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

freedjfreedj Registered Users Posts: 15 ✭✭
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

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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
  • mikeomikeo Solar Expert Posts: 385 ✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.
    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.
  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.BB. Super Moderators Posts: 26,870 admin
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.

    Attachment not found.Attachment not found.
  • rollandelliottrollandelliott Solar Expert Posts: 755 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    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.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.
    freedj wrote: »
    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.

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

    You probably won't like my thoughts. :roll:

    How much did you get paid to haul that load of trash away?
    BZ charge controller: notoriously no good.
    Interstate batteries: gee, I got almost four years out of the same ones (after one had to be replaced within 1 month of being bought brand new).
    Trace inverter: good in its day, but that day is long past. No wonder it buzzes; the transformer windings are probably loosening.
    Three 80 Watt panels? 240 Watts isn't going to recharge 460 Amp hours of battery. Even if a BZ controller worked.

    When it comes to solar equipment, check out new before you buy used. The stuff devalues as fast as computer equipment and for the same reason.
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Hope you didn't pay more than a couple hundred bucks for the package. the BZ is valueless, the used batteries are worth scrap, unless they have been well taken care of, the inverter of little value. The PV themselves are worth ~$.50/watt at most.

    Sorry for the bad news,

    Tony
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Thanks for the thoughts guys! :)

    As it turns out, i paid $375 for the lot, and i assumed that the batteries were probably scrap.
    I also figured I was rolling the dice on the electronics and as it turns out, i lost that one, but im hoping that it works well enough for my needs.

    When you say the BZ is notoriously no good, do you mean that it doesn't work at all, or that they fail quickly, or that they are just really inefficient?
  • PhotowhitPhotowhit Solar Expert Posts: 4,276 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Small 12 volt panels still get close to $1 a watt around here. I think the BZ has a poor rep and is an older technology. Give the batteries a try, equalizing them will be tricky since you don't really have enough solar to charge them, since they are at 12.5 volts they have a chance. Hunt around on Xantrex (Xantrex, now owned by Schnieder, owns Trace) site and see if you can find specs on the Trace inverter charger, it may allow you to charge the batteries since you could do it via grid current. It may have some equalizing ability, if not, once well charged you should try to do an equalizing charge with the BZ and solar.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    A number of people have done good bench tests with BZ congrollers and hve found them to be almost useless. I bench tested one, and found that rather than increasing MPPT charge current, it actually allowed less charge current than no controller at all.

    It really is a piece of junk. Buy a cheap PWM if you need a controller, or buy a Rogue or Morningstar small MPPT controller.


    Tony
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    I've found the manual and specs on the trace and it will do up to a 30amp rate of charge when plugged into the grid. It does not mention equalizing, but does mention bulk, absorption and float.
    Once i've gotten the batteries all charged up and done my best to equalize them, Do you all think I should downsize to the best 2 of them to try and keep the system in balance?
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    I Let the system run as it is on monday and gathered data. It was a cloudy day, and it seemed like the system was averaging around 5 charge amps (according to the BZ) and i saw a peak of 9.8amps at one time. The battery voltage started at 12.51v in the morning, and peaked at 13.57v around Noon. Once the system had stopped charging I got final readings for the next three hours to let the battery stabilize. My final battery voltage for the evening was 12.71v. I should add that this data was gathered by having a camera setup with time lapse on the bz charge amps every 10 minutes and reading the battery bank voltage with a independent volt meter every hour or so.

    Can you draw any conclusions from this info about the state of my charge controller and battery bank?
    Attachment not found.
  • BB.BB. Super Moderators Posts: 26,870 admin
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Cannot tell for sure--But I would guess that your battery got to around 80-90% state of charge. Ideally, it should have reached ~14.5 volts and held that for 2-4 hours.

    And, what was the battery resting voltage after ~3+ hours of no charge/discharge? 12.7-12.8 volts is, in theory, 100% state of charge. But the battery did not rest enough for an accurate estimate from resting voltage.

    12.5 volts resting voltage in the morning before the sun starts is ~90% state of charge.

    What is the battery type (flooded cell/AGM)? What is the battery bank temperature (~77F/25C is when SG/temperatures should be measured without going through temperature correction)?

    Have you verified that the voltage meter on the charge controller is accurate with a "known good" DMM?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Bill, after 3 hours of no charage/discharge the battery was at 12.71 as indicated by a separate digital multi meter. How long should I wait after charging to get accurate estimates from resting voltage?
    My battery bank is 4x 6v Flooded cells in series/parallel for a 12v bank. The voltage meter on the charge controller differs from my DMM (which is what i was using in the chart) by about .15-.2v.

    Does that .2v make a big enough difference to the charge profiles that I should change out the charge controller on that basis alone?

    The batteries are in the basement, so the ambiant temp is around 70*. I have an IR thermometer that I could use to get temps on the cells themselves. Where should I measure to get useful information?
  • BB.BB. Super Moderators Posts: 26,870 admin
    Re: Need help sizing a panel to run router/modem for extended blackouts.
    freedj wrote: »
    Bill, after 3 hours of no charge/discharge the battery was at 12.71 as indicated by a separate digital multi meter. How long should I wait after charging to get accurate estimates from resting voltage?

    3 hours minimum is a good start. So it does sound like the bank is pretty well charged.

    Checking the specific gravity of each cell every 1-4 weeks is always a good idea to make sure that cells are in balance and that the battery is really fully charged.
    My battery bank is 4x 6v Flooded cells in series/parallel for a 12v bank. The voltage meter on the charge controller differs from my DMM (which is what i was using in the chart) by about .15-.2v.

    0.2 volts difference is getting significant at 12 volts. If the charge controller is reading high (typical, especially if the wiring from the charge controller to the battery bank is long/smaller gauge wire--more voltage drop). The difference between 14.4 vs 14.6 volts can cause a longer charging time/lost useful panel energy.

    However, it appears your profile did not "hit" the bulk/absorb transition point (typically around 14.5 volts)--So, all you are losing is a few watts (maybe 1-2 watts) if this is voltage drop in the charge controller wiring.
    Does that .2v make a big enough difference to the charge profiles that I should change out the charge controller on that basis alone?

    There are lots of reasons to think about replacing the BZ controller--the 0.2 volt difference is probably not one of them.

    If you have a 240 watt solar array and an MPPT controller, I would expect on a good day (near noon, cool/clear weather, and a battery bank accepting the charging current) to have an average peak current of around:
    • 240 watt array * 0.77 panel+controller derating * 1/14.5 volts charging = 12.7 amps

    So, if you are not seeing around 10-13 amps every so often--I would begin to suspect the controller having issues. If you are seeing ~1/2 that current on good days with a "low battery bank" (not hitting absorb set point and controller not in "float" of ~13.6-13.8 volts, then I would double check solar array wiring (disconnect or cover with cardboard one panel at a time, check if each panel is contributing ~1/3 of the total current/power) and think about replacing the controller.
    The batteries are in the basement, so the ambient temp is around 70*. I have an IR thermometer that I could use to get temps on the cells themselves. Where should I measure to get useful information?

    Sounds like a good setup. Check the temperature of case or the +/- terminals of the battery. As long as is it is around 70-80F then you don't need to worry about temperature correction too much.

    You can also double check the temperature of the BZ controller... A hot charge controller (on sunny wall) can move the absorb/float voltages down. The controller should be at, roughly, the same temperature as the battery bank.

    -Billl
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • techntrektechntrek Solar Expert Posts: 1,366 ✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Since you already know your weak link is the cable system's repeaters (usually 1 every mile, and it only takes one to go down to interrupt your service), have you looked into a small cell data plan as a backup? For what you spent on this system you could easily have purchased that instead. Something like 250 MB/month won't let you keep current on the latest videos but its plenty for some surfing and keeping up on emails. Unlike cable or DSL downed power or data wires won't cause an immediate outage on the cell system, and long-term I'm sure the cell companies have on-demand contracts with local LPG suppliers to keep at least key cell towers online. Even if your entire area went down you could still take your computer somewhere else where the cell system is up and stay online.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    I have considered getting a teatherable device and a data plan to go with it. It seems that when our power goes out here, it's only for the neighborhood, so it's possible that the repeater is outside of the effected area. I'll know more next time the power goes out. Also, there are no cheap data plans. I think the least you can spend is $20, and to get a reasonable amount of data is closer to $30. I imagine if i was conserving bits, i could make it through a workday with less than 250mb, but i normally use more than that. Fortunately with verizons month to month billing, I could only pay for months with power outages.
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    I still have two questions about my installation for optimization.

    Should i stick with the 440ah battery bank, or shrink it to 220ah. I know that I don't really have enough panels to support the 440 and that it would be on the bottom end of the 220 for charging. Would shrinking the battery to 220 really save the batteries that I do have and make the whole system work better, or would i be better off sticking with the 440 until they die, and then buying batteries that are more properly sized for the array? Is there a way to shrink it to 220 and still use the other two batteries, perhapse with a manual switch to swap between smaller banks weekly or something?

    I looked at the wire that is connecting my array to the charge controller. It is about 50' of 10awg wire. By using the wire chart on this forum, it looks like i am giving up %10 to %15 of my power as wiring losses. Much of this length is unnecessary and I will be trimming it out of the system, but i don't think i can drop the distance from the array to the batteries much below '25. I have found a couple strands of 6awg wire on CL for what ammounts to .30/ft. Would it be worth swapping out the wire for the 6awg wire for around $20? It seems to me like gaining %10 efficiency for $20 is a good value. Is my math wrong on this? 240w, 50ft 10awg, max observed charge amps at the controller: 9.8
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.
    freedj wrote: »
    I looked at the wire that is connecting my array to the charge controller. It is about 50' of 10awg wire. By using the wire chart on this forum, it looks like i am giving up %10 to %15 of my power as wiring losses. Much of this length is unnecessary and I will be trimming it out of the system, but i don't think i can drop the distance from the array to the batteries much below '25. I have found a couple strands of 6awg wire on CL for what ammounts to .30/ft. Would it be worth swapping out the wire for the 6awg wire for around $20? It seems to me like gaining %10 efficiency for $20 is a good value. Is my math wrong on this? 240w, 50ft 10awg, max observed charge amps at the controller: 9.8

    When you are using an MPPT controller, the current going into the controller is usually lower than the charge amps. If you tell me the Vmp or the Imp of the panels, I can tell you what sort of loss you have in the 50 ft 10 gauge cable.

    For example, if the Imp of the panels is 5 amps then you are putting up to 15 amps through 50 ft (one way) of #10 cable. At maximum power (240 watts) your voltage drop is 1.53 volts and 22.9 watts will be lost in the cable. At lower powers the losses are much less.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • freedjfreedj Registered Users Posts: 15 ✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.

    Vmp: 17.3v
    Imp: 4.6aAttachment not found.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Need help sizing a panel to run router/modem for extended blackouts.
    freedj wrote: »
    Vmp: 17.3v
    Imp: 4.6a

    That's not too far off from the assumptions I made. Three of those panels in parallel through 50 ft of #10 cable will have a voltage drop of 1.4 volts (8.12%) and will dissipate 19.4 watts in the cable. All of the various connections (fuses, combiner box, etc) will also introduce losses.

    I recommend that you use heavier cable.

    btw, those numbers are for full power. At more typical lower powers the losses will be less. The voltage drop is proportional to the power produced. The watts lost in the cable are proportional to the sq root of the power produced (thus at half power the power lost will be about 4.8 watts).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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