Looking at solar power n need help

KF0AWL

Hobo
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Jul 3, 2009
Messages
164
Location
Iowa
Im looking at going solar for field operations in the future and WOW there is a lot to learn!
One question I have is controllers, I see the famous BLUE controller on amazon and all over that the price fairly low but I have read a few people say don't bother...
Whats the negatives of them? Im one of those if I dont use it ALOT and it works good while I decide if I like the idea I'll buy inexpensive to start people.
Bearing that in mind what should I look for for a minimum solar panel to maintain my Marine deep cycle that will keep it charged and run my hf rig and a two meter rig yet when the sun goes down ill have a few hours of play time left for after dark.
I would prefer a folding panel so its not so cumbersome to pack and carry.
And most of my operating will be day trips in my vehicle to set up in a park.
Thanks everyone for sharing your knowledge with me 😁
 

mmckenna

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From the land of sky blue waters!
The big challenge with controllers is that you need to find one that doesn't spit out a lot of hash on the DC power, or RFI, if you are going to be using the radio while the controller is working. I have 3 very remote repeaters that I inherited at work that are solar powered. All three are identical, and only one of them has some annoying noise over the audio. Haven't had time to fix it yet, but all the controllers are the same, just one causes issues.

For portable use, a small gel-cell is a good inexpensive solution. If your budget allows, there's some nice Lithium Ion and other chemistry batteries that are much lighter, but more expensive.

Panel size will really depend on how much size you can pack in/out of the area.

One good option is to charge a battery before you go, and just keep the solar panel there to extend your run time. That may allow you to use a smaller battery.

The sizes for all this depends on how much current consumption you'll have. I know you said HF and 2 meters, but how much power will you be running?
 

KF0AWL

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Iowa
I would be intrested in gel over a big marine battery!
The power usage i would have to do my figures and out were I would need. Power to be. I see 200 watt, 100 watt panels but is there a big difference?
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
You might research the receive current on the radios you want to run from the battery then the transmit current then estimate your receive and transmit time during a 24 hour period. Some radios can draw 2 amps on receive while others can be less than .5 amps. A 100 watt HF rig in SSB mode might draw 8 to 12 amps average during transmit even though its specs say 20-22 amps, which would be worse case in FM mode. Your choice of radios can have a big impact on how long they can run before the battery is depleted and in danger of being damaged.

Also consider whatever you use out of the battery, it takes about 1.5 times that much to put back during charging, so if you calculate you might use 20 amp hours a day playing with the radios, it can take 30 amp hours of charge to make up for it. With a fixed solar panel you will get maximum charge rate for 3-4 hours then the panel has to be moved to track the sun or you put up with a decreased charge rate. Clouds and seasons will also take their toll on getting 100% out of your solar panel(s).

As a starting point to judge what you might need, 30 years ago I ran an old Kenwood HF rig off a single 100AH gel cell battery charged with a 60 watt solar panel in sunny So Cal. I monitored the battery closely and could operate the radio for a couple of hours a day and never pull the battery down far enough to worry. That HF rig drew less than 1 amp on receive and 8 to 12 amps average on transmit. If I added a 2m/440 rig that drew another amp on receive and a solid 8 to 10 amps on transmit I believe I would have needed more solar panel to keep up with power used.

Today I still use a 100AH class gel cell when camping but I charge it with a 200w solar panel that I move with the sun and that has powered a lot of radios and a 500 watt HF amp used during both daytime and evening hours. I have never run out of battery power yet as the battery is topped off late afternoon and has enough to run my radios and amplifier during the evening before starting the charge process first thing in the morning. At my home I have 400w of solar panels on the roof charging four big 6 volt golf cart batteries in series parallel for about 440AH.

More battery is better but there are some rules to follow when paralleling batteries for more current or amp hours. Compared to 30yrs ago solar panels are cheap and the last 100 watt panels I bought were in the $80 range so its not expensive to overbuild your system a little.
 

KF0AWL

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Jul 3, 2009
Messages
164
Location
Iowa
You might research the receive current on the radios you want to run from the battery then the transmit current then estimate your receive and transmit time during a 24 hour period. Some radios can draw 2 amps on receive while others can be less than .5 amps. A 100 watt HF rig in SSB mode might draw 8 to 12 amps average during transmit even though its specs say 20-22 amps, which would be worse case in FM mode. Your choice of radios can have a big impact on how long they can run before the battery is depleted and in danger of being damaged.

Also consider whatever you use out of the battery, it takes about 1.5 times that much to put back during charging, so if you calculate you might use 20 amp hours a day playing with the radios, it can take 30 amp hours of charge to make up for it. With a fixed solar panel you will get maximum charge rate for 3-4 hours then the panel has to be moved to track the sun or you put up with a decreased charge rate. Clouds and seasons will also take their toll on getting 100% out of your solar panel(s).

As a starting point to judge what you might need, 30 years ago I ran an old Kenwood HF rig off a single 100AH gel cell battery charged with a 60 watt solar panel in sunny So Cal. I monitored the battery closely and could operate the radio for a couple of hours a day and never pull the battery down far enough to worry. That HF rig drew less than 1 amp on receive and 8 to 12 amps average on transmit. If I added a 2m/440 rig that drew another amp on receive and a solid 8 to 10 amps on transmit I believe I would have needed more solar panel to keep up with power used.

Today I still use a 100AH class gel cell when camping but I charge it with a 200w solar panel that I move with the sun and that has powered a lot of radios and a 500 watt HF amp used during both daytime and evening hours. I have never run out of battery power yet as the battery is topped off late afternoon and has enough to run my radios and amplifier during the evening before starting the charge process first thing in the morning. At my home I have 400w of solar panels on the roof charging four big 6 volt golf cart batteries in series parallel for about 440AH.

More battery is better but there are some rules to follow when paralleling batteries for more current or amp hours. Compared to 30yrs ago solar panels are cheap and the last 100 watt panels I bought were in the $80 range so its not expensive to overbuild your system a little.
Thanks! That was very helpful!
 

mmckenna

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From the land of sky blue waters!
I have 200 watts worth of panels on my toy hauler. It works pretty well mid day, but charge current drops during morning and late afternoon, so as prcguy said, tracking the panels is important. Mine are more or less flat on the roof, and parking under tall pine trees isn't ideal, but it provides plenty of power to keep 2 marine deep cycle batteries topped off even with house loads and my wife's damn cpap machine running all night.

If you are packing all this stuff in more than a few hundred feet, you'll really want to consider weight. A 100ah gel cell is a nice thing, but they are heavy, and I'm getting too old for that sort of crap. I've had to move a few thousand of those over my career and it's one of my least favorite parts of the job.

I'd probably look at less RF power, less RX current, and more efficient antennas before I'd be looking at large gel-cell batteries and 200 watt panels, unless you are basically working out of the back of your car.
 

prcguy

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So Cal - Richardson, TX - Tewksbury, MA
For solar charge controllers there are the big name brands for big $$ but I've bought a bunch of cheap Chinese units and have had great success. Here is one of the dozen or so I've tried and they are so cheap its hard to believe they even work but they do and offer lots of options.


These charge to the right voltage and are completely programmable for low voltage cutoff, high voltage cutoff and other parameters. They don't seem to produce any RFI but they do modulate the battery buss with a pulsating DC while charging. Most equipment doesn't care but my Elecraft KX3 radio with spectral display is very sensitive to rapid voltage fluctuations and can affect the optional spectral display.

There are many types of solar chargers from electronic switches that simply connect and disconnect the solar array when it reaches a prescribed voltage to switching regulator types that can squeeze the most out of the sun and still charge when the panels dip below battery voltage. In other words if the panels are down to 10 volts or less these controllers can buck boost the voltage up to maintain some charge current.

Another thing to consider is solar panel rating vs what you can actually get from the panel. Most panels for 12V systems will put out 19 to 21 volts full sun and no load. So a 100 watt panel would be maybe 21 volts at 4.7 amps. Problem is the most the panel will put under any circumstances is about 4.7 amps so if you figured 100 watts at 12 volts which is 8.3 amps, that's not what your going to get. This is where an MPPT or other buck boost solar charger will get you more charge current and make the most of your solar panels.

My camping setup is completely portable but it doesn't go much further than about 20ft from my vehicle or my travel trailer because the battery is heavy. The 200 watt system is two 100w panels screwed together with a piano hinge and it folds up with glass facing inward for travel and I put a rope carry handle on it. I also put a folding leg on it so when I fold out the panels they can sit at about a 45 deg angle to the sun. I have another system a friend bought me thats around 120w and it folds up into a nice carry case with a built in charge controller. I think that one was $119 complete with shipping.

I also have a 60 watt solar panel and 100AH battery in my small travel trailer and that usually only powers the water pump and some LED interior lights that draw nothing but I have run a few radios temporarily from that battery system. Since the panel is flat on the roof it doesn't make the best use of the sun but its overkill for what it powers.
 

KF0AWL

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Jul 3, 2009
Messages
164
Location
Iowa
For solar charge controllers there are the big name brands for big $$ but I've bought a bunch of cheap Chinese units and have had great success. Here is one of the dozen or so I've tried and they are so cheap its hard to believe they even work but they do and offer lots of options.


This is the famous blue controller! 😁
You have good luck with it then?
 

vagrant

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Nov 19, 2005
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2,188
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California
@KF0AWL

Solar Controller
I had no idea what the famous Blue controller is you referenced. I personally use Renogy PWM controllers and have zero problems with RFI. One handles SLA and two newer versions handle lead acid batteries as well as Lithium. Instead of spending extra money on an actual MPPT controller, I used it toward another 100W flexible panel. Depending on the rating of the controller, they can typically handle multiple panels when wired correctly and 9~10 Amps is nice in a best case scenario using two panels. ( Note: Some controllers labeled MPPT are actually PWM. Read further on the description on that link. Still, I could be wrong. )

Solar Panel
I mostly use flexible and folding, they are in great shape and still kick out plenty of power due to the occasional use. Additionally, I store and transport the 100W flexible panels in the boxes they shipped in, after removing the other support material inside. When I deploy the flexible panels, I put the cardboard box under them when on a flat surface such as my hot vehicle roof. This keeps the temperature down on the panels and improves longevity and power output. During the course of the day my panels are in three positions to track the sun. That has worked well enough for me.

Power Output
My flexible 100W solar panels will give me 4.5~5 Amps in full sun. My 50W folding panel does about 2.8 amps maximum after using several meters to confirm. Still, there's going to be some give and take between panels and when used due to clouds etc. I measured using an inline meter as well as a DC clamp meter simultaneously. Still, not all 100W panels are the same.

Where to begin
You could start out with a PWM controller and a single 100W panel whether folding or flexible. If you figure 4.25 amps charge current on the safe side, it would handle the RX amp draw and still put some charge back into the battery. Figure two panels giving you 8.5Ah minus 2A for the RX draw and you would enjoy 6.5 Amps charge, or say 6 Ah to play it safe.

The next step
Everyone should consider the power draw of their radio at different power levels and the actual dB gain. I recommend testing at 20, 40, 80 and then 100W while noting the amp draw. Then look up the actual dB gain difference between those output watt settings. The point here is the power saved and whether a single 100W panel will do the job, or if one needs two or more. I often use 20W and may step it up to 40W at times, or 80W if I really need to make a particular contact.

The more important part
An efficient antenna is critical. Consider the power draw of using 100W and a poor performing antenna, versus 20W with an efficient one. You see, your endeavor actually starts here. Still, some operators don't want to think about it and want to slap 100W through their antenna no matter what. Some antenna manufactures make accessories like a loading coil that will handle the 100W power which mostly dissipates the heat versus providing equal gain per watt. Those operators are having fun and there's nothing wrong with that as far as they are concerned.

Anyways, my advice above has phone use in mind. If you are using digital modes one would typically TX using lower power. Still, an efficient antenna is the most important part regardless of mode.

@prcguy - I would like to know more about, or a link to that 120W complete system for $119 shipped. That sounds fantastic!
 

KF0AWL

Hobo
Joined
Jul 3, 2009
Messages
164
Location
Iowa
For solar charge controllers there are the big name brands for big $$ but I've bought a bunch of cheap Chinese units and have had great success. Here is one of the dozen or so I've tried and they are so cheap its hard to believe they even work but they do and offer lots of options.


These charge to the right voltage and are completely programmable for low voltage cutoff, high voltage cutoff and other parameters. They don't seem to produce any RFI but they do modulate the battery buss with a pulsating DC while charging. Most equipment doesn't care but my Elecraft KX3 radio with spectral display is very sensitive to rapid voltage fluctuations and can affect the optional spectral display.

There are many types of solar chargers from electronic switches that simply connect and disconnect the solar array when it reaches a prescribed voltage to switching regulator types that can squeeze the most out of the sun and still charge when the panels dip below battery voltage. In other words if the panels are down to 10 volts or less these controllers can buck boost the voltage up to maintain some charge current.

Another thing to consider is solar panel rating vs what you can actually get from the panel. Most panels for 12V systems will put out 19 to 21 volts full sun and no load. So a 100 watt panel would be maybe 21 volts at 4.7 amps. Problem is the most the panel will put under any circumstances is about 4.7 amps so if you figured 100 watts at 12 volts which is 8.3 amps, that's not what your going to get. This is where an MPPT or other buck boost solar charger will get you more charge current and make the most of your solar panels.

My camping setup is completely portable but it doesn't go much further than about 20ft from my vehicle or my travel trailer because the battery is heavy. The 200 watt system is two 100w panels screwed together with a piano hinge and it folds up with glass facing inward for travel and I put a rope carry handle on it. I also put a folding leg on it so when I fold out the panels they can sit at about a 45 deg angle to the sun. I have another system a friend bought me thats around 120w and it folds up into a nice carry case with a built in charge controller. I think that one was $119 complete with shipping.

I also have a 60 watt solar panel and 100AH battery in my small travel trailer and that usually only powers the water pump and some LED interior lights that draw nothing but I have run a few radios temporarily from that battery system. Since the panel is flat on the roof it doesn't make the best use of the sun but its overkill for what it powers.
Can you point us to the $119 unit to check out?
 
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