Backup Power

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Greetings,

I'm an electrical moron in need of some advice about a small project involving backup power. All feedback will be greatly appreciated.

I'm trying to come up with one relatively inexpensive solution to two problems:

1. I live in an area of frequent thunderstorms. When they come up, I unplug computers, tv, and telephone lines. Because I need to be online during most of the daytime and evening hours for business purposes, this shutdown is much more than just an inconvenience. Sometimes the storms hang around for hours, sometimes they come and go. Either scenario is a major pain.

2. Once in a while we lose power completely. I'd like to be able to operate a fluorescent table lamp (~40 watts), a small fan, and a table radio or boom box for up to six hours at a stretch, for a couple of days max. I think the total wattage wouldn't exceed two hundred. Once in a while I'd need a few minutes with the laptop to handle email, but I could turn the radio and fan off while I did that.

My tentative solution is one of the largest Concorde AGM batteries (maybe the PVX-2580L ??), plus an appropriate charger and an 800 watt inverter. I'd like to keep the battery in the house, charged and ready to go. Very basic, for a basic guy.

Any solar-oriented possibilities?

The Wind-Sun technical guy said he'd feel safe running the laptop off the battery during a thunderstorm, with the charger simultaneously plugged in and charging. I feel uneasy about this, but what do I know? Even if it's safe, will using the battery in this way shorten its life at all?

Thanks for reading.


Mike

Comments

  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
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    Re: Backup Power

    This is the same place I started.  I regularly disconnect from the grid during a storm and turn the chargers on to maintain the batteries as I go.  Our power "flicks" a lot and this completely eliminates this.  If the power does flick or even go out everything keeps running, and as long as I have grid power the batteries stay topped off.  Granted I have either 8A8D AGM's and two 2500w inverters and two Iota 55 amp chargers, so as long as I am not pulling more then 1500w I am basically running from the grid.

    One thing I would recommend is spending the money for a sine wave inverter from the get go and a good charger.  If you get an AGM battery you could ruin it pretty quickly with a cheap charger.  Either that or get a cheap "marine" battery from Sams or Walmart and start with that.  I have some more info on my web site at
    http://www.uwgb.edu/nevermab/solar.htm
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • System2
    System2 Posts: 6,290 admin
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    Re: Backup Power

    Hi Mike,
    definitely can be done. I was looking at the battery quick: 258 ah wont get you very far. im not sure how far you can discharge that battery type but its not going to be the full 258AH or anything near it.

    since you needs are simple I would forgo the inverter and get a wide input range 12v power adapter for your notebook (i do this), and a 12v light and fan. not sure about the fan but notebook charging and lighting are very easy at 12v. just guessing, id bet it would be lower overall cost allowing you to put more $ into solar. an efficient 12v fan and light wont be much power draw but the laptop will pull a few amps. mine uses something like 3-4amps at 12v while charging. using an inverter would increase these numbers notably.

    since i have to refer to one of these chart/guides myself every time i do something, check this out:
    http://www.thesustainablevillage.com/essays/simple_sizing.html

    according to that (if i did the math right, dont hold your breath there) you need to make 1440 watt hours per day if going on 200wx6hrs+20%.
    so say you get 4 hours of sun: you'd need 360w of panels.

    to have 3 days worth of backup (no sun) youd need to add 360AH to a battery, add 20% inefficiencies and -
    if the battery doesnt recommend less than 50% discharge, youd need twice that: so say get 4 of those batteries paralleled. that would require 1032ah worth of batteries to run 200w 6 hrs a day for 3 days with no sun.

    theres are some simple guidelines for how many watts of solar per the size of your battery bank, i forget what it is: i think it wads the equivaluent ah converted to watts of panels, something like that . someone will help me here. that would about make sense (1000w of panels) but you will get far greater detailed info here. but since no replies i thought id get the ball rolling.

    the VERY good news is you probably wont need 200w an hour for the equipment your talking about :);)
    a measurement will probably show it to be alot less.

    i just saw brocks post while typing: yep might be cheaper using a charger and not solar, depends on what is important to you
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Backup Power

    Have you installed good grounding rods and surge suppressors on your main panel? And lightning rods on the roof of the house?

    Also, I would suggest that you not just throw a solar panel outside and connect that to batteries/inverter in your kitchen for use during possible lightning conditions. The exterior solar panel and long wires are just as supseptable (if not more so because of the lack of proper grounding) to damage (and worse) as your AC mains. And it can bring the lightning's energy right into your home (again, if not properly grounded).

    Permanently installed panels/wiring/protection is a good thing. Using a couple of heavy duty batteries for lights and a laptop, not connected to panels/chargers (during periods of lightning), with short cables (not 100' extension cord from the garage to the kitchen) should be very safe.

    If you need to stay communicating for business... I assume that you have thought about cordless phone and "extra" base stations (in case of a hit). And if you have cable/dsl, you use a wireless wifi router (again cheap and disposable with a pre-configured/tested backup unit in the drawer) for Internet access. Both of these would keep you and a battery connected laptop & remote phone charger very safe from lightning strikes while still able to take calls and use the Internet. (for the cordless phone, try to get one that does not use the 2.4 GHz frequency of the typical wifi wireless network cards--having both at the same frequency can prevent them from working together at the same time).

    I don't live in lightning country--so I can't offer you very much experience with home protection, other than what I have read (and designed office communications equipment for).

    Regarding power usage... A desktop PC is pretty power hungry compared to a typical laptop PC. If you can get away with using the laptop during a storm and leave the decktop off (25-35 watts vs 200-300 watts). Assuming you want 200 watts for 8 hours, the battery capacity you would shoot for:

    Batt Cap: = 200 watts * 8 hours * 1/98% (agm charge eff) * 1/90% (invert eff) * 1/50% (battery capacity)=3.628 kWhrs

    Batt amphrs = 3,628watt*hrs / 12 volts = 302 amphour capacity minimum...

    You can see, if you drop this to 40 watts (laptop + a CPFL light or two) instead of 200 watts over eight hours, your battery would only need to be 60amp*hours of capacity (1/5 the size).

    Lastly, I have solar panels at my home too, but unless you do a permanent installation (with proper grounding), you probably would be better off just getting a small Honda or equivalent gasoline generator (eu1000i or eu2000i) and an AC line-powered battery charger (like Brock's Iota chargers). Just to power you for eight hours per day, you probably would need something like 400 watts of solar panels (assuming there is lots of sun during your storm season), and, if you wanted to run for three days without sun (as an example) you would want 3x more battery capacity.

    All very doable--but for random use, Solar is not very cost efficient. The 400 watts in panels would probably cost around $2,000. An eu1000/2000(i) generator would be in the $700-$900 delivered to your home. And 5 gallons of gasoline would keep you running for approximately 25+kWhrs worth of energy (or 25,000whr/300 whrs=) 83 hours of uptime (or approximately 10 work days at 8 hours per day and 300 watts--assume some extra losses). Generator and Gas is not quite as "nice" to use as Solar, but probably more practical as an emergency backup (use fuel stabilizer and change the 5 gallons every 6-12 months).

    Even the generator, outside for safety, would be susceptible to a lightning strike... So yo would probably want to run it through a suppressor and ground rod for safety.

    If you follow Brock's story--it sounds like he started were you will... A few batteries, inverter, and a charger, then went up from there--That is a good way to learn and experiment. However, you will probably also eventually experience the creeping requirements/costs of going solar.

    Also, a good place to start measuring your AC power use is with a ~$31-$35 kill-a-watt meter like here:

    http://www.amazon.com/gp/product/B00009MDBU

    The meter is also very helpful for measuring other loads (like the fridge) to understand where you can work to keep you utility bills down too.

    Good Luck!
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
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    Re: Backup Power

    Mike
    If all you need is some minimal back up power then I would suggest just getting a small Honda generator. Something like the EU1000i would work well for your purposes. Once you get into batteries, then you have to maintain them and charge them, and no matter how well you treat them they are still going to have to be replaced in time. Also the generator would probably be cheaper. Just a thought,
    Larry
  • System2
    System2 Posts: 6,290 admin
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    Re: Backup Power

    Thanks a bunch for all the info you guys have furnished so far. Lots to think about.

    I do occasionally run the laptop, using its battery, during lightning storms. When I'm on the Internet, I put my wi-fi router at risk, which is very cheap to replace. The DSL modem might be more of a problem - I think I'd have to buy a new one from BellSouth (time + money).

    We keep a non-wireless phone around to plug in when the power's out, plus my wife has a cell phone (which barely works from our house in the best of times).

    I'll do some reading about solar panels and generators.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Backup Power

    Just to be clear, the 10 days of power on 5 gallons of gasoline assumes that you you have your 8 hours of battery and run a 55 amp Iota charger for approximately 4 hours per day (according to Honda, either the eu1000i or eu2000i would use about the same amount of fuel). Perhaps somebody can answer this better than I, but I am not sure that a Honda eu1000i is large enough to reliable run an Iota 55 amp charger--anyone with experience?

    If you are just running the generators, Honda rates them at 1/4 load for 15 hours on 1.1 gallons of gas @ 400 watts (eu2000i) and 0.6 gallons @ 225 watts for 8.3 hours. So, you should expect 5 gallons to last you, roughly:

    http://www.hondapowerequipment.com/gensup.asp

    eu2000i hours: 15h *5gal/1.1gal tank = 68 hours or about 8 eight hour work days (and you have 200 watts to spare)
    eu1000i hours: 8.3h *5gal/0.6 gal tank = 69 hours (again, 8 work days but no extra power to spare)

    In either case, I still like the idea of 8 hours or so for one day on battery backup power. Generators are noisy and expensive to run if you don't have to ($15 in gasoline vs $2.50 in equivalent utility power). And for the 95% of the time where you just wanted eight hours of lightning protection, you just use the Iota charger plugged into the wall through a well grounded surge suppressor (disconnected from wall during storms--if want to be very careful) to your laptop and lights. You can use a $100 UPS w/ surge suppressor for the telephone base station, and wifi BroadBand/DSL/dialup router on a separate circuit so that you are safe and don't lose anything expensive (like PC and data) if, heaven forbid, your house and/or wiring gets a direct hit.

    (by the way, you can get wifi plug-in cards for your desktop machines too).

    And only break out the generator when you have a real power failure.

    In any case, you will still probably want to FIRST ensure that you have your home and AC mains well protected by somebody that knows how to install proper lightning suppression gear to reduce the risk to life and property.

    And if you do make a battery backup system for your computer and a few lights, you probably should also bond the negative battery terminal to your home's ground rod/grounding system/cold water pipe for added safety with a good mechanical clamp and 6-8 awg copper wire. If you are not electrically knowledgable in grounding--talk to a local professional to help you with all of this. Improper grounding or multiple independent grounding can make you somewhat more susceptible to the equipment damaging effects of a nearby lightning strike rather than protecting you.

    -Bill

    PS: A second backup DSL modem (configured and tested as working on your connection) may be just the price of doing business.

    You can also find active and passive repeater/antenna systems for some cell phones out there (different companies use different frequencies and standards--have to find one that matches your cell phone service).

    If you are trying to be as safe as possible, you probably would want to split the DSL/wifi Router/phone base station on its own battery/charger/inverter or cheap UPS. (the idea being to keep you a) safe at your keyboard, and b) able to run during minor emergencies).

    -BB
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
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    Re: Backup Power

    also if you're interested in conserving power (makes sense either way) while your at it, corded phone AND a non wireless router would use less power during those times.
  • System2
    System2 Posts: 6,290 admin
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    Re: Backup Power

    and another little solar plug: an added benny: if you went with a solar solution : you could run off it on nice weather while your batts were charged minimizing your houses power uasage during those times. i do this w/my pc.
    still, as is obviouse it wont be the least expensive option to implement.
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
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    Re: Backup Power

    I had read somewhere that the Honda 1000i sometimes won't run the Iota 55 amp charger because of the power factor, or if it did lock in and charge the genset ran full throttle and can't run anything else at the same time. Running a single Iota 55 amp charger on a 2000i allows the genset to idle down even while at full charge and idle way down once it gets in to the float stage and allows other loads to be run at the same time. Obviously this also makes for less noise and likely faster charge times. For the slight increase in cost personally I would opt for the 2000i.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI