[NSRCA-discussion] 8- cells?

[Keith Hoard]

Thanks for all the input. . . as I said in my earlier post, all I've heard
is rumors.  Glad I got the facts before hitting the "Buy" button.

I think I'll stick to the Koopowitz plan - "8S + 2S for insurance" . . . .
. don't mess with success . . .

Keith Hoard
Collierville, TN
khoard at gmail.com




On Tue, Mar 27, 2012 at 7:51 PM, Peter Vogel <vogel.peter at gmail.com> wrote:

> I'm not sure why you would want to go to 8s.  Ultimately it takes a
> certain amount of power (W) to accomplish a series of maneuvers and that
> takes a certain amount of time (W-hours).
>
> Watts = amps * volts
> resistance increases with the square of the current (amps)
>
> If you reduce volts by 20% you increase current by 20% to achieve the same
> power, that means you increase resistance (and therefore loss of
> efficiency) by 40+%,
> that resistance loss turns into heat, in general as electronic things heat
> up they get less efficient as well.
>
> For any given airframe, etc. if I determine I don't need 20% of the power
> I have on board, I'd much rather reduce amp hours available than reduce
> voltage, keep the system running cooler and probably save just as much
> weight by reducing cell capacity as I would by reducing the # of cells for
> a given capacity.  Checking...
>
> Zippy Compact 8S 5000   (25C) 1030g (2x4S), 905g (8S brick) You probably
> would want to move to 35C which looks like it would weigh more...
> Zippy Compact 10S 4000 (25C) 1013g (2x5S), 908g (10s brick)
>
> So pretty much a wash as far as weight goes -- why not stay with the
> higher voltage, higher efficiency setup?
>
> Peter+
>
> On Tue, Mar 27, 2012 at 5:03 PM, Keith Hoard <khoard at gmail.com> wrote:
>
>> I was checking if anyone who's flown 10S has tried 8S.  Heard rumors, but
>> want to hear from guys who've flown both before this years battery
>> purchase.
>>
>> Sent from my iPhone
>>
>> On Mar 27, 2012, at 18:52, J N Hiller <jnhiller at earthlink.net> wrote:
>>
>>  Kicking it around. I feel confident I can build an 8S E-powered
>> option-160 under 10 lb. I'm in the process of detailing the design and
>> probably won't commit until I have some basic airframe parts on the bench.
>> An 8S-5000 looks to be about 8 oz lighter than a 10S-5000. Don't know if a
>> 10S-4000 would be enough. Too many unknowns but probably worth a try in
>> masters. FAI may be too demanding. How much more does it take on a windy
>> day? 20%? ??
>>
>> I know nothing, yet.
>>
>> Jim H
>>
>>
>>
>> -----Original Message-----
>> *From:* nsrca-discussion-bounces at lists.nsrca.org [mailto:
>> nsrca-discussion-bounces at lists.nsrca.org]*On Behalf Of *Keith Hoard
>> *Sent:* Tuesday, March 27, 2012 3:53 PM
>> *To:* General pattern discussion
>> *Subject:* Re: [NSRCA-discussion] 8- cells?
>>
>>
>>
>> Nice..  ;-)
>>
>>
>>
>> ROFL
>>
>> Keith Hoard
>>
>> Collierville, TN
>>
>>
>> On Mar 27, 2012, at 17:35, Derek Koopowitz <derekkoopowitz at gmail.com>
>> wrote:
>>
>> I've been using 8 cells for the past couple of years... however, I keep
>> another 2 cells as insurance.
>>
>> :-)
>>
>> On Tue, Mar 27, 2012 at 2:06 PM, Keith Hoard <khoard at gmail.com> wrote:
>>
>> Is anyone trying 8 cells this year in their 2 meter plane?
>>
>> Keith Hoard
>> Collierville, TN
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>
>
>
> --
> Director, Fixed Wing Flight Training
> Santa Clara County Model Aircraft Skypark
>
>
>
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