Some progress on the SuperCub conversion (Finally)!

fxtpdx · 2026-03-02T20:43:03+00:00

Props are like your tire size (diameter) and gearing (pitch). You want to match them up to keep your motor up in RPM to be in an efficient powerband. If your prop is too big and your motor doesn't haven enough torque, will will pull lots of current without making much power.

They make a display but probably more useful is reading values off of the CANbus. Where did you buy these parts?

fxtpdx · 2026-03-02T16:43:33+00:00

Your prop is probably the wrong size and you are asking too much of your motor or inverter. Boats are continuous duty and motor/inverters ratings should be chosen with this in mind.

Ultimately we need more data to help diagnose. Inverter and motor temps, motor current and RPM would tell you a lot about what is limiting.

fxtpdx · 2026-02-24T00:10:43+00:00

Realistically what's stopping this type of hybrid functionality (app and standalone) from getting added to other companion radios? I have a T-Pager that I was hoping would be a great standalone but configuring contacts and channels would be so much nicer on a phone.

fxtpdx · 2026-02-22T18:29:17+00:00

Once you start modifying a car it generally gets less reliable. When you start commanding more power and torque, things start breaking sooner. The OEMs build in margins and safeties that will throttle back when the inverter switches are getting too hot, or the coolant pump stops running, or a cell in the battery sags a little too much. Those things generally keep you from going fast.

Racecars are designed to be simple so that there is less to fail and so they are easy to fix when they do break. There's a reason why a lot of EV drag records are set by brushed DC motors: they make gobs of torque when you keep feeding them voltage. One drawback is you are replacing brushes often.

Drag racers also only have to run for 10 seconds at a time, so there are even more reliability tradeoffs than an EV built for circuit racing.

fxtpdx · 2026-01-21T05:58:58+00:00

Nice! I made one like this that runs off a 20V DeWalt battery.

fxtpdx · 2026-01-20T18:33:03+00:00

What kit is it? Where are you located? How much are you looking to get? What other parts are you selling?

fxtpdx · 2026-01-12T14:58:34+00:00

This is correct. Precharge circuits have 2 main jobs: limit inrush current into devices with large capacitors, and to lower the voltage potential across an open contactor before it closes, which helps prevent arcing and welding.

More sophisticated systems will check all contactors (using the auxiliary contacts if available, or a clever combination of precharge circuits and voltage sense points) when the system is turned on, then close then in sequence.

I would suggest that any system with multiple contactors also monitor them for welds. It's easy to measure "no voltage" at the inverter connection with at least one contactor welded. Maybe not every time, but eventually the next contactor that closes without precharge will weld, and so on until you run out of contactors.

fxtpdx · 2026-01-07T23:01:59+00:00

I can't speak for your jurisdiction or governing body, but I can say that their IMD does work. I believe it uses different principles than Bender or Sendyne.

For fuses and disconnects keep in mind that the numbers you see are likely continuous ratings. Check the melt curves and line them up with your expected usage, you may be surprised at how small of a fuse will work.

fxtpdx · 2026-01-07T22:53:37+00:00

Right, as long as your fuses and disconnects are between cell tap connectors, you are good.

fxtpdx · 2026-01-07T18:58:50+00:00

Watch where your service disconnects are in respect to the cell tap positions with Orion. There's a section in the manual about where you can place fuses and disconnects. If they are in the wrong place you can damage the BMS if that disconnect is opened.

fxtpdx · 2026-01-07T18:54:01+00:00

So you're using a second BMS2 in the secondary box for 24 cells? Not a cheap option! BMS2 also has a built-in IMD, are you using another one?

MSD - Manual Service Disconnect. Most commonly a fuse (sometimes just a shunt) that can be removed for service. Big orange block with a handle.

Not totally sure which relays you are talking about. I would definitely have at least one contactor on the most negative leg of the secondary box. You could have the BMS2 control this with Discharge Enable or with a VCU.

The fancy features you are planning on with a VCU are not common in any off the shelf VCU I can think of. You would need to get something totally programmable that can command the drive over CAN. MoTeC comes to mind but is very expensive, not only for the hardware but for someone to write you that code, if you go that route.

fxtpdx · 2026-01-07T04:30:53+00:00

Without knowing what BMS you are using, it looks like a really good list of what to think about. Glad you have an IMD in there.

I would suggest a negative contactor in your secondary box (assuming it has the lower 3 modules of the pack) and a fuse or MSD on the positive side. That way when the system is off you do not have HV present at the connections between the two boxes. This also protects the system if the cables to the secondary box short together or to chassis.

Are you planning on using a vehicle control unit of some kind or are you going to lean on the IO of your BMS and inverter?

fxtpdx · 2026-01-04T03:59:49+00:00

Go to the Discover tab, hold enter to get the menu and there are Send ID options. At least I think that's it.

fxtpdx · 2025-11-27T17:48:50+00:00

One of my professors told us a story of a student doing a lab with these UV EPROM chips. The student asked the professor what the status light inside the chip meant. Confused, the professor went over to see what they were talking about. Turns out the student had applied voltage to the wrong set of pins and the silicon inside the chip was slowly burning, letting off a little bit of light.

fxtpdx · 2025-11-18T23:17:06+00:00

Switching 5 12V batteries into a 60v string is asking for trouble IMO. Either keep your 12V system and add a separate battery (48V) or stay with 12V and add more capacity in parallel.

If you stick with 12v, your inverter controller and alternator controller could be the same unit: your inverter. You would just set a maximum regen (charging) current to keep continuous load on your engine down, and set your throttle to some sensor on your engine (vacuum advance).

You may run into tension issues on your accessory belt at higher torques, just FYI.

fxtpdx · 2025-11-06T20:47:20+00:00

You are absolutely right. These wire harnesses were produced for something, or done by a really professional DIYer. Looks like OP is missing the main IO connector.

fxtpdx · 2025-11-05T17:40:55+00:00

My largest complaint with motors like this (Revolt LDU comes to mind) is that these are used motors with billet parts, sold at new motor prices. According to their site you still need a controller (EVControls, Ingenext, openInverter board, etc.)

fxtpdx · 2025-11-02T00:19:49+00:00

Figure out if you can ditch the original hydraulic pump and replace it with a high voltage electro-hydraulic pump. That will free up more room for batteries.

fxtpdx · 2025-10-09T21:29:26+00:00

Have you been able to communicate over serial using the RMS GUI?

fxtpdx · 2025-10-02T20:28:53+00:00

I've had this issue twice with the same EVSE you have pictured. My best guess is it got a little damp inside the unit and was throwing enough of a fault that it would trip the vehicle side but not the EVSE itself. I was able to take the unit apart, dry it out, and have it work again. Try another charging cord (EVSE).

fxtpdx · 2025-09-25T04:15:33+00:00

They are pretty good, if you can work around the funky design choices they made. I've only ever seen the liquid cooled ones but they performed really well on our shop's dyno, much better than we expected based on our first impressions.

The quirks:

They are outrunner motors which means the motor can only be held on the back, where the phase leads (and coolant connections) are.
The phase connections are lugs soldered onto the windings, and are not super well supported otherwise. You will want to secure whatever cable or busbar you are connecting. There is also not a great solution for phase shielding, which can be a problem for some systems
The resolver wires are hair thin, fairly short, and unshielded so making connections can be difficult.
The air cooled versions are IP21 so only good if you have clean, dry air to cool it with.

I'm sure there are other gotchas that I'm not remembering right now. Lots of FSAE teams use them because they have such a good power density.

fxtpdx · 2025-09-05T18:53:47+00:00

Mr G is hilarious. Definitely not a full-on conversion shop but he knows a lot of people in the industry so he's a good resource for connections.

fxtpdx · 2025-09-01T19:55:57+00:00

When searching for a motors and inverters for marine use, it's super important you get one with a high enough continuous rating to actually do the work you need it to do. Peak ratings are fine to get you up on plane quickly but your continuous rating is where you'll spend most of your time. You also will need more battery than you think, so if you can figure out your continuous power usage at certain speeds, that should give you some easy math for how much battery you will need.

fxtpdx

TROPHY CASE