[MLB-WIRELESS] Solar power for access point

[Robert Farrar]

They will be repeaters...


----- Original Message -----
From: "Clae" <clae13 at yahoo.com>
To: <melbwireless at melbwireless.dyndns.org>
Sent: Monday, 10 September 2001 2:03 PM
Subject: Re: [MLB-WIRELESS] Solar power for access point


> is this a remote repeater, or will it be ethernetted into a box some
where?
> if so, you might consider one of the power-over-ethernet schemes
>
> >Apple Airport Current consumption WITHOUT modem: 180-290mA (2.16-4.08W)
> >
> >Power on (3 orange lights): 230mA
> >Boot phase (1 red light): 180mA
> >Final boot (link light on wireless card only): 290mA peak
> >Normal Operation: 280mA
> >Flash ROM write:        290mA
> >ETH flood:      290mA
> >Wireless flood: 340mA peak
>
> this is a *lot* lower than i was expecting;  solar powering this unit now
> looks quite feasible.
>
>
> the basic components you will need are as follows:
>
> solar panel (and/or wind generator) into charge controller into battery
> then either
> into inverter (into plugpack?) into AP, or
> into voltage regulator direct into AP
>
> >so basically you need a big battery (or 3) powering the airport that can
do
> >at least 410mA peak,
>
> call it 500mA = 0.5A , it makes the math easier, and it's always best to
be
> a little generous.  that way your solar rig will last longer, as it's not
> running right up to the rating of each component.
>
> more important than the power RATE of the battery (410mA not being that
> great a challenge) is the total power STORAGE in amp-hours.  ie 1 Ah = a
> load of one amp running for an hour.
>
> you should get acceptable service if you allow for two days run-time with
> no charge - the panels will still charge some on totally overcast days, so
> you should only lose service a couple of times a year - allow for more if
> you can budget for it, but like a lot of things, it's the last few % of
> efficiency that really costs.
>
> anyway, that equals 48h x 0.5A = 24 Ah of storage.  the storage capacity
of
> a battery is written on the side somewhere.
>
> now the next thing to remember is that you can't really run a lead-acid
> battery all the way down - because you'll kill it.  not the first time,
but
> fairly quickly.  so you'll want to double that, for a "deep-cycle"
battery
> designed for this kind of abuse, or 4x it for a normal car/motorbike
> battery.  so then we're back up to 48Ah, or 96Ah.
>
> does the airport run from a 240v source directly, or via an external power
> adapter/plugpack?  if it's a plugpack, check its label and see whether its
> output is AC or DC.  If its DC, and under 12 or 24 volts, then you can
> probably run the AP directly from your solar rig.  you'd just need to add
a
> voltage regulator (cheap) as insurance.
>
> i notice that the power ratings from the perth page given in the previous
> reply are all at 12 volts, ie 0.41 A x 12 V = 4.92 W.  myabe this means
the
> AP runs at 12 volts, this would make life easier...
>
> if on the other hand it uses an AC plugpack, or direct 240v, then you'll
> need an inverter to boost up to 240v.  luckily, you can get away with a
> very small/cheap one at this power load.  try http://www.jaycar.com.au ,
> they should have a suitable one for around $100.
>
> so now you need to allow for the power conversion (in) efficiency of the
> inverter - typically 85%.  that means an effective load of
> 0.410 A / 0.85 = 0.48 A , still within the 0.5 we're using for an
estimate,
> but cutting a bit fine, so you might want to over-rate some of these
> components along the way.
>
> and get a solar panel that puts out enough juice to
> >keep up. i think overkill would be the best idea ;)
>
> using the estimate of 4 x the load for charging, you need a 2.0 A @ 12 V
> panel.  solar panels are sold by the watt, so this is  24 watts worth of
> panel.  average price is $10 per watt.  and this is *peak* watts - for
> direct, bright sun - hence the apparent 4x oversupply
>
> so we're looking at:
>
> panel:             3 x 10 watt                = $300.00
>                or  6 x  4 watt                = $240.00
>
> battery:           3 x 18 Ah sealed lead acid = $266.85
>
> charge controller: 12 A max 12 V              = $ 87.95
>
> (inverter:         60 watts 12v to 230v       = $ 79.95)
>
> odds n sods, wire, mounting, casing etc       = $100.00
> ------------------------------------------------------------
> rough total                                   = $700 to 800
>
> these prices are all from the jaycar site, just because it's a handy
> reference.  their prices are not bad, but feel free to shop around with
the
> specialised solar places.  solar panels are occasionally available
> second-hand, and batteries can be obtained second-hand (with somehwhat
> degraded storage life) from places that service wheelchairs or forklifts.
> alternatively, a suitable truck/car battery might be cheaper. and
obviously
> you can scrounge up materials for the mounting and casing.
>
> another thing to consider is whether you need this link up 24/7 - could
you
> accept it going down between say 1am and dawn some days?  you could then
> budget a bit on the batteries.  instead of 48 hours of storage, you might
> only need 12 or 24.  i would suggest adding a circuit to switch off the
> power when the batteries get down too far.  the more often and the deeper
> they are run down, the shorter thier service life
>
> and adding a small wind generator would also extend your battery life - as
> well as charging at night, and possibly allowing you to go down to 3x or
2x
> load on the panels.  and presumably you're on a hill or some other high
> place, so the wind available should be quite good.
>
> the batteries and other components need to be waterproofed, kept out of
the
> sun and dust - if , and the panels need to be anchored down well so they
> won't blow away in a gale.  and consider a lightning rod.
>
> you need to point the panel north, at an angle to the ground.  this angle
> depends on your location, as it is optimised to catch the most sun over
the
> year.  there are lookup tables for your location available in solar power
> reference books at your local tech library, or on the net.  and use fairly
> chunky wire and short as possible runs on the 12 volt side - it'll cut
down
> on any losses.
>
> keep us posted.
>
> clae.
>
>
> >
> >the guerrilla.net folks have some more info
> >
> >http://www.guerrilla.net/gnet_power_systems.html
> >
>  à  >----- Original Message -----
> m: Robert Farrar
> >To: melbwireless at melbwireless.dyndns.org
> >Sent: Monday, September 10, 2001 12:04 AM
> >Subject: [MLB-WIRELESS] Solar power for access point
> >
> >
> >Hello All,
> >
> >I would like to put a RG-1000 / apple Airport access point in a location
> >that does not have direct access to power, so I would like to get power
to
> >the unit via solar & battery backup.
> >
> >Has anyone from the group got any experience in solar powered devices or
be
> >able to source a how to on making such a unit ?
> >
> >Any help would be welcomed.
> >
> >Regards,
> >
> >
> >Robert Farrar
> >Mt Gambier, South Australia
>
>
>
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