Newbie seeking info on small project

[elile]

Hello good people of Solar Panel Talk,

I am a complete newbie to solar. I'm trying to do a small project extending my wifi from my house. I've got an Eero wireless router (model J010001) that I'd like to place outside and power with solar. The router's designed to be plugged into a wall outlet (110-240V AC, 50-60 Hz) but of course it uses an adapter that has an output of 5V/3A DC 15W. Most introductory videos/articles on solar include an inverter but I'm guessing if I could get a setup that fulfills those DC requirements that wouldn't be necessary. Any general advice on what I need? Like I said, I'm pretty much starting from level 1 here, so any and all info would be welcome. Types of battery, battery capacity, charge controller models, solar panels, other sources of info, etc.

[bob-n]

That's an excellent question. Unfortunately, the answer requires some assumptions / facts.

We know that the router needs 15W. That's important.

We need to know how much time you will have sun and more importantly, how long you will have to go without sun. Do you have cloudy days with little sun? Those count. Are you OK if the router drops out at night or drops out after a day without sun?

Once we know how long you have operate in darkness, we simply multiply 15W * x hours and get the watt-hour rating that you must be able to deliver. Let's dumbly assume 3 straight days of really dreary = 72 hours. That means the battery must be prepared to deliver 15W * 72h = 1080 watt hours.

In theory, a deep discharge 1000 watt-hour battery can deliver 1000 watt hours. In practice, even deep-discharge batteries hate to be deep discharged, so you'll probably buy twice the battery, or 2000 watt hours. That's lots of battery and could set you back $500. Ouch. Let's hope that you can accept the idea of running until midnight, and then turning off the router until the sun comes back. That will greatly reduce the battery needs.

Then you have to recharge the battery. Assuming that you're guaranteed 4 hours of good sun on the day after those 3 dreary days, you have to recover 1000 watt hours of energy in 4 hours, so you need 250 watts of solar panels. If you don't need to deliver 1000 watt hours, you probably don't need 250 watts of panels either.

Between the solar panels and the battery you need a 250 watt (or whatever) solar charger. Between the battery and router, you need a 12V to 5V 3A DC/DC converter. That DC/DC converter will be the cheapest part.

One more consideration is that your router probably don't use 15W continuously. It probably only needs 15W for peak demand. There's a cheap meter called a Kill-A-Watt P4400. Try to borrow or buy one and use it to measure your actual router power usage. You can set it to display watts. You can also set it to record watt hours over an extended period of time, so that you can see how power usage fluctuates. Let's hope that you can get by with less average power and save even more on batteries, on panels, and on chargers.

I hope this gives you some of the tools to start making calculations with your real situation.

[bcroe]

I'm trying to do a small project extending my wifi from my house. I've got an Eero wireless router (model J010001) that I'd like to place outside and power with solar. The router's designed to be plugged into a wall outlet (110-240V AC, 50-60 Hz) but of course it uses an adapter that has an output of 5V/3A DC 15W.

Just because the (max) output is rated 15W, does not mean the load will actually consume
that much power. I would expect the DC power used to be much less, BUT if you use the AC
adapter the total power likely will be much increased. Bruce Roe

[azdave]

Doesn't it seem like there should be solutions for this already? All you need is an outdoor solar rechargeable storage unit with a USB charge port. I see those all the time on Amazon for campers and hikers but is there one with enough capacity to work for you long-term unattended? Don't know myself.

Amazon.com solar usb charger - Google Chrome 6112020 51042 AM.jpg

[chrisski]

I'm just getting started on my first 12 volt system for my RV, so take what I have with a grain of salt.

Need to start doing some math based off the 15 watts you talked about, plus the inverter to run it. There's stickies on this. It also depends on how far north or South you live with how many cloudy days you have.

If you decide you need to run this 2 days straight without being able to recharge the batteries, you need about 720 watt hours alone to run the router. You then would double that and you need around 1500 watt hours to keep your battery from draining. You'd need a 125 Amp Hour battery at 12 volts, but that does not take into account any losses for the inverter or temp changes. You can bump that up to 200 amp hour batteries and be more comfortable. Things can be done like maybe you choose not to run this wifi on cloudy days, but how do you shut this off? If the battery is drained it'll disappear quickly, to a point it can't be recharged. Properly sized, you still need to plan on battery replacement as soon as two years.

The solar generators I look at just don't seem to be built to do this day after day, exposed to the elements.

Once you price this system out, I think you'll see that getting a line installed from your house to your lawn is probably a much cheaper option. Even if the system works good, the cost of the free electricity because of battery replacement will still be more than grid supplied power.

[SunEagle]

I'm just getting started on my first 12 volt system for my RV, so take what I have with a grain of salt.

Need to start doing some math based off the 15 watts you talked about, plus the inverter to run it. There's stickies on this. It also depends on how far north or South you live with how many cloudy days you have.

If you decide you need to run this 2 days straight without being able to recharge the batteries, you need about 720 watt hours alone to run the router. You then would double that and you need around 1500 watt hours to keep your battery from draining. You'd need a 125 Amp Hour battery at 12 volts, but that does not take into account any losses for the inverter or temp changes. You can bump that up to 200 amp hour batteries and be more comfortable. Things can be done like maybe you choose not to run this wifi on cloudy days, but how do you shut this off? If the battery is drained it'll disappear quickly, to a point it can't be recharged. Properly sized, you still need to plan on battery replacement as soon as two years.

The solar generators I look at just don't seem to be built to do this day after day, exposed to the elements.

Once you price this system out, I think you'll see that getting a line installed from your house to your lawn is probably a much cheaper option. Even if the system works good, the cost of the free electricity because of battery replacement will still be more than grid supplied power.

I agree that once you provide the battery, solar panels, charge controller and possibly an inverter you will end up spending a lot of money and then have to spend more when the batteries fail in a few years.

The OP did not mention any distance between the router and house grid power but based on what I have spent to build a 200Ah 12V solar/battery system I would have spent a lot less to just run a 15Amp 120v circuit to my shed.

[chrisski]

I agree that once you provide the battery, solar panels, charge controller and possibly an inverter you will end up spending a lot of money and then have to spend more when the batteries fail in a few years.

The OP did not mention any distance between the router and house grid power but based on what I have spent to build a 200Ah 12V solar/battery system I would have spent a lot less to just run a 15Amp 120v circuit to my shed.

I do admit for my RV solar project, it is about more than just the money. I'm spending a bit on it. Some people like to go on cruises, but that's not just for me. Have to spend it on something.