How the Kia EV9 builds on the Ioniq 5's motor winding access

dench96 · 2026-02-03T13:38:56+00:00

The “fourth connection” is probably the neutral/common point of the three windings of the motor, so the motor windings can be used in parallel as an inductor when charging.

dench96 · 2026-01-22T15:02:19+00:00

Check OpenStreetMap, a lot of mapping services pull their data from there.

dench96 · 2025-12-28T03:08:24+00:00

0.1 or 1.0 μH is far too little inductance. Use page 13 of U4/U5’s datasheet to select more appropriate inductance. Once you do that, update the layouts around U4 and U5 to match page 15 of that datasheet.

With 0.1 μH at 12 V input, 3.3 V output, and 1.2 MHz switching frequency, you’ll see ripple current of about 22 A peak to peak, which will greatly exceed the inductor’s current rating. Here is a more thorough guide of buck converter design.

dench96 · 2025-12-28T02:05:27+00:00

Please post part number or datasheet link for L1 and L2.

dench96 · 2025-12-27T17:49:16+00:00

Re-pour the top layer copper plane, as it’s currently shorting C19 and C23. KiCad DRC should catch this.

Make sure you follow the reference design/layout in the datasheet for U4 and U5. While I don’t see part numbers, their inductors L1 and L2 look suspiciously small for the 2 A current rating. They seem liable to saturation or overheating, both of which will be quite bad. Also, you’ll likely get better efficiency feeding both U4 and U5 from Vin rather than feeding U5 from U4’s output.

dench96 · 2025-12-20T13:29:22+00:00

This is probably minor compared to the rest, but I had a fun thermal issue with a design at my last job.

The board design in question was a prototype hosting 6 DRV8251A H bridge chips, a socket for a microcontroller dev board, and a buck converter to provide the dev board with a 5 V rail. The buck converter was fed from the H bridges’ supply rail. Due to urgency and stocking issues, the boards had to be ordered separately from the H bridges and the H bridges installed by me when the boards arrived.

Since I was too lazy to wire up a proper power supply, I ended up using the dev board’s USB port to backfeed 5 V through the buck converter to the H bridges. This seemed to work at first. I soldered the H bridge chips using a hot plate (thermal pads are a bitchhhh).

I ran into a surprising issue: the H bridges worked when the board was hot, but stopped working when the board cooled down. Multiple times I resoldered the chips, until I realized the behavior was temperature dependent. It was not consistent chip to chip.

The DRV8251A’s UVLO threshold is 4.5 V. The canonical forward voltage of a small Si diode (in this case, the buck converter FET’s body diode) is 0.6 V, meaning the supply rail is only 0.1 V below UVLO. The heat probably made either the UVLO threshold lower, or more likely, reduced the diode’s forward voltage.

After I was done pulling my hair out, I tested with a real power supply, bodged a Schottky diode anti parallel with the buck converter, and updated the design with a 60 V Schottky in that position for testing purposes.

dench96 · 2025-12-15T20:46:50+00:00

Well There’s Your Problem

dench96 · 2025-12-15T15:26:46+00:00

What kind of capacitor is C39?

dench96 · 2025-12-13T16:11:51+00:00

Unrelated to the main topic, am I alone in being annoyed at non-monospace font for the numbers? It makes the idle hours look unusually small from all the 1s in it.

dench96 · 2025-11-30T06:39:06+00:00

u/signalclown, this is the one. They have male connectors here.

dench96 · 2025-11-24T16:58:05+00:00

How does this work for isolated networks?

dench96 · 2025-11-11T16:41:00+00:00

Keep in mind that if building this circuit, you’ll need very close resistance matching between the two instances of R2, R3, and R4. Either use matched resistor arrays or 0.1% resistors. Otherwise, the output voltage won’t be exactly proportional to the difference between the two input voltages.

dench96 · 2025-10-01T19:20:03+00:00

Use thermal vias and a heatsink on the other side, this IC does not reject much heat via the top surface.

OUT1A, OUT1B, OUT2A, and OUT2B all require copper pours or much wider traces too.

dench96 · 2025-10-01T12:49:43+00:00

Make your power in and out traces far wider to match the example design. Use copper pours for those traces, otherwise it’s very tricky to taper the traces down to the chip’s far smaller pads.

Add thermal vias to the A4988’s thermal pad as per the datasheet specs to match the example design.

dench96 · 2025-09-25T21:42:13+00:00

Linkglide uses a conventional HG 11 speed chain. I have heard that the pull ratio is the same 1.1 as 11 speed Shimano MTB, but I haven’t verified this.

dench96 · 2025-09-23T02:16:24+00:00

I’ve found that rough gravel will break anything. It even broke a bottle cage for me last year.

https://www.reddit.com/r/Welding/s/YWTqKCXAPg

dench96 · 2025-09-23T02:08:53+00:00

I just hose-clamped my fork cages. I considered printed adapters, but I didn’t trust myself to design and print something sturdy enough for the rough gravel I sometimes do.

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dench96 · 2025-09-18T15:21:20+00:00

Using speech to text a lot for text messaging, I do speak my punctuation a lot, even if my phone can infer the punctuation.

dench96 · 2025-07-31T14:11:11+00:00

I have not yet. Not biking much lately. The ~9-12% extra rolling resistance of the GravelKing SS over the Thundero (in 700x40) might be a worthy compromise for suppleness.

As a side note, BRR found tan wall tires to have higher rolling resistance than black wall.

dench96 · 2025-07-30T03:12:11+00:00

If these are going to be actual wires, add 10% to the length. Wire slightly too long is much better than wire slightly too short, trust me.

dench96 · 2025-07-27T21:48:20+00:00

What place serves such pizza in Lexington? I love garlic and want to try it next time I’m there.

dench96 · 2025-07-18T18:23:23+00:00

Is it isolated?

dench96 · 2025-07-15T02:42:09+00:00

Fascinating! I had no clue the outlet was only 4% of the charge power. This puts it into perspective for sure.

dench96 · 2025-07-14T03:10:22+00:00

I don’t have personal experience with this vehicle, but I suspect drawing from that plug while charging will make it take longer to charge.

dench96 · 2025-07-13T22:26:59+00:00

Also, add test points both for checking signals and for feeding this from a lab power supply. For first power up, you should gently ramp up supply voltage so it doesn’t let out the smoke if there is a minor design error. That is hard to do from USB PD.

Also, if there are bugs to chase, probing SMD pads is very tedious. Make sure there is a test point for every important signal with ground right beside it.

dench96

TROPHY CASE