Off-grid, all-season, very light but continuous load

**Sunking** · 11-03-2015, 06:40 PM

Chris you have already go off on the wrong foot. Your first huge mistake is you bought stuff. You have no clue if it will work or not. After 12 years doing this stuff, anyone who does this always fails and finds out they did not buy near large enough equipment, and what they bought cannot be used.

The very first thing you have to determine i show many watt hours you need in a day under worse case conditions. Then you take the location, time of year use, shading issues and then design the system. So stop what you are doing and start over.

No one single person here can help you until you define what it is is you need it to do, where it will be used, etc. You just jumped on a plane and took off without checking fuel, weather, or even a clue where you are going. End result is you planned to crash and burn.

**ChrisAtYork** · 11-03-2015, 09:12 PM

No, no, I haven't bought anything yet!

I had the max load in mind when I selected those parts: constant 11W * 24h = 264Wh daily. Government resources and academic publications agree that December is the worst month for my region, with 50-60 kWh/kW, depending on tilt angle and year-to-year variations, which is an average of 1.61-1.93 kWh/kW daily. With a 160W panel that gives a ballpark estimate of 258-310 Wh generated daily.

This is in line with PV array recommendations from Canadian commercial websites, for example http://www.matrixenergy.ca/cottagepv...tml#fragment-1

As for battery selection, the sources I've checked out are pretty much consistent with this tool http://www.batterysizingcalculator.com/ and the results it gave me are in the attached pdf.

If it helps, I have a BA in Geography and I'm almost finished my BSc in Physics, so you don't have to worry about me being a total buffoon

Attached Files

TrojanBatteryCapacityCalculator.pdf (218.3 KB, 4 views)

**lkruper** · 11-03-2015, 09:21 PM

Originally posted by ChrisAtYork

No, no, I haven't bought anything yet!

Sunking scared me so bad, I STILL have not bought anything.

**ChrisAtYork** · 11-03-2015, 09:45 PM

Originally posted by lkruper

Sunking scared me so bad, I STILL have not bought anything.

Huh... Good to know! But I'm sorry to hear it. Buying stuff is fun right?

Shall we start with one of my easy questions: should crimped lugs be used at a controller's power terminals or is bare wire fine?

**lkruper** · 11-03-2015, 09:52 PM

Originally posted by ChrisAtYork

Huh... Good to know! But I'm sorry to hear it. Buying stuff is fun right?

Shall we start with one of my easy questions: should crimped lugs be used at a controller's power terminals or is bare wire fine?

Well, I did get a generator and a manual transfer switch for my cabin. I do not need solar or batteries, but I will eventually get them. As for your question, I know enough to be dangerous and most of the time keep my mouth shut when I don't know that much about a subject. I am going to buy professionally made cables when I deploy, as making them is not a skill I am going to need in quantity and I want to make sure I don't create a fire hazard.

**Living Large** · 11-03-2015, 10:45 PM

Hang in there Chris, you'll get some help here. Dereck (Sunking) can be very helpful, when he slows down and actually reads posts before replying. Sometimes he takes off like a rocket ship. Kudos to you for wearing a flak jacket on day one. It sounds like you've done some good homework already. By saying "any and all advice is welcome" you set the stage. Welcome to Solar Panel Talk!

**lkruper** · 11-03-2015, 11:33 PM

Originally posted by Living Large

Hang in there Chris, you'll get some help here. Dereck (Sunking) can be very helpful, when he slows down and actually reads posts before replying. Sometimes he takes off like a rocket ship. Kudos to you for wearing a flak jacket on day one. It sounds like you've done some good homework already. By saying "any and all advice is welcome" you set the stage. Welcome to Solar Panel Talk!

BTW, don't forget to tell the new guy that Comic Sans MS font means joke, kindov!

**Sunking** · 11-04-2015, 12:18 AM

Originally posted by ChrisAtYork

No, no, I haven't bought anything yet!

OK great. My bad.

OK I have already told you what you need to do. Scrap your list for now. If you have a degree in science, this will be easy as most of it is 6th grade math. Well 6th grade math in every country except the USA. Otherwise Phd level in the USA. Yeah that was a joke, but the irony is there is some truth to it. Hang around and you will understand.

So let's get started and you have to do this on your own. You have to get a handle on how many watt hours you need in a 24 hour day. Only you can do that, we cannot read your mind or the equipment specs.

Watt Hours is a terribly complex equation Watt Hours = Watt x Hours. Told you it was complicated. Another one is Amp Hours = Amps x Hours. But for now forget Amp Hours as it is just th eend result of Watt Hours at a specified voltage.

So what you need to do is look at all your equipment specs together and determine how many watts they use while running. Then determine how many hours a day they will run in a 24 hour day. Example say you have a Telemetry radio that uses say 20 watts and runs 10 hours each day. 20 watts x 10 hours = 200 watt hours = 200 wh = .2 Kwh.

I am going to stop here and ask you to read this sticky as it will walk you through the process, and maybe enough for you to go it alone. Then come back with your numbers and questions if you have any. The painful part is December and January in your area as it will dictate most everything and will put the hurt on your wallet. Off-Grid systems use worse case.

**Living Large** · 11-04-2015, 12:58 AM

Originally posted by Sunking

OK great. My bad.

OK I have already told you what you need to do. Scrap your list for now. If you have a degree in science, this will be easy as most of it is 6th grade math. Well 6th grade math in every country except the USA. Otherwise Phd level in the USA. Yeah that was a joke, but the irony is there is some truth to it. Hang around and you will understand.

So let's get started and you have to do this on your own. You have to get a handle on how many watt hours you need in a 24 hour day. Only you can do that, we cannot read your mind or the equipment specs.

Watt Hours is a terribly complex equation Watt Hours = Watt x Hours. Told you it was complicated. Another one is Amp Hours = Amps x Hours. But for now forget Amp Hours as it is just th eend result of Watt Hours at a specified voltage.

So what you need to do is look at all your equipment specs together and determine how many watts they use while running. Then determine how many hours a day they will run in a 24 hour day. Example say you have a Telemetry radio that uses say 20 watts and runs 10 hours each day. 20 watts x 10 hours = 200 watt hours = 200 wh = .2 Kwh.

I am going to stop here and ask you to read this sticky as it will walk you through the process, and maybe enough for you to go it alone. Then come back with your numbers and questions if you have any. The painful part is December and January in your area as it will dictate most everything and will put the hurt on your wallet. Off-Grid systems use worse case.

See post #3. OP uses a constant 264wh per day, and has planned for December insolation. Doesn't have a science degree (yet).

**MikeCanuck** · 11-08-2015, 09:07 AM

Hi Chris, I registered to make my first post here since I wanted to encourage a neighbour; I'm in the northeast part of Toronto.
I'm a newbie with a very small 100w hobby setup to power led lights around my shed to discourage racoons from pooping on my shed roof every night. Working very well since beginning of summer. Only had to scrape off two huge piles of poop after the one night I decided to test what would happen if I didn't turn on those lights

.

So I don't remotely qualify to give you any expert or experienced opinions, but doing small scale solar is fun, expensive, but fun, and didn't want you to be turned off for lack of responses to your post.

From everything you posted so far, I think you seem to have done your homework well based on the expert sticky threads on this forum:
- you calculated your daily watt hour requirement
- you sized your solar panel and battery taking into consideration lowest solar insolation in december and it looks like you should be able to recharge fully even when getting only 2 sun hours in a day here in the great white north, and you should be able to go 1 or 2 days without any sun before your battery gets to below 50% dod
- you only have a small DC load and no inverter so no losses converting DC-AC
- you plan to use mppt controller instead of pwm so minimize losses there
- you plan to use 10gauge solar wire for short runs for the low amperage between panel and controller and controller and battery, so minimal losses there
- you are fusing these connections so safety is a check
So it looks like you have most of what little I know about covered.

I'm also using 10gauge wiring just like your plan, but fused with 15amp fuses to be on the safe side based on this chart for maximum amps for power transmission:

American Wire Gauge Chart and AWG Electrical Current Load Limits table with ampacities, wire sizes, skin depth frequencies and wire breaking strength

http://www.powerstream.com/Wire_Size.htm

AWG Wire size chart and ampacity table for design engineers including skin depth frequencies and tensile strength data; electrical cable size

I'm surprised that the panels you are considering don't come with MC4 connectors attached to the junction box.
But since you are just planning a single panel to charge controller, seems to me going direct from the panel junction box to charge controller via bare ends should be ok as long as it is waterproof at the panel junction box and the controller is inside. If you ever need to add a panel then you could add MC4 connectors to make wiring in parallel or series easier.

So, newbie to newbie, your plan seems to look ok to me, doublecheck your calculations, measure twice, cut once...
And hopefully the real experts here can chime in and confirm or spot anything glaringly wrong when they have time...
Then go have fun spending lots of money

Originally posted by ChrisAtYork

I had the max load in mind when I selected those parts: constant 11W * 24h = 264Wh daily. Government resources and academic publications agree that December is the worst month for my region, with 50-60 kWh/kW, depending on tilt angle and year-to-year variations, which is an average of 1.61-1.93 kWh/kW daily. With a 160W panel that gives a ballpark estimate of 258-310 Wh generated daily.

This is in line with PV array recommendations from Canadian commercial websites, for example http://www.matrixenergy.ca/cottagepv...tml#fragment-1

As for battery selection, the sources I've checked out are pretty much consistent with this tool http://www.batterysizingcalculator.com/ and the results it gave me are in the attached pdf.

**ChrisAtYork** · 11-10-2015, 03:25 AM

Originally posted by MikeCanuck

Hi Chris, I registered to make my first post here since I wanted to encourage a neighbour; I'm in the northeast part of Toronto.
I'm a newbie with a very small 100w hobby setup to power led lights around my shed to discourage racoons from pooping on my shed roof every night. Working very well since beginning of summer. Only had to scrape off two huge piles of poop after the one night I decided to test what would happen if I didn't turn on those lights

.

So I don't remotely qualify to give you any expert or experienced opinions, but doing small scale solar is fun, expensive, but fun, and didn't want you to be turned off for lack of responses to your post.

From everything you posted so far, I think you seem to have done your homework well based on the expert sticky threads on this forum:
- you calculated your daily watt hour requirement
- you sized your solar panel and battery taking into consideration lowest solar insolation in december and it looks like you should be able to recharge fully even when getting only 2 sun hours in a day here in the great white north, and you should be able to go 1 or 2 days without any sun before your battery gets to below 50% dod
- you only have a small DC load and no inverter so no losses converting DC-AC
- you plan to use mppt controller instead of pwm so minimize losses there
- you plan to use 10gauge solar wire for short runs for the low amperage between panel and controller and controller and battery, so minimal losses there
- you are fusing these connections so safety is a check
So it looks like you have most of what little I know about covered.

I'm also using 10gauge wiring just like your plan, but fused with 15amp fuses to be on the safe side based on this chart for maximum amps for power transmission:

American Wire Gauge Chart and AWG Electrical Current Load Limits table with ampacities, wire sizes, skin depth frequencies and wire breaking strength

http://www.powerstream.com/Wire_Size.htm

AWG Wire size chart and ampacity table for design engineers including skin depth frequencies and tensile strength data; electrical cable size

I'm surprised that the panels you are considering don't come with MC4 connectors attached to the junction box.
But since you are just planning a single panel to charge controller, seems to me going direct from the panel junction box to charge controller via bare ends should be ok as long as it is waterproof at the panel junction box and the controller is inside. If you ever need to add a panel then you could add MC4 connectors to make wiring in parallel or series easier.

So, newbie to newbie, your plan seems to look ok to me, doublecheck your calculations, measure twice, cut once...
And hopefully the real experts here can chime in and confirm or spot anything glaringly wrong when they have time...
Then go have fun spending lots of money

Hi Mike, thanks for diving in to help a fellow citizen! Good to hear the system's been helping with the racoon... situation.

I agree with your slightly-more-experienced assessment of my plan! The 25A fuses are what's recommended in the charge controller's manual, since it's designed to function at 15A. No reason to worry--rather than being turned off, the replies have given me a lot of food for thought. Sunking's sticky post mostly reinforced my original considerations. The battery lifespan may turn out to be a bit shorter than I'd figured, but that remains to be seen. What will really help is good data on the average power consumption of our load, and I'm arranging to get the sensors needed to collect that data during prolonged operation. My project has a bigger scope and bigger complications than I've mentioned so far, but I'm all ears for suggestions.

The scope: this is actually going to be used with a rooftop cosmic ray detector prototype, which we intend to replicate at high schools in our region as a science outreach and education project. Called SOLTA, which stands for Southern Ontario Large-scale Time-coincidence Array, we even have a blog. While we certainly don't want to throw away money, misjudging our power needs the first time around isn't the end of the world. With that charge controller we have the option of switching to 24V, adding another battery and swapping in a 250W panel, for instance. We already know that some will require more storage, array wattage and/or topping up with a grid-tied battery charger. There are schools in downtown Toronto where the skyline will probably exclude solar generation, but for its educational value we'd like to use PV electric where we have suitable sites.

The complications: because our power consumption is so low, we may need to expend some energy just to keep the system warm in the winter. I'm redesigning the detector's housing with plenty of thermal insulation and passive solar thermal features such as heavy thermal mass and possibly a trombe wall but I'm still concerned about the equipment dipping much below 0 °C (32 °F). I can't have the battery capacity taking a dive when we need it most! Anyone know how risky is it to have an AGM battery in a very enclosed space? I knew flooded batteries were out of the question... :/

**Mike90250** · 11-10-2015, 11:11 AM

Originally posted by ChrisAtYork

.......Shall we start with one of my easy questions: should crimped lugs be used at a controller's power terminals or is bare wire fine?

It depends on what the terminals are designed to have attached. The manual will state.
My 60A controller has compression fittings that will only work with bare wires ( a round hole with a setscrew )

Sometimes, Bad crimps are hard to identify, and if you do not have experience with compression crimping, leave it to someone who does. The $15 crimper & lugs at the auto parts store, is not good for power cables.

**Mike90250** · 11-10-2015, 11:23 AM

......The complications: because our power consumption is so low, we may need to expend some energy just to keep the system warm in the winter. I'm redesigning the detector's housing with plenty of thermal insulation and passive solar thermal features such as heavy thermal mass and possibly a trombe wall but I'm still concerned about the equipment dipping much below 0 °C (32 °F). I can't have the battery capacity taking a dive when we need it most! Anyone know how risky is it to have an AGM battery in a very enclosed space? I knew flooded batteries were out of the question....

Attempting to run electrical heaters from a battery in cloudy (not sunny) weather will quickly drain the batteries.
AGM batteries are fine in cold weather, and under "normal" conditions, they are benign. A fully charged battery is good to about
- 75° F (really chilly), as the battery charge decreases, it will freeze at warmer temps, as the electrolyte becomes more like water.
AGM cells can be frozen without too much damage, but cannot be charged till they thaw. Regular flooded batteries, if they freeze, are going to most likely be destroyed by the ice formation.

And, as temps go lower, Battery Capacity DOES decrease.

**MikeCanuck** · 11-10-2015, 11:41 PM

re: this is actually going to be used with a rooftop cosmic ray detector prototype, which we intend to replicate at high schools in our region as a science outreach and education project

Very cool! I'll look for your solar/cosmic ray detector setup when passing by high school roofs next year then

[so..you guys gonna be able to detect when those cosmic rays are going to scramble all the computers in the world? I wonder if that would be before of after the next solar flare EMP? sorry, I digress...]

The scope of your project is definitely way outta my league, again fun stuff planning to spend serious cash for science though

Like you said, better doublecheck loads, battery sizing, possible future expansion needs like cellular network gear to transmit/access the data etc. Solar panels you can add, but there are lots of posts on this forum about killling battery life when trying to add a mismatched battery to a battery bank. cheers!

Off-grid, all-season, very light but continuous load

Off-grid, all-season, very light but continuous load

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