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Author Topic: Off-Grid Operation in My Shack  (Read 1260 times)
NB6Q
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Posts: 65




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« on: June 27, 2019, 10:36:12 AM »

I have made the decision to make my shack 100% off-grid-capable, even though it is inside of the home and runs on 120V AC now.  I'm doing this for a few reasons, one is to learn more about solar power on the cheap (vs. putting up an array for the entire house) and to get the cleanest DC power available.  I don't expect to save any money on electricity or to save the planet.  This is purely part of my hobbyist interest to come up with a design and execute on it successfully.  Amateur radio has provided me with a perfect lab specimen to use for this experimentation and execution.

There appears to be an entire solar product ecosystem geared towards and scaled for RVs with solar panels, batteries, chargers, regulators, inverters and just about anything else required to setup an RV for this same purpose as I intend for my shack.

One question I have is there any way to tell how "quiet" these products are before buying them?  I've watched a ton of YouTube videos by RVer's who have setup their solar panels and battery systems.   Are these products quiet enough for amateur radio or do I need to look at different equipment?

Another question is should I be using the "RV Approach" for my shack or should I be looking at something else?  I don't have a budget for this but I want to avoid over-engineering anything and wasting money on getting too fancy.  I would also like to eventually run a small A/C unit off this system when the sun is high overhead and my battery and solar panel capacity is sufficient to do this.  I would also want to augment charging capability from house power when the sun is not shining.
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KB1GMX
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« Reply #1 on: June 27, 2019, 06:53:25 PM »

OK,  big bite to chew.

First RV/Sail are not the only thing.  Panels are sold in all
sizes and voltages and prices.  Batteries are the next big item.
Charge controllers and inverters as needed are less costly.

First you run nothing off the panels, peak currents and widely
varying voltages are a solar fact of life.

a 100W panel will not run a 100W radio!  A 100W radio wants
about 20-30W during recieve and 240W during TX.  It also want
to be 13.8V +-15%.  Solar panel 100W is 21V open circuit, and
loaded to 5.56A (maximum power point) will be at 1&V and if you
try to draw more the voltage goes down.  So you store power
in batteries.

AC units, 5000btu is about 600W (for typical 120V AC powered),
to run it for say 6 hours you need 3600WH of power.  That would
need to be supplied  by batteries of greater than 12V 600AH size. 
To charge a little 900W of solar when the sun shines.   You need
more solar to recharge the battery if it runs after low sun hours.
Simple you don't want to sit in a cool room with dead battery when
its dark.

The inverters (for things that must run off 110V like rotor and
controller) and charge controllers are all over the map from
dead silent to drive you mad.  Ask around as many are quiet.

Example system Mine:
400W of solar for 12V system  (plan about 1.45$/watt purchased with shipping)
I spent less from on line sources and two used panels in excellent condition. 
More than that is either special application foldable or robbery.

150AH industrial NiCd (large flooded type) lucky find used very good condition
and most of all free.   Bought new something over 2100$. That is 10 cells at
nominal 1.25V.   Marine deep discharge lead acid are lower in cost and first
time a good idea.  There are caveats...

WIth batteries more is always better but there is a item to consider a
600AH battery needs a peak charge current near 60A (C/10) to keep
things up and the cells equalized.   For mine the 400W of solar hits
the minimum of 15A,  actually 22A.  The excess as flooded NiCd
tolerate over charge well.  Typical use I've rarely seen 10A peak.
Where lead acid (deep discharge types) its not recommended
for best life.

Charge controllers are fairly cheap I built mine but 120$ would do as well.

Only one item needs AC power that is the HAM-IV and its box a small 200W
unit does it for the short time needed.

One amp, 120W 2M for SSB wants 28V so a purchased module at 30$
provides that.  It is in a die cast box with filters to keep it quiet.

Caveat on battery voltages.  NiCd has a higher average voltage so the radios
never see under 11V even in the january VHF contests.  With lead that is more
like 13.2 with charge and can sink under 11V, and some radios dislike that.
The fix for that is a MFJ or other 12V booster to get closer to 13.8V (nominal)
when the battery is low.  Why booster, nominal 12V battery rests at 12.6V and
even a large one will sag to under 12 before you have used 30% of the capacity.
Also with lead stop discharging at 10.6ish to keep the life in the cells.

Wire, there is #4, #6, #8, and #12 wire to deliver those currents without
excessive voltage drop.  The wire is sized and fused according to size.
For example #4 wire fused at 70A and #12 uses fuses of 20A.

Protection, circuit breakers and fuses to excess.  Big batteries mean huge
currents if there are shorts.  The 150AH NiCds will easily dump far more
than 1000A into a short so fuses are there to protect the wires from melting
down.  Fusing is on several levels, protect batteries, interconnects, and then
distribution to radios, accessories, and lighting (mostly led) and redundant. 
Key is the 12ga wire never has a fuse larger than 20A and fast blow at that.
Marine switches are handy for shut off on circuits as they come in sizes to
several hundred amps as needed.

Location and air flow, most batteries even AGM type produce some hydrogen
gas so venting the battery rack outdoors is advised.   

Space, batteries don't like heat or cold so where they go is important. Also
long leads will have to be very fat to avoid line drop.  The 10 cells I have fill
a 14"wide x 23" deep x 18" high space. They live outdoors but protected
and that results in short but heavy leads (#4 copper).

The above is solved several ways, big wires, or higher voltages.  By higher
voltages  24, 36, and 48 volt systems are used to fight I^2R loss in wire.
Higher voltage means lower currents for a given power level.  The yabut
is then you have to convert the higher voltage to 13.8 for radios or
120V AC.  There is a price for conversion, linear designs will eat power,
produce heat, and low efficiency.  Switching type can be efficient and
come with potential noise issues.  Either way watts in the battery are
not watts available to the radio and gear due to limits of efficiency.

As you may guess it does not scale easily from small system to
very large.

Some things may seem out of scale but here in New England winter
sun when available only illuminates the panels for maybe 3.5hours
so excess solar helps especially with a foot of snow on them (must
be cleared).  The other is enough power total to run the station for
a VHF/UHF contest 24hours at full or reduced power.  Full power
means Exciter radio (Tentec 6n2) at 10W drive to amps for 6 and
2M at 120-160W or barefoot at 20W.  UHF is a FT817 with amp
(50W).  For HF a single radio Tentec Eagle at 100W or throttled
as needed to conserve power.  During the summer with more
than 8 hours of  sun there is always excess unless its overcast
then a few amps from the panels will be about all.

In the end the station is effectively off grid including computer
and display which are also picked for power efficiency and will
run on a 12V automotive system (13.8V +-15% or better).

Likely more than you expected and likely fire hose to sip from.

Start with a QRP radio, 12V gell cell and a 20W panel plus a small
charge controller to get the feel.  Thats manageable on small budget
and portable too.

Allison


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NB6Q
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Posts: 65




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« Reply #2 on: June 27, 2019, 11:37:20 PM »

Thank you very much. 

I am in NorCal so the weather is mild year 'round.  I plan to have the batteries in a semi-insulated patio box just outside of the shack.  The run from the batteries to the inverter inside is about 1 meter through a 3" conduit portal.  I am not decided on batteries yet, be it type or number but I am thinking at least 500AH 13.6V.

Although the goal is to be off-grid I do plan to have house power with a charging circuit to keep the batteries topped off if the sun is not providing sufficient charge.  I also have a Honda 2000 generator that I would like to somehow integrate into this setup as a backup source if house power is not available (i.e. nights, cloudy days when power is out).

I forgot to mention one thing.  Although we have mild Mediterranean climate weather we also have earthquakes in California.  A very serious earthquake could mean days or longer without any power.  Solar is fine but for realistic and practical purposes the Honda generator needs to be part of exercise.
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K5LXP
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« Reply #3 on: June 28, 2019, 04:57:17 PM »

I've been doing this for years in one way or another, mostly portable in the field.  But I have an RV too so the notion of a power budget is 2nd nature.  There's a lot of give and take depending on how flexible you are in operating your loads, and how long you're willing to wait for the bank to recover.  Keeping an oxygen machine running through the night every day has a different priority than missing a 2M net.  So with that in mind I would start with what you think will cover some degree of operation, then you'll learn and adjust as you go.  There are a number of factors unique to your installation you can't predict so putting something up and getting some Ah through it to establish a baseline of performance will give you a better idea of what it will take to operate load scenarios.   Having a battery monitor that counts Ah in and out will make knowing where you're at pretty easy.  And, when "all else fails" there's always the generator... 

Mark K5LXP
Albuquerque, NM
 
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NB6Q
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Posts: 65




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« Reply #4 on: June 28, 2019, 05:59:52 PM »

I've been doing this for years in one way or another, mostly portable in the field.  But I have an RV too so the notion of a power budget is 2nd nature.  There's a lot of give and take depending on how flexible you are in operating your loads, and how long you're willing to wait for the bank to recover.  Keeping an oxygen machine running through the night every day has a different priority than missing a 2M net.  So with that in mind I would start with what you think will cover some degree of operation, then you'll learn and adjust as you go.  There are a number of factors unique to your installation you can't predict so putting something up and getting some Ah through it to establish a baseline of performance will give you a better idea of what it will take to operate load scenarios.   Having a battery monitor that counts Ah in and out will make knowing where you're at pretty easy.  And, when "all else fails" there's always the generator... 

Mark K5LXP

Thank you.  I understand your advice to approach this while being load conscious, somewhat in simulation mode for when the batteries and solar are really needed.

I plan to have two "generators" (house power and the Honda 2000).  I was even planning on having a audio noise source to simulate "generation" was taking place when house power was switched on and charging.  The Honda 2000 is just another source of generation that would be the true generator.  The house power would serve as simulated generator power.

In reality, earthquakes are a real threat here in NorCal.  We have freeze-dried food, fuel and water stored so we would survive for awhile but solar power with a cache of batteries to store power is very desirable when the grid goes down.

Albuquerque, NM
 
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K6AER
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« Reply #5 on: July 04, 2019, 05:06:04 PM »

For back up I would buy a 4000 watt gas generator.
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K6AER
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« Reply #6 on: July 04, 2019, 06:15:54 PM »

Addition to the above.

Harbor Freight...$400. You want enough generator to run everything and charge batteries,

Also solar regulators can be very noisy in the RF spectrum. Test befor you buy. You might be better off with a 48 volt battery/solar system and use a 48V to power a 120 volt AC inverter. 4000 watt DC to AC inverters are not that expensive.

You battery requirement is how many watts you will need at0 night plus 30%. Your solar erquirement is how many watts you need during the day and the extra to fully charge the batteries plus 30%.

Solar batteries must be able to take thousends of deep discarges. Normal Gel Cells will not survive in this application.
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KC6RWI
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« Reply #7 on: July 08, 2019, 12:55:54 PM »

The yl wanted a refrigerator back up, because of power outages, and possible earthquakes. I spent the week end listening to diy vids.
What I found in the biggest expense is the battery. First I hear all about a telsa battery with tons of capacity, so much that I don't want to post the value as it may make it sound like I heard it wrong. I will, its 5100 amp hrs. The the utuber who was touting this as the best value and capacity. Then he  changes his story ( it has to be charged at the right rate and its touchy). He now recommends a battery with 10yr warranty but a high high price. Funny he would do that, $$$$$.
The battery is battle born lithium ion phosphate..but its $950 and only 100 amp hrs. So now I am stumped. I'm spoiled after hearing about a tesla battery.
I'd like to have 200 or 300 amp hours and run the frig.
« Last Edit: July 08, 2019, 01:07:06 PM by KC6RWI » Logged
W9IQ
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Posts: 3231




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« Reply #8 on: July 08, 2019, 01:03:34 PM »

You may find that a propane powered refrigerator is a much more economical and viable option. They are commonly used in RVs and boats. Many have 3 way power - 12 VDC, 120 VAC and propane. If you choose to use the 12 VDC connection, you can at least avoid the inverter.

- Glenn W9IQ
« Last Edit: July 08, 2019, 01:07:13 PM by W9IQ » Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KC6RWI
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Posts: 172




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« Reply #9 on: July 08, 2019, 01:09:08 PM »

I didn't make it clear, we wanted for the home back up system, yes, thats a tall order for batteries running into an inverter.
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W9IQ
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« Reply #10 on: July 08, 2019, 02:41:40 PM »

Even if you run it off of 12 VDC instead of propane, you at least avoid the inefficiency of the inverter. Of course, the trade-off is that  you must have the right gauge / maximum length of wire.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K5LXP
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« Reply #11 on: July 08, 2019, 08:28:53 PM »

The yl wanted a refrigerator back up, because of power outages, and possible earthquakes.
I'd like to have 200 or 300 amp hours and run the frig.

Anymore it's not unheard of to use residential refrigerators running off of kW inverters in RV's.  The loads are not really all that extreme for the most part.  But the $64K question is, for how long?  The battery bank to run a fridge and some other stuff for a 24 hour period is one thing, to run it a week or more is something else.  Define the requirement and that will shape the solution.  Unless you have deep pockets and a dedicated space for a battery bank you will rarely use, the likely solution will involve some number of batteries but also a generator.  For emergency purposes, one that runs off propane can be stored "dry" and propane doesn't spoil like gas does.  This would be the #1 standby power solution for me.

Mark K5LXP
Albuquerque, NM
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VK2NZA
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« Reply #12 on: July 09, 2019, 08:46:17 PM »

Hi NB6Q, I run an all DC solar powered shack and have been on standalone power since 1982 on our 300 acre rural property in Far Northern NSW, Australia.
I have an 10 KW solar array feeding 48 volt battery bank and 6KVA (continuous) sine inverter an also a 6KW solar array feeding a 24 volt battery bank and 3 KVA (continuous)sine wave inverter that run my house and sheds plus diesel generator backups.
However for the shack I am using 6 250 watt panels feeding a 24 volt 250A/H battery bank.
The 24 volts is passed through a 35 amp 13.8 reducer/regulator and my equipment are all DC powered.
I do not use an AC inverter for supply as I have found that no matter the quality some RFI is radiated from them.
My household inverters are high quality Euro designs and are very good however although minor there is some generated noise, over the years i have utilised a number of differing units, however not as yet found a totally silent rig.
The regulators are American  "Outback" brand 80 amp MMPT and work silently, my solar arrays are also silent creating no RFI at the shack.
On evenings when i choose to do some DX'ing with my rigs I shut down my large inverters and have an entirely RFI free environment being 5klm from my nearest grid powered neighbour in a comparetively remote area.
Other advantages of DC only operation are reduced heat in rigs as i have bypassed the internal AC power supplies in say my IC 761 and 765, my Paired  IC 7410's (diversity reception) and various other VHF/UHF rigs are happy with high amperage 13.8 VDC although I am converting an Icom IC-2KL to operate on 40 volt DC for a little more power.
For mobile ops in my RV I utilise 2 130 A/H AGM 12volt batteries via an MFJ -4416C battery booster for a constant 13.8 VDC and a Kenwood TS 480SAT transceiver.
While this system operates the whole RV including compressor fridge, Sat TV LED lighting, etc, I only usitilise the MFJ voltage controller for the rigs.
There are plenty of low cost  20 -30 A/H MMPT regulators available for converting my 2 250 A/H panels
to charge/regulate the batteries, in my case the panels are household panels at 36 approx volts each, and an MMPT 30 amp regulator will accept the higher voltage, up to 100vdc and auto recognise the battery voltage for appropriate  charging.
Contrary to some views, there are many Chinese made solar products that work very well and my RV solar gear, panel, AGM batteries and regulation are all Chinese manufactured and have been very reliable.
E'bay has a plethora of cost competitive items available a quick search will reveal a multitude of choices.
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KC6RWI
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« Reply #13 on: July 10, 2019, 08:20:49 AM »

You are man made power station! I'm all for that, followed all you said. I'm a little taken back in looking at solar. Wanting to use an inverter, I found there is an idle drain and a loss of 8 to 10% in operation. So it just means that you need a good battery bank to be able to spend those electrons. I also found the (controller?) some have a fan in them, more loss, the unit that takes the power off the panels. I will investigate the AGM batteries. Thanks
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K5LXP
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« Reply #14 on: July 10, 2019, 05:12:19 PM »

 
When you're operating a load that's kWh in a 24 hour period, the Wh's of idle current and a fan are the least of your worries.  AGM buys you an incremental increase in discharge efficiency at a not so incremental premium in price.  For what you'd spend on AGM you could buy a lot more Ah with flooded.

Mark K5LXP
Albuquerque, NM
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