Solar office

dave g
dave g Registered Users Posts: 17
Hello! I've been lurking in your fine forum off & on for maybe a year. I *think* this is my first post. I'm finally getting around to my first modest little PV project: Running all the stuff in my home office. This is primarily a "hobby" project, although the power goes off here with some regularity so the promise of uninterrupted power is appealing too.

I have a tiny little south-facing roof surface over the back door of my house, almost exactly the right size for the 3 panel, 45 watt set of panels that Harbor Freight sells. So I've ordered those, and went out and bought a battery today as well.

Here's what I've got / going to have:

- The HF solar "kit": http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599

- From Wal-Mart today, an "Everstart Marine" battery #27DC-6. Says "Trolling, Deepcycle, RV" on it. 115 Amp Hours, 720 Marine cranking amps, 600 cold cranking amps.

- An "Aims Power" #PWRINV400W modified sine wave inverter, 400W constant, 800W surge.

And, while waiting for the panels to arrive, I'm using a Harbor Freight "Automatic Battery Charger" with an output of 1.1 amp. Supposedly this charger will stop charging when the battery is fully charged; it seem to work as advertised with car batteries, not sure if it's good for this purpose...

I've been measuring the power consumption of the stuff in the office to be operated and it totals about 150 watts. I've got everything connected and running off the battery right now, in fact. I'll fully change it tonight and see if everything will run all day tomorrow.

A few basic questions:

Will I hurt anything if I have the charger connected (and running) at the same time the inverter is running?

Is there any danger in having the battery in the room with me?

I've read (here, I think) that the HF controller that comes in the kit is not a "real" charge controller; what's up with that? Will it work to keep the battery changed properly from the panels?

Thanks! I'm really looking forward to all this :-).
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Comments

  • Dapdan
    Dapdan Solar Expert Posts: 330 ✭✭
    Re: Solar office

    Hey dave,

    I dont want to be-little or discourage your efforts since any in terms of RE is good even though sometime they maybe not the most prudent (applies to everyone IMHO). I believe your money may have been better spent if you bought a good Si panel (you can get a 200w panel for $500 now). If you do the cal you will realise that the 45w panels from HF will only give you 135wh of energy on a good solar day (45w*6hr*50% eff). Given your loads of 150w you will only be able to carry them for 54mins and then start to deplete the battery and invariablely end up charging it back up with grid juice (which i think defies your original intent)

    If you check the charging percentage of the panel it is also below the 5% min and you will not be able to equalize this battery either(this maybe not as critical for you). I believe if you added a couple more $100s you would be able to get a much better panel with much better warranty and be able to run your office strickly off that single panel. One 200w panel would give you 600wh under the same conditions of the above cal and run your loads for 3hr.


    Cheers...
    Damani
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar office

    As as been said quite often,,,do your math. Calculate your loads,,, using a kill-a-watt or some similar device. Then calculate your potential from any give set of PV hardware. A simple calculation is (not perfect,, but simple) take the name plate rating of a PV panel, multiply that by the number of hours of GOOD sun, (usually ~4 in most cases over the course of a year,, maybe as much as 6 if you are in a really good location) and divide that number by 2. This will give you the useable 120volt watt hours (wh) you can expect in an average day. The number two factors in all the system (in) efficiencies, panel, wiring charge controller, inverter losses etc.

    For example,, your 45 watt panel, 45X4hours/2=90 watt hours,, enough to light 15 watt cfl for 5 hours.

    Now a couple of other things to consider. Modified sine wave inverters CAN destroy some electronic devices right away. They can also burn out 120 vac motors quite quickly. Also most cheap MSW inverters have terrible efficiency curves,,,so the above example only gets worse.

    If I could give two pieces of advice to newbies, the first would be avoid the "ready, fire , aim" syndrome by doing your math,, and doing your homework. The second would be buy from experienced, dedicated solar retailers rather than Harbor Freight, Northern Tool, or much of E-bay. There are good reasons that people like this site sponsor have good reps to go along with the products they sell. They have been tried and tested by some very smart people,,, such that newbies don't have to reinvent the wheel.

    One other piece of advice I would give newbies is battery based solar is, on average, twice the price per watt hour as grid tie. If you are looking to do any solar to "save money" you are twice as far behind using a battery. Even grid tie is not going to save you money,,, unless you have done EVERTHING you can do to conserve,,, and then you have to build a real system,,,, and even then the payoff comes in multiple number of years,, at best.

    Tony
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar office
    dave g wrote: »
    A few basic questions:

    Will I hurt anything if I have the charger connected (and running) at the same time the inverter is running?

    Is there any danger in having the battery in the room with me?

    I've read (here, I think) that the HF controller that comes in the kit is not a "real" charge controller; what's up with that? Will it work to keep the battery changed properly from the panels?

    Thanks! I'm really looking forward to all this :-).

    Probably won't hurt anything to have the charger connected at the same time the inverter is running.

    If that is not a SEALED battery - then YES THERE IS DANGER in having it in the room with you. The battery will vent hydrogen into the room when it's charging, and if you've never seen hydrogen burn...well it burns extremely fast. In fact it burns so fast that, like black powder, it doesn't seem to burn at all - it seems to explode. And letting hydrogen build up inside a room at night while you are sleeping...that is a BAD idea.

    Don't know anything about the controller that comes with that kit. Search here for 2manytoyz, he's got that same kit and has pages on his web site about it.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar office

    2manytoyz' personal Website:

    http://2manytoyz.com/

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    Re: Solar office

    About the HF charge controller. The one with the single LED's is junk. Now if you get the one with a digital voltage display. Then that will work for you. I had both, the digital display one lasted 3-4 months till I upgraded to more powerful system. Also, the HF for some reason have good resale value. Plus, if you got them directly from HF, you can return the kit with in 30 days. So I would use it for 20 days get your feet wet, then see if you like it or not.
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Solar office

    I also started with an HF kit. Used it about 9 months until I started buying the "serious" gear! ;)

    A few comments about the HF kit based on my experience - reinforced by reading others' comments in various places:

    - Their 45W rating is VERY optimistic! I don't think anyone has actually see that. (In fact, I think they got that rating by taking the short-circuit current and open-circuit voltage to multiply together.) In my case, the very best I *ever* got was 30W, and that was the day I opened the box and very carefully pointed the panels directly at the noontime July sun. Normal daily operation is more like 18-20W with occasional forays to 25W. (And yes, all three panels are still working.)

    - I have the "new" digital-display charge controller and I'm not all that impressed with it either. It's a very crude controller, just applies panel power to the battery until the terminal voltage rises above its internal setpoint then switches them off until it falls below another setpoint. With the controller I have, that switch-off setpoint was alarmingly high - I didn't want the battery going that high. (Haven't used it since last summer, so can't remember exactly but it switched off somewhere between 14.5 and 15V.) Far as I know there's no way to adjust that.

    I wound up buying a small better-quality charge controller from NAWS, and been much happier. It implements the three-stage charge algorithm - bulk, absorption, then float.

    - The controller and panels have no reverse-current protection, so if you leave the whole kit set up overnight current will flow backward from the battery into the panels. The kit does mention not to leave things hooked up "when unattended", but doesn't mention why. I had a Watts-Up meter inline with my panels, which is how I noticed. I eventually installed diodes in the panels - there was *just* enough room inside the junction box on the back of the panels. (You could also just put a diode at the controller.)

    - Some have worried about the glass on the panels, as it's (apparently) not tempered. (Not that I would know how to tell myself...!) But others have said theirs withstood hailstorms, and mine are fine so far - although they haven't seen much if any hail.

    I still have mine on the roof, they charge the various batteries I have laying around for miscellaneous projects, or keep the battery topped up in my seldom-used car. Having said all the "negatives" above, I will say one nice thing I like about them (and amorphous panels in general) - these things start producing *some* current as soon as it's barely light! And keep producing right up until the sun goes down. Might not be a whole lot, but it's still better than zero!
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Solar office

    A note / question about the battery issue.

    I used an AGM battery with my HF set, sat right on the bench with everything else (powered part of my ham bench). I like not worrying about battery acid leaking out if I tip it over! :)

    But, I do have a question for everyone regarding the hydrogen gas issue. Because in the past I've had regular wet-cell batteries (usually one of the Wal-Mart "marine" batteries such as the OP bought) in the house. Used them, charged them, everything - usually in a very rough manner, I didn't know then what I know now about batteries. Never had an issue.

    I'm not saying there *isn't* a problem, by any means. However, I have to wonder - how much hydrogen gas (by volume) does a battery actually generate when charging? Certainly I can see a battery - or worse, a whole string - in a small enclosed space being able to generate sufficient gas to reach volatility. But one or two car-sized batteries in an open room?

    Also, how much gas is generated from "normal" charging as opposed to equalizing? My understanding is that equalizing is where you really generate the gas, but that doesn't happen often (if at all, in a very small setup). Would normal bulk / absorption charging generate much?

    One of the things that made me wonder about all this is checking my T105s after they had been set up for a few months. The water level has barely budged from where it was when I bought them, so I'd hardly think they could have generated much gas at all.

    I started wondering if this was perhaps along the lines of the warnings they put on gas cans (heck, just about EVERYTHING now) that warns of hideous, dire consequences if you just look at the can wrong. When I was a kid, we had a gas can for the mower in the garage (attached, with gas water heater and furnace) and it almost never had a cap on it - for that matter the caps they provided then were nowhere close to sealing! (Of course, we also didn't store it right beside the water heater either!) Really, the only gasoline-caused garage fires I remember reading / hearing about were always because someone had actually spilled a large quantity on the floor.

    Again, I am NOT saying there's no risk! I just wonder (I really, truly would like to know) what the real risk actually is. I have so far not found anything that tells me that! Something like "one T105 emits roughly X parts hydrogen gas per Y time while charging, and it (only?!) takes Z PPM to go *BOOM*! :p
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    it all depends on how concentrated the gas gets just like lng or propane. a battery or 2 probably won't be a problem.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Solar office

    My personal hydrogen worry level:
    only when in EQ, or something goes wrong.

    It's produced at a fairly low rate, even in EQ, and then, you'd have to have a way to gather it, in a room, with a person walking by every hour, the room full of air would be stirred to dilution. Any window cracks, that air exchange will pull some H out with it.

    But, that's my personal feeling, in contrast to what the fire departments and insurance companies want you to do.

    And when something goes wrong, you have little time/chance to get it right.

    If there was a single battery, in a house, on a UL, 3 stage charger, something else is far more likely to happen:
    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 ,

  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Solar office

    And how many times on this forum have I seen it said that only sealed batteries should be used *inside* an RV?

    :D

    True, the risk IS low, but it is there. And I have no way of knowing if the OP is leaving his windows cracked, but I can bet he's not walking by every hour while he's sleeping. :)

    As to figuring out how much hydrogen, here's something I found by googling:

    http://www.multi-shifter.com/hydrogen.htm


    Here's something else I found:

    http://www.allaboutcircuits.com/vol_1/chpt_11/5.html

    Here's the interesting bit:

    "The author has been a firsthand witness to a lead-acid battery explosion, where a spark created by the removal of a battery charger (small DC power supply) from an automotive battery ignited hydrogen gas within the battery case, blowing the top off the battery and splashing sulfuric acid everywhere." (Emphasis added by me.)


    It doesn't take much hydrogen to make a very exciting day if there happens to be a spark or flame wandering around...I wonder if the OP smokes...
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar office

    One can always build a properly vented battery box, with properly voltage controlled vent fan(s) Not very hard to do,,, pretty safe too.

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    as i said dwh it does depend on how concentrated it gets. my father also experienced his car battery exploding when it sparked from disconnecting his charger.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Thanks, everyone!

    In practice, it seems that the stuff I want to power draws less than I guessed - about 60-70 watts, measuring the 12v going into the inverter. (Assuming I'm measuring correctly: using a clamp-on meter, I get an average of about 5.1 amps at 12 v, or 12v * 5.1a = 61 watts, right?)

    I realize that I could get better equipment if I spent more money, but the money isn't there :-). Also, that little roof surface I'm going to mount the panels on is the only space available (without big bucks in construction work) and it's just the right size for the HF panels.

    I'm not trying to save money; I expect to spend money :-). The main goal is to screw around with solar stuff for fun.

    Thanks for the info on connecting the charger and the inverter at the same time, and the math on how long it takes to change. Based on that I went out and got a bigger (10 amp) changer yesterday (Schumacher SC-1000A), and have the battery at full change now.

    The charger is kinda noisy so I'm going to relocate everything to the basement and put in a little exhaust fan to get rid of the hydrogen. There is a good spot directly under where the panels will go - I'll only need about 12' of wire from the panels to the charge controller.

    Diodes to keep current running backwards at night - part numbers, wiring diagram on line somewhere?

    How does one monitor the battery's state of charge? By voltage, or what?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar office

    Regarding ventilation--for a small system, the fan may use as much power as your panels generate. Using natural ventilation (low vent for fresh air, raised outlet for vent) and/or using a fan that only turn on when the panel is generating power will help conserve power.

    Any standard diode rated for voltage/current will work. Here are a few from our host.

    To check battery charge, you can use a hydrometer (for flooded cell batteries, cannot use on sealed batteries). Good for occasional use--not handy to use every day.

    wind-sun_2050_3042969Freas HD98C Precision Hydrometer Set

    Or an accurate DVM measuring battery voltage after a few hours of resting (no charging, no loads). See Battery FAQ for details.


    Or, for larger installations, the best real time method is to use a Battery Monitor--pretty pricey for a small system (Trimetric is a good/low cost unit).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar office

    Zepher fan draws ~3 watts,,, the controller I had built ~1/2watt.

    T
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    i believe you still need to get a charge controller and be careful with that auto car battery charger as that type is unregulated and it can boil out the electrolyte in the battery. some controllers from the morningstar line may suit as well as from xantrex. morningstar has some smaller sunsavers and xantrex has the c line like the c35 and c40. some of these may be overkill for a 45w hf system, but you may want to expand in the future. try to get the c line as they have remote battery temperature sensors available and i recommend using a battery temp sensor. the morningstars have one built into the controller, but it's the battery temperature you need and not the controller's.
    also, note that i had a schumacher that failed on me and sent ac down the line blowing out my controller at the time. do not use unregulated auto chargers unattended.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Would 12 ga wire be OK to run from the HF panels down to the controller (about 12', I think)?
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar office

    #12 wire will carry ~20 amps safely. 12' run will have minimal loss.

    Tony
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Would this do me OK? - http://www.morningstarcorp.com/en/sun-guard
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    that is one of the sunsavers and although it says temperature compensation, it is in the controller and not able to go remotely to the battery. for morningstar, the tristar or prostar have the remote temperature sensor ability, but you have to buy the sensors separately for most controllers just so you know. i made the xantrex c line suggestion due to cheaper costs, but what you get is up to you.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Well I ended up ordering one of these yesterday: http://store.solar-electric.com/ss-6.html

    Looks like it has some idiot lights on it to tell me what it's doing, which will be nice :-)

    I'm not particularly worried about over heating the battery - sounds like the HF panels are going to have a hard time charging it at all, let alone cooking it.

    I am still eagerly awaiting the arrival of the panels... Wouldn't you know it's raining today and probably will be tomorrow as well.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    do understand that this is not to prevent the battery from overheating, but is to skew the voltage slightly to properly charge a battery when its temperature changes and it will change. putting a sunsaver against the battery will not work either and would be ill advised for you to do that. the electronics in those controllers will cause an artificial rise in the temperature that will not reflect the battery or even ambient temps making it useless to have in the controller itself. it must be remote.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Progress! I've made an aluminum rack to hold the panels and they are on the roof. Made the rack big enough to hold a 4th panel once I've got a spare $80. Once it stops raining I'll run the wires between the panels and the stuff in the basement.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office
    niel wrote: »
    do understand that this is not to prevent the battery from overheating, but is to skew the voltage slightly to properly charge a battery when its temperature changes and it will change. putting a sunsaver against the battery will not work either and would be ill advised for you to do that. the electronics in those controllers will cause an artificial rise in the temperature that will not reflect the battery or even ambient temps making it useless to have in the controller itself. it must be remote.

    Ah, now I get what you're saying. But there are a lot of small systems that don't have this battery temp adjustment and they work OK, right?

    In the mean time, it seems to be working! It's a cloudy day, but my battery voltage is definately climbing this morning. The better controller is supposed to be delivered this aternoon & I'm looking forward to hooking it up (and ditching the HF controller).

    Just couldn't help myself and orderd a 4th panel from HF yesterday.

    What size fuse should I put in the line running from the panels to the controller? (The array will be an overly-optomistic 60 watts when complete.)

    I think I may do an about-face and instead run things at night off this system, rather than during the day.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    yea, maybe they seem to work ok, but under and overcharging can have cumulative effects that you may not readily see. without battery temperature compensation it is advised that you be sure the battery stays close to 77 degrees f when going without the remote battery temperature compensation, but your new controller will vary the temperature based solely on the controller's temperature making even that effort moot. las vegas anybody?:p
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    Well I installed the new controller early yesterday. Battery voltage was 12.2 in the morning, 13.4 in the evening. I'm guessing the sun was out maybe 50% of the day, otherwise cloudy. I connected up my TV (19" CRT), DTV converter, and a 20 watt CFL light to the inverter. Measured about 132 watts on the 12v side of the inverter with all this stuff running. Watched TV (not much on though...) from 8:00 to 11:00 with the light on, as usual. No problems! Battery voltage was 12.4 early this morning. I'm pleased :-)
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar office

    If your battery is 12.2 volts in the morning you may drawing them down too low. Many people think that a routine discharge of ~40% is too much.

    State of Charge 12 Volt battery Volts per Cell
    100% 12.7 2.12
    90% 12.5 2.08
    80% 12.42 2.07
    70% 12.32 2.05
    60% 12.20 2.03
    50% 12.06 2.01
    40% 11.9 1.98
    30% 11.75 1.96
    20% 11.58 1.93
    10% 11.31 1.89
    0 10.5 1.75

    Tony
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar office

    did the battery ever get to a good charge voltage as i doubt that it may have? it seems you may have not allowed it to reach 100% soc.
  • dave g
    dave g Registered Users Posts: 17
    Re: Solar office

    niel - You mean has it *ever* been charged to 100%? If so, yes, on the plug-in charger prior to the arrival of the panels. I have not used the charger since connecting up the panels on the 30th.

    Tony - Thanks for the info - I've printed that and hung it on the wall near the battery :-). Note that the voltage was at 12.4 this morning after running the TV & stuff last night (not 12.2).

    If 12.7 is 100%, what's going on when I read 13+ ?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar office

    The only accurate method to measure state of charge with a voltmeter is to have the batteries rest for 3 or so hours (no charging, no discharging). The 13+ volts, could be a "surface" charge that would quickly "burn off" with use, or after setting for several hours.

    Also, batteries are fairly sensitive to temperature--so if the banks are very cold, you will read higher voltages too (but there is less capacity in a cold battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset