothesis...

Here's the proposed conversion:
1969 Datsun L521 Pickup
HPEVS' AC-50 Drive System w/ Curtis 1238-75
108V Pack Voltage (18x6V Lead-Acid)
Est. final weight: 3000-3500lbs (depending on the batteries used, ie: size and AH)

Driving conditions for application: 90% of driving will be relatively flat street driving. However, I have a couple of large-ish hills (maybe 1/4 mile) at the beginning and end of my commute. Also, I will also be driving for a few miles (maybe 5 miles each way) on the freeway each day, going around 60mph. I don't need a speed demon, but need it to have "safe" acceleration to maneuver the many crazies in Los Angeles traffic.

Finally, here are some specs from the service manual I have...my model is L521 from all indications I could find.




















One follow up question would be that if I used Anaerin's calculator, I get a gear ratio of 8.2:1 needed for a top speed of 65mph, which would be fine. Would that provide enough low speed torque for direct drive?

Also, I was looking at the Coda specs, and wondering if they are really using a motor with 134hp, or is that the "ICE equivalent hp"?
http://www.codaautomotive.com/tech_specs.html

It's sounding like I may need to keep the transmission, but if I could make it work, it would be nice to have a simpler direct drive system.

EDIT: Oh, I forgot, I do know someone who has this motor controller combo installed in a 2009 Ford Ranger and I've been trying to make it down to give it a spin. Should I try to drive it from start to freeway speeds in 2nd to see how it performs? Of course that car is a beast, like probably 5500lbs., so it may not be the best indication, I mean if it doesn't perform well. Can I damage his motor from driving in 2nd alone? Any recommendations?


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## Anaerin (Feb 4, 2009)

meanderingthemaze said:


> Ok, so thanks to everyone for the MANY replies. I can't respond to each one, but here's the rundown again in case it will help anyone give me useful hypothesis...
> 
> Here's the proposed conversion:
> 1969 Datsun L521 Pickup
> ...


My suggestion would be to first ask him how he drives his ranger. And 8.2:1 may get you to 67MPH, but that's best case scenario, and absolute maximum possible value. I'd personally spec for about 7:1, to give some overhead (and some capability for overtaking)

That does all depend on availability, however. Using the highest of the listed differential gearings you have there (5.143:1), you get a max speed of 171KPH (106MPH). Given that your torque curve is flat to about half that (85KPH or 53MPH), then tapers off higher, this may be the ratio to go with, however it will mean you need a fair amount of umph (A high amperage capable controller) to get things started.

I doubt you'd damage his motor driving in 2nd alone (Provided you don't overspeed it - check to see if he has a working and accurate tacho before you try), but my best suggestion would be to find out how he drives his Ranger, and what kind of performance he gets out of it. It may be that he drives in 2nd for most things, shifting up to 3rd on the highway. If that is the case, getting a final drive ratio that's somewhere between the total of 2nd and 3rd would probably be your best bet.


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## DIGGER11 (Mar 16, 2010)

Has anyone got a powerful set-up in a heavy car (say >3,000lb) that they can test direct-drive i.e. just use 4th gear ???

I cannot see how if you can provide 10 - 15 seconds of 1,000 amps at say 160V from your battery pack and controller to any reasonably sized motor, that this will not be enough to move even a heavy vehicle.

Of course if you use 72V or 500amp controller, or underpowered batteries then that is a different story.

My still developing plan is a Soliton1 or Zilla1K HV with 190V of LiFe P04 batteries (160ah) driving a suitable direct drive DC motor (I think 9" will do but could be 11").
The battery pack will sag to the desired 160V max. under load so should get an effective 120kws at the wheels (160 x 1,000 x 75%), which, when combined with the large torque from idle of an electric motor, should get the heavy car moving.
I cannot see why this will not work - but would love to be proven otherwise before I commence the build.

BTW: My contingency plan is to use a DC motor that can be paired in series in case I need more motor in the future. 
and With a 3.7 final drive ratio, I will get 3,000 RPM at 100kmh and 1,800 RPM at 60kmh, which appears to be well within the working limits of most 9 and 11" DC motors (with maybe a bit of extra forced cooling for the low RPM's).


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## CPLTECH (Sep 14, 2007)

In all of this discussion, it seems that this planned setup is totally unrealistic and doomed to failure.

RE: 108V
Most recommend 144-156V or even more for freeway speeds to overcome all that wind at high MPH. That is why gas mileage gets worse at higher speeds. Usage of electrons increases for us, too. That is why production electric vehicles look like a jelly bean and not a Datsun brick.
At such low voltages listed by mfg chart, the current draw is 300-500A. I use a 250AH battery, about the largest commonly used in our EV’s. For the sake of them, I try to keep the drain under 250-300A max. In such a low voltage setup you are planning, the batteries cannot stand that abuse and will have a short life, for sure. Then those of us who use lead acid batteries are plagued by the “Peukert Effect” whenever we exceed, as in my case, 25A draw.
I suggest you look at EVAlbum.com for the ones built in your state and see what has realistically worked for them.

RE: No Trans
Electric motors, AC or DC, start off drawing massive amounts of current until they reach design RPM. It’s called the motor principle of “BEMF”. Again the batteries will take the brunt of it, and will affect range.

It is certainly a good thing that you have posed these questions beforehand.


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## toddshotrods (Feb 10, 2009)

After all the hubbub I was left thinking the same thing - based on the specs provided. That setup is relatively low voltage and pretty mild, plus indicated usage included a quarter-mile (I think) hill or grade and freeway runs.

The choice is either go big or keep the tranny. You would need a big motor and bigger battery pack capable of higher voltage and current loads. I am not familiar with AC, but the one well-known direct drive AC car - the Tesla - runs close to 400 volts, if memory serves me correctly.

I think you may want a clutch, or converted auto transmission, as well. In LA traffic, with grades, and higher speeds, plus a relatively low-power setup you may need to swap ratios occasionally.

I'd like to see a purpose-built direct-drive street vehicle though. Maybe a Warp 11, keep the weight down, a big LiFePo4 pack, and a Soliton. I bet it would be a blast to drive, and feel very 21st century.


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## Coulomb (Apr 22, 2009)

CPLTECH said:


> Electric motors, AC or DC, start off drawing massive amounts of current until they reach design RPM. It’s called the motor principle of “BEMF”. Again the batteries will take the brunt of it, and will affect range.


The back EMF is low at low speeds, so the controller applies low voltage to keep the current reasonable. The current isn't "massive" unless you have a massive controller, or you attempt to connect the motor with a contactor controller or some such.

The battery doesn't "take the brunt of it"; at low voltage, the power level is low, so the battery current is low. The battery current will actually rise as the motor speed and hence motor back EMF and hence controller output voltage and hence controller output power and hence battery power increases.

In fact, I don't think that you need to increase your battery capacity merely because you choose direct drive. Certainly the motor will need to be larger to provide low speed torque, and it may get hotter than a smaller motor with a transmission because of the increased current. But I think that the lack of a transmission with its ~10% power loss would more than make up for extra copper loss in the direct drive motor.

So you need more motor and controller [edit: for direct drive], but not more battery, if I am right.


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## AmpEater (Mar 10, 2008)

Coulomb said:


> So you need more motor and controller [edit: for direct drive], but not more battery, if I am right.


You got it


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## Coulomb (Apr 22, 2009)

AmpEater said:


> You got it


Thanks for the vote of confidence, AmpEater.

However, now that I think about it, if you don't drive more conservatively, you'll be _tempted_, and able, to hit the battery harder with a direct drive setup, as a consequence of the larger motor and controller.

Even if you start with the same torque and therefore power drain from the battery, you won't have the upshift that automatically reduces the load on the battery, so assuming you keep demanding the same torque (and why not? ), you'll end up chewing more current from the battery than with the gearbox-kept conversion. So while it isn't strictly necessary to increase the battery capacity with the extra motor and controller power, it's probably a sensible move, to take full advantage of the extra money you have to spend on the motor and controller.

I guess you could program a battery current limit into the controller, to allow the same battery to have the same longevity and performance as with a gearbox-kept conversion, but again, it means you won't be getting full value from your extra motor and controller investment.


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## AmpEater (Mar 10, 2008)

Coulomb said:


> Even if you start with the same torque and therefore power drain from the battery, you won't have the upshift that automatically reduces the load on the battery


My experience is that an upshift generally increases the load on the batteries.

As you hit the top end the back EMF goes up, and motor current goes down. Shifting lets you get back into the middle of the rpm band and continue to "pull" harder. With a direct setup you've got no options once torque starts to fall off.

But 50kw of "acceleration" delivered to the wheels is 50kw, whether it went through a transmission or not. The transmission multiplies the torque, but it doesn't change the amount of power.


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## meanderingthemaze (Jan 25, 2010)

I'll post when I have more information about the Ranger conversion. 

I do know that he drives it on the freeway and even over some steep-ish freeway grades. However, he has told me that he does have trouble maintaining highway speeds on the steep freeway grades when the battery is somewhat depleted, and so he ends up in the slow/truck lane going about 40-45mph until he gets over the peak. 

Based on the huge difference in his weight to mine (probably about 2000lbs.), I am confident that my design will work, however, I am starting to think it might just be safer to keep the tranny, because this is all really conjecture and speculation. I could always change it later, if I felt I was able to drive continuously in a single gear.

If mine does work, it will be a good example of what does work and I will post performance data.

Thanks


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