Hybrid PWM/Contactor controller turbo-boost

[bennelson]

Holy K-Rap!

I just broke 60 MPH in a home-built cheap-o electric car!!!!


The batteries are urgently recovering on the charger.....

This thing is fast.

Put the car in 4th - get up to 45 - let off the gas pedal and kick in the turbo - it will push you into your seat (just a little, but it does!) and then take it up to 55. I made it to just a hair past 60 mph.

Wait a minute, that was in a 55 zone. There's that speeding thing again. I still got passed by by an F-350...

Why should I need to precharge my controller caps? They can't hold a charge for a minute or two?

I do need some sort of amperage limiter. My ammeter went straight to the top of the scale and stayed there! It just sucks as many amps as the batteries can give.

I pulled over and felt all the cables, the batteries, motor, and contactors.

The motor, contactors, and most cables were dead cold. The cable between the most positive battery and main contactor was warm. I think that's an issue because that's where the fuse, and a couple other small power connections are. I think I need to clean it up and put a better terminal on there.

I also felt all the batteries. One of the middle ones in the back was warm. That's one that I know always has lower voltage than the rest.

The Turbo seems to work pretty good.

I am not planning on engaging the turbo again without a few minor changes, but man does it work!!!

[MetroMPG]

Cool!

I hear it's warm (relatively speaking) in Wisconsin today. Evidently you've got tinkerer's spring fever.

[MetroMPG]

PS - your amp limiter when doing a direct battery-motor connection is your gearbox. Downshift a gear next time you do it and you won't peg the ammeter (ensuring you know what speed is your max safe motor RPM for that gear beforehand - don't want you grenading your motor!).

[rmay635703]

I was always under the impression you could leave your controller in place but use a contactor to put a battery in series between the motor and the controller giving higher CONTROLLED speed. Basically that battery would always be pushing through the motor & flyback diode so you would need to have sufficient speed so you don't push too many amps. Also note that the battery on the flyback side would always be pushing current even if you try to let off the gas (which is a bad idea in this configuration).

Issue is you can also fry your controller if you let off the gas without a contactor to shut off the pedal to the motor and you can also fry the controller if it can't handle the increased amp level.

I was positive that a battery on the "other side" of the controller didn't push the volts too high because it was apart of the motor side flyback circuitry, maybe someone else here has done more experiments than I with this alternative method.

[bennelson]

I'm not sure about adding a battery to the string AFTER the controller.

Sounds like trouble. Also, since there are at least three cables connecting the batteries, motor, and controller, I am not quite sure where you would actually want to add that battery in.

I wanted to take my controller totally OUT of the equation, so that I DONT fry the controller.

I will have to do some testing on limiting amps, because my batteries are NOT happy pulling that many through - can you say Puekert Effect?

No, really, can you? I have no idea how you pronounce it. Lets just say that when you pull amps fast, your batteries run out even faster.

I actually pulled over on the way back just to rest the batteries for a bit.

I e-mailed a couple guys saying what I did, and one response was good enough that I need to repost it here.

Be carefull sounds like another ticket. You speed deamons could make us ev'rs look dangerous like those bikers! OOPS you are a biker also. HA HA.

[bennelson]

OK, here's some actual details on what I did.

I started by digging up two reversing contactors out of my box of parts I have stripped off forklifts. Forklift parts are great because they are BEEFY! (and cheap)



I cleaned up the contactors a bit, including bending back one bent terminal. They are almost pure copper, so they are very soft. You have to be careful wrenching them down.

I cut a scrap of plywood to fit under the hood and over the motor. Both contactors got screwed down to it.

Then I disconnected the M- and B- connections from the controller, and ran them to the contactors instead. That means that I had to dig through my pile of forklift parts again to get more cables to make all the connections.

The extra cables were all connected so that the contactors went to the connections on the controller, batteries, and the motor.

The two middle connections on the contactors go to that yellow Anderson connector (disconnect) which is run to inside the car, where the cables connect to two additional batteries.



That's right, I am out of space and now resorting to just placing the batteries on the floor. No passengers allowed in experimental flights anyways!

I ran a pair of control wires from the front to the batteries on the floor here. Those connect 24v of power to the contactor coils to engage "Turbo Mode"

I ran that power through a momentary-on three way switch pulled, again from my forklift parts pile. The switch is rated for up to 200 volts.

With the drive wheels jacked off the ground, I drove the wheels with the PWM controller and then flipped on Turbo Mode. The car instantly dies, because I have the Anderson connector to the extra two batteries disconnected.

Phase 1 testing looks good.

I then (with the car still jacked up) get the wheels up to speed with the PWM controller, let off the go pedal, and hit the Turbo. Instantly, the wheels get another burst of speed. I turn off the main contactor, and disengage the turbo.

Phase 2 testing passes well. No smoke from the magic box!

I then took the car out on the road, got up to speed, let off the gas, and hit the turbo. It's like it has a whole 'nuther gear - more powerful, like a low gear, yet faster like a high gear! How is this possible? Only through the magic of high-voltage!!!

As I rocket down the road, the issue of suspension and steering suddenly come to mind. Even though the car is two batteries heavier (about 150 lbs more) the suspension doesn't seem bad. I think part of that is that higher-speed roads are usually a bit better designed for smoothness.

Steering wasn't a problem either. It drove like a real car!

I have heard lots of hints on web forums about people theorizing about how to design all sorts of different types of controllers.

Well, I can tell you, it's a whole lot more fun to ACTUALLY DO IT than just talk about it.

If I end up frying my controller, I will dissect the whole thing and figure out what went wrong, and tell you all about it!

[xtian999]

So, instead of tossing the old contactors on my Citi, I can re use them for a turbo circuit? cool!
and since the turbo batteries are not charged or run with the others, they can be different? (older,smaller,cheaper)
good.
and the main controller can be smaller, cheaper?
nice.
And the dash gets a shiny, candy-like button?
The best!

[bennelson]

Yep, you pretty much summed it up.

[ev59rag]

any news or progress? did you finalized your setup? using it regularly? any issues? did you change anything since your last post?

thanks.

[bennelson]

More than anything, it was just a fun experiment.

I would much rather just go to a higher voltage controller than anything else.