Open Source Electric Supercharger

[AN]

I was wondering why the spacer has the 5th hole ? couldnt help with air sealing the housing right ?

Since I am most interested in this motor , I wanted to you opinion on which one would be better the KDE or the Leopard. The leopard has 40k max rpm, can run 24v or 36v setup .... and external fans are available for these .

Motor:
http://www.leopardhobby.com/proviewe...=1&gid=65&pt=3

Fans:
http://www.kershawdesigns.com/Brushl...aleSystems.htm

[neutron256]

Originally Posted by AN

I was wondering why the spacer has the 5th hole ? couldnt help with air sealing the housing right ?

Since I am most interested in this motor , I wanted to you opinion on which one would be better the KDE or the Leopard. The leopard has 40k max rpm, can run 24v or 36v setup .... and external fans are available for these .

Motor:
http://www.leopardhobby.com/proviewe...=1&gid=65&pt=3

Fans:
http://www.kershawdesigns.com/Brushl...aleSystems.htm

The 5th hole is just a mistake in machining. We didn't include a tool offset. Rather then redo the whole piece I decided to leave it and fill it with JB weld.

Leopard has a sort of middle of he road reputation, but it might be a really good motor to go with he Seadoo supercharger. I'm also curious if the numbers the list are for continuous or peak output. If it's for peak output then how long can it safely run at peak.

It looks like that one can be found for about $130 so not a bad price at all.

[AN]

I have a few more questions regarding motor selection :

I understand that a lead acid battery shows as much as 14.8v while fully charged. Does that mean that for a 3 battery setup, I should get a motor rated at 3X 14.8v = 44.4v ? This means I have to get a slightly lower KV motor.

However, I believe as soon as the motor/esc starts drawing large amounts of current, the voltage instantly drops and even on a fully charged battery you would be luck to see an even 12v. This means that with a 44.4v motor with a lower KV value, I will never be able to provide 44.4v and will never see its peak RPM.

Another way of phrasing is, when a given motor is available in so many V(max)/KV settings, should I get 36v version for 3 battery bank or the 44.4v version ?

Also, I read on this a little bit but please correct my understanding if it is in-correct. the way a brush-less ESC works is, it passes on the the input voltage straight to the brush-less motor, but with pulses. The pulse width dictates the RPM the motor runs.

Are there any ESCs that only pass on a slightly lower Voltage pulses to the motor? i.e. I can have a 36v bank and the ESC runs the motor at 28v. That way, even when my battery voltage drops a little by the end of a WOT run, the ESC will be able to provide 28V to the motor and get full rpm/power out of it.

[rusty959]

Originally Posted by AN

I have a few more questions regarding motor selection :

I understand that a lead acid battery shows as much as 14.8v while fully charged. Does that mean that for a 3 battery setup, I should get a motor rated at 3X 14.8v = 44.4v ? This means I have to get a slightly lower KV motor.

However, I believe as soon as the motor/esc starts drawing large amounts of current, the voltage instantly drops and even on a fully charged battery you would be luck to see an even 12v. This means that with a 44.4v motor with a lower KV value, I will never be able to provide 44.4v and will never see its peak RPM.

Another way of phrasing is, when a given motor is available in so many V(max)/KV settings, should I get 36v version for 3 battery bank or the 44.4v version ?

Maybe. Maybe not. Slightly more voltage isn't going to insta-destroy a motor. Its all about duty cycle, and heat. If you can keep it cool and only overvolt it a little for short periods of time, you will probably be fine. Might shorten the life a little, but as far as I'm concerned shorter life is just part of pushing things past what they were "designed" to do. (thats what forced induction is in the first place)

Crappier motors will have more of a problem with it than well built motors. But you are correct, most batteries will be in the general area of 12v under some load. Usually the only reason they would be over 13v or so is if they are currently being charged, and as soon as you start drawing more power than the charger is supplying the voltage will drop to the battery resting voltage or below.

Also, I read on this a little bit but please correct my understanding if it is in-correct. the way a brush-less ESC works is, it passes on the the input voltage straight to the brush-less motor, but with pulses. The pulse width dictates the RPM the motor runs.

That is sort-of how it works. Rpm isn't tied directly to the pulse width, but it is related. Under identical loads it will be generally true. But under no load a short pulse width (throttle) can still give you a maxed out rpm.

Also, I believe many brushless ESC's work by having a pwm within a pwm. The 1st level of pwm is tied to the rotation of the motor (the pulse has to fire at the right time else the motor wouldn't spin) while the inner pulse width is what the typical 8khz or 16khz seen in esc spec sheets, and this controls the effective power level of the motor. I'm not 100% sure this is how the ESC's work, but I know of some similar hardware that works this way.

There will still be pulses on a brushless motor even at full throttle. This is because the ESC is directly controlling the coils. In a brushed motor ESC full throttle would just be a 100% duty cycle pulse width, with a lower

Are there any ESCs that only pass on a slightly lower Voltage pulses to the motor? i.e. I can have a 36v bank and the ESC runs the motor at 28v. That way, even when my battery voltage drops a little by the end of a WOT run, the ESC will be able to provide 28V to the motor and get full rpm/power out of it.

Maybe. It would be hard to control, as you would probably need something to dynamically adjust the max throttle relating to input battery voltage. I feel reasonably confident a 36v setup at 66% throttle (assuming linear throttle) wouldn't cause a problem with a 24v motor. But thats just my speculation on the way pwm works.

answers in the quote

[AN]

Originally Posted by rusty959

answers in the quote

Very informative ... thanks ...

So , can I conclude that I should be OK with a 36V motor with 3 battery setup? Since close to full throttle, the battery will have so much load that it wont be able to provide a voltage higher than that ..

[neutron256]

I guess I've been feeling inspired this week. I started working on my 24V battery/charger setup.

The base is 1/2" Delrin with 1/8" aluminum sides. I pulled one of the end caps off of the MinnKota charger, rerouted the wire from that side out the bottom, and bolted it down to the Delrin base.

The next step will be to figure out all the wiring and battery posts.




Edit: I weighed the battery/charger combo and it's 49.6 lbs. The stock battery is 29.6 so 20 additional pounds on the nose. Not too bad.

[AN]

Great packaging ... good job there.

How naked/insecure did the MinnKota feel after the end-cap removal ? or was it just an external bumper thingy ?

In the PDF manual of the MinnKota, there is a diagram of the internals and it doesn't look all that busy in there. I was wondering if we can open it up and move the internals to a more compact and size-suiting housing.

[neutron256]

Originally Posted by AN

Great packaging ... good job there.

How naked/insecure did the MinnKota feel after the end-cap removal ? or was it just an external bumper thingy ?

In the PDF manual of the MinnKota, there is a diagram of the internals and it doesn't look all that busy in there. I was wondering if we can open it up and move the internals to a more compact and size-suiting housing.

It's pretty solid inside. The electronics are connected to the housing so it can act as a heat sync.

[rusty959]

Originally Posted by AN

Very informative ... thanks ...

So , can I conclude that I should be OK with a 36V motor with 3 battery setup? Since close to full throttle, the battery will have so much load that it wont be able to provide a voltage higher than that ..

Probably. I can't say for sure for the same reasons I can't promise you a 36v motor will work fine running from a ideal 36v power supply.

But, I'd be willing to try it on my own setup.
If you do it, just check the voltage under load to see what it does under load.

[AN]

Originally Posted by rusty959

Probably. I can't say for sure for the same reasons I can't promise you a 36v motor will work fine running from a ideal 36v power supply.

But, I'd be willing to try it on my own setup.
If you do it, just check the voltage under load to see what it does under load.

Kool ... thanks.

[AN]

This should be helpful in getting the rpm reading from a regular 12v alternator positive lead.

http://www.bestbuy.com/site/directed...uId=1304823197

I guess it can be fed to Arduino.

I was thinking that a robust Arduino setup with all the compressor speed control logic can be developed. Not only that, the data logging capabilities can be built into the Arduino as well. It can log motor rpm,engine rpm, Throttle %, boost , Air intake temperature, battery voltage (each battery and whole bank) ESC duty cycle, charge rate , discharge rate .. pretty much everything. Since these are new waters, such logging will be of immense help in understanding and eliminating bottlenecks.

[AN]

@neutron256 , could I please trouble you to measure the dimensions of the MinnKota MK 03 DC .. the 36v version. Specially with the bumpers off from both sides? .
If I remove the bumpers. Can I seal it closed with some simple aluminum or plastic plates with appropriate holes wor cables and screws ? How much length will I save this way ?

Thanks.

[neutron256]

Originally Posted by AN

@neutron256 , could I please trouble you to measure the dimensions of the MinnKota MK 03 DC .. the 36v version. Specially with the bumpers off from both sides? .
If I remove the bumpers. Can I seal it closed with some simple aluminum or plastic plates with appropriate holes wor cables and screws ? How much length will I save this way ?

Thanks.

Without the end-caps it's H 3.25" x W 6.875" x L 11.875".

The end caps add about H 0.125 x W 0.375" x L 0.75".

Just replacing the end caps isn't going to save much space because part of the cap is a recessed space where the cables come out. Depending in how you want to mount it and run the cables a lot of space can be saved by drilling a hole on the underside and rerouting them there like I did in one end.



I just used the end cap itself as a drill templet when drilling the holes in my baseplate.

[AN]

Thanks a lot. Any progress on powering up your compressor. Have you run the motor at some rpm to see if the whole drive is balanced ?