IF you need to power 48V equipment from a 12 or 24V battery system take a
look at these 9-36V input 48V output DCDC converters/POE inserters.
It is much more efficient than going the inverter to 120VAC and back to
48VDC route. They supply 30W so should power most 48V equipment.

http://store.wisp-router.com/itemdesc.asp?ic=TP-DCDC-1248&eq=&Tp=

Regards, Scott

-----Original Message-----
From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
Behalf Of Christopher Erickson
Sent: Thursday, August 27, 2009 9:36 PM
To: WISPA General List
Subject: Re: [WISPA] solar site

48VDC equipment is almost always carrier-class and that is where
the expense is.  That isn't quite the same as having a 48VDC power
plant with non carrier-class equipment running on it.

What is really absurd is converting a 12/24/48VDC battery plant to
120VAC to feed a piece of equipment that is going to convert it
back down to 5VDC and 12VDC using a reasonably reliable but highly
inefficient computer type switching power supply.

Cisco and Motorola make some of the most power-inefficient networking
and radio equipment on the market.

No big deal when you are on the grid.  But a real big deal when you
are not.  I guess off-grid sites are just too tiny a portion of their
market to worry about.

"My advice is always free and worth every penny!"

-Christopher Erickson
Network Design Engineer
5432 E. Northern Lights Blvd., Suite 529
Anchorage, AK 99508
N61?11.710' W149?46.723'


> -----Original Message-----
> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org]on
> Behalf Of ralph
> Sent: Thursday, August 27, 2009 1:26 PM
> To: 'WISPA General List'
> Subject: Re: [WISPA] solar site
> 
> 
> But isn't your panel expense 2 to 4 times as much?
> I looked at powering some Tropos and Cisco mesh with solar and compared
48v
> with 12 volt.
> The 12 volt used a really high efficiency inverter to 120v and then to the
> radio.
> It was less than half the overall cost of the 48v system.
> 
> Ralph
> 
> -----Original Message-----
> From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
> Behalf Of Christopher Erickson
> Sent: Thursday, August 27, 2009 2:31 PM
> To: WISPA General List
> Subject: Re: [WISPA] solar site
> 
> * 48 volt power system (actually -48VDC) is a telco standard and
> there is a LOT of carrier-class telecom equipment and charging
> systems designed to operate on that voltage.  Especially a lot
> of remote management control and monitoring stuff.
> 
> * For the same watts, when voltage goes up, amperage goes down.
> This means less percentage energy loss from voltage drop in
> wiring and the ability to use smaller gauge wire for power.
> 
> * Using high-efficiency Picoverters to power 12VDC and 24VDC
> devices from 48VDC means that your 12VDC devices can still
> operate reliably when the 48VDC battery plant is down to near
> exhaustion.
> 
> "My advice is always free and worth every penny!"
> 
> -Christopher Erickson
> Network Design Engineer
> 5432 E. Northern Lights Blvd., Suite 529
> Anchorage, AK 99508
> N61?11.710' W149?46.723'
> 
> 
> 
> > -----Original Message-----
> > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org]on
> > Behalf Of Chuck Profito
> > Sent: Thursday, August 27, 2009 11:09 AM
> > To: 'WISPA General List'
> > Subject: Re: [WISPA] solar site
> > 
> > 
> > Chris,
> > Re #4:  Is that because the usable voltage? Ie: 11.2V of 12, 18 of 24?
> 36-38
> > of 48?  Are these close to correct for std POE? Or what WISP's use?
> > 
> > -----Original Message-----
> > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org] On
> > Behalf Of Christopher Erickson
> > Sent: Thursday, August 27, 2009 10:53 AM
> > To: WISPA General List
> > Subject: Re: [WISPA] solar site
> > 
> > I have designed a fair number of off-grid radio sites and in general,
> > I have come up with a few additional guidelines.
> > 
> > 1. Have enough battery capacity to run for 7 days with zero charging.
> > This will give you a window of response time if the charging system
> > suffers a failure (or theft/vandalism) or there is an extended
> > episode of inclement weather.
> > 
> > 2. Avoid as many power conversions as possible.
> > 
> > 3. Avoid any equipment that has a built-in cooling fan.
> > 
> > 4. 48 volt power systems are more efficient than 24 volt power systems
> > are more efficient than 12 volt power systems.
> > 
> > 5. Avoid inverters and equipment that is 120VAC only.
> > 
> > 6. Don't forget to consider environmental issues and projected
> > temperature extremes.
> > 
> > "My advice is always free and worth every penny!"
> > 
> > -Christopher Erickson
> > Network Design Engineer
> > 5432 E. Northern Lights Blvd., Suite 529
> > Anchorage, AK 99508
> > N61?11.710' W149?46.723'
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: wireless-boun...@wispa.org [mailto:wireless-boun...@wispa.org]on
> > > Behalf Of Mike
> > > Sent: Thursday, August 27, 2009 10:35 AM
> > > To: WISPA General List
> > > Subject: Re: [WISPA] solar site
> > > 
> > > 
> > > Instead of talking 33.3 days and 24 hours of sun, let's just take an 
> > > average day.
> > > 
> > > At optimal output, and for the sake of argument, let's say our 60W 
> > > rated panels only produce 45W; optimally. Let's lob off 12% of that 
> > > to satisfy the naysayers and devil's advocates, and to account for 
> > > inefficiencies.  We have a power output of close enough to 40W.
> > > 
> > > Not all can do it, but for the short run repeater, and with two 
> > > radios, let's say we run it at 12V, while loosing less heat at the 
> > > voltage regulator on the radio.  Since we're rounding numbers, we'll 
> > > call that 3.3A.  The radios require .8A.  During optimal conditions, 
> > > there are 2.5A free to charge the battery.  On our average day, we 
> > > have 6 hours of optimal sun, maybe more, maybe less. We have gained 
> > > 15AH of charge to send to our battery.  For 3 more hours of the day 
> > > we will receive less than optimal output -- 2.5A, for another gain of 
> > > 5.1AH.  We now have 20.1AH more than we need to run the radios.  We 
> > > will get another hour of diminished 1A or less output but will not 
> > > consider that here.
> > > 
> > > So, during our 24 hours, we are either generating enough, or excess 
> > > for 9 hours.  We have to store power for the 15 hours where our 
> > > system is not generating power.  We have to provide 12AH for dark 
> > > time.  We have already generated an excess of 20.1AH.  We can provide 
> > > 8.11AH on our average day to keep our battery charged.
> > > 
> > > If the 12V storage battery is capable of 800AH, and it is topped off 
> > > with our system it CAN keep the repeater going for 41 days.  If you 
> > > monitor battery condition, you should be able to see a net loss 
> > > coming way before it shuts down the repeater.
> > > 
> > > Assumptions:
> > > We are using efficient radios capable of running at 12V or 
> > > less.  Let's say both are Atheros based Deliberant radios.
> > > The CAT5 run to our radios is insignificant, and not some 200' run.
> > > Hams, geeks and wisp owners are cut from similar cloth.
> > > 
> > > Mike
> > > 
> > > 
> > > 
> > > 
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