[NSRCA-discussion] Going Electric - Battery Questions

Fri Dec 7 17:14:02 AKST 2012

Let’s stop writing about it then.  Last note however, if you ever handle 55 gal drums of glow fuel, you will definitely notice the large weight difference between 15% and 30% nitro.

From: 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 PresidentAMA 1294 Scientific Leader MemberSPA 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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