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Author Topic: Solar, am I on th right track?  (Read 20253 times)
KG6YSF
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Posts: 91




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« on: October 19, 2013, 08:42:11 PM »

I am looking at setting up solar to power my station. What I am planning is to get a 70W panel and a 10a controler. I Have already purchased 2 115ah marine deep cycle batteries. I plan on a second panel in a year.
My station consists of a Yeasu FT-8900, a Drake TR7 and a MFJ 969. I operate about 4hrs a week tx and about 100hrs rx.
I will add some LED lighting to provide light for the desk.

Drake: 35a max at full tx, 3a rx
Yeasu: 10a at full tx power, 1.5a or 2a rx
MFJ 969: Just a light is being driven for the swr/power meter
LED lights: 12v 0.06a, 10 modules

So you think I have a reasonable plan? I am wanting to be able to operate even if the power is out which happens frequently come winter from a few hours to a few days. As well when the fire season is in we can be out of power for days at a time due to the fires. I would love to get a 200w array with an eight battery bank but that isn't feasible for me in less than probably 5 years. One panel and 2 batteries a year is about what I can do. If you who have experience with solar think that this will work to start with than I will continue, if not tell me if it is attainable with out much more initial cost.

Thanks all,
73's
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
N7BMW
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Posts: 113




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« Reply #1 on: October 20, 2013, 12:55:28 AM »

With batteries in parallel it is best to use the same type and age batteries and parallel them from new.  As batteries age they will have different internal resistance and unequal batteries will end up discharging from the stronger to the weaker just bringing the whole bank down. 

It is also best to not discharge the battery bank to less than 50 percent charge.  The shallower you discharge them the longer they will last.  So with two 115 AH batteries no more than 115 amps should be drawn out before recharging.  The proper way to measure a battery's state of charge in to measure the voltage of a fully rested battery - one that has not been discharged or charged for 24 hours.  This is a difficult thing to do with an actively used battery bank.  You can also measure the specific gravity of the electrolyte.  An amp-hour meter is a ballpark figure.   It works on a sampling algorithm and cannot track the rapidly changing load of an SSB or CW transmission.

A single 70 watt (5 amp) panel is just a trickle charge.  Depending on your location a good rule of thumb is six hours full output from the solar panel per day when you have 12 hours of daylight.  The panel will only produce full power around noon unless you plan to constantly angle the panel towards the sun.  Also, at best 85 to 90 percent of the power recharges the battery - the rest is lost to heat.  That 70 watt panel is good for about 25 AH per day, in the tropics, as long as the sun shines.  The farther north or south of the equator you go, the less you can depend on that output. And of course shorter winter days mean less power.  Stay away from so called self regulating solar panels.  There must be a voltage differential for power to flow.  The open circuit voltage of the panel must exceed 15 volts (18V is better) if you are going to get a full charge. 

I lived aboard a sailboat for many years and depended on solar for most of my power.  I could get 5 years out of a set of batteries by following what I wrote above.

73,

Brian




 
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K8AC
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« Reply #2 on: October 20, 2013, 05:42:59 AM »

The current draw you listed for the Drake TR7 in transmit mode is incorrect.  The max draw key down will be 25A, not 35A.
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W4KYR
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Posts: 517




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« Reply #3 on: October 20, 2013, 07:49:27 AM »

Unless you use a voltage booster, you won't be putting out 13.8 volts into the transceiver, that may or may not be an concern but something to consider. Some radios do not perform well at 12.4 volts, I ran my Icom 730 on a deep cycle battery and the ham at the other end said it sounded like my rig was FM-ing.


In addition to solar,... you might want to look into the feasibility of using wind power as well.
A quick Google search showed a 450 watt wind generator cost $489. A Solar panel set up for 450 watts cost $2200. It looks like when you get into up to several hundred watts, wind power might be the best way to get additional power for the least amount of money.

5 year battery life sounds about right (if it is properly maintained), something to consider in the overall budget of things and figuring cost per year average. Assuming each battery is $100 each (for simplicity sake) x 2 = $200. The batteries will cost you $40 a year to replace at the theoretical end of life cycle x5. Figure in inflation too, that $100 battery could cost $110 each in 5 years..so figure that in too.

Experimentation is the key. But for starting out, solar is the way to go. Sounds like you are on the right track. Good Luck
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KG6YSF
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Posts: 91




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« Reply #4 on: October 20, 2013, 01:24:08 PM »

Thanks all for the input. I was going on memory of power needs for the radios. I added a little for the HF to be safe.
I understand that a 70W panel is small however I have seen smaller setups work. I just don't know how well. I also have a generator for emergency power. I usually use it for the fridge and freezer, that being said it is a 5k unit so it can do more. I am located in a very rural area of N. Cal so we get good amount of sun on a daily average. I have thought of a wind generator as well. I just have to save a long time to get that done.  I am financially way below the average budget of most hams as I have found out over the last few years. I wont rant on that, I will go ahead and do the best I can with what I have.
I thank you all again.
73 
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KD4LLA
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Posts: 454




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« Reply #5 on: October 20, 2013, 02:59:37 PM »

I have a 60 watt solar panel (3 amp output) going to (10 amp capable) controller at a river side cabin on my farm, powering lights and a ceiling fan.

What I have found is that the battery never get fully charged @3 amps.  I now realize I should have purchased two more (60 watt) panels, a total of 180 watts.  I wouldn't try to use two batteries, I tried bigger batteries, but the bigger battery has a higher resistance and would not fully charge either.

In other words, how long will it take you to charge you battery @3 amps?  Your average day is 8 hrs of sun (w/ out tracking).  Generally I have found it takes 8-10 hrs to charge a auto/ marine battery @10 amps.

After replacing and charging batteries five times, in ten years, I finally bought a Honda generator...

Mike
« Last Edit: October 20, 2013, 03:06:55 PM by KD4LLA » Logged
KG6YSF
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Posts: 91




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« Reply #6 on: October 24, 2013, 06:02:12 PM »

I found a Qualcomm model: CXPRS051 power supply with battery backup.It still puts out power with the battery disconected which I figured would need to be don so as not to have battling batteries What I am wondering is since it puts out 12v 5.19a can I get or build a charge control switch to work with this item to allow me to charge my deep cycle so I can use the radio. Would a 10a solar charge controler work for that or is there a way to make a voltage gate to do the same thing, ie. open and charge until a set value is reached and then shut off, for less. I have seen $10 charge controlers but I don't know if those are junk or not. So let me know what your thoughts are and if you know of a scematic would you please point me to it?

Thanks,
73
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KG6YSF
Member

Posts: 91




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« Reply #7 on: November 04, 2013, 10:29:08 PM »

After a lot of reading, talking to solar techs and They all agreed that a 50w panel at 2.7amps and the 115ah battery should handle the needs of my operating habits. They said that I could run two batteries in a bank with the panel and charger I bought.  I have a plan to buy a battery every other month until I get four. Then buy a second 50w panel to add to the system. Once that is done I am thinking of making a wind generator. I am thinking of using a small 12v DC permanent magnet motor as the generator. Buying a prop, nose cone and a hub from an Air-X micro wind generator, aluminum square tube and plate as boom and tail. Run that to the battery bank and use it to power an inverter for what ever is needed at the time.   
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
N7BMW
Member

Posts: 113




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« Reply #8 on: November 05, 2013, 12:04:30 AM »

KG6YSF, re-reading your original post I have an alternative suggestion.  Skip the solar and wind for now.  Get a ten amp smart battery charger.  230 AH of battery should be able to provide power when the AC power is out and a multi step battery charger should cost far less than solar and/or wind generation.  Save your money and evaluate where to go from there. 

Your home made wind generator may not be a good idea.  An AirX is pretty much useless unless you have consistent winds of at least 15 knots.  Your home brewed generator will be far less efficient.

Repeating from my earlier post.  Paralleled batteries should be the same brand, capacity and age.  Buying an additional battery every other month will shorten battery life and battery capacity.  Save up your money and buy the whole battery bank at one time.
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KD0WZW
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« Reply #9 on: November 05, 2013, 07:19:01 AM »

  I have a plan to buy a battery every other month until I get four.

I would re-think this if I were you.  There are two issues here, 1, adding 4, 12 volt batteries in parallel makes it easy to charge/discharge them unevenly.  You will end up cooking one battery while the others go under-charged.  Also, you should never mix batteries of different ages.

I would look at getting a couple GC2 (golf cart) batteries.  They are 6V and you can series them together to get your 12 volt bank.  You will want to charge them with around ~20 amps of current to keep them happy.
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W8JX
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« Reply #10 on: November 05, 2013, 08:23:27 AM »

With batteries in parallel it is best to use the same type and age batteries and parallel them from new.  As batteries age they will have different internal resistance and unequal batteries will end up discharging from the stronger to the weaker just bringing the whole bank down. 

The ONLY time I have seen a battery bring down a bank is when one developed a internal short. Never seen a problem otherwise. They do not need to be closely matched.
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KD0WZW
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« Reply #11 on: November 05, 2013, 12:52:01 PM »

With batteries in parallel it is best to use the same type and age batteries and parallel them from new.  As batteries age they will have different internal resistance and unequal batteries will end up discharging from the stronger to the weaker just bringing the whole bank down.  

The ONLY time I have seen a battery bring down a bank is when one developed a internal short. Never seen a problem otherwise. They do not need to be closely matched.

the problem is when charging and discharging.  You can wire the banks to draw on the positive on 1 side, negative on the other, but one battery will still get pulled down more than the other because the resistance through that parallel circuit is different than the others.  Then when the bank charges, the batteries that weren't pulled down as much get over charged.  This can be due to variances in the batteries, or more commonly, in the cabling for each parallel battery.  I've built, maintained, and fixed a fair amount of solar setups that have had this exact problem, my own included.   It's somewhat easy to catch this early with FLA batteries because you will see that they require vastly different amounts of distilled water at their maintenance periods.  The best bank layout is one that minimizes parallel connections through use of lower voltage cells in series to attain your desired bank size.
« Last Edit: November 05, 2013, 12:59:13 PM by KD0WZW » Logged
W8JX
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« Reply #12 on: November 05, 2013, 05:18:31 PM »

With batteries in parallel it is best to use the same type and age batteries and parallel them from new.  As batteries age they will have different internal resistance and unequal batteries will end up discharging from the stronger to the weaker just bringing the whole bank down.  

The ONLY time I have seen a battery bring down a bank is when one developed a internal short. Never seen a problem otherwise. They do not need to be closely matched.

the problem is when charging and discharging.  You can wire the banks to draw on the positive on 1 side, negative on the other, but one battery will still get pulled down more than the other because the resistance through that parallel circuit is different than the others.  Then when the bank charges, the batteries that weren't pulled down as much get over charged.  This can be due to variances in the batteries, or more commonly, in the cabling for each parallel battery.  I've built, maintained, and fixed a fair amount of solar setups that have had this exact problem, my own included.   It's somewhat easy to catch this early with FLA batteries because you will see that they require vastly different amounts of distilled water at their maintenance periods.  The best bank layout is one that minimizes parallel connections through use of lower voltage cells in series to attain your desired bank size.

Never seen it happen once. It is not a problem. I have used mixed dual batteries in SUV's and plow truck for years and never had a mismatch problem.
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KG6YSF
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Posts: 91




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« Reply #13 on: November 05, 2013, 08:04:20 PM »

I have never had problems with mixing batteries on the Jeep either. I drove class A trucks for years and never had an issue with it either how ever I have seen a bad battery kill a good one but when connected together. As for the addition of batteries in this instance I have to get them this way because it is the only way I can afford to do this. Buying the Panel and charge controller will cut me really short this month. I live on Veterans Affairs Disability so money is real tight all the time. I am lucky if I can  get $75 in one month for entertainment. I have been in contact with the manufacturers' tech support and they say that this should not be a problem. However they did say that they do not recommend more than two of the batteries that I am using per panel. So I will only get one more battery. That will give me 230ah of batteries with a 50w 2.78a solar panel. Probably wait till next year to buy another panel to add to the system and then two more batteries. And yes they will be spread out over several months. I am going to get the parts and assemble the higher amp, probably a 20amp, controller myself as a fun little project.

73s
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KD0WZW
Member

Posts: 34




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« Reply #14 on: November 06, 2013, 06:50:31 AM »

are we talking mixing batteries in vehicles here, or in a deep charge/discharge solar applications?  They are two totally different scenarios and use different batteries for each.  If you're using a couple mis-match batteries in a vehicle to run your radios, yea I agree no problem, but when you're talking about pulling your battery bank down to 50-60% on a nightly basis (and recharging it fully the next day hopefully) these mis-matches become a very big issue over a few months time.

Here is a good read if you want to parallel the banks together, along with some different ways to wire the bank. 

http://www.smartgauge.co.uk/batt_con.html

anyways, just my .02c.  To the OP, you will want to charge your bank with a plug-in charger occasionally as 2.78a is only a 1.1% rate of charge and the bank won't be very happy with that rate, ideally you'd like to be in the 8-10% range.

I'm not sure where you are getting your gear from, I've had good luck with solarblvd.com, solar-electric.com and also the alte.com store.  I've found the best prices on panels at solarblvd.com and run some of the Solar Cynergy panels that power my cabin.  solar-electric.com also has a great forum on the subject that will keep you busy reading for weeks should you desire.

« Last Edit: November 06, 2013, 07:06:44 AM by KD0WZW » Logged
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