Thats what a number of peopke have said but personally I dont see how "decent/equal torque through the whole rpm range" equals "no need for a multispeed gearbox"

Well look at the Tesla Roadster. It's a very fast sports car. 248hp motor, 3.9 seconds 0-60mph, 125mph top speed, with a single speed 8.25:1 gearbox. A two speed automatic was considered, but not implemented.

 

my thoughts are that the single speed is the 'brute force' approach. What you trade for ratio is large current capacity and it's resultant problems. I'm thinking variable speed transmissions in 1-3:1 ratios. Ported or variable fluid torque converters might also be of use.

 

Thats what a number of peopke have said but personally I dont see how "decent/equal torque through the whole rpm range" equals "no need for a multispeed gearbox"

Like I posted in post #12, A planetary transmission like a single stage Lenco, would give a low gear for slow going and a 1:1 for road use. The Lenco type gear set doesn't need a clutch and would greatly extend the usable RPM range and torque of the electric motor.

This is something I've played around with in my mind for a couple of years. If I wasn't so old I'd probably try it myself. But I've got my hands full with the build of a '37 Ford truck hot rod build that I hope to get done before I kick the bucket

 

Well look at the Tesla Roadster. It's a very fast sports car. 248hp motor, 3.9 seconds 0-60mph, 125mph top speed, with a single speed 8.25:1 gearbox. A two speed automatic was considered, but not implemented.

Right but in the absence of a badass motor like that, the rest of us need another option. If I remember correctly from all the ev research I did a few years ago guys were using powerglide 2 spd and 3 speed trannys.

 

That is one heck of a PM, the weight to power is great, is it possible to over volt a PM or AC motor like the DC motors to increase power output? On a series DC motor you can double the rated voltage with out mods and with some mods you can go x3 or higher for short periods of time like 0 to 60mph.

With a three phase motor and a VFD you don't over voltage but over/under frequency the motor. You can go from ~50% to ~200% of normal frequency of the motor.

 

then again, maybe Strantor's spare eddy current clutch will come in handy.

 

my thoughts are that the single speed is the 'brute force' approach. What you trade for ratio is large current capacity and it's resultant problems. I'm thinking variable speed transmissions in 1-3:1 ratios. Ported or variable fluid torque converters might also be of use.

Torque convertors have quite a bit of slip except in a small RPM range. Most of the DIY EV's that do use an automatic drive the trans directly to the input shaft.

 

Right but in the absence of a badass motor like that, the rest of us need another option. If I remember correctly from all the ev research I did a few years ago guys were using powerglide 2 spd and 3 speed trannys.

Is it possible to keep the transmission that already exists in the vehicle? I have never worked on cars (nor driven one... soon though) so have no idea if a typical transmission would be up to it. I imagine the extra torque and RPM could damage it.

 

Right but in the absence of a badass motor like that, the rest of us need another option. If I remember correctly from all the ev research I did a few years ago guys were using powerglide 2 spd and 3 speed trannys.

The Lenco is a very simple form of a Powerglide. A low and high gear but with out the hydraulic system and torque convertor.
http://www.lencoracing.com/TheLENCOfamilyoftransmissions.html

 

One other thing to consider for an EV is providing the 12V power for most accessories as well as lighting, pumps, fans (for cooling/heating) and entertainment. Of course this would all need to be certified by a gov't agency to be road legal.

You could go the route of some EVs, which is to use a separate 12V battery for all these accessories and charge it while running. But this is needlessly complicated; why not power the accessories straight off the main batteries? Plus, you need to find a battery charger that can run off your high voltage battery pack to charge your 12V battery when it runs down.

A computer power supply will run well off a 350V battery pack, and should run right down to 140V (100Vac), if it has built in PFC. In my experience most continue a stable output at low power down to around 80V on the main filter cap, and the active PFC can allow the power supply to operate on lower voltages (perhaps as low as 85Vac = 120V) because it essentially boosts the battery voltage.

Make sure you budget power as a single headlamp bulb uses 30-50W. With all front lights on, that would be up to 200W, plus the fog lights, braking lights, and all the control units ABS, electric windows, etc. So I'd recommend a 500-600W power supply unit, with an active PFC boost circuit, with at least 50A provided across all 12V rails. Ensure the unit can *actually* supply its rated load with a decent MTBF (50khrs min); consider a dual redundant setup so you do not loose lighting while driving at night etc. Provide adequate cooling to the power supplies.

[For a redundant setup, use a relay which switches over on 12Vmain < ~10V, and optionally some EDLC's to provide backup power during the switch over. A warning indicator would be essential.]

A PC power supply could be used with the ignition circuit. It would not need to run when the car is parked, but can still provide 5V standby @ 2A for some basic control circuit. Or a little AC plug pack could be used to provide 12V standby. Ignition would turn on the PSON line by grounding it, starting the power supplies.

You may want to tweak the internal adjustments which usually allow for a small adjustment in output voltage. The 12V rail could be set to provide 13.5 or 14V, which most accessories are specified at. Consider upping the filter caps, to provide lower ripple voltage.

Isolation from the battery pack is essential due to the high voltages present. All signals driving the gates must be optically or galvanically isolated. A PC power supply provides full isolation.

There are a few things you can do in addition to 12V. You could provide 28V, which could be used to run a more powerful audio amplifier, or even 42V or 60V (a safe limit for electrocution.) However, that would require a custom power supply design, or extensive modifications to a PC power supply.

 

Make sure you budget power as a single headlamp bulb uses 30-50W. With all front lights on, that would be up to 200W. So I'd recommend a 500-600W power supply unit, with an active PFC boost circuit, with at least 50A provided across all 12V rails. Ensure the unit can *actually* supply its rated load with a decent MTBF; consider a dual redundant setup so you do not loose lighting while driving at night etc. Provide adequate cooling to the power supplies.

Now you've gone and done it!!!! "They" will be along any time now to close the thread due to the TOS, no auto lighting talk.

 

Has anyone built their own motor? Would be interested in hearing about that.

 

Uh oh...!!!

 

With a three phase motor and a VFD you don't over voltage but over/under frequency the motor. You can go from ~50% to ~200% of normal frequency of the motor.

So changing the frequency and keeping the voltage constant will change the power output, Right?

Is it possible to keep the transmission that already exists in the vehicle? I have never worked on cars (nor driven one... soon though) so have no idea if a typical transmission would be up to it. I imagine the extra torque and RPM could damage it.

Yes, you can do just about anything, it's all about efficency. Depending on design you could direct drive, use 1 or 2 gears (Lenco is very efficent (read spendy)), CVT (Constant volicity trans) where the motor runs at the same speed all the time, Automatic transmission with stock torque converter or with a lock up torque converter or no torque converter at all and use a external fluid pump insted.

One other thing to consider for an EV is providing the 12V power for most accessories as well as lighting, pumps, fans (for cooling/heating) and entertainment.

Like you say, this one is easy. A lot of switching power supplies have
AC or DC inputs, you can find them used every where. The main pack should be isolated from the body and have a GFI for safety.


There are even A/C compressors that run off high voltage DC, 12 volt electric assist steering, and electric coolant pumps, there is nothing left to run off the drive motor.

 

With a three phase motor and a VFD you don't over voltage but over/under frequency the motor. You can go from ~50% to ~200% of normal frequency of the motor.

with the inverter duty motors some of them are rated @60hz but can go up to 400hz and I run them all day every day @ as low as 2-3hz and they don't overheat. one has been in service in my plant running 5hz max for about 8 or 9 yrs.

then again, maybe Strantor's spare eddy current clutch will come in handy.

very strange. how on earth did you know I have a spare eddy current clutch?

Is it possible to keep the transmission that already exists in the vehicle? I have never worked on cars (nor driven one... soon though) so have no idea if a typical transmission would be up to it. I imagine the extra torque and RPM could damage it.

yeah guys do it all the time. with a manual its common to just stick it in 2nd gear an leave it. no need for clutch. I need to do some more reading to understand why. seems to me you could just use the transmission the same way you did with the ICE. for the DC setups I think they tear up transmissions a lot and so they upgrade them.

The Lenco is a very simple form of a Powerglide. A low and high gear but with out the hydraulic system and torque convertor.
http://www.lencoracing.com/TheLENCOfamilyoftransmissions.html

thanks for the link. looks cool. ill see if anyone over on the DIY EV forum has used one.

 

So changing the frequency and keeping the voltage constant will change the power output, Right?

No, you increase the voltage as you increase the frequency. for an open loop (no encoder) the VFD will perform according to V/freq table. add an encoder and the drive gets a little smarter.

 

Has anyone built their own motor? Would be interested in hearing about that.

In high school I built one. But seriously electric motors are very hard to design and build, there are a lot of magnetic lines flying around and every design decision matters. When done wrong the motor will overheat and produce lots of smoke very quickly. (Ha Ha Ha I LIKE smoke)

 

In high school I built one. But seriously electric motors are very hard to design and build, there are a lot of magnetic lines flying around and every design decision matters. When done wrong the motor will overheat and produce lots of smoke very quickly. (Ha Ha Ha I LIKE smoke)

Lol. how about getting one rewound for different performance? I remember reading that guys were having AC induction motors rewound different performance. I.E. they would have a motor rewound to double the speed. If I brought a 230V 3450rpm motor into a rewind shop, could they rewind it for 6900rpm? 13800 rpm?

 

Lol. how about getting one rewound for different performance? I remember reading that guys were having AC induction motors rewound different performance. I.E. they would have a motor rewound to double the speed. If I brought a 230V 3450rpm motor into a rewind shop, could they rewind it for 6900rpm? 13800 rpm?

Now I know for a fact that I have no idea of how a VFD works, the more I learn the less I know.

We have a person in the EV club that has a patent on a AC motor/controller, from what little I understand he put two sets of motor windings in the same motor and use's two controller for the one motor.


We do almost the same thing with DC motors, we stack the motors and use one controller but series/parallel the motors for shifting, start in series and then shift to parallel for higher speed, in series each motor sees half battery voltage for reduced arcing on start and in parallel each motor sees full battery voltage for speed.

 

Quote Strantor "with the inverter duty motors some of them are rated @60hz but can go up to 400hz and I run them all day every day @ as low as 2-3hz and they don't overheat. one has been in service in my plant running 5hz max for about 8 or 9 yrs.
"
Yeah, I was just making a general statement about the motors/VFD. The manuals for the Teco VFD's I have on my surface grinder and Bridgeport use those as a range of use. The only thing when running a low Hz is the need for an external fan to cool the motor due to the built in motor fan not giving enough cooling.

I'm glad you started this thread! A lot of ideas getting thrown around.