Power needed for remote wireless signal repeater

10 Posts
Jul 8, 2008 10:55 am
Power needed for remote wireless signal repeater

I need to provide power for a remote wireless antenna setup and am completely new at this. Here's what I know and think I need; I'd appreciate any advice.

-- 2 radios draw 400mw at 12V
-- Monitoring camera (optional) draws 5V at 1A (Linksys WVC54GCA)
-- Mean daily insolation at my location (45° 34'N): annual 4.4 kWh/m2; November worst case 2.5 kWh/m2

I would like to get the power from a solar array but am not sure how to calculate what wattage would be needed and what components I would need for the system. The radios would be on 24/7 and I would like to have sufficient power from batteries to last at least 3 days without any sun.

The site is located on a rock outcrop and weather conditions can be extreme (+40C to -40C). I can build a weatherproof container to protect batteries and electronic equipment as needed. The camera is optional in part because I'm not sure it can withstand the conditions. The site is ~600m from my house with the only other access from a wilderness park area so I would like some sort of security.

Wind is an option but I haven't got data about it for the location; however, a wind generator would be more visible and thus less secure.

Background: Although I cannot get a decent signal at my house, my property has a ridge where we were able to get a good signal from hot spots of a local wireless provider. He is willing to put up the tower and antennas if I can provide the power. This will give me high speed access and give him the ability to provide service to a number of other nearby locations.
 
20 Posts
Jul 9, 2008 12:05 pm
Re: Power needed for remote wireless signal repeater

Well, here goes a try at being of some help.

First, lets just work with the two radios.  Together they need 800mw at 12v.  That's 19.2wh per day or 576wh per month or only a little more than a half a kilowatt-hr per month.  Use .6 to up to 1KW-hr per month and use the "off-grid" calculator under the "learn" tab of this website.

If we add in the power for the camera using 5V and 1w. That comes to (1w x 24 hr x 30 days) = 720wh per month.  Again, add the 576wh-month from above and you get to 1,296wh per month.  Go to the calculator and enter about 1.5KWH/month.

I'm unsure how this will work out since using a 5v camera with a (most likely) 12v system isn't going to work.  A 12v camera would make things simpler for you.

Hope this helps or at least spurs some clarifying discussions.

Eric
 
20 Posts
Jul 9, 2008 12:18 pm
Re: Power needed for remote wireless signal repeater

Well, here goes a try at being of some help.

First, lets just work with the two radios.  Together they need 800mw at 12v.  That's 19.2wh per day or 576wh per month or only a little more than a half a kilowatt-hr per month.  Use .6 to up to 1KW-hr per month and use the "off-grid" calculator under the "learn" tab of this website.

If we add in the power for the camera using 5V and 1w. That comes to (1w x 24 hr x 30 days) = 720wh per month.  Again, add the 576wh-month from above and you get to 1,296wh per month.  Go to the calculator and enter about 1.5KWH/month.

I'm unsure how this will work out since using a 5v camera with a (most likely) 12v system isn't going to work.  A 12v camera would make things simpler for you.

Hope this helps or at least spurs some clarifying discussions.

Eric

My bad!  The camera uses 5 watts per hour or 120 watts per day or 3600 watts per month.  The camera really changes things!  Again use the calculators you will find on this website.

Eric
 
10 Posts
Jul 9, 2008 01:41 pm
Re: Power needed for remote wireless signal repeater

Thanks for the response Eric. I'd tried the calculator but couldn't get it to work -- until I tried it again today with IE instead of Firefox. (In Firefox, it doesn't do any calculations and hangs up for some reason.)

Since there are no sun hour figures for where I live (Quebec, Canada), I guessed that we'd be similar to Rochester NY. With that, it looks like I could manage with a single 30 watt panel if I don't include the camera.

I can see that if the camera really does add 3600 watts per month, my panel requirement goes up to 126 watts which would add quite a bit to the cost. I'll reassess the options in that regard.

However, your followup notes that the camera would use 5 watts per hour but wouldn't it be less if the voltage is only 5V? The camera I looked at comes with one of those 120V converters but the technical specs say 5V so I assume I would be able to provide the power directly from a DC source. Is there some way to tap off just 5V from a 12V source? (This is where I feel like I'm getting over my head!)

The other item that came up from using the calculator relates to the lowest temperature the battery would experience. When I put a value of <0, the calculator displays a capacity of "NaN" but if I used 1, it displays "187" amp hrs at 12V.

Is this just a function of the calculator, or do I need special batteries to withstand very low temperatures? I assume people in places like ND or AK would encounter similar cold -- and certainly my tractor and car manage with their batteries in temperatures that go much lower than 0°F.

Eric
 
20 Posts
Jul 9, 2008 02:34 pm
Re: Power needed for remote wireless signal repeater

In simple terms the voltage time the amperage equals the wattage.  Or, V x I = P.  Therefore, 5 volts times 1 amp = 5 watts for the camera.

Yeah, I believe the on-line calculator doesn't like low temperatures.  Look at the "Batteries" section of this site to see the different types and their characteristics.  Looks to me like you could easily use AGM batteries and allow for less drawdown (discharge) and be just fine.  Instead of allowing for 50% discharge, plan on using only about 20% and calculate your battery needs accordingly.  These "less drawdown" percentages will give you longer battery life, too.

Camera at 5V versus system at 12 volts.  Yep, this is a problem.  With AC power it is a matter of using a step down transformer, but in DC that isn't the case.  You would need a resistive load (in series)that would dissapate about 7 volts to get this to work.  That's a lot of load just thrown away, so to speak. 

Consider, for example, if you put a lightbulb rated for 5 volts DC in a 12 volt circuit with a battery, the bulb will most likely be very bright for a very short time (seconds) and burn out.  If you did the same thing with an 18 volt rated lightbulb, it will glow dimly but for a very long time.  Your camera will work best if set up in a circuit that provides the correct voltage.  12volts may very well ruin it in a "flash!"

Eric
 
220 Posts
Jul 12, 2008 04:14 pm
Re: Power needed for remote wireless signal repeater

intriguing

mr. fletcher,

 at first glance the problem you pose seems very reasonable to accomplish. but upon further study what will be required is right on the cutting edges of available technologies.

 i state the above, not to throw cold water (in this case solid ice) on your project but to made us aware of the limitations of todays systems in extreme cold conditions.

 when we take a look at how the big boys do it. we see that they most always employ a genset along with their pv sites. why is that we ask? with the exception of a few very exotic battery examples-all battery chemistries shut down at very low temperatures. there is however a few pure pv repeater systems that have come on-line right up in your neck of the woods. check out nwtel. this is the interesting part. they are employing the use of something called phase change materials (pcm) to enclose their battery boxes. i have never seen anything like this before. these pcm's store heat as a chemical reaction when they change from frozen to liquid states and release it back when they change back to a solid! interesting to read about.

 back to our problem. we have to find a way to keep the batteries at a reasonable operating temperature (in this case warm enough). i would shoot for a comparatively balmy 0*c. and from what i see. a simple insulated box ain't gonna do it. first- we can look into how many joules of heat we might extract from our equipment. second -we can look at building a thermal mass like a solar slab that gets charged with a trombe wall of some kind. third option might be to heat the batteries with the batteries like they do on some of spacecraft and rovers.

 im sorry to have posed all questions and no answers to your problem but there are ways of doing this i'm certain.
just for fun i'll start doing some numbers on the second option (thermal mass) and see what i find and get back to you. perhaps there are other options as well? anyone? perhaps running a 1/4 mile of wire isn't such a bad option?

also i think the motor in an auto acts as a thermal mass of sorts to help you start your car in the morning.

all the best, dave
 
220 Posts
Jul 12, 2008 11:19 pm
Re: Power needed for remote wireless signal repeater

sir,

 in the previous post i should have said that the chemistry of the battery all but shuts down in extreme cold conditions. we still may be able to get a fraction of our capicity- say 10 or 20%. but would force an increase of storage capicaty by a factor of ten. ie.. where a 200ah might work we would need something in the order of a 2,000ah bank for extreme cold operations. yikes!

all the best, dave
 
10 Posts
Jul 13, 2008 01:01 am
Re: Power needed for remote wireless signal repeater

Yes, the cold is an issue Dave. However, I have a tractor that sits outside and a car in an unheated garage, and both have batteries capable of enough cranking amps to start even in the coldest weather, so I was hoping that I'd be okay with this.

I've done the analysis and feel inclined to go with the wire through the woods method. The estimated cost for the solar without a camera is $863; the 515m of wire I need is $855 -- and with wire, I can power a camera. I still like a solar solution but I guess for the immediate issue, I'll go the traditional route.

Thanks for everyone's help; I've learned a lot.

Eric
 
10 Posts
Sep 1, 2008 12:05 am
Re: Power needed for remote wireless signal repeater

I thought I should update this thread... I now have a tower installed and the antennas are giving me good high speed Internet access.

It turned out that running wire was too complicated: voltage drop, cost, aesthetics -- and most troubling, liability issues. So for now, everything is running off a single 12V battery, but of course that won't last for long. We're monitoring the power drain and will add either a small wind generator or solar panels to the tower later.

Putting up the tower was a chore: a 200' near cliff (mostly 75°+ rise) meant everything goes up on someone's back. The tower parts weren't too bad, but the gas powered corer and the 18 gallons of water we needed to bore anchor holes was pretty challenging! But the view is amazing and the throughput is better than anticipated so it is worth all the hassle.

Thanks for the advice and ideas.
 
220 Posts
Sep 1, 2008 10:38 pm
Re: Power needed for remote wireless signal repeater

hi eric,

  it's so good to hear that you went ahead with your project despite all the obstacles.

  that sounded like some job drilling for those anchor bolts, thankfully that was a one time effort.

  i have thought about your project and wondered what solution you came up with. so thanks for the post.

  are you able to monitor the battery soc remotely? the numbers work out to about 4 days power from a 100ah battery with a 800mw draw and a deep 20% soc (80% dod) it will be interesting to see how the hard real world numbers compare.

  have you started working on your battery enclosure yet? i'm very curious to see how you make out. if you can get it insulated up to about r-50 and divert some power to warm it during Arctic conditions..maybe some soapstone in there as a sink? very very curious.. on the other hand, if it goes down for a day of two during a record cold snap there won't be any real harm done i would think.

  on that 200' outcrop there must be a nice stiff breeze most of the winter. check out the ampair micro turbines. we have used the little 100watt unit at the boat yard with good results. i have found the ampair 100watt out preforms the air x 400watt turbine in our installations. we always go with a pv setup alongside the turbine installations though.

  thanks again for the update. it's always interesting to hear about other peoples projects.

good luck, dave
 
220 Posts
Sep 2, 2008 11:48 pm
Re: Power needed for remote wireless signal repeater

hi eric,

  i was just playing with the calculator and i see that it is aprox 40 days not 4 days! for that 100ah battery example. thats more like it. somehow i lost a zero in the math. oops!

all the best, 73 dave
 
14 Posts
Nov 25, 2008 07:50 pm
Re: Power needed for remote wireless signal repeater

Eric:

I have about the same setup you are looking at.....repeater for wireless internet.   I built a 100' tower at the top of my mountain, and ran 2 -#8 wires 2300' down the mountain for powering the radios.   My internet provider came up with some neat plastic conduit that looks like black plastic water pipe with a slick silicone inside and had a pull rope in it.  I just laid the conduit on the ground down thru the woods, and it's been fine for 4 years now.....I only buried it down where it comes to the shop where my power source is located.

I was laughing at your experience with the tower construction.....lot of it sounded familiar !  Love to swap photos and notes with you if we can figure a way to email without post it public....

andy
« Last Edit: Nov 25, 2008 07:54 pm by Andy Davenport »
 
10 Posts
Nov 25, 2008 11:00 pm
Re: Power needed for remote wireless signal repeater

We are having our first real snow here tonight, and I'm astonished that I can actually get online: yesterday I had to hike up to my tower and carry the two 32kg batteries down to be charged. Luckily, I had a "spare" car battery up there already, and it seems to have sufficient power to keep me running for now. I don't look forward to having to slog through snow tomorrow to haul the other batteries up though...

Why did they drain out? Well, it seems that an 80W solar panel just can't produce enough power to both run the radios and recharge the batteries. According to the very useful Canadian govt site (https://glfc.cfsnet.nfis.org/mapserver/pv/municip.php?n=3457&NEK=e), I can only expect 51-59 kWh/kW of photovoltaic potential at my location in November (vs up to 138 in July). The current setup is draining at 14.4A/day, so my two 100Ah batteries will drain in 12.9 days without sun. With only 80W, I calculate it would take 11.3 days of sun to recharge -- very unlikely here in November! A 2nd panel would reduce this to 5.3 days; better, but still on the edge.

I am intrigued by your solution though: are you running 120VAC to the tower and then using it to charge batteries for the radios? Have you had any sign of animal damage to the conduit?

About pictures and notes... if you Gmail me, I'd be happy to send you a link. To avoid bot harvesters, I won't spell it out, but the 10 characters are the initials of my first & 2nd name (EJ) followed by my surname.
 
1 Posts
Jun 3, 2009 12:52 pm
Re: Power needed for remote wireless signal repeater

This shouldn't be a problem. We use multiple types of wireless radios from many different suppliers. They range from Free Wave 900 mhz ethernet radios that use 12 vdc @ 100 ma to larger higher power output tropos routers that use
24 vdc @ 3.5 amps. I work with a Govt Agency that use a wide variety of batteries for remote location surveillance work. The batteries we choose are Lithium and are called
BA-5590 these are Lithium SO2 and are not rechargable and expensive to purchase($50ea) but work well when a few are used in a series circuit arrangenment. The higher the amperage that is drawn the more batteries we add to the series circuit.
Their is also a re-chargeable version of this battery they are called BB-390B/U These are Nickel Metal Hydride NiMH and their cost($240.00ea) but they are rechargeable. They work well but need to be re-charged as used.
On sites we use Solar charging power supplies(batteries) we use Gel Cell Batteries that are usually 6 volts ea. We then configure these in a parallel circuit to give us 12 vdc while arranging them into a series circuit as well to take the amperage use off the batteries. The reason we use lower voltage gel cells is they are Great! for solar charging arrnagements and don't cost alot. Even re-chargeable batteries need to be replaced every so often.
You my freind could use common 9vdc lithium batteries built in a circuit to give you your needed fov and get alot of use from that remote router.Even if a router is sitting with no traffic it still is drawing power. The only thing that changes is traffic which equals trasnsmissions which equals power use. If using any type of commercial lithium batteries Never!! use batteries manufactured in China, they are very poor quality and last maybe! 1/3 of the American made batteries. If ordering over the internet, you need to specify--Made In USA-Only! or they will send you Foriegn import batt's. Hope I helped, I'll check again to see if other questions come up.  Thank You,    KM,
 
10 Posts
Jun 4, 2009 01:41 am
Re: Power needed for remote wireless signal repeater

The problem I face is the cold though Ken: by late November, the battery chamber was below -20C at night, and with almost no sun and 24/7 power drain, the batteries couldn't stay charged, and dropped way below the threshold they need. They are deep cycle renewable energy batteries (made in the US even though we are in Canada) and cost ~C$275 each. By January, when we frequently dip below -30C, the batteries had dropped to 3.5VDC and nothing worked.

We have subsequently purchased a wind generator (WG), and will install it on the tower mid-June. We've had to figure out how to keep the batteries warm in winter though, and hopefully have a solution now. Once the batteries reach fully charged state, some custom electronics will divert the power coming from the WG to a radiator with some glycol and water and a 12V heater to keep the battery chamber warm. In summer the extra power can run a fan to cool it because the summer highs exceed 35C. With a 400W wind generator, I should have enough power.
 
220 Posts
Jun 5, 2009 03:07 am
Re: Power needed for remote wireless signal repeater

 
thanks for keeping us updated on your repeater project. seeing this one through looks like your goal and anything less is not an option. cheers on that sir!

 this was never an easy project from the onset and your glycol "solution" to storing enough btu's to maintain operating temps is sure to work!

 have you worked up any estimates of tank size needed, exposure area/r-values and the like?

good fight. best regards, dave
 
10 Posts
Jun 5, 2009 11:08 am
Re: Power needed for remote wireless signal repeater

Yes, I guess you nailed it David: seeing it through is the goal now!

Like a lot of this project, the first approach to the "problems" has been to just jump in and try to figure it out on the fly. Not very scientific, but with tips and resources on the web -- like this forum in fact -- we've been able to make decent progress.

Determining the BTUs is complicated because the characteristics of my insulated container are not well known. I have been recording inside/outside extremes since last October, but opening the door in -25C skews the minimum pretty rapidly! Having a much better record of the temperatures will help, so I'll be installing a weather logger.

The tower is now becoming a bit of a test bed for some other ideas too, so stay tuned...

Since you guys have been a part of helping to get it to its current state, here's a link to what it looks like (at least as of winter; the page will be updated when we have the wind generator up on it): http://www.chesleyhouse.com/Egypt2007/wt_Tower2.html

The bear shown near the end has been back, but now the tower is just part of the scenery so I guess he isn't as interested!
 
220 Posts
Jun 6, 2009 01:29 pm
Re: Power needed for remote wireless signal repeater

 eric: thanks for sharing that project page you put together. nice job documenting the progress. quite the cast of characters helping with the build- everyone brings a little something to the table. nice to see. that view is fantastic! you are truly in GODS country there. nice touch with that automatic game camera, they have come a long way in the last few years. maybe you could put a ham on a chain and set up a bear powered generator!

kind regards, dave
 
6 Posts
Jun 14, 2009 11:20 pm
Re: Power needed for remote wireless signal repeater

Way back at the beginning of the thread there was the question of installing a camera, with the problem of powering a 5v camera from an otherwise 12v system.

One of the posters said the only way to do it was with a resistive load.  This is not true - they also make devices known as "DC-DC" converters - essentially they are an oscillator that converts the source voltage to AC, a transformer to step it up/down to the target voltage, and rectifier circuitry to turn it back to DC at the desired voltage.  They aren't 100% efficient, but aren't as bad as doing a resistive load.  They do need to be fairly well matched to the load for good performance...

I don't have a specific source, but I'm sure Google can find a bunch of them...

ART
 

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