Thursday, April 24, 2014

AC motor Inverter Kit

I bit the bullet and decided to take on the challenge of building an inverter for AC induction motors. I have no formal education in electronics but I can follow directions and I can solder. I will be asking a crap load of questions along the way and will be posting as I go along. The goal is an inverter I can use as a control for the AC motor I have so I can use it to charge my pack. I am going to be using a VW engine for now to drive the AC motor and the inverter to control the output to charge the pack. It is now my intention to charge the pack without the help of the Synkromotive controller being involved at all. If I can make this happen I will have figured out how to make a simple tag along charge trailer that can charge a pack or if possible even run the motor that is currently in the car as well as charge the pack when the load is not as high so the output can charge the pack. Sort of like a Volt Range Extender. If I run the engine maybe the output can run the drive motor directly. Not sure yet. One step at a time. I am also in need of help coming up with a coupler that I can use directly on the motor shaft. The one side is a taper shaft. Odd but it does have a key. The other end is a straight shaft with key which I may use. I have a simple way to connect but need that coupler.

The coupler design will be like this: The left side is the input shaft of the transmission and sticking through an empty transmission. The transmission is mounted solid and the engine is mounted to that. The universal joint is mounted to the end of the input shaft. The other end is bearing mounted and then somehow connected to the motor on the right. The motor on the right is an old Starter/Generator and there are actually two mounted on this Dyno for a load and checking torque. The end of the transmission case is cut to allow access to the end of the input shaft. The input shaft is connected into the clutch of the engine. No clutch is being used but that is the connection. Simple, easy and when checking the VW engine it can be pulled from the car and directly mounted without having to remove the clutch. Perfect. I should be able to duplicate this with little trouble. How to connect a universal joint to the motor is the issue.

As you can see (I think) this end of the motor has a taper shaft with key. An odd fit. 

This end is a straight shaft with a key and as on both ends a screw to mount a tightening nut. Since it is an AC induction motor I can use either end and have it work. I am hoping to figure out how to build a coupler to utilize the end of a crank shaft for the VW and have an adaptor built so this can be mounted in a VW at some point for on the road testing in an actual car to see how viable the little motors will be for street use. 

Anyway I am going to need help building this AC Induction motor inverter to run this little sucker. 

Pete :)


A much needed item for the Roadster. I was trying to cut corners and find a decent seat on Craigs List. Don't bother if its for a Bug. Most of the aftermarket seats are not designed for the narrow chassis of the Bug. Soooooo, I stopped into Bugformance of Sacramento today and picked up a set of front seats and sliding mounts. The sliding mounts will be delivered on Tuesday. I have the seats at home now. I also figured out a way to make the throttle cable connection to my Pot better and cleaner.  So with the seating out of the way I will be taking my ride out for a first spin in a couple days. These are typical racing suspension seats for buggies or what ever. They are quite light weight and fit my rear quite well. These are ready for 5 point harnesses for racing if you desire. I still need a roll bar but that will come later. I also need carpet but that will be the very last thing on the interior. I will be doing some aluminum panel building and need to hone my skills with aluminum welding again. I have an old Heli Arc welder that will do AC Tig welding. Not as much control as with the new style Tig welders but it will do.


So I did some testing but still have more to go. I found that when they say don't charge above the recommended limits. Even with the recommended limit they can be fast charged in 20 minutes. I tried to charge at 40amps and that is well above the limits and just when the cell was nearly full the PowerLab shut itself down due to overheating. The cell was filled but well over the maximum temp limits. So charging too fast will overheat the cells and put them in the danger zone. The temp was up in the 150 degree range and the upper limits are 130 F. So at 10 amps the cells respond quite well and don't overheat but they do get a bit on the hot side of warm. The discharge at 40 amps is quick and they don't overheat. I am not sure if they can handle a discharge of a constant 50 amps but they may. As for peak discharge I'd say if you decide to do 120 amps then stick to the 10second rule. That is like 48C. Not to bad for a cylinder cell of LiFePO4. I think it was rumored that they could do 70C but that is not so. It is only 48C peak. 120 amps from a 2.5ah cell is a whole lot. They do have a safety vent on top so if you do tab weld them you should have a hole punched so the vent is not covered.

Here are a few discharge/charge graphs. The average rating is 2.3 ah but I am doing a charge of 10amps and a discharge of 40 amps. So fast charge and normal discharge will lessen the total ah of the cell. True usable capacity that is actually usable I'd say is 2.1 ah and that is doing fast charge and normal discharge. So a 40 amp discharge is like 16C. Better than the prismatic. Not sure how well they live in this condition but they can do it for short periods.

I am hunting for a way to test for 120 amps out of one of these suckers. I am also looking to build a spot welder so I can have better connections for building larger packs for higher amperage loads to test them. As a single cell they get hot fast. It could be because of the way I have my connections to the cell. When I first did the test the cells made some funky fast clicking sounds. It was a crappy connection. Once connected better that went away. I think I could still do better.


Below is the graph where I charged at 40 amps. Too fast and too hot. 152 F.

Here is a link to the PDF Spec Sheet

Sunday, April 13, 2014

A123 26650 LiFePO4 Cells

New cells arrive on Wed or Thursday. I need to come up with a way to test these little power house cells. A pack that is only 25ah in size will provide a whopping 1750 amps worth of lightning and thunder. Wonder how well they will actually do. If these don't prove as good I am sure they will do fine for a small Aux cell for something. Maybe even a small pack for my bicycle. So 8 cells and 24 volts I could do 70 amps which is way more current than the little controller can dish out. Might be good for a few miles anyway.

Might use them for my Quad Copter power source that will give me a pretty good range and should be light enough for my machine.

25ah and 1750 amps available with these cells. That is way more than I can pull with my setup. So for a nice race vehicle these cells will be just killer. So for a decent DC setup with dual controllers for double the amperage I could do a 192 volt pack that will have 1750 amps available and pump it into a single motor for a trip or two down the track. My controller will deliver 900 amps and at double that I could reach the 1750 amps out of the small pack for a trip down the track. If I just use one motor and controller in a very light weight buggy I could very well get 192 volts and little sag because the cells can actually provide that high current. That would push a little buggy pretty good down the track. Small controller and small pack and glass body and light weight frame with maybe even glass floor pans. Light and agile. These should be a total game changer for those who like the LiFePO4 chemistry.

Pete :)

So testing of the A123 cells begins. I hope to put together a good setup that will run on its own for some time with out intervention and record the charge/discharge graphs.

Thursday, April 10, 2014

Extended Range Trailer Project

I went to pick up my AC motor today. I decided on a different motor than pictured in the other post. The motor is pretty much the same but in my opinion better. It is a 7 1/2" Diameter AC Induction Motor and from end to end 14" in length. It is a dual shaft motor and does included the encoder bearing. I did find out that these AC forklifts use Curtis AC controllers as well as a few others. So these motors will work just fine with the Curtis Line of AC controllers. With that out of the way, it is time to get things moving along. The motor is only a 36 volt 6.3kW motor. I am quite sure that this would pump out way more than 6.3 kW at a higher voltage and amperage. So this motor has a good chance to be not only a generator but with other projects it could be a killer motorcycle motor and even an outboard motor. So without wasting too much more time lets get started.

I have bitten off more than I can chew but think this is going to work well. Jehu Garcia did a video where he had his friend tow his Electric Samba while in Regen Mode. With that he was able to charge the pack just by towing in regen mode. So, lets take that a step further. Lets connect an AC Induction motor to a gas engine and drive the motor in regen mode or generator mode to provide power to charge a pack of batteries. Now if I had a pack that was like 72 volts and my controller for this project was a 72 volt controller I could just connect to the pack and charge directly using the controller to stop the charge.

Now the issue for my situation. I will have a pack voltage of 192 volts nominal. The Curtis controllers don't go higher than 144 volts nominal. So I would be even with the highest possible controller unable to charge my 192 volt pack. Well, not so fast there. Since my controller for my car is a Synkromotive controller it is also a charger. All I need is a voltage of 120 volts and as much amperage as possible for an output voltage and amperage while the motor is being driven in generator mode. Take that output DC and instead of running directly into the pack I can run it through my controller and run that through an inductor first then into the controller to boost the voltage to the required charging voltage and as high of amperage possible. With the controller taking care of the generator functions I don't need any complex setup. It is not designed to be used while driving.

Many conversions are quite limited in space for batteries but the person may want or need to drive an extended distance. So without having to purchase a crap load of expensive batteries to put into a trailer to get a bit further down the road I figured I'd make a range extender so you don't have to worry about the excess batteries and so I don't have to worry about finding a charge station. It is the intent to build a fast charge setup so I can charge at a level above level 2.

So if there is any other things I may need for this project to work please let me know. Any ideas would be good and no, I don't want to make this a complex affair. I don't believe it needs to be complex.

I need advice on getting the motor connected to a VW engine. I need a controller for the motor. Hoping for one that is updated by HPEVS so I can plug in special parameters. I think a 96 volt 650 amp controller would be just fine. We will set it up for lower power settings at first then slowly ramp it up.

Pete :)

Saturday, April 5, 2014

AC Motor

I am going to pickup my AC motor on Wed. This motor is going to be used for a couple projects but the main one is to use it directly with an engine so I can have a generator I can tow along with my EV so I can charge anywhere I need as needed. I was thinking originally of using a small Diesel engine but the engine is not really powerful enough to provide a gob of power for charging. It does work but not for fast charging. I figured that I could mount an AC motor to the drive shaft of a small VW engine and use it directly and run that 3 phase into a 650 volt 200 amp rectifier which I have. I have one mounted already to a nice aluminum finned heat sink. I could even connect a relay to shut the engine down when the battery pack is full. I think the AC motor will provide a better more stable power source for charging the pack. I could if I had another Synkromotive controller build a charger that would actually charge while driving to extend the range. Then when the pack does empty I can stop and charge again. Yes, it would require gasoline but it would be a reasonable priced range extender that could allow you to go much further than with electric alone and at a much lower cost than buying a larger pack which would not fit anyway.

The idea is to be able to drive to EVCCON next year rather than tow the car. Or to the beach or where ever. The idea is NOT to worry about finding a charge station. Since there are very few available fast charge stations and ones that are voltage specific for the average DIY build, taking your own fast charger is the ONLY way to do this. Im looking at a good 60 mile range with the little Bug between charges.

I had to fix a few unexpected little things on the build and now very close to getting this sucker on the road. I also now have 60 CALB SE 100ah cells for a 19kWh pack. Should do nicely. I will set my controller for 120 volts for driving at first and 500 battery amps. I am not sure how well the Kostov will handle higher voltages than 120 volts as recommended by Kostov.

                                     7" Raymond Forklift Motor. 3 Phase Induction Motor.