Paul & Sabrina's cheap DIY 144v motor controller

[MazdaMatt]

ebay, forklift resellers, scrap yards... all the places you go to look for anything used. Many people are running "48V" rated motors at 144V. You just need to make sure (from what I have read) that your brushes are tuned correctly and you don't exceed the WATTAGE rating. (this is just from my reading... i'm no forklift over-volting expert)

[bennelson]

Originally Posted by GrahamMc

Hey, where can I get one of those....

There are plenty around. Ask about. Visit a junkyard. Look up "forklift" in the phone book. Don't let the 48V rating fool you. Those motors were designed to be abused!

I know it's outside of this forum, but for anyone interested in modifying forklift motors for EV use, please visit the thread on DIY Electric Car.

[Roger Heuckeroth]

Originally Posted by SteveU

I’m already speculating and projecting too much. Please show us where you are now so I don’t look stupid making bad assumptions.

Cheers,
Steve

Steve,

You don't look stupid, just uninformed. What is your background? Are you considering doing an EV conversion? Your assumptions suggest that you don't have a good understanding of the basics of what Paul is trying to acheive. This is a simple DC motor controller for EV conversions that use these very simple motors. There are a number of commercially available DC motor controllers, but they are expensive. Paul is developing, with the help of others, a DYI cheap motor controller that will lower the investment required to do this type of conversion.

These motors are normally have the feild and armature in series, and they pretty much max out at 160V or so. Above that you will burn the brushes, so high voltage components are not that important as long as voltage spikes are well controlled.

Discussing the benefits of other motors such as BLDC or ACIM is off topic. It would be great to have an open source AC motor controller program also, but that's for another forum.

Roger

Roger

[SteveU]

Well put Roger. I was worried that my comments would appear critical and I want to emphasize how impressed I am with Paul’s contributions. I think we all understand how difficult it is to find time and energy to do something like this. In particular, a huge thank you to Paul’s wife for supporting him. While Paul’s electronics may be a bit basic, I’ve seen much worse from people who are supposed to be EE’s. I should keep my ideas to myself until I’ve tried them myself but I’ll make one more suggestion: Ask your controller experts if rewiring the motor to bring out the field coil separately could be useful, both for improved speed and torque control, and for regenerative braking.

Way cool stuff guys,
Steve

[MPaulHolmes]

Hey Steve! I didn't feel like you were being critical. In fact, I finally got on the ball today and added the watchdog timer to the program to avoid the hanging u-controller. Thank you for the awesome suggestion. Now, if there is some strange thing that makes the micro-controller freeze up, in a half a second the watchdog timer times out and restarts the program. The human will notice that there is a sudden loss of power, and they will have to take their foot off the gas and then just go right back to driving. It shouldn't be a problem, as I've never had the microcontroller hang, but it must happen enough for people to invent a watchdog!

Thanks again, Steve! I haven't been wanting to wade through the documentation to understand how to do the watchdog until now. It turned out to only be 2 new lines of code, but it was like 4 hours of reading and debugging! haha! It's now tested and working in real life! One of the hard things was the fact that the stupid simulator on the computer doesn't restart when the simulated watchdog times out. Makes me mad! I would take that simulated watchdog to the pound.

[Wherewolf]

Originally Posted by GrahamMc

Hey, where can I get one of those cheap and abundant forklift motors to make my car go 70 mph? I would like to eventually run at least 144 volts. I don't really know enough about DC motors to know what I could get cheaply and make work. DC, brushed, series wound, but voltages usually around 48v?

A word to the wise if you decide to get into one of the BIG electric forklift (Like a Hyster E50B 48v - 5500lb capacity) dismantling projects - it's not for the feint of heart. And you will need big tools and toys to dis-assemble it. This is BIG IRON... If you happen to get it with the battery - the battery weighs in at 3200 lbs by itself - one piece. Most backyard mechanics don't have the gear to deal with that kind of weight - The main traction motor (over 200 lbs) is a great big series one, but be advised, it's a ***** to get out (has to go out the bottom - how do you lift a 10K forklift 20 inches in the air? safely? ) , and some mods might need to be made - for instance: The traction motor bolts directly to the transmission, no problem there; but - the big bearing for the end of the armature is carried by the forklift transmission; NOT the electric motor end plate. The endplate only has an oil seal since it was an open bearing fed by transmission oil.....that presents a big problem when trying to bolt to a car tranny. I'm having the endplate machined to accept a sealed bearing of the identical size - it's all doable, it just takes a bit of thinkin', drinkin', cussin' and ingenuity.
and money....but there is a guy who has this motor in a dragster puttin 96V direct to it for door blowing 1/4 mile runs - and says the motor doesn't even get warm....lots' a' torque.....
If anyone gets into the Hyster line, I've got some part numbers from the older 48v motors for brushes and bearings...PM me if you need them.
Totals:
Forklift $300
Trailer & Gas to get it $75
Voltage Drop Test & Repair, and reseal Fields $25 (burnt off lead)
Test, Turn, and undercut Armature $175
Mill endplate $30
Brushes (4 sets of 2) $80
Replace insulated studs for Arm & Fields (free - but should have been $42 each)
Found a rebuilt motor identical at a forklift parts place.....$3872.00

Good Luck (and be careful!)

Wherewolf

[MPaulHolmes]

Wherewolf, it sort of sounds like you are talking from experience. hehe! Your car is going to be scary and awesome once it's done. Are you going to drag race?! It sounds like you got a really good deal overall. Way cheaper than $3800! What's the diameter? Can you take pictures of how you mount the motor in the car? I have a puny 6.7" diameter motor which just hangs in the air, only attached by the face to the junky homemade adapter plate. Once we have a bit more money, maybe in the fall or winter, we'll probably do a truck conversion, with a real 9" motor and 6 volt trojan batteries. That would be a good test for the controller too. I hope by that time there are a bunch of beta testers with safe controllers.

I'm hoping for 40-50 mile range and freeway speeds. That reminds me: I want to learn how to make professional adapter plates and couplers. The mill probably could do the adapter plates. I don't know how, though.

[Intrigued]

Originally Posted by SteveU

Well put Roger. I was worried that my comments would appear critical ... I should keep my ideas to myself ... Ask your controller experts if rewiring the motor to bring out the field coil separately could be useful, both for improved speed and torque control, and for regenerative braking.

Way cool stuff guys,
Steve

SteveU, I don't want you to think I thought you were being critical at all. We just have to be easy on Paul, so that he don't get stressed out and beat one of those smartmouth kids like a red-headed stepchild, and lose his day job... at least until he can start making more money doing other things, anyway!

PLEASE do NOT keep your ideas to yourself. You already sound like you have more experience with electronics than a lot of folks. We have a small handful of experienced people who have found this thread, and have been great help in the design of a controller that could help make electric cars for the common man affordable. One more helper will just help to make sure it gets done right!

Me, I'm just hoping I can get a version of Paul's controller that I can solder or bolt together without screwing something up...

When you ask about separating the field coil, are you thinking of field weakening? I have heard the Citi/Commuta-cars do that, and believe that there is a thread mentioned earlier about building motors, where such things would sure help folks like me understand what's going on...

[MPaulHolmes]

Intrigued! Get back to your final project!

[Intrigued]

Originally Posted by MPaulHolmes

Intrigued! Get back to your final project!

Sir, Yes, Sir!

... the caffeine has about reached the neurons anyway...