Electric Surf Board

Boats, Jet Skis, Kayaks etc., including hovercrafts
ZR38   1 µW

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Re: Electric Surf Board

Post by ZR38 » Apr 17 2018 10:56am

Frizzo wrote:
Apr 17 2018 8:25am
Would be interesting to build a flumen. So you actually could measure the impeller effency, the torque, amps, rpm and also optimize the nozzle and stator geometry.

have a look at this:

http://efoil.builders/t/home-made-flume/794
Hello Frizzo,

Thanks for your link!
When I have chosen my engine, I will rethink to this project :)

chris_kline   10 W

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Re: Electric Surf Board

Post by chris_kline » May 03 2018 5:05am

quick update

my mgm controller failed. they will not repair or replace it, and suggested i buy a new one.

thats pretty bad customer service in my opinion.

looking at alternatives, incl self developing a controller.

Animalector   10 kW

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Re: Electric Surf Board

Post by Animalector » May 03 2018 5:10am

I don't understand this. I thought controllers had current limiting. Therefore really they should never fail unless there is a manufacturing defect or reverse polarity or something.

Anyway, good luck.

Andy

chris_kline   10 W

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Re: Electric Surf Board

Post by chris_kline » May 03 2018 5:26am

that was my thoughts when i sent the esc back for diagnosis.

nevertheless they will not honour their warranty in this case.

srn   1 W

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Re: Electric Surf Board

Post by srn » May 03 2018 8:03am

what did you do ?

the controller should also shutdown in case of too high temp ?
My MGM controller will arrive end of next week.

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parabellum   10 MW

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Re: Electric Surf Board

Post by parabellum » May 03 2018 8:22am

chris_kline wrote:
May 03 2018 5:05am
my mgm controller failed. they will not repair or replace it, and suggested i buy a new one.
If you did nothing evidently wrong with the controller, like hammering a nail in it, I would open a case in consumer protection institution of your location. This controller is everything but cheap and they should back their claims by law (in civilized society).

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fabianpusch   10 mW

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Re: Electric Surf Board

Post by fabianpusch » May 05 2018 2:20am

Hey Chris
Can you give me some details of your installation.
Especially the lenghts of cables, cross sections, connections, placement of the additional cappacitors.
I had the same failure twice. My first thoughts had been also the same:
Should shut down automatically
internal safety algorithms
Couldn't bei damage without mechanical impact
...
But last but not least, high internal currents habe killed my MGM twice. In the end it is now working very stable.
But it was a very expensive and hard way...

Would like to help you

Bye Fabian

P.S. self developing should be the best in the end 😃

chris_kline   10 W

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Re: Electric Surf Board

Post by chris_kline » May 05 2018 2:25pm

fabianpusch wrote:
May 05 2018 2:20am
Hey Chris
Can you give me some details of your installation.
Especially the lenghts of cables, cross sections, connections, placement of the additional cappacitors.
I had the same failure twice. My first thoughts had been also the same:
Should shut down automatically
internal safety algorithms
Couldn't bei damage without mechanical impact
...
But last but not least, high internal currents habe killed my MGM twice. In the end it is now working very stable.
But it was a very expensive and hard way...

Would like to help you

Bye Fabian

P.S. self developing should be the best in the end 😃
thanks for the info Fabian

although its not really applicable for my case.

looking forward to hearing what IC your running on your custom esc when you get a minute.

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Re: Electric Surf Board

Post by srn » May 05 2018 3:00pm

Chris, do you know what went wrong?

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Re: Electric Surf Board

Post by fabianpusch » Jun 02 2018 8:20am

Hello @all

I am again in Corsica and testing the board.
This year everything is running stable - after this morning run I have some swelled capacitors on the ESC.
What do you think stop or go on?
Two years ago I have killed the ESC :roll:

Greetings from Corse
Fabian

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Re: Electric Surf Board

Post by srn » Jun 03 2018 3:59am

Is it the MGM ESC ?
I would contact the supplier directly. Maybe now they would just change the capacitors while when you go on, you destroy more..

fabianpusch   10 mW

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Re: Electric Surf Board

Post by fabianpusch » Jun 03 2018 1:38pm

Hi
yes it is the MGM ESC. I am a little sad about the situation. We have still 7 days left and I am not sure if I can do an additional ride.
At home there are some capacitors - f***...
I have already contacted the supplier via Email.
But it is weekend - so no response ;-)
But in the end I do agree with you...it will destroy more.

Have a nice evening and a good start into the new week.

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Re: Electric Surf Board

Post by srn » Jun 04 2018 1:13am

Hello Fabian,
did you read the log of the ESC ? Was ist long time full load? Too hot? High peak load ?

fabianpusch   10 mW

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Re: Electric Surf Board

Post by fabianpusch » Jun 05 2018 1:33am

Hi & good morning

Longtime full load is about 240 Amps for 5 seconds.
Not too much - I think the problem will be the cable lengths from the battery to the controller.
There are indication high internal peak currents (about 600Amps) and this is too much for the caps.
Maximum temperature was about 105°C of the ESC, I think the problem ist that I have used some speeds of 70% - and that is not too good fort the FETs.

At the moment I am waiting for an answer of MGM if I can go on or have to stop testing...

Bye Fabian

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madin88   100 MW

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Re: Electric Surf Board

Post by madin88 » Jun 05 2018 10:59am

fabianpusch wrote:
Jun 05 2018 1:33am
Hi & good morning

Longtime full load is about 240 Amps for 5 seconds.
Not too much - I think the problem will be the cable lengths from the battery to the controller.
There are indication high internal peak currents (about 600Amps) and this is too much for the caps.
Install the controller as close as possible to the battery and twist the wires. This will reduce the inductance and lower the stress on the capacitors (less voltage and current ripple). Long motor wires are not a problem, more the opposite, but long battery wires are!
Maximum temperature was about 105°C of the ESC, I think the problem ist that I have used some speeds of 70% - and that is not too good fort the FETs.
At the moment I am waiting for an answer of MGM if I can go on or have to stop testing...
105°C is quite high for a controller and the caps don't like this as well.
Speeds of 70% should be no problem if it has the so called "active freewheeling".
Only the very first or cheapest BLDC controllers don't have this.

From the specs the MGM controllers are not impressive.
They have no FOC control or other new stuff which you would expect in view of the high price.

Kontronik Kosmik ESCs for instance have FOC control with current measurement on each phase and outstanding efficiency, but unfortunately the largest model can only do 14s max and 200A. Otherwise i would suggest to try out a kosmik.
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srn   1 W

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Re: Electric Surf Board

Post by srn » Jun 05 2018 4:35pm

madin88 wrote:
Jun 05 2018 10:59am
fabianpusch wrote:
Jun 05 2018 1:33am
Hi & good morning

Longtime full load is about 240 Amps for 5 seconds.
Not too much - I think the problem will be the cable lengths from the battery to the controller.
There are indication high internal peak currents (about 600Amps) and this is too much for the caps.
Install the controller as close as possible to the battery and twist the wires. This will reduce the inductance and lower the stress on the capacitors (less voltage and current ripple). Long motor wires are not a problem, more the opposite, but long battery wires are!
I dont understand the issue with cable length. I understand that long cables have high resistance, but how about the current peaks at long cables from battery to controller ? Can someone explain this ? And is it really better to have longer cable from controller to motor than from battery to ESC ?

Thank you for further explanation and best regards,

Soeren

fabianpusch   10 mW

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Re: Electric Surf Board

Post by fabianpusch » Jun 06 2018 12:40am

Yes that is right...short cables from battery to controller.
It is very complicated to explain this in english for me. But look for induzierte Spannungsspitzen, lange Batteriekabel vs. lange Motorkabel...
Also very interesting is the SLS Sinus Leistungssteller.
And in the end, the Kosmik would be a nice one.
Yes temperature was high, but in the end the ESC and the caps should handle this.
Freewheeling is always on

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madin88   100 MW

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Re: Electric Surf Board

Post by madin88 » Jun 06 2018 2:21am

srn wrote:
Jun 05 2018 4:35pm

I dont understand the issue with cable length. I understand that long cables have high resistance, but how about the current peaks at long cables from battery to controller ? Can someone explain this ? And is it really better to have longer cable from controller to motor than from battery to ESC ?

Thank you for further explanation and best regards,

Soeren
Yes, the longer the battery wires the higher the resistance, but thats not the problem. The problem is the inductance.
The Mosfet's can be seen as a switch that turns on and off very quick.
Lets say one bank of FET's is in on stage and 200A are flowing into the motor at 60V.
At the moment when this bank of FET's turns off (and another bank turns on eg), there will occur voltage spikes which can be much higher as the battery voltage itself.
The higher the inductance of the battery wires incl. the bus bars in the controller, and the higher the motor current (which will be always abruptly interrupted by the FET's), the higher the voltage spikes will be.

The caps are now there to smooth out those spikes keeping them below a level which would be dangerous for other electronic components.
If you now have very long battery wires, the caps have lots of work (current ripple) and they can get hot and swell.
If the caps (partial)fail, the voltage spikes will kill the FET's.

Longer motor wires are absolutley no problem assuming the cross section is large enough so they can handle the amps :wink:
Twisting the battery wires or put them as close as possible beside each other helps to reduce the inductance in the supply line.
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methods   10 GW

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Re: Electric Surf Board

Post by methods » Jun 11 2018 1:50pm

Nice simple answer to a complex question.

Much more useful than a complex answer to a simple question.
.
.
Complex vs Polar.png
Complex vs Polar.png (48.46 KiB) Viewed 979 times
When we learned it in trade school it started out as cranking out conversions between polar and complex notation on fairly complicated LRC circuits. All those omegas and Zsubs scare most people off.

In trying to teach a 5yo (by starting off teaching my CPA) I focus first on believing/understanding the most basic Boost Circuit, then by completely understanding

T = 0 and
T = Steady State

First for caps and then for inductors

At some point it clicks for many people, but to expect a higher order concept to click on top of minimal mathematical foundation begs for faith instead of confidence... and I dont support faith based conclusions... so I dig deeper and deeper back into simple proofs backed by experiment.

I would ask - what is the ratio of the inductance of the System Configuration A vs the inductance of system configuration B, by isolating the motor and measuring, isolating the wiring and measuring. Then we can prove it without any trust involved.

-methods
Increasing battery voltage and controller current limit will result in a non linear experience

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methods   10 GW

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Re: Electric Surf Board

Post by methods » Jun 11 2018 2:01pm

ahhh... lost my response.
the punch line:

If you stack out capacitance at the load input it will eliminate the root cause of the inrush currents flowing thru the parasitic inductance in the long cabling by - effectively filtering the high frequency content and leaving only nice slow content running down your long cable.

The byproduct of this seemingly perfect fix (which will allow you to run a mile of DC power cable) is that Inrush at T=0 will become nasty - so you have to deal with that by adding additional R

(where did my damn first response go... arg...)

So as the poster said - you can navigate any issues you find by:

Adding L
Removing L

Adding C
Removing C

Adding R
Removing R

Or using active circuitry that changes thru time.

There are no works or does not work - only different ways to make what you want work.
(and lots of rules of thumb)

-methods
Increasing battery voltage and controller current limit will result in a non linear experience

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bigbore   1 kW

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Re: Electric Surf Board

Post by bigbore » Jun 27 2018 12:08pm

madin88 wrote:
Jun 05 2018 10:59am
fabianpusch wrote:
Jun 05 2018 1:33am
Hi & good morning

Longtime full load is about 240 Amps for 5 seconds.
Not too much - I think the problem will be the cable lengths from the battery to the controller.
There are indication high internal peak currents (about 600Amps) and this is too much for the caps.
Install the controller as close as possible to the battery and twist the wires. This will reduce the inductance and lower the stress on the capacitors (less voltage and current ripple). Long motor wires are not a problem, more the opposite, but long battery wires are!
Maximum temperature was about 105°C of the ESC, I think the problem ist that I have used some speeds of 70% - and that is not too good fort the FETs.
At the moment I am waiting for an answer of MGM if I can go on or have to stop testing...
105°C is quite high for a controller and the caps don't like this as well.
Speeds of 70% should be no problem if it has the so called "active freewheeling".
Only the very first or cheapest BLDC controllers don't have this.

From the specs the MGM controllers are not impressive.
They have no FOC control or other new stuff which you would expect in view of the high price.

Kontronik Kosmik ESCs for instance have FOC control with current measurement on each phase and outstanding efficiency, but unfortunately the largest model can only do 14s max and 200A. Otherwise i would suggest to try out a kosmik.
What about these Flier ESCs?
This one seems crazy to me
http://www.fliermodel.com/en/prc-show.asp?id=684
22S and 800A are still 31kW if we divide the specs in half

Or this one
https://www.ebay.es/itm/400A-Boat-ESC-W ... SwzJhZ0Rgt
Is still 11kW with the same specs halved

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parabellum   10 MW

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Re: Electric Surf Board

Post by parabellum » Jun 27 2018 11:09pm

bigbore wrote:
Jun 27 2018 12:08pm
What about these Flier ESCs?
This one seems crazy to me
http://www.fliermodel.com/en/prc-show.asp?id=684
22S and 800A are still 31kW if we divide the specs in half

Or this one
https://www.ebay.es/itm/400A-Boat-ESC-W ... SwzJhZ0Rgt
Is still 11kW with the same specs halved
I think, Luke tried 22s 400A ESC from alien and it could hold 50A and 100A for few seconds before plasma, spinning propeller and it was called an outstanding performance for ESC at the end.
Maybe better divide by 8 ?

EDIT:
P.S. Finally found the tread, it was "24s 420A" ESC, here is the result of this long story: viewtopic.php?f=2&t=44897&start=650#p1236920

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Re: Electric Surf Board

Post by srn » Jul 23 2018 6:45am

Hello,

my board is finally running (atm only dry for testing).
Now I am thinking about cooling. I have the watercooled Torqstar 3 and the watercooled MGM 40063.

How do you get cool water into your Motor and ESC ? Do you use external water or maybe a closed internal water circle with pump ?

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bigbore   1 kW

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Re: Electric Surf Board

Post by bigbore » Jul 23 2018 10:03am

The water is generally drawn through the outlet nozzle with a radial outlet

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Re: Electric Surf Board

Post by bigbore » Jul 23 2018 10:04am

Ops!
Last edited by bigbore on Jul 23 2018 10:07am, edited 1 time in total.

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