Solar power battery system for WRT54GS

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I have need to set up a bridge in a location visible to myself and a
secondary source.  No AC power is available.   Where would I go to buy
'Solar power systems' with batteries and the like for a WRT54GS?

What price should I expect to pay?  I'm trying to find out if it's
financially viable.  If so, I'll be buying and installing in the next
two weeks.

Re: Solar power battery system for WRT54GS

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You can buy solar panels and batteries from loads of online retailers.  You
just need to consider what current is drawn over the hours of darkness -
then get a battery big enough.  Also get a solar panel big enough to give
the required charge and actually run the router during the day.
Then work out your figures on whatever you consider it to be financialy
viable against.

Re: Solar power battery system for WRT54GS wrote:
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What does it draw at 13.8 volts?  IIRC my WAP54G is just a few watts.
Depending on where you are installing it, and your insolation
available, the calculation is pretty simple:

Find the power consumption, call it 5 watts just to have something to
talk about (confirm this before buying anything).

5 watts times 24 hours per day is 120 watt-hours.

Solar panels are rated at peak output at a nominal one sun input
(1000W/M^2), and most places in the US get between 4 and 5 "peak sun
hours" per day.

Divide 120 watt-hours by 4 to get 30 watts of solar panel.  You want
to upsize a bit to cover recharging after extended outages, so get at
least 40 watts. has 40-watt panels for $285,
which probably isn't awful.

How many days of battery backup do you want?  Since you are only using
10 amp-hours per day, and you don't want to use more than half of your
battery capacity, you need between 50 and 100 amp-hours. has a UB27 for $125 that looks OK.

You also need a 5 amp or better charge controller, that's probably an
ASC 12/4 for $44.  Check to be sure it can be set up for charging gell

If you can get to the site and top off the battery water occasionally,
you could save some money by using a pair of golf cart batteries for
$100 and no charge regulator.  HydroCaps can keep the need for battery
maintenance down in this situation, but they add $50 to your initial

Call it $500 plus or minus (do you need a housing for your WRT?
External antennas?  Do you need cabinets or boxes to put all this
stuff in?  Is it subject to very high or low temperatures?  Vandalism?
Is there anything else you haven't told us?)

Don't forget $50-$75 for the WRT, plus whatever you are using as

Re: Solar power battery system for WRT54GS

William P.N. Smith wrote:

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Now, I know you hang out in the homepower group, William, so you should
realize those numbers don't compute.

If you want a 50amp-hour battery, you really need to be able to get a 10amp
charge into it.  If you're charging a 50-100amp-hour battery with a 5amp
charge controller, you run a risk of never really getting a full charge
into your battery, and shortening its life.

Re: Solar power battery system for WRT54GS

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Yeah, but the tradeoff is spending another $1000 to provide the ideal
charge environment for a $100 battery.  Hence my suggestion to get
golf cart batteries and no charge controller, which seems to work well
for the Coast Guard.

FWIW, I looked up the power consumption data on the WAP54G I took a
while back, and it was just under 3.2 watts from 4.2V to almost 20V.
I'll characterize a WAP54G someday, but don't hold your breath.

Yeah, the OP needs to better characterize his load, his insolation,
his maintenance needs, and other things, but the concensus of $500
"plus or minus 3 dB" seems to get him in the right ballpark.

Re: Solar power battery system for WRT54GS

William P.N. Smith wrote:

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Good point.  I'm embarrassed...

Re: Solar power battery system for WRT54GS

Derek Broughton wrote:
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50 watts of solar sells, in a 12 volt configuration, won't be putting
out more than 5 amps. A sealed lead acid battery should be charged at a
rate of not higher than C/10 (capacity divided by 10), which would be a
5 amp charge rate.

Re: Solar power battery system for WRT54GS

[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

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Powerup Bsp40-12 40 Watt Solar Panel for $242

GE 45w 12v Solar Panel for $257
Ip50f, 50w, 12v, Fiberglass Solar Module for $270

Sharp NE-80E1U 80w module for $320 shipped.

John Navas     <

Re: Solar power battery system for WRT54GS

Any suggestions for mounting the Fiberglass panel so it can't be
stolen, or otherwise damaged by horses?

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number of them, but I'm not certain which one to choose

Re: Solar power battery system for WRT54GS

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Here are some discussions you would be interested in:

I like this one:

Re: Solar power battery system for WRT54GS wrote:
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You can probably set it up for around $350-400, depending on how you're
planning to mount the panel and the battery. Is it an outdoor location?

That unit draws around 6 watts, so figure around 50 watts to account for
the panel not being aimed at the sun all the time, plus being able to
both operate the unit and charge the battery at the same time.

See " "

Buy a sealed lead acid battery and a controller

" "
" "

A 12 volt/12 amp hour battery (144W) would be good, which will give you
some buffer for cloudy days.

Too bad you can't buy a surplus roadside call box somewhere.

Re: Solar power battery system for WRT54GS

SMS wrote:

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Oops, this isn't enough, my mistake. Use a 55AH battery
(" ")

Re: Solar power battery system for WRT54GS

I couldn't find a manual on-line for this device, but I have run a
Dlink DWL-900AP+ wireless on batteries. The factory supplied power
supply is a 5V switch-mode wallwart. For simplicity, I built my
portable device to run from 6 C cell nicads, then used a low drop-out
voltage regulator that I built using a Texas Instruments chip. [If
relevant, I can dig up the number.]

If you are going to use an off the shelf 12V solar system, you will
need to build a DC/DC converter to reach 5V, most likely a buck
configuration. If you used a LDO linear regulator from a 12V supply,
more than half the power would be used in just dropping the voltage.

It would be more work on the solar cell side of the task, but I would
set up a 6V system using a gell cell, then build a 5V regulator using a
low drop out chip. I specify low drop out in that these devices use
PMOS pass fets rather than a PNP, so they are very efficient, not to
mention more stable. [The PNP in those cheap bipolar  regulators sits
near saturation, which leads to much power wasted in the base driver
current, plus difficult circuitry to keep the PNP from entering
saturation. It's ugly.] The skill required to build a switcher is an
order of magnitude higher, both in circuit design and in layout
(construction).  The low drop out linear regulator is just the chip and
a few capacitors. You would need basic soldering skills, but not much
beyond that.

I know very little about solar cells themselves. My guess here is you
would assemble enough to float the gell cell, and use a Schokty diode
to prevent back flow when light is no longer shining on the cells.

Your first step would be to determine how much current your router
draws. The wall wart is often overated, that is the router draws much
less current than the wall wart could put out. I simply got a bench
supply, built a cable, and measured the current while the box was
operating. Once you know the current required, you can narrow down the
LDO regulator choices.  The maximum voltage you will get out of the
solar cell and the current requirement of the router will determine the
power dissipation required by the LDO. If you go this route, just do
another post and I can pick the part. Texas Instruments has the most
product in the high power LDO market, so that is where I would look. wrote:
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Re: Solar power battery system for WRT54GS wrote:
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Not for the WRT54GS. 12 volts is fine.

Re: Solar power battery system for WRT54GS

Like I said, I couldn't find a manual. However, it is uses a 12V wall
wart, what current does it draw?

If a repeater would do the job (rather than a bridge), SMC has some
boxes that run off of 5V @1A.
The product is described as a bridge, but it lists repeater in the
modes. I'm not much for the details of networking, but I know there is
a difference.

The big expense in this project will be the solar cells, so you want to
get as low of power on the electronics as possible.

SMS wrote:
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Re: Solar power battery system for WRT54GS hath wroth:

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The WRT54G and GS uses a switching regulator down to 3.3VDC.  It will
run on anything from about 4VDC to about 18VDC.  The regulator will
probably handle a higher voltage, but I'm worried about the input
filter cazapitor.

The current drain is:
   Volts   Amps
    15      0.25
    12      0.3
     5      0.8
     4      1.0
for about 4 watts dissipation.  The actual current drain varies
somewhat with hardware version.  This is for my V3.0 WRT54G.

The WRT54G/GS will run quite nicely directly from a 12V gel cell.  For
charging, a small solar controller (i.e. Morningstar) will do just

The problem is that it burns about 4 watts continuously.  To run for
24 hours without a charge (required for mid-winter operation), and
keep the battery at 75% charge, the 12v battery would need to be rated
at   30 A-hrs min.  I threw together a spreadsheet for the purpose. It
was made for commercial and ham radio repeaters, but should work for
Unfortunately, to recharge a 30 A-hr gel cell in one day or less
requires a 400watt solar array (non-tracking).  The WRT54G will burn
94 watt-hrs/day.  The solar array would need to equal that in order to
prevent the battery from running down.  At 25 watt solar array would
do the job.  oh-oh, I think I just found a mistake in the spreadsheet.

Some photos of a solar powered Wi-Fi box (not mine).

Jeff Liebermann
150 Felker St #D
Santa Cruz CA 95060
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Solar power battery system for WRT54GS

Thanks for the technical data. I think the input capacitor won't be an
issue given the amount of money you will be spending on the rest of the
system. Throw enough money at the input cap and the problen will be
solved. I've built pulse generators for LDO testing that needed very
stiff filtering, and if money isn't an issue, you can get the
capacitance quality you need.

Since you know the market, is there some module or other wifi box that
is lower power?

Jeff Liebermann wrote:
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Re: Solar power battery system for WRT54GS wrote:
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The input cap is rated way above the 13.8 or so volts you need for a
decent solar system, so that's not a concern.  As Jeff pointed out,
the Linksys boxes have a wide-input-range power supply that draws a
fairly constant power.

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Lower than four watts?  Depending on what the OP needs/wants (we
haven't heard back from him), he could use a WAP54G, which is 25% less
power consumption, but the numbers work out about the same.

Now that I think about it, wiring (or buying) the panel for 6V
operation would let you save $50 by only buying one golf-cart battery
(and double the charge current, which is better for the battery), and
only require three HydroCaps, which saves another $20, but you are
still going to need something around 40 watts of panel and that's
pretty expensive.

Re: Solar power battery system for WRT54GS

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You don't want liquid electrolyte batteries inside a sealed outdoor
box.  The electrolyte will outgas and rot the circuitry.  Hydrocaps
are a great way of preserving water but still leak corrosive gases.
We have to clean these at least once per year, despite the vented box.
Some idiot (me) installed the main fuse and disconnect inside the box,
which corroded away in about 5 years.

Much better are gel cell batteries.  The vent less gases.  They are
not totally sealed and will vent if overcharged.  If you want a fun
test, put a gel cell inside a plastic bag, and rapid charge it for a
while.  It's a gas.

However, gel cells are losing favor and are being replaced by AGM
(absorbed glass matt) batteries.  They're sealed and internally
recover all the vented gasses.  Internal resistance is VERY low.
Therefore they dont get hot.  Self-discharge rate is zilch at perhaps
2% per month.  Prices are coming down.

Another not so minor problem is ambient temperature.  I help maintain
a few mountain top weather stations and a generator.  It doesn't get
very cold in California, but it's still cold enough for the capacity
of the battery to approach useless.  My favorite screwup was to run a
circuit that requires 10.0 volts on a 12V gel cell battery.  When it
got cold, the terminal voltage drifted down towards 10VDC under load
(due to increased internal series resistance).  There's probably
enough headroom to run the WRT54G LDO regulator on 6VDC and still have
enough to supply the minimum 4.0VDC, but I still would prefer 12V
battery just to be sure.  Also, 6VDC solar cells are not too common.

As for golf cart batteries, our local ham radio repeater is in the
middle of a golf course.  Golf carts everywhere.  If you want some of
the worlds deadest golf cart batteries, I can make you a deal.  When
the golf course is done with them, they're genuinely dead or close to
dead.  Using an automotive battery for stationary battery applications
is a very bad idea.  I'll spare you the techy details (unless somone
really wants them) but the construction of vehicle batteries are quite
different from stationary cells.

Drivel:  One of my quaintances has a combination solar and wind power
Wi-Fi, cordless phone, and cell phone repeater located on his ranch.
The theory is that when the sun isn't shining, the wind is blowing.
Rather than buy a commercial wind charger, he built his own.  A small
permanent magnet generator with a 3 blade flexible fiberglass fan for
feathering.  The wind really blew for a few days last month, causing
the blades to almost lay flat against the sides of the alternator.
That eventually sheared off all the wires and bashed in the contoller
box.  Sorry, no photos.

Generally good advice (although I disagree with some of the minor

Jeff Liebermann
150 Felker St #D
Santa Cruz CA 95060
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Solar power battery system for WRT54GS

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The battery box at the base of this tower holds a couple of golf cart
batteries: was not only
cheap, but turns out to be pretty corrosion-resistant, and except for
the frogs, is holding up pretty well.  8*)

Initially it had a single 20W panel and just ran the VHF repeater and
the weather station with no problems.  Adding the fixed-cell phone put
it into a negative power budget, so I added another 20W panel, and it
seems to be holding up, though it's due to be replaced with an AGM
battery, float charger, and grid-tied solar power system.

It did toast the first pair of off-brand golf cart batteries after a
couple of years, I've got HydroCaps on the second set, but they aren't
going to last long enough to see if that helps.  8*)

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