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diy solar

Powering a small shed with solar.

Mikein

New Member
Joined
Feb 3, 2023
Messages
2
Location
Sioux City, IA
I have a small shed where I keep lawn tools. I have begun switching yard tools from 2 stroke to battery. I want to set up a small system to keep batteries charged on tools and float charge mower batteries. Keeping in mind I have to mow 2x a week would one 100w panel and a smaller maybe 50 amp life po battery and inverter be enough to stay on top of it all? I don’t need to power a mower, just a trimmer and blower. And I realize I’m probably burning money because I can plug in in the house it just seems like a fun project.
 
Is there a DC charger available for your batteries? For example, DeWalt and Milwaukee sell car chargers that run off 12V. If so, you can cut out the inverter.

If you want to keep things simple you could just use a small solar generator and a 100W panel - I've charged my DeWalt batteries that way for years. Having something mobile also allows you to use it for other things in the months when you're not doing yard work in northern IA.

If it's more of a fun project so you want to install components, a 50 Amp hr LiFePO4 battery, small PWM SCC, and 100W panel would easily be sufficient for 2 amp hr - 9 amp hr 18-20V tool and trimmer/blower batteries on a DC charger. For a mower battery you'd need to check the charge requirements.

Keep in mind that you'll need some type of low voltage disconnect if the tool batteries are left on the charger, and that you can't charge the tool/trimmer/blower batteries or your main LiFePO4 battery when it's below freezing.
 
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Thank you! Starting from the bottom in the winter I would just bring it inside. I believe the chargers have a built in ability to stop charging and prevent discharging but I will be certain of that before I give it a whirl.
I do want to go the inverter route which would allow me to have a radio to listen to if doing shed chores. The shed gets full sun all day so as long as it’s sunny. I will give it a whirl and start looking for components.
 
Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.

Well that's the thing about solar systems, there is no 1-Size-Fits-All answer. Your system will need to be designed to fit YOUR needs. When you design and built the system, it's not going to be the perfect system for me, or Will or 12vInstall or anyone else, but it Will be the right system for You and that's the goal.

As for where to get started, let me throw my standard blurb in here to help point you in the right direction. There's going to be a lot of math and research involved, but that's going to be a LOT cheaper than just buying parts off of someone's list and finding out that it doesn't do what you need.

Don't panic on the Power Audit, you'll actually be doing that a few times. When you do the first pass put in ALL the Things that you might want. AirCon? Sure. Jacuzzi? Why not. MargaritaMaster-9000? Go for it.

The second pass will be the "I Absolutely Need This To Survive" list that isn't going to have much on there.

The third pass will be the "This is what is realistic" audit that you'll use to design the rest of the system.

The Power Audit is going to tell you 3 primary things: 1: How big does your inverter need to be to power your loads? 2: How much battery bank do you need to last $N number of days with krappy weather? and 3: How much solar panel will I need to install to refill those batteries in a 4 hour day (the average usable sun hours rule-of-thumb).

Once you know what you Want and what you Need and what your budget can Afford there will be somewhere in that Venn diagram where those three things meet.

After that, THEN you can start looking at parts.

Yes, it's a long drawn out process, but it's worth it in the end. Not every house has the exact same floorplan, not every vehicle is the same make & model, and not every solar system is designed the same.
 
I will give it a whirl and start looking for components.
Check your local online market places for big cheap panels. Its not hard to find a big panel for less than $.50 per watt.

Things like this:
 
Having an inverter will give you more flexibility if you don't mind the added cost - just make sure that whichever one you choose can power the loads you need it to power and that the battery you choose has the discharge capacity to support it. There's a big difference between running a charger for a DeWalt battery and running a big corded power tool.

One thing I forgot to mention previously, if you go with LiFePO4 and want the option to charge it with an extension cord from the house on occasion, you'll need a charger with a LiFePO4 profile or the ability to set up a custom profile.

Battery-powered tools have low voltage protection to prevent them from over-discharging the batteries used with them, but I wouldn't expect a battery charger plugged into an inverter to stop charging when the main system battery gets low - the inverter should shut down when the battery voltage gets too low to power it, and the battery BMS should also have low voltage protection, but I wouldn't rely on those things as routine low-voltage protection for a system that's not monitored on a daily basis.

Sounds like you have minimal loads you need to power (at least right now) so don't feel the need to build a huge system unless you really think you need/want it, especially for your first system.

Enjoy planning your system and let us know how it goes!
 
I have a small shed where I keep lawn tools. I have begun switching yard tools from 2 stroke to battery. I want to set up a small system to keep batteries charged on tools and float charge mower batteries. Keeping in mind I have to mow 2x a week would one 100w panel and a smaller maybe 50 amp life po battery and inverter be enough to stay on top of it all? I don’t need to power a mower, just a trimmer and blower. And I realize I’m probably burning money because I can plug in in the house it just seems like a fun project.
Careful...I had a similar idea just to add some lights to my storage building. Now I'm getting close to $1000 to run a 16' LED strip. :LOL:
 
I'm doing the same thing to my shed. I have the pieces at home. I'll be doing part of it tomorrow. Then the panels on a nice weekend .
I'm enjoying it. Lots to learn.
I'll posts a few of my thoughts and stuff I got later when I'm home.
 
As a point of reference, I’ve got a weekend cabin. 200 watts solar, one 12volt battle born, and a little victron charge controller. It keeps all my Ryobi batteries charged with a 12 volt charger and runs my laptop. Dozens of pretty good tools run on the Ryobi 18 volt platform. Including surprisingly, a kick arse little chain saw.

Cheaper than battle born and victron definitely an option.
 
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