Thanks for the great info Chuck!  Almost made the trojan battery mistake.
what exactly is the battery technology and brand you suggest?  if I have a 5
watt system you suggest a 120W  solar panel.  Also 30 days or 360AH of
usable capacity at 12V?

Thanks for  the clarification, and the pics that make your experience clear!

On Wed, Nov 19, 2008 at 7:38 PM, Chuck McCown - 3 <[EMAIL PROTECTED]> wrote:

> At 60% depth of discharge they freeze at 0F.  Once frozen they are dead.
> Liquid electrolyte batteries need to be liquid to work.
> Not to mention the risk of a broken case. (You most likely mean you try to
> avoid taking them below 40% DOD, but 60% has a nice freezing point to
> exploit for purposes of rhetoric).
>
> Trojans were designed for the cabin with the fireplace and the intermittent
> use of the residential solar application.    (Really, they were designed for
> golf carts).
>
> Constant load, constant nightly cycling, periods of no charging and deep
> discharge during the coldest days of the year is a different application and
> takes a different battery technology.
>
> Here is a good VLRA white paper on the temperature issue:
> http://www.cdtechno.com/custserv/pdf/7953.pdf
>
> We use VLRAs inside central offices where there is HVAC.  Not in the field.
> And they are much better than flooded cells like the T-105
>
> AGMs go in the field. And for solar only a few types of AGMs can be
> trusted.
>
> This app note is full of lots of good info.  It is on the batts we use that
> will still deliver 40% of their power at -40 degrees.
> http://www.enersysreservepower.com/documents/US-GPL-AM-003_0906.pdf
>
> But the only really important point is that in a solar situation, where you
> have weather and you have low temps, very few batteries will totally recover
> from an extreme deep discharge.  And that happens all the time when people
> scrimp on their battery capacity and solar panel capacity.
>
> 20X watts 30 days autonomy = you will sleep all winter long.
>   ----- Original Message -----
>  From: Blair Davis
>  To: WISPA General List
>   Sent: Wednesday, November 19, 2008 7:56 PM
>  Subject: Re: [WISPA] Remote Powered Access Pont
>
>
>  Ok.  our answer to that problem has always been to double up on our total
> battery size so we never discharge them below 60%
>
>  Sounds like you are in a much more inaccessible environment than we are!
>  And in that kind of location, I'd likely be looking for the same thing.
>
>  But, for us, inaccessibility won't last more than a week or so...
>
>  Chuck McCown - 3 wrote:
> We buy batts that are rated to give you the energy down to -20F.
> Survive being at-20F while discharged to a stone cold state.
> And recover when the next available bit of sunlight hits the panel (perhaps
> days later).
> And last 2000 cycles.
> For that you pay 30 cents per watt hour.  And can sleep at night.
> (we used to get these for 20 cents, I don't know why they are so much more
> now)
>
> I just found a website selling a T-105 for $160\each
> 6 volts, 225 aH  That comes to 11.8 cents per watt hour.
>
> The Trojan website says "avoid locations where freezing temperatures are
> expected".
> It also says the must be kept fully charged when freezing.  Hard to do with
> solar on a mountain top.
>
>
> http://www.trojan-battery.com/Tech-Support/documents/UsersGuide_0708_English_003.pdf
>
> So, if you have a nice warm place to keep the trojans then they are a very
> good value.
> (assuming they are in an air conditioned place in the summer too, else they
> won't last too many summers)
>
> But most solar powered sites don't have a heater to keep them from freezing
> and splitting.
>
>
>  ----- Original Message -----
>  From: Blair Davis
>  To: WISPA General List
>  Sent: Wednesday, November 19, 2008 7:25 PM
>  Subject: Re: [WISPA] Remote Powered Access Pont
>
>
>  What type of battery's are you using?  That price sounds very high.
>
>  4x T-105 will provide 225Ah at 24V for a cost of about $500
>
>  Chuck McCoy's - 3 wrote:
> I would use a 100 watt panel minimum.
> And a one month battery.  5watts * 24hours * 30 days = 3600 watt hour
> battery
> If you are running a 24 volt system then you need 3600/24=150 aH battery.
> If you are running a 12 volt system, you need a 300 aH battery.
>
> You will pay about 30 cents per watt hour for a battery.  So $1080 for the
> battery.
> You will pay about $5/watt for the panel, so $500 for the panel.
> Charge controllers are about $100 or less.
>
> If you build it this way it will always work.  You can put in half the
> battery for half the price.  But then you have only two weeks of insurance
> against bad weather.
>
> Never ever go below 10X the load for the panel, that will just barely cut
> it
> in the sunniest of climates.
> Even then you will probably have to put in a back up generator and you will
> be cycling the crap out of your batts causing them to only last a couple of
> years.
>
> If you want 99.999% reliability you have to use a panel 24X the size of the
> load (unless you have a tracking mount, then you can reduce that).
> I try to always use 20X panels and no less than a 2 week battery.  But even
> then, a week or two of snow on the panels and gray skies every day can
> cause
> an outage.
>
>
> ----- Original Message -----
> From: "Scott Parsons" <[EMAIL PROTECTED]>
> To: "'WISPA General List'" <wireless@wispa.org>
> Sent: Wednesday, November 19, 2008 5:33 PM
> Subject: [WISPA] Remote Powered Access Pont
>
>
>  I'm looking into setting up a remote access point/repeater.
> Power requirements are 5W. No access to grid power.
>
> I was curious what you guys use for this type of thing?
> I figure I need a 30W solar panel, controller, battery and enclosure.
> How much should I expect to pay for a setup?
> Is there anything available off the shelf?
>
> Thanks for your help.
> Scott
>
>
>
>
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