Newbe starting small

[Kornbread]

Been interested in DIY solar for some time but finally starting to enter the fray ... or at least trying to learn a bit before getting in over my head.

IMO, when you do it yourself you can take more pride in the results than if you just plunked down the $cash. I've been into diy speaker design/building for several years. More recently, learning the basics of reading a schematic by building a vacuum tube preamp from scratch. Than came another tube preamp. Now working on a Tripath amp with matching woodwork. There's just something about learning a new skill and putting it to use.

Starting small and working my way up. Dad has a small hunting cabin which needs improvement above his single car battery and Harbor Freight panel. If the power were available, he would occasionally use various hand tools like a skill saw, saber saw, table saw, and more often lights, fan, radio, tv, etc. and I would like to get him a small AC unit for the hot summer months. The AC is iffy. Off grid only. He's there maybe a week per month during the hot summer, but ~two weeks or more per month, during the winter.

Due to the location of the cabin, it is fairly likely anything expensive couild be stolen by a meth head, so this must be an economical build. Plans are of ordering a pallet of used cheap panels from someone like SanTan, Signature, or off the Bay, and using 4-6 panels on the cabin for ~1-1.5k (the wooded surroundings will have an effect on output). A low cost charge controller (maybe something like the Fangpuson 50a charge controller), and if possible, 24v batteries. Some of the Trojan FLA golf cart batteries can be had <$200. Then add a pure sinewave inverter of what, 3k?

Am I going in the right direction? Where am I messing up and how do I fix it?

 

[FilterGuy]

Been interested in DIY solar for some time but finally starting to enter the fray ... or at least trying to learn a bit before getting in over my head.

IMO, when you do it yourself you can take more pride in the results than if you just plunked down the $cash. I've been into diy speaker design/building for several years. More recently, learning the basics of reading a schematic by building a vacuum tube preamp from scratch. Than came another tube preamp. Now working on a Tripath amp with matching woodwork. There's just something about learning a new skill and putting it to use.

Starting small and working my way up. Dad has a small hunting cabin which needs improvement above his single car battery and Harbor Freight panel. If the power were available, he would occasionally use various hand tools like a skill saw, saber saw, table saw, and more often lights, fan, radio, tv, etc. and I would like to get him a small AC unit for the hot summer months. The AC is iffy. Off grid only. He's there maybe a week per month during the hot summer, but ~two weeks or more per month, during the winter.

Due to the location of the cabin, it is fairly likely anything expensive couild be stolen by a meth head, so this must be an economical build. Plans are of ordering a pallet of used cheap panels from someone like SanTan, Signature, or off the Bay, and using 4-6 panels on the cabin for ~1-1.5k (the wooded surroundings will have an effect on output). A low cost charge controller (maybe something like the Fangpuson 50a charge controller), and if possible, 24v batteries. Some of the Trojan FLA golf cart batteries can be had <$200. Then add a pure sinewave inverter of what, 3k?

Am I going in the right direction? Where am I messing up and how do I fix it?

Welcome to the Forum!!!

Yes.... you are going in the right direction.

Here is some advice I give all beginners:

1) Don't buy anything till you have a full design. Too often people will get excited and start buying stuff and then realize they should have bought something else!!

2) Ask lot's of questions. Most of the active members on the forum like to help people learn. Specific questions will typically get more answers than something like "how do I build a solar system"

3) Check out the resource section of the forum. (There is a button for resources in the top blue banner of every page). There is a *lot* of very valuable information available to anyone willing to go look for it. There is a beginners sub-section of the resource that is targeted at beginners.

4) Don't get discouraged. You *will* make mistakes. We all do!. Learn from it and call any costs 'tuition'. Then move on. (I suspect you have already learned this from your Audio work) If you are really brave.... share your mistakes so we can all learn!

5) Expect differences. Like any other field, there are many different ways to build a system.....and every way has followers..... sometimes religious followers. Listen to what everybody says, be open to different opinions, ask questions, and then decide what works for your situation and your value set.

Now.... a bit of advise that is specific to your post:
You already have some ideas formed on what the system might be, but do you have a good handle on what the system will need to do? My guess is you wouldn't try to build a tube amp without know what wattage you want out of it.... don't try to build a solar system without knowing what wattage (and watt-hours) you want out of it. There are many on-line tools for doing energy estimates but I like the spreadsheet from this resource:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

Good luck and happy electron herding!!

 

[FilterGuy]

anything expensive couild be stolen by a meth head,

Buy a bunch of "Danger !!! High Voltage " stickers. ?

https://www.amazon.com/dp/B07DNSX5QZ/ref=sspa_dk_detail_0

I had a similar situation and actually considered getting an electric fence system to energize a few metal things they may touch..... but never did it.

 

[Kornbread]

Ouch. The energy audit says I need a 6k inverter w/surge of 11k, 650w-hrs and 250a-hrs of battery, and 1.4k solar wattage. That is w/o a small ac window unit. Only a couple led lights and mini frig will run all the time while the hand tools will run ~an hr total all day long. Don't see how the surge or full usage would ever get that high using only a few items at a time. A lot of things, like the hand tools, will only be used during the day so battery size should not be affected much as long as the solar array is large enough to make up the difference. I thought a 3k inverter would be overkill.

 

[FilterGuy]

Yes... the spreadsheet it very conservative and calculates for everything on at once.... so you can back down on that. Same thing with the surge.

mini frig will run all the time

The Mini frig will be on all the time...but will only be running occasionally. What I like to do on things like the fridge is to use a Kill-a-watt to actually measure the usage over several days and then use a daily average.

 

[FilterGuy]

If you want to PM the spread sheet too me I'll look it over and see what jumps out.

 

[Kornbread]

Already deleted the spread sheet. I'll do it again tomorrow afternoon if time allows. Need to get a kill o watt.

Am I on the right path upsizing the panels to cover the extra consumption of the hand tools during the day?

 

[FilterGuy]

Generally speaking hand tools are high wattage, but they are typically only used for less than 30 seconds at a time. You might use a skill saw all day long and only put a total of 1/2 hour run time on it. Consequently, hand tools tend to want inverters with high surge currents but don't really require all that much for battery and solar. (That is why they came out with so many battery powered hand tools that don't need huge batteries.) Having said that, more is generally better than not enough so I won't try to talk you out of adding solar.

 

[Rednecktek]

So just to throw my $0.02 in here, I've got a camp in a similar situation that is currently kludged together due to short bursts of time & money combined with a loooooooong learning curve. I'm currently looking at revamping it all and putting in a 3kw AIO system with my little generator as a backup/supplemental power supply. I'm only NEEDING less than 1kw of power right now but for the cost difference of the 1kw I need and the ability to add in a 120v mini-split later, I figured I'd just jump straight to the 3Kw system now.

Having said that, it does NOT run my well pump at 220v/2500w split phase.

The reason I mention this is because it might be worth considering doing a smaller solar system for running the TV and coffee pot and a smaller AirCon system, then getting a generator when he decides he wants to build a new shed or carport to run the power tools.

Looking at the cost of a solar system capable of running my well pump, the batteries, the panels (the bulk used is the way I'm going too), clearing the trees to put up enough panels, etc, it's SIGNIFICANTLY cheaper to just get a generator capable of running the well pump for the 20-30 minutes a day I might need it than to have a $BigMoneyMoney solar system capable of taking the load, but mostly idling through the rest of the time.

Also, if you're designing a system to run power tools, things like miter saws and circular saws have an immense startup draw that most readily available inverters just can't handle, so you have to be really picky and choosy about which models you get that are a Low Frequency and can handle that initial oomph the power tools need.

There's planning, and then there's the reality check that just bounced.

Now, if your last name is Bezos or Musk then well... yeah...

 

[Kornbread]

When Pops needs power out there, he uses a small Honda generator bought way back in 1985. And I can for sure see your reasoning for using a gas generator ... no comparison in cost, but it would be so nice not to have a motor running when sitting around the hunting camp.

AIO?

 

[Rednecktek]

AIO = All In One, the MPP and Growwatt units that are the charge controller, inverter, and monitoring All-In-One. Plug in the battery bank, plug in the solar panels, connect to your AC panel, turn it on.

I'm kinda curious to see your energy audit that calls for that big of a system for a cabin. Unless you're running a deep well pump which kicks you right up into the more expensive setups.

 

[FilterGuy]

the MPP and Growwatt units that are the charge controller, inverter, and monitoring All-In-One

I see more issues on the forum with Growwatt than MPP (for whatever that is worth).

 

[Rednecktek]

Sadly Growwatt has the corner on 3kv 24v systems, MPP only has 2.4Kw and then steps up to 48v which kinda screws with my options for my camp project.

Now, if you can go straight to a 48v system, which it sounds like you'll have to with that kind of load, MPP seems to be the better way to go.

 

[Kornbread]

Been reading through the 'up in smoke' section and it's enough to have me rethinking the diy route. Cabins with off grid systems that are only attended to intermittently, appear to be magnets for fires. Don't want to burn down pop's cabin and the whole darn woods, just for convenience.

 

[Rednecktek]

Forethought will help mitigate that a lot. If you check on my Check My Work thread you'll see that I've arranged my system so I can disconnect the batteries and kill all the load to the cabin. The only thing I'll have powered on is a small 200w system just to keep the batteries topped up.

All the hardware will be mounted on a piece of concrete board so if anything does decide to go wonky, it can't catch anything on fire.

Yes, there's always a risk, you just do the best you can to mitigate it.

Now, DIY Lithium batteries are a different thing altogether. That scares even me and is one of the reasons I'll never go Lithium at my cabin.

 

[Kornbread]

Been researching and day dreaming.
For the cabin, the $30 Santan panels cannot be beat, but, there is a $300 shipping charge making the otd price of ten panels a bit too steep for my blood. At twenty panels per pallet the cost drops $.06 to $.20 watt. Nice price, but don't really need more than a half-dozen for the cabin. Would use the others on the house but considering their condition and no labels, they are simply not able to be grid tied.
Hmm....
Rummaging through flebay, I can get a pallet of used astroenergy panels from gogreensolar, delivered, for $.28 watt, and they have labels. Bit more than I wanted to spend, but thinking an on-grid system could be built at home with the remaining twenty four panels returning some of that initial price. Unfortunately, our electric coop only gives credits off the bill for power fed into the grid, and it's at wholesale price.
Nope, not doing lithium batteries. I think some reasonably priced fla golf cart batteries can be purchased locally.
Sound like a plan?

 

[Kornbread]

Is this correct? With four 230 watt panels into 12v, the SCC will need to be ~100amp? What happens if it's a cheaper mppt and only 30 amps? Will four panels really generate this much power?

 

[FilterGuy]

Could you provide a link to that calculator? I come up with different numbers.

4 x 230 W = 920W total.

The highest current will be when the 12V battery is at a low voltage so the current would be 920W/12V = 76.7A.
It looks like they added 25% to the rating. 76.7 x 1.25 = 95.8. This would keep the controller from running at it's max, but I don't usually add a buffer like that. The reality is that the panels are not likely to perform to full spec to start with.

 

[Kornbread]

The link scc calc
I do think they added in a rather large safety buffer. More than likely, the panels will be dealing with considerable shading but it recently frosted so the trees will be mostly bare in a week.
Guess I didn't realize that only four panels could generate this much power.

 

[Kornbread]

Wish I had taken pictures of the setup.

Weize (SRNE, Renogy, etc.) 30amp mppt solar charge controller. Two Hyundai 250w panels in parallel because of shading, but may try series later and compare which works best. 12awg from panels to SCC. 6 awg from SCC to battery. 6awg from battery to 12 way fuse block and small buss bar. DIY insulated battery box made from an $11 WallyWorld plastic storage bin, some thin scrap pieces of plywood, and a few cans of expanding foam. Just enough room for two batteries. Used several of the cheap breakers that generally trip before their rating. The SCC is mounted vertically inside a plastic Wallyworld bin with cement backer board behind the SCC to protect the plastic from heat. Built in a large screened vent on the lower bin cover and screened vents on the upper side of bin for airflow and shelter for those times rain blows in under the canopy. The screen should keep the critters out. The 6awg was copper service entrance wire sourced from Lowe's clearence bin for $.51'. Two strands of thhn and a woven ground. Stiff to work with, but for the price, I'm not complaining.

If weather and work overtime allow, this weekend we will add a convenient small four-way panel that includes an on/off switch, usb and power outlet, and voltage meter, near the dining table. Also, fuse and wire up his small inverter.