Paul & Sabrina's cheap DIY 144v motor controller

[jackbauer]

On my bmw the vss is just an open collector signal that pulls low with every rotation of the crownwheel in the diff if thats any help.

Adam is scaring me right now with all these features! Today a motor controller. Tomorrow fembots!!

[dcb]

that should be easy enough to interface w.

re one wheel sensor wheel slip detection, I did some browsing on EV album, and probably half the diy cars are rear wheel drive, and I'm sure plenty of fwd cars are like yours where it doesn't sense just one wheel, but the ring gear or carrier.

Adding a wheel sensor isn't too awful, but I think most drivers can compete with just their brain and their foot too where wheel slipping is concerned. The other approach is to look for a large jump in rpm, but it is largely guesswork at that point as to what the vehicle speed "should" be. So maybe not much demand for the wheel slip thing.

[squiggles]

Originally Posted by dcb

The other approach is to look for a large jump in rpm, but it is largely guesswork at that point as to what the vehicle speed "should" be. So maybe not much demand for the wheel slip thing.

Or a sudden drop in current, particularly if we are operating using a torque control method.

[dcb]

Originally Posted by jackbauer

Ok probably a stupid idea but here goes. today i had a scare when the throttle stuck wide open. Not a failed controller. Could we have a large button or a keypress that immediatly commands zero throttle regardless of input?

what about a brake signal? you tap the brake and the throttle goes to zero?

[adamj12b]

Originally Posted by dcb

what about a brake signal? you tap the brake and the throttle goes to zero?

I was actually thinking something like that. it could also kill the contractor output incase you were on the brake and still had high throttle...Would have to turn it off to do a burnout though

-Adam

[dcb]

Lets let the burnouts worry about how to disconnect it

But it plays into cruise/rpm lock nicely.

[MetroMPG]

A good suggestion was sent in that we should have a dedicated sub-forum for the Open ReVolt controller. (The amount of interest in this thread suggests it would be well used.)

I've moved this thread into it (existing links here & bookmarks are preserved), and set up the new forum here:

Open ReVolt: open source DC motor controller

It's a child forum to the main "Fossil Fuel Free" one.

[bennelson]

I can't believe we hijacked a thread so bad that Darin had to banish us from it!!!!



Ooops! I should be posting this in the NEW thread...

[williamson]

Paul: What do you think is the best source for home-built BMS (LIFePo4) and high-power charger(230V)? Kindest regards to all.

[MPaulHolmes]

Hi Williamson! I made a basic 6kW charger design and am in the midst of prototyping a single bms node for LiFePO4 batteries. With lithium batteries, you can't make a charger who's voltage output is too sloppy voltage wise, because if the voltage goes over the 3.75v limit (or so), you will be destroying the batteries. In my case, that meant having a good sized inductor and big input filter capacitor. You want to charge the whole pack so that you stop the constant current as soon as a single battery hits like 3.8v. You need pretty fine control of large current at high voltage, and it's not terribly cheap. In my case it's about $600-$700 for the parts. But the good news is, if you go buy a 6kW charger with CAN interface, it's like $6000 haha. so maybe that's not so bad.

The bms will be very noise tolerant because it uses CAN for the communication with the charger and controller. There are some other good open source designs like Greg Fordyce's.

Hey, I soldered my first surface mount components (in my whole life! for the bms):
This is a 1.25v reference (+/- 0.2%). It costs like $2.80 just for that microscopic little sucker! I thought it was a piece of dirt when it was on my desk.

This is for a mosfet that turns completely on with gate voltage of only like 2.5v! haha! ya!

Here it is with the mosfet attached:


I had to make little adapters with the mill for prototyping. And that meant tuning that sucker so it didn't have the slop anymore! ya! I bet it's +/- 0.001 or +/- 0.002 now! ya! I did a tiny plus sign that showed how much x and y were off, and then corrected for that. It took a few plus signs before it was tuned really good! Now it's perfect! ya!

By the way, an expert in the industry is going to make a "how to build a reliable pcb" to help people reliably put together their own stuff. I'm starting a thread for him, so check it out. ya!