[NSRCA-discussion] E Stuff

Mon Jan 23 07:08:47 AKST 2006

Hi Keith,
Yes, Yes, and Yes but it ain't that simple ... and I won't comment on the caffeine! 
It is easier to get higher efficiencies with higher voltages and lower currents.
All the voltage drops across the resistances in the system, from the switching transistors to the coils in the motor/generators are a smaller portion of the total voltage available.
Of course, nothing is that simple, and the no-load currents of high voltage motors might actually be a higher percentage of the actual running current.
When calculating the mechanical power available from a motor, the no-load current (I-zero) is subtracted from the current and the result is multiplied by the drive voltage minus the voltage lost across the winding resistance plus the wiring and ESC resistances. 
For a couple of years now, the buzz in the automotive worls was 42V ( 3 normal car batteries in series) but hybrid and future power trains will probably be at or over 100VDC.
That works out to just under 10 Amps per horsepower, after conversion losses.
Happy Monday friends!
    Dean

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Keith Hoard
Sent: Monday, January 23, 2006 10:46 AM
To: 'NSRCA Mailing List'
Subject: Re: [NSRCA-discussion] E Stuff

Aren't automobiles supposed to be going to higher voltage system due to all of the electrical components people are adding to cars?  

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Wouldn't this also work for electric motors to reduce the amount of amps. . . same number of cells, just run them all in series and reduce the current?

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Isn't a Watt is a Watt; whether it is 100amps at 14 volts, or 100volts at 14 amps?

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Maybe I should cut down the caffeine this early in the morning. . . .

Keith L. Hoard

Collierville, TN

khoard at midsouth.rr.com

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From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Dean Pappas
Sent: Monday, January 23, 2006 9:30 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] E Stuff

Hi Stu,

They'll quit at 10S, or 42VDC. That's the voltage above which electrical codes (both local and  international ) say you need to treat wiring as if it was "mains" wiring, with insulation and creepage distance requirements. It's not a big deal, really. You have a house full of wiring, including the power supply of everything that plugs into a wall, that meets the requirements, without having to do anything fancy. LiPoly is easier to construct for high current discharge. With Li-iion, it is easier to get high energy density, at the expense of current delivery. Some of the early 2S lithium-ion setups for flight packs were actually dropping down below the regulator voltage setpoint under peak loads. Don Szczur's Dad diagnosed that one, at least in this part of the country. It's gotten better since then.

later,

Dean

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Stuart Chale
Sent: Monday, January 23, 2006 8:08 AM
To: 'NSRCA Mailing List'
Subject: Re: [NSRCA-discussion] E Stuff

I just read where Dewalt will also be offering Li-ion powered tools.  I think they are running at 32 volts.  Didn't we start with 9.6?  If this keeps going you will be able to electrocute yourself with these tools soon enough :-)

Is there a significant weight savings with Li-poly compared to Li-ion?

Stuart

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From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Dean Pappas
Sent: Sunday, January 22, 2006 5:59 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] E Stuff

Hi Stu,

As it turns out, Lithium Ion cells are just as touchy about overvoltage, and the like. About 75 cell phones a year explode. A buddy of mine used to be the strategic supply-line guy for Motorola phones. His contacts in the engineering group there told me that Mot puts overvoltage protection, internal cell pressure detection, over-current detection, and undervoltage charge prevention protection in every pack/phone. That is what they determined to be necessary to make litium ions acceptably safe. After all that, you hear about problems, ususally with non OEM cells. Also since all cell phones run with 1S packs, there are no balance issues.

I can see Milwaukee pack powered Sport stuff in our future, though! I'm guessing they are 7S or 8S, based on the 28V marking on the box.

later,

Dean P.

-----Original Message----- 
From: nsrca-discussion-bounces at lists.nsrca.org on behalf of Stuart Chale 
Sent: Sat 1/21/2006 5:40 PM 
To: 'NSRCA Mailing List' 
Cc: 
Subject: Re: [NSRCA-discussion] E Stuff

We already have two power tool companies with Li+ ion power packs.  As I understand it Li+poly are lighter per amount of energy but it seems more dangerous with respect to charging.  (any battery guru's are welcome to better explain some of the differences, I would be more than interested).  

I would suspect that saving a few ounces on a battery pack for a hand tool if not as safe would not be in the toolmakers best interest.  

Anyone know of other industries that would use LI+Poly and require the discharging abilities that we do?

Also on a quick google search lithium fiber batteries popped up.  Maybe there is something even more promising on the horizon?

Personally I would like to see the next generation of batteries before buying several sets.

Stuart

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From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of vicenterc at comcast.net
Sent: Saturday, January 21, 2006 5:12 PM
To: NSRCA Mailing List; NSRCA Mailing List
Cc: Jerry Stebbins
Subject: Re: [NSRCA-discussion] E Stuff

Jerry,

Today we got two e-mails.  One with 30 cycles the other over 170.  At the Nats. a very well know pilot told me 60 average.  As we can see, it is all over the map.  I would like to go electric and the advantages of electric power in pattern are evident.  However, I am not ready until battery companies give us some minimum expectation in regard battery life.  Clearly time will tell.  I believe that when we start to see the power tools manufacturers installing LiPo in their equipment we would be able to expect a decent life of this packs under high current draw conditions.

Vicente Bortone  

-------------- Original message -------------- 
From: "Jerry Stebbins" <JAStebbins at worldnet.att.net> 

Vicente, I hope that is "tongue in cheek", because any battery manufacturer to warranty to that, or almost any extent would be killed by his/her lawyers. They would have so many "exceptions" that they would "never be at fault". 

If that is anyone's criteria it wll be a long time before they switch.

Jerry

----- Original Message ----- 

From: vicenterc at comcast.net 

To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  ; NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  

Sent: Saturday, January 21, 2006 2:51 PM

Subject: Re: [NSRCA-discussion] E Stuff

Scott,

I am waiting for my second Abbra.  If Tanic gives me a written warranty that the battery is going to last around 250 cycles of Master rounds I will make the switch.  Is that possible?  I will follow charging and break in instructions.

Thanks 

Vicente Bortone  

-------------- Original message -------------- 
From: "Scott Anderson" < scott at rcfoamy.com> 

Vicente,

You also have to look at replacing bearing, changing batteries in the support equipment (glow driver/ electric starter) and servos after a time from vibration, this will increase your glow cost per flight .. Dan Landis and I are using Tanic packs and he flies FAI and has a set of sticks ( Battery) with over 170 flight and you can't tell the diffrence from that pack and on with less time on it.. I have just started using Tanic and the results are very good, Just follow there "breakin" for the packs.

I made the jump to electric in 05 and after the first flight I was hooked and sold all glow fuel and glow planes.. If you look around you still make the conversion without  breaking the bank.

Just my 2 cents

Scott Anderson

D3 AVP nsrca 529

Team Tanicpacks.com

Team PMA

----- Original Message ----- 

From: vicenterc at comcast.net 

To: NSRCA Mailing  <mailto:nsrca-discussion at lists.nsrca.org> List ; Discussion List,  <mailto:nsrca-discussion at lists.nsrca.org> NSRCA 

Sent: Saturday, January 21, 2006 1:35 PM

Subject: Re: [NSRCA-discussion] E Stuff

Unfurtunetely, I have to estimate the cost.  I did an estimate how much is the cost to run my 2c motor per flight.  At $15/gallon using 14 oz of fuel per fly the cost is $1.75 per flight.  This number is correct since I usually flight between 200-300 flights per year.  

The question is: what is the life of the batteries?  Base of the feedback I got at the Nats. the life flying F3A is around 60 flights.  Therefore, if I am correct the cost per fly is $11.  Assuming that I do 250 flights per year the cost of electric is $2,750/yr.  The equivalent cost of glow (2C) is $440/year.  With two kids in college my option is clear.  I am assuming that the cost of batteries is $640 but not sure now.  

Probably I am wrong in these numbers.  Clearly the cost of the batteries has to come down or the cycles have to go up to around 400 cycles to get equivalent cost to glow.  

Any information on this regard is welcome,

Vicente Bortone

-------------- Original message -------------- 
From: "Earl Haury" <ehaury at houston.rr.com> 

The E info on the list has been scant. Probably some are reluctant to hype / criticize products because of their involvement with suppliers. Some of us are just blindly exploring options, gathering data / information, and forming opinions without experience to back up our conclusions. Certainly information offered by those with experience is very welcome and appreciated. Those who are qualified experts in the various fields that can correct / clarify information gained through the school of hard knocks are not only welcome, but I suspect somewhat obligated to protect the rest of us. As this entire topic expands there will be conflicting opinions which in themselves provide info - that's what this list is for and no one should take offense that some prefer other views.

After teasing the E guys at the Nats I recognized that the E powered airplanes flew better (I'll admit to being obstinate - but not totally dumb). There were also differences that seemed related more to E equipment choices than differences in pilot skills. The info published by Jason, Frack, Adam, Chad, and others (in RCU forums) provided an insight to the various equipment choices (and passionate defense of same in some cases). Interestingly, a lot of the discussions revolve around equipment type rather than the effect on flight characteristics.

So - I set about trying to determine if E flies better and why. So far the answer is yes and I'm not sure. While differences in dynamics can be identified, it's hard to quantify the effects. For example, the lighter / slower rotating E prop generates a lower gyroscopic precession force during looping maneuvers than glow - this also suggests the lower rotating mass of a geared motor might be better. The lighter motor (compared to glow engine) up front can result in a lower pitch moment of inertia if the tail is light enough to allow the battery mass to be close to the CG. Airplane smoothness in rough air is markedly better with E. (I did most of my comparisons with twin Partners - one glow and one E - at about the same flight weight.)  This may be an effect of the large diameter prop or lack of vibration effect on the servos. As others have noted, thrust application is very good with E as the slower prop is efficient and the mo! ! ! tor is instantly responsive and very linear. E can be flown slower than or as fast as glow, the airplane is more stable with E when slow  - again probably the large prop effect. Overall, it's easier to fly well with E but E won't fix sloppy flying.

As with most things in model aviation - there are learning curves. Some suppliers are better than others, some equipment is better than others, some choices will be revisited after experience is gained. The hardest thing to get used to is the metrification of cost - kilo dollars. Not that E is that much more expensive than glow - just that very little from glow is useable with E. That means one must acquire motors, controllers, batteries, chargers, power supplies, meters, connectors, wire, props, etc. pretty much from scratch.

If there's interest in this becoming a thread I'll discuss the reasons for some of my choices of equipment and the data I've generated / will generate with the full understanding that I might be operating under false assumptions and some of this stuff will change - I'm still learning.

Earl

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