VESC for ebike ?

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Bouteille51
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VESC for ebike ?

Post by Bouteille51 » Mon Oct 16, 2017 3:52 am

Hello all,

I have been looking around for the perfect controller and I am more and more interested about VESC project.
The 'only' problem is to switch it from skateboard power levels to something more adapted for ebike use.
I LOVE Marcos project and other members using IGBTs etc, but it's way overkill for an ebike and wayyyyyy beyond my skills (basically soldering through-hole components and not understanding much of the actual electronics).

I see two options here, I would need your opinion on both approaches:

1. First one (suggested by ElectricGod) briefly consists in buying a VESC, changing caps and mosfets, shunts, power the mcu, changing cables, and voila.

I suspect that changing mosfet for beefier ones requires a taking good care of specs. Gate resistor and surrounding components are supposed to match closely with the mosfet. Is it a big concern or am I splitting hairs ?
As anybody done this kind of mod already ?

2. Second option I see is to use Marcos design which decouples logic from powerstage and building a reasonnable powerstage for my needs.

I love how Lebowski gave instruction to build powerstage for his controller. I'd like to take inspiration from his post but I guess that marco's design assumes mosfets drivers should added there too. Is this correct ?

I think Marcos wants to focus on super-high powers only, but can someone think about an easy DIY powerstage for all ebike people craving for a VESC controller ? :D



I suspect that rising VESC specs to 100V (120V?) would be enough for most ebikes builds. Allow for 200A phase amps and you have a ton of people interested (just a guess though).

marcos
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Re: VESC for ebike ?

Post by marcos » Mon Oct 16, 2017 8:07 am

For the board I made you'd only have to design a powerstage pcb with gate drivers, mosfets, dc link cap, phase voltage/current sensors and vbus voltage.

Don't hack a stock VESC, it already has perhaps the beefiest mosfet available in that package. If you use a mosfet with lower Rds and higher current, it will require more gate driving capabilities from the DRV which i already hitting its limit at some switching frequencies.

If we can make a powerstage mechanically compatible with the vesc I made I woud be happy to add it to the master repository. I'd aim at 120v, although I'm not a fan of bootstrapped gate drivers so if I design it it would be a fully isolated gate driver board.

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ElectricGod
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Re: VESC for ebike ?

Post by ElectricGod » Mon Oct 16, 2017 11:27 pm

Hi Marcos...I started this in a PM, but didn't think to post it out there for far smarter people to think about.

My thinking is this...
what am I missing?

1. The fet driver chip is the power supply for the MCU. It is rated for 6 to 60 volts. This IC runs great at 12 volts so a small DC-DC step down converter that outputs 12 volts and can handle your battery pack voltage needs to feed this chip power. Disconnect it from batt+.

2. Remove the existing 60v mosfets and replace with 100v mosfets.

3. Replace the large capacitors with 100 volt versions of the same capacitance.

4. Since you want more phase current, the IRF4468 is a good 100v choice and you still have a 6 fet controller, but at double the wattage. You can wire them in exactly like the original 6 mosfets and mount them to the shell of the controller.

5. There are 3 shunts on the controller. They are too low wattage for your mosfets. Get the same value shunt, but in 2X or more the wattage and replace all 3 of them.

6. The battery and phase wires are too small. Replace with at least 12 awg and preferably 10 awg wires. However power gets from the battery wires to the mosfets, reinforce these traces on the board by soldering additional copper to them.

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Re: VESC for ebike ?

Post by marcos » Mon Oct 16, 2017 11:48 pm

ElectricGod wrote: what am I missing?

1. The fet driver chip is the power supply for the MCU. It is rated for 6 to 60 volts. This IC runs great at 12 volts so a small DC-DC step down converter that outputs 12 volts and can handle your battery pack voltage needs to feed this chip power. Disconnect it from batt+.
The job of the gate driver is to drive the gates, powering the mcu is very secondary. If your half bridges operate at 100v the gate driver will need to generate more than 100v to keep the top gate enabled, you can't detach it from the battery voltage, hence the 60v limit.

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ElectricGod
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Re: VESC for ebike ?

Post by ElectricGod » Tue Oct 17, 2017 5:10 pm

marcos wrote:
ElectricGod wrote: what am I missing?

1. The fet driver chip is the power supply for the MCU. It is rated for 6 to 60 volts. This IC runs great at 12 volts so a small DC-DC step down converter that outputs 12 volts and can handle your battery pack voltage needs to feed this chip power. Disconnect it from batt+.
The job of the gate driver is to drive the gates, powering the mcu is very secondary. If your half bridges operate at 100v the gate driver will need to generate more than 100v to keep the top gate enabled, you can't detach it from the battery voltage, hence the 60v limit.
So the VESC can't be run at higher than 60 volts due to gate driver limit. I was wondering how it would drive the high gates if it couldn't run at the battery voltage. Could an opto isolator be used to isolate the gate driver output from the mosfet gates? That way what the gate driver sees and what the mosfet gates see and the voltage difference between them would be irrelevant. I was thinking I had seen a thread on ES that is a VESC variant that used high voltage IGBT's and opto isolators.

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Re: VESC for ebike ?

Post by marcos » Tue Oct 17, 2017 5:43 pm

Yes, google isolated gate driver. HighHopes, Arlo, zombiess and me use those for higher voltage applications.

Building a higher voltage vesc is just a matter of using a higher voltage gate driver, like for example an isolated driver.

However, you can't simply replace the original gate driver of the vesc, that DRV chip has no easy way of increasing its operation voltage, so you need a custom layout to accomodate for a higher voltage gate driver. In this post you can see which part is the actual gate driver, and its easy to see the isolation barrier (slot on the pcb plus soldermask removed)
https://endless-sphere.com/forums/viewt ... 5#p1303859
There are much smaller drivers for 120v, the board of the link can work at 800v.

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ElectricGod
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Re: VESC for ebike ?

Post by ElectricGod » Wed Oct 18, 2017 10:42 am

marcos wrote:Yes, google isolated gate driver. HighHopes, Arlo, zombiess and me use those for higher voltage applications.

Building a higher voltage vesc is just a matter of using a higher voltage gate driver, like for example an isolated driver.

However, you can't simply replace the original gate driver of the vesc, that DRV chip has no easy way of increasing its operation voltage, so you need a custom layout to accomodate for a higher voltage gate driver. In this post you can see which part is the actual gate driver, and its easy to see the isolation barrier (slot on the pcb plus soldermask removed)
https://endless-sphere.com/forums/viewt ... 5#p1303859
There are much smaller drivers for 120v, the board of the link can work at 800v.
Thanks! I've been watching that thread for a while now. My hopes was for a simple set of mods that a "how to" thread could show. Then someone with some basic electronics skills could do the mods themselves and have a higher voltage and amperage controller. The VESC looked like a decent option in this regard. For most folks, 12S is fine for basic stuff, but if you want more and of course more wattage, then the VESC won't cut it. It's a great little controller, just not capable of handling the sorts of things I'm likely to do. If the controller can't run at 82 volts, that's a show stopper for me.

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Re: VESC for ebike ?

Post by marcos » Wed Oct 18, 2017 1:23 pm

ElectricGod wrote:My hopes was for a simple set of mods that a "how to" thread could show. Then someone with some basic electronics skills could do the mods themselves and have a higher voltage and amperage controller.
I'm afraid its not possible.

However if there is a proven 120v design in this forum I could take a look to see if we can make a powerpass out of it for the vesc controller.

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Re: VESC for ebike ?

Post by Rube » Thu Oct 19, 2017 4:42 am

marcos wrote:However if there is a proven 120v design in this forum I could take a look to see if we can make a powerpass out of it for the vesc controller.
Sounds like an opportunity/ challenge for the highly talented folk on the forum. Unfortunately, not in my skill set but I'd be super keen for a higher power VESC.

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ElectricGod
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Re: VESC for ebike ?

Post by ElectricGod » Thu Oct 19, 2017 7:56 pm

The Lebowski is another option, but you have to build the entire controller. I wanted to NOT build a controller. LOL

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