Need help sizing a panel to run router/modem for extended blackouts.

[freedj]

Hello! You guys have an amazing forum, I would love some advise on my little project.

I am looking to experiment with solar power and add a level of redundancy to my home office. I work from home and need a reliable internet connection and my local power company cant seem to keep the lights on. We've had 5 outages in the last 2 months, ranging from less than an hour to most of a day. We've also had outages last year that were up to a week long. I am looking to get a small solar backup system that will keep my router and modem running and top off my laptop as necessary.

I've got a kill-a-watt and have the following results:
Modem and Router only:
- Amp .29
- Watts 22
- VA 35
- PF .62
- KwH .13
- Hours 6

So it seems like they are using about .02 Kw/h per hour

Also, I plugged in my dead laptop to the same power strip as above and got instant results of:
- Amp .5
- Watts 50
That includes the router and modem as well as the charging, running laptop.

I would like to be able to run the modem/router from the system all the time, completely independent of the grid, and connect the computer if necessary when in an extended blackout.

Coordinates: 42.4605767, -83.1346688 near Detroit, MI

I am sure that i've forgotten some necessary details, but any thoughts would be appreciated.

James

[Cariboocoot]

Welcome to the forum.

You've given a good amount of info to get started with. Of course you realize you need more than just a solar panel, right? You will also needs at least batteries nd a charge controller. If this can't ll be run on DC you'll need an inverter as well.

Let's look at some of the numbers so you can get an idea of what is needed.
35 Volt Amps (or "real" Watts) will run most of the equipment. Over 24 hours that becomes 840 Watt hours. That is no small amount of power. On 12 VDC that's a need for at least 140 amp hours of battery which would need about 200 Watts of panel to keep it charged.

That doesn't include the laptop.

In case you're wondering, I run two laptops plus satellite modem, router, and VOIP phone from solar here. It is one of the biggest power users in the place. The modem/router/phone set up alone uses over 40 Watts, but it is on mostly only during the day. Add in the two laptops and the average climbs to nearly 60. If the whole lot were on 24 hours it would be 1440 Watt hours. The refrigerator only uses about 1200.

These "small" power consumers add up to a significant amount of Watt hours over time.

[icarus]

You might look to see if you can run your modem/router/lap top on native 12 vdc rather than using an inverter. It might not be worth the effort, since using a Suresine 300 inverter is pretty darn efficient. We run a VoIP. Unit, cell modem/router nearly all the time, turning it off at night. One trick, charge (and use ) the lap tops while the sun is out, since they are the biggest draw. Time shifting the loads can have a considerable increase in EF.

tony

[mikeo]

I am looking to get a small solar backup system that will keep my router and modem running and top off my laptop as necessary.

Depending on your hardware, i do nearly the same thing on a 100 amp hour marine battery and a Gopower 20 amp charger. I have my router/dsl modem, weather station and wireless access point all hook up to the 12 volt battery. I can run for several days on battery power with out recharging. The modem/router work well on 12 volts and I have a simple 6 volt regulator that runs the weather station. If you are without power for a week at a time, solar or not you will need a small generator to recharge the battery in case of inclement weather. You might take all this into consideration while designing your backup system.

[mike95490]

What's the source of your internet connection ?
TV Cable based systems have 2 or 3 hour batteries in their repeater boxes, phone companies/DSL have 24+ hours in their giant in-house banks. 3G & 4G cell systems have a day or 2 of backup at the cell site, for calls, no idea if the data service has backups. No sense building up a system for a week if the internet goes dark in 4 hours.

[freedj]

Thanks for all the feedback!

I do see what you mean about the small loads adding up over time and being significant! I thought i was in better shape with such a small AH reading from the Kill-A-Watt.
I am aware that I need batteries, a charger and inverter to round out the system.
I can run the modem from 12vdc but the router (time capsule) is more complex with a built in power supply that I would have to open up to use anything other than 110.
Starting out with a battery and inverter and then adding a PV array and charge controller later might be a good way for me to spread out the costs and still get some backup power while building twards something more robust. I have a AGM charger on hand for keeping my car's AGM battery topped up during the off season.
My internet comes in on the cable. I don't know how far down the line the repeater is, but it seems that our neighborhood looses power more readily than the surrounding area (about a 1 sq mile area). I hope the repeater is outside that radius, but I won't know until i get the system up and running.
It sounds like to get a workdays worth of backup power I will need ~100w of pannel and 70amp/hours of battery and to have it be on all the time during blackouts i'll need to bump that up to 200w/140AmpHr. I know that I want a pure sinewave inverter for the computer/electronics. Are there any features I should be looking for in a charge controller?

[BB.]

When using a Kill-a-Watt meter... And measuring current. Note that Power=Voltage*Current.

The kill-a-watt meter operates at 120 VAC... If you have a 12 volt battery bank, the current at 12 volts will be 10x that at 120 Volts...

All of a sudden, the battery bank starts looking really large.

And, how many hours do you expect you will need the backup power?

Solar panel implies that you want "days" of backup power--Possibly much longer than your local Internet circuits will remain active in a large scale failure.

If you want only "shorter term" backup power, then solar panels would not be the most cost effective solution--But a battery bank + a small backup genset (a Honday eu1000i or eu2000i or similar inverter/generators plus a couple gallons of gas per 12 hours of blackout) may be a better solution.

A 100 watt panel will only power a 100 watt load for ~2-3 hours per day (winter/summer).

-Bill

[niel]

maybe you should find out where that repeater is first or you could be buying allot of stuff needlessly. if uncertain after inquiring then buy a small cheap modsine inverter hooked to your car battery (while it's still in the car if possible) to test during an outage to see if all will still be on as far as the cable co goes. run an extension cord to the router from the inverter as the 120vac will travel better than 12vdc needing to be physically lifted close to everything.

[freedj]

Thanks for all your help earlier!

I found what i think is an unbeatable deal on craigslist, which I have now brought home and have setup for testing.

The system includes:
3x 80w Photowatt 12v Panels
Trace TS812 Inverter /w SB Option (Battery charger & transfer switch)
4x Interstate 6v U2200 Flooded Deep cycle batteries (Age Unknown) 12.5v at rest
BZ Products M12+ charge controller

This should give me 240w, 15a of panels
460ah of battery bank.

Based on the date on the inverter, I would say the panels, inverter, and charge controller are around 10 years old.

I've built a battery box, and have everything wired up as it makes sense to me. Also, i've used all the pieces that came with the installation.
Today was very cloudy and by the time I got everything hooked up there was not much sun left, but it did seem to be charging the battery bank (3amps).

I have two questions:
My inverter makes an obnoxious buzzing sound that is fairly loud whenever it is making power. Is this normal in an inverter of this age? When it is in search mode it has what sounds like a rapid relay click, and when it is off, it is silent.

The manual for the inverter says that the device must be grounded, i've used a cold water pipe, and that in most cases the Negative battery conductor must be bonded to the ground in one place. I have built a ground buss bar into my battery box, and i could add a connection from the neg terminal on the battery to the bus bar. That feels wrong to me for some reason.

I am including a few pictures of battery box as it currently sits. The lid still has to be made and the cabling needs to be rerouted through the grommets before the lid will fit. Also, im planning on adding a shelf or 'wall mount' for my charge controller (tucked in beside the inverter right now).

I would love any thoughts you all have on this rig.

[rollandelliott]

you can get a 12v power adapter for just about Any laptop and there are many 12v modem/routers available.
Add a trickle charger and battery and there isn't any really need for a solar system unless you need power for many days.
I know this does not help the original poster, but for those that want a similar set up for just half a day or sooo...without the cost it can be done easily.