[NSRCA-discussion] Going Electric - Battery Questions

Fri Dec 7 19:51:57 AKST 2012

I've seen guys spend $100 or more to get rid of an ounce on their planes.
I'm just sayin..

Verne

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of PhilS.
Sent: Friday, December 07, 2012 9:09 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Going Electric - Battery Questions

OK, so if my calculations are correct, a 10% difference in nitro amounts to
a 0.14% difference in weight.  In a 20-oz tank of fuel, I can't think that
will make a noticeable difference in overall aircraft weight or balance.
So, doing all thehigher math -- actually, since the fuel is going to fly, we
must get into computational fluid dynamics!  ;-{) -- I calculate that 20 oz
of 25% fuel weighs 0.96 oz more than a 20oz tank of 14% nitro.  If my calcs
are correct, that is hardly anything to write home about!!!

Phil Spelt, KCRC President
AMA 1294 Scientific Leader Member
SPA 177 Board Member
(865)435-1476v, (865)604-0541c

On 12/7/2012 8:17 PM, Dave Burton wrote: 

Actually it does! nitro is approx 9.4 lbs per gal,  methanol is approx 6.7
lbs per gal.

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of PhilS.
Sent: Friday, December 07, 2012 7:45 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Going Electric - Battery Questions

Sorry, Verne, more Nitro doesn't cost us more weight.  ;-{)

Phil Spelt, KCRC President
AMA 1294 Scientific Leader Member
SPA 177 Board Member
(865)435-1476v, (865)604-0541c

On 12/7/2012 7:15 PM, Verne Koester wrote: 

Larry, 20C is 10% nitro, 40C is 40% nitro. Like nitro, more C is more weight
as well in most cases. 

I fly Masters with 20C batteries and have my throttle governed back to make
it easier to manage the excess power. I started last season with 25C
batteries and had to govern it back even more. Using 40C batteries would be
like sticking a YS 170 on a 110-size plane while probably putting you over
the weight limit.

Verne

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Larry Diamond
Sent: Friday, December 07, 2012 6:18 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Going Electric - Battery Questions

Interesting point... I don't understand how changing from 20C to 40C pack
makes a difference using the same Motor and ESC combo. If it's battery heat,
my electronics background would tell me the pack is probably being dicharged
too deep. Not good for the life of a battery.

I suspect the result of not changing the Motor/ESC and only changing the
battery will reult in a shorter battery life; and, over loading the power
plant which will probably result in damaging the ESC and/or the Motor.

I could be wrong, cause I really have no experience with electric power set
ups in planes. I just don't understand the logic going from 20C to 40C and
the result being "too hot for intermediate".

It wouldn't surprise me to see Masters or FAI having a higher power set up,
like 3,500 to 4,000+ watts. Then depending on the max current draw,  40C may
make sense.

My set up will be about 2,700 to 3,000 watts based on specs... It may not be
sufficient for Masters or FAI.

Perhaps this will turn out to be a good constructive discussion for a number
of people like me, but I'm curious as to other opinions who have practicle
knowledge.

Larry Diamond

From: Patrick Harris <harris7148 at gmail.com>
To: General pattern discussion <nsrca-discussion at lists.nsrca.org> 
Sent: Friday, December 7, 2012 2:02 PM
Subject: Re: [NSRCA-discussion] Going Electric - Battery Questions

Larry,

You have received all good advice. One thing to keep in mind, is you are not
going to be able to fly two full sequences with pretty much any setup. With
the Himax in a Monolog flying Intermediate, 20C's are going to be perfect.
With 20C's and good throttle management you are going to be able to fly the
full Intermediate and maybe four or five more maneuvers. If you go up to
40C, you will find the Himax way to hot for Intermediate, and you won't add
that much flying time. 

Another thing about the Himax is it really needs an aggressive throttle
curve on the bottom. If you just fly it out of the box it will have zip for
low end and nuts for high end all at about mid throttle. On the low end, you
will just keep pushing and pushing and nothing seems to happen until you hit
mid throttle and it will go nuts. The best throttle curve on my Himax looks
like a snake. It ramps up really fast on the low end, tappers off at mid
throttle and then heads back up on the high end, but you need to work it out
for your set up. Trust me, spending a good amount of time getting this right
is going to pay big dividends. If you don't, your uplines are going  to be
way too hot.

Hey Larry,

As everyone is telling you, the BIG difference between what you're proposing
and what you're accustomed to with Glg to below is that you'll fly 90% of
your sequence at half throttle.  Not figuratively half throttle... but
literally half, or below.  Even a vertical upline does not need full motor
on these setups.   Flying intermediate even less so.   Also, at full
throttle you'll likely only pull about 75amps, so even 15C batteries would
get the job done, but I would stick with 20 and higher.

Mark Atwood
Paragon Consulting, Inc.  |  President
5885 Landerbrook Drive Suite 130, Cleveland Ohio, 44124
Phone: 440.684.3101 x102  |  Fax: 440.684.3102
mark.atwood at paragon-inc.com<mailto:mark.atwood at paragon-inc.com>  |
http://www.paragon-inc.com/<http://www.paragon-inc.com/>

On Dec 7, 2012, at 1:37 PM, Larry Diamond wrote:

OK, play nice... Never dealt with electrics before... I could be way off
base, but here is a stab at it...

Is my math flawed?

Motor - Himax 6330-210 F3A Motor (210KV)
ESC - Phoenix Ice 80HV - New V2 Version
Battery 10s - 37VDC

Plane - 2M Monolog

Max power range is about ~2,700 to ~3,000 watts with this set up...

Calculated Battery Discharge Rate = 80Amps (ESC rating) divided by 3,500mAh
(battery capacity) = 22.9C

Based on this math I suspect that a 30C dicharge rate is good on paper...
additional discharge performane = $$$ and I don't want to spend money on
battery performance I don't need...

Class - Intermediate

What is the recommended battery capacity and discharge rate...?

I understand the many variables associated with the answer like, prop size,
temps, wind, throttle control, yada, yada, yada...

I would like to fly the Intermediate sequence a couple time without having
to refuel electrons...

Larry Diamond
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