[NSRCA-discussion] Luminex Power supply

Wed Jul 13 10:27:52 AKDT 2011

In practice I think a 20% loss from the generator output to the lipo
input...plug losses, wiring losses, PS loss, charger loss, etc.

Using Honda 2000 Inverter, IOTA supplies, and TP chargers (1010 and 820).

Regards,

Dave

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Bob Kane
Sent: Wednesday, July 13, 2011 2:19 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Luminex Power supply

Ah . .  .  the "Fashion Factor".  That is more difficult to measure.   :)

FWIW, I want a nice 4-stroke generator also, mainly to avoid mixing the gas
and oil.

I have no idea how hard you plan to recharge your batteries.   I personally
use a 1C rate, which is roughly 210 watts for a 5000mAH 10S pack
(4.2V/cell*10cells*5A). The math here is pretty simple, double the charge
rate, double the power. 2 packs at the same time, double the power. Assuming
a 12V supply and factoring a 10% loss to heat (thanks Mark), you will need
at least a 40A capable power supply to charge 2 10S packs at 5 amps at the
same time.  At this power consumption you are using roughly half of what the
Harbor Freight generator is rated, a safe place to be.

Also, look at eBay for 4 stroke generators, there are some non-Honda units
out there that look reasonable.

Bob Kane
getterflash at yahoo.com

--- On Wed, 7/13/11, Scott McHarg <scmcharg at gmail.com> wrote:

From: Scott McHarg <scmcharg at gmail.com>
Subject: Re: [NSRCA-discussion] Luminex Power supply
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Date: Wednesday, July 13, 2011, 1:18 PM

Bob,
  Thank you VERY much.  This is good news!  I still want a nice
generator...maybe for Christmas but it's good to know my Harbor Freight
cheapy is OK.  :)  Thank y'all again!

On Wed, Jul 13, 2011 at 12:13 PM, Bob Kane <getterflash at yahoo.com> wrote:

I feel compelled to respond to this . . . . 

While it is true many electric powered devices are sensitive to the
frequency of the incoming AC power (linear power supplies and anything that
contains one, classic TVs, AC motors and anything that contains one, etc.),
digital power supplies are not as sensitive. They rectify the incoming AC
power directly into DC to power their own high frequency generator (this is
what the "switching" part of the name is all about) which in turn goes
through a transformer and is rectified again to produce DC power.  There is
a rule in transformars that the size of the transformer for a given power
rating is inversely proportional to the operating frequency.  So by
generating a very high frequency AC signal, the transformer can be much
smaller for a given power rating than the equivalent 60Htz transformer. That
is why a 600 watt switching power supply is much smaller and lighter than
the linear equivalent.

In the end, as long as you are not at the power limits of a cheap generator,
I would not worry about it.

Bob Kane
getterflash at yahoo.com

--- On Mon, 7/11/11, Keith Hoard <khoard at gmail.com> wrote:

From: Keith Hoard <khoard at gmail.com>
Subject: Re: [NSRCA-discussion] Luminex Power supply
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Date: Monday, July 11, 2011, 5:30 PM

Scott,

Something I learned from one of our club members who owns an HVAC business.
. . get a generator with an inverter.  The cheaper generators (like my $199
Tractor Supply special) are basically an alternator connected to a Bliggs &
Sratton motor with a mechanical governor keeping it on speed.  
.
If you start approaching its power limits or the motor begins losing it
rhythm, bad things happen with the volts and Hertz and then you let the
magic smoke out of your power supplies and chargers in a big $$$$-shaped
cloud.

Keith Hoard
Collierville, TN
khoard at gmail.com <http://mc/compose?to=khoard@gmail.com> 

On Mon, Jul 11, 2011 at 2:42 PM, Scott McHarg <scmcharg at gmail.com
<http://mc/compose?to=scmcharg@gmail.com> > wrote:

Thanks Mark.  I appreciate this.  I was looking at the Luminex Chris Moon
sells and just wondering if my little generator would hold up.  

On Mon, Jul 11, 2011 at 2:40 PM, Atwood, Mark <atwoodm at paragon-inc.com
<http://mc/compose?to=atwoodm@paragon-inc.com> > wrote:

The math is correct, but you need to add about a 10% loss factor, or even a
little more.  My Iota 55am power supply under a full 55amp load pulls about
850.   More importantly, my Iota will frequently deliver in excess of that
55amps for short periods of time and draw over 900.  I'm currently using a
Honda 1000watt generator without any problems.

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
<http://mc/compose?to=mark.atwood@paragon-inc.com>
<mailto:mark.atwood at paragon-inc.com
<http://mc/compose?to=mark.atwood@paragon-inc.com> >  |
www.paragon-inc.com<http://www.paragon-inc.com/>

On Jul 11, 2011, at 3:24 PM, Scott McHarg wrote:

Can someone give me a rough idea of how big a generator I need to run the
Luminex power supply?  I have a small 2-stroke 800W generator from Harbor
Freight but not sure how to tell how many Watts I need to power the Luminex
supply. Volt x Amps=Watts?  So, can I draw the conclusion that something
that puts out 55 Amps at 13.4 Volts needs 737 Watts input?

Thanks y'all,
Scott

--
Scott A. McHarg

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