VESC 6 voltage/design limits?

General topics and discussions about the VESC and its development.
MatthiasU
Posts: 2
Joined: 30 May 2017, 09:09

VESC 6 voltage/design limits?

Postby MatthiasU » 30 May 2017, 09:31

What's the maximum number of cells you can safely use with the VESC? (Specifically Vesc 6)

My current Ebike has 14s; I want to replace the controller because it only has a binary brake/regen input which doesn't work at low speed; plus I want to add features like theft protection (electronic wheel lock, not just shorting the motor).

If 14s is too much for safe regen braking on a stock Vesc, what's the limiting component?

JTAG
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Joined: 05 Apr 2016, 13:08
Location: Leeuwarden

Re: VESC 6 voltage/design limits?

Postby JTAG » 30 May 2017, 10:10

12S is currently the advised max. What prevent us from designing higher voltage VESC's easily is the DRV that is limited to 60V. In the future (in about 3 months? isch) when the VESC framework is a bit more hardware independent we might be able to design a higher voltage.

MatthiasU
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Joined: 30 May 2017, 09:09

Re: VESC 6 voltage/design limits?

Postby MatthiasU » 31 May 2017, 07:43

Thank you. I should be able to support that effort, either financially or by doing some actual work (both coding and hardware).

lizardmech
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Joined: 19 Jan 2016, 10:54
Location: Australia

Re: VESC 6 voltage/design limits?

Postby lizardmech » 31 May 2017, 09:16

I have a custom one running up to 80V. The two biggest issues are always current sense and a suitable voltage converter. Hall based current sense are slow while high end isolated solutions use delta sigma modulators or differential analogue outputs. At the moment I use LM5161 buck converters which work well and support up to 100V. I haven't been able to find a nice compact solution that has a wide input range such as 30v-200v, all the ICs for small chargers and USB adapters usually have 70v UVLO and only support flyback. Anyone know of an IC with a very wide input range that can deliver 1A current and supports buck or flybuck designs?

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TheFallen
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Re: VESC 6 voltage/design limits?

Postby TheFallen » 05 Jun 2017, 13:09

Problem with wide input ranges is minimum 'off' times. Converting 5W (5V @ 1A) at 30V vs 200V requires 15 times longer 'on' time so it'll be really inefficient at anything other than the design voltage.

rew
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Re: VESC 6 voltage/design limits?

Postby rew » 06 Jun 2017, 06:12

Why 15 times and not 8 times?

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TheFallen
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Re: VESC 6 voltage/design limits?

Postby TheFallen » 06 Jun 2017, 06:50

Yeh, sorry, closer to 8 than 15, but either way the massive difference in input voltages kinda kills efficiency.

lizardmech
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Joined: 19 Jan 2016, 10:54
Location: Australia

Re: VESC 6 voltage/design limits?

Postby lizardmech » 06 Jun 2017, 08:03

Efficiency doesn't bother me that much, lower voltages would mainly be for testing, having 80V minimum voltage is just annoying if you trying to configure it or testing various settings. 80V+ DC power supplies aren't common even if you have a 120v battery pack in an ebike you probably don't want to have to remove it every time you want to run the controller on a desk.

Jackl
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Joined: 12 Mar 2017, 22:23

Re: VESC 6 voltage/design limits?

Postby Jackl » 19 Jun 2017, 19:27

Why not hook up a bench powersupply to supply the low voltage rails during tests/programming on the desk?

Requires a spare power supply of course, but there are quite cheap ones on the market...

TilmanBaumann
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Joined: 15 Feb 2018, 16:50
Location: Germany

Re: VESC 6 voltage/design limits?

Postby TilmanBaumann » 16 Feb 2018, 11:43

Hey lizardmech, you mention modifications to allow higher voltage ceiling.
Can you share some details? I'm not afraid to mod my controller. :D
If you got a working solution...

I have heard about that possibility a few times now. But I could never find anything concrete.

Is what you are doing to just putting a DC-DC in front of the DRV chip? I kind of assumed it needs to run rail to tail on the power bus.
Sorry for asking stupid questions. I always try to understand things, even if I'm not at all prepared for the topic.

I just want to gauge my options. Short term and long term. (I see the High Power VESC thread and I'm very interested in the outcome. It seems to be quite a beast. More than what I need now. But I already have ideas...)
I'm really stuck between a rock and a hard place. I'm super excited about VESC and the possibilities for my scooter. (Xiaomi m365)
It's going to run on stock 10S pack in the beginning. But that was intended only for initial tests.
Of course because I'm impatient I ordered the controller already. :)

From my experience with the thing I can tell it would benefit greatly from some 'tuning'. The motor seems to cope with 16s quite fine actually.
It would certainly be more fun and justify me ripping out the nice controller of the scooter. (It's really nice hardware actually.)

Things I'm looking into right now is to add a very aggressive high current 60V crowbar circuit. But Honestly if I can just frankenstein my controller a bit I would prefer that greatly.
I would love to go to 16S.


Truth is, I have more bigger projects in the pipeline. Where 60V is for sure a limiting factor.


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