Solar Generator Project

[juiced]

Hi all!

  This is my first diary entry. Ive posted lots of small, unconsequential toys in the past but this is the real deal.

   I cant go too far into specifics just yet because i might actually market this idea. It is a very sweet package.

   Basically, as is i have 65w @ 12v / (by ohms law) 5.41 amps (by manufactuers ratings) 4.85 amps

  First can someone explain the discrepency in amps? (15w + 50w)

 Now, I can expand the amount of panels on the array in the future but what im worried about is buying batteries.

   By the numbers i understand 5A is good to charge @ 4.5A after losses. I dont want to go further then 20% on the batteries, so is 4 x 4.5A (http://www.batterymart.com/battery.mv?p=SLA-12V4D or similar) the right idea?

  This setup will allow for 18AH per day (4x5-lo%s) charging power to my pack. This will give me about 2.8(ish)A per hour reliably and keep my batteries in the 20% discharge range?

   My real question starts here. The above figulation was done assuming there will alwas be a load to discharge to. Of course i have a charge controller but should i consider 2 more batteries for extended periods of charging without use?

  My second question is, I think i can fit about 200w total on the array. Im scared to buy these small batteries because at 200w the numbers change. So would these batteries have to go for sale at that point or could i efficiently add more 4.5AH batteries as i expand? This is a real killer for me. Im sooo close but i hate jumping onto loose stones

 

[Opera House]

"65w @ 12v / (by ohms law) 5.41 amps (by manufactuers ratings) 4.85 amps"

Watts = Wolts X Amps.   Trouble is, 12 volts is just never 12 volts.  Panels put out their maximum wattage in the 17-18 volt range and operate mostly at a current source.  Charged batteries operate between 12.6 and 14.5 volts.   You can operate a switching power supply to do the wattage conversion.  Frankly, power point switchers are BOOOOOOOOOGUS if you use the same voltage panel on the same voltage battery.

[ghurd]

Yes. PVs are a current source. The short circuit to the max power rating is very close.

BTW, For people who will say the rating is a rip-off, the Gov't mandated this system.

You have way too much PV for the battery.  See the other new post.

The controller will kick in fast. You are not going to get the ah's into the battery that it sounds like.

Save some money. Get the 7ah batteries.  I don't see any gain by parralling 4@4.5ah over 1@18 ah.  1@18 will be lighter and smaller, probably cheaper.

G-

[juiced]

Well, my genny passed it first test! Nobody stole it!! (I live in the ghetto)

   Now im kinda confused Ghurd. I should go for 7AH or 18AH? Also is it safe to do so for future expansion purposes? I thought if im not carefull, when i get more panels i will need to change my battery math and therefore need a differant batt.

  The reason i thought several batteries instead of one was to avoid depleting them to far. Maybe my thinking is still wrong on this?

   When i built this thing, i didnt realised the reality of losses and etc. I basically made it to be able to store about 12x standard sized car batteries. So now i feel like i have all this open, unused space. The giant battery bank was also an extended security feature, as i anticipated the weight to be tooo heavy to try to lift.

    good thing i haven't ripped to much apart to build it!

[juiced]

Aww man. I dunno what happened. The test light on the battery booster pack (large) is green. But im only getting 9.xx V out!! whyyyyyyyy.. I did accidently short it out for a micro-second, but that shouldnt matter.... Its like -30 out but I did have it wrapped in some sweaters and a rubber jacket.

  My invertors all have low voltage cut-off switches so i dont see how i could have drained it too far. Man this kills my spirits ever so slightly.

  If this thing is as dead as my multimeter is showing, i think there'll be another exchange for crappy tire.

   

[juiced]

Scratch the above comment.

  It must be a fuse limiting the voltage, because i threw my digi-invert on it and its reading 12.3 (almost a full charge in one!)

  Id really like to figure out the AH value of this battery but its sealed in a carry case.

    Can i test the amps (i just did and i think its too high for my multi-meter. i got 7-9 and then a 19.3 and then 1.) and then use ohms for that?

[juiced]

I have almost all the same equipment as this guy: http://www.otherpower.com/wardsolar.html

  "Solar Panel--BP 75 watt, from an internet distributor. $310 new, plus $20 for shipping. Wired to contoller and battery bank with #10 Romex.

Solar Panel Mount--Home built from 1 inch aluminum angle, adjustable for summer and winter positions. About $20 total for aluminum stock, nuts, and bolts.

Charge Controller--An industrial model from Jade Mountain, rated for 16 amps (to provide room for adding more solar panels later), and cost only $62. Ward had to buy 2 fuse holders and 20 amp fuses, mount this controller on a home-made aluminum heat sink and build a cover himself....but for the price he'll be able to add 2 or 3 more solar panels without a new controller.

Inverter--A 350-watt Wagan from Harbor Freight, only $40. Includes fuse on main power cable and overload shutdown. DanB has used one of these for a year, heaping abuse and neglect on it, and it's performed like a champ. The only drawback of this model is that the fan is on all the time, and produces a little noise. Ward plans to to turn the inverter off at night, and during the day while he's at work.

Metering--Cheap digital multimeter, only $10. Not real accurate, but enough to determine general battery state of charge. Plus, the controller has an LED to indicate full charged condition. "

 However he has: "Battery Bank--4 golf cart batteries. 6 VDC, 220 amp/hours, only $45.99 each from Sam's Club. Wired in series and parallel, these give 440 amp/hours of storage. That's more than enough for the minimal loads in the cabin, especially when you consider that the owner is away from home at work during the day, giving the system time to charge back up."

   Should i mimic his battery bank? He seems to actually be using his loads alot more than i intend to. Im running off a laptop, cant remember wattage off the top.

 

[ghurd]

Well, my cost for a 7ah is less than a 4.5ah, a lot less.  More common I guess.

I could use 4 @ 7ah for 28ah, for less money than 4 @ 4.5 for 18ah.

I think 20ah is 20 ah. For 1 battery or 10.  I don't see a reason to 10 if 1 is cheaper.  If you only need 18ah, thats all you need. I don't know what you are making.

A good way to think about the PV to battery ratio... If you have a 170w 10a PV, and a 1ah battery, there is a lot of power getting wasted. Same with a 5 or 10or 20ah battery.  Somewhere it balances out, but the load comes in along the way.

G-

[ghurd]

His battery is oversized to the PV for everyday use. Nice for a sometimes on the weekend cabin type use. He is losing a solar hour output a day to self discharge.

Everyday use, I bet a pair of 6v or a single 105ah would be a fine match for a 75w PV. Probably even a 85ah.  

Thats assuming a 75w PV can keep up. Big batteries don't make up for a greater load greater than the PV will handle. 75w is only about 4.4a.

G-

[juiced]

Well it seems to have failed its second test regardless.

  As stated before, i am using booster packs for now. 1 pack has been on the charger for 2 days. its approx -30 now and i totally drained the booster trying to get my car started. Now unless i come across a mechanical problem,  im assuming the battery wasnt actualy full. Lying little LED.

   

[ghurd]

Charge controllers. Temperature compensation. -30'.

The little yellow 7a ones do not have temp comp. (I think they are still yellow?)

I C P roblems with the controller, if you know what I mean.

Those are extreme temps for a battery. Try a Morningstar SG-4 for 4a, a SS-6 for 6a.

Temp comp is in them.

And battery meters and little lights don't have temp compensation either. They lie when it gets cold.

The batteries in the big 'starters' are SLA. (the pocket ones are 10 D ni-cds. lol!) They really don't like being used that way. Could be the SLA is worn out.

Are the batteries inside? Then it could just be this dang snowstorm~ you're in it right?

G-

[juiced]

Thanks for the heads up.

  Yes, im 100% sure its an SLA. What do mean exactly by they dont like being used that way?

  As for temps, yes very cold here. Fingers are frozen from playing... No snow yet though. The batteries were all outside... I think that combined with the no-temp controller probably is my issue here.

[BT Humble]

His battery is oversized to the PV for everyday use. Nice for a sometimes on the weekend cabin type use. He is losing a solar hour output a day to self discharge.

Everyday use, I bet a pair of 6v or a single 105ah would be a fine match for a 75w PV. Probably even a 85ah.  

Thats assuming a 75w PV can keep up. Big batteries don't make up for a greater load greater than the PV will handle. 75w is only about 4.4a.

I'm using a 24V system, with 560W of solar.  That's around 19A to the batteries at peak.  I'm using a 1000Ah battery bank.  As a rule of thumb I'd consider a battery bank for daily use should be around 30 or 40 times your solar panel's output, or in the case of a panel delivering 4.5A, about 150Ah.

BTH

(Off the grid for 9 months, and only started the generator once.)

[ghurd]

At 150ah, with a 4.5a panel, that is 33.33 hours of solar insolation per day.

For the North America population the average is about 4.5 hours a day.

[ghurd]

They only like being charged 'so' fast. Say 10% of the ah rating.

They do not like being discharged too fast either.

Say the battery in there is a 17ah, and the car pulls 250a to start it. Thats 1500%.

It'll work a few times. Stuff boils for lack of a better word. Torn ligaments. Hernias. Arthritis. Stuff like that. Can't do it forever. Harder it works, the shorter it works (like don't use the battery below X% state of charge).

G-

[ghurd]

And batteries at -30' is for sure an issue!

G-

[juiced]

I started gathering materials to build a combiner/junction box. Im trying to keep the expansion capabilities open, so i decided a 16 terminal box would do well.

  As i gathered my stuff, i realised... I have no idea how to do that and not conduct electricity through the bolts to the frame! Im assuming there are rubber grovets that can be bought.

  I thought that to keep my box neat, i should use a speaker output panel from an amp. Seems like a standard surround sound setup. 4 + 2 + sub .. ok maybe 14 terminals.

  I like the idea of having inline fuses but as it is i am having a hard time replacing the ones im using.

[ghurd]

I often use a fused distribution block from the auto parts store. It has 6 ATC blade fuses. The battery connects to a #10 screw. The PV controller feeds in through 1 fuse, the other 5 can feed out.  Kind of pricy for what it is, but it is neat and easy.

G-

[BT Humble]

At 150ah, with a 4.5a panel, that is 33.33 hours of solar insolation per day.

For the North America population the average is about 4.5 hours a day.

Mate, you don't run the battery down to 0% every night!  The idea is to have sufficient battery capacity to only run it down to ~80% capacity after 2 or 3 days of no solar input (i.e. you're only actually using 20% of the available battery capacity).  Shallow-cycling like this helps to increase the life of your battery.

Also, since you can't get out more than you put in, it's usually a good idea to make sure that your daily solar Ah production is about 125%-150% of your daily Ah usage.

Sorry, it appears that I wasn't being clear with what I meant.  I hope that clears things up! ;-)

BTH

[ghurd]

That didn't read too well did it.  I don't even understand it.

It was supposed to mean something like thats about a week of reserve power.

I understood what you meant.

G-

[Gary D]

Juiced, not sure if wallmart or sam's clubs are in Canada or not. If they are, you could get a 300 watt 4 panel "plug and play" setup for about 1800.00 US (300 watt inverter and charge controller included- but no batteries). The panels are assembled in Canada... probably Chinese tho.

 If not with a little research, possibly you could find out where in Canada they are assembled and just buy one or more 75 watt panels with no across the border tax / ripoff... and not deal with Sam's club.... The link is below... type in solar panels in their search (if you got the bucks) Might be cheaper than buying 15 watt units  Gary D

www.samsclub.com

[juiced]

Hi Gary, thanks alot for the lead. I didnt know walmart has gotten in the market.

  I actually picked up the 15w at 40$ below my (dealer) cost price. Theres a method to my madness! lol

   I actually carry a 300w kit by ICP for 3400$ CDN (ive been told thats a great price!) which is 2,752.47 USD. I am quite sure i couldnt get that low! If possible, id love to see a pic or a name of the walmart brand.

  Also, if you are price savvy. i will have a post in the classifieds in a few minutes. Check it out and tell me what you think.

[juiced]

Well here i am. I now have a welder, metal and still few ideas about how to design the frame to be A> expandable B> Secure C> Light.

    I suppose a pic or technical drawing is in order here.

  Basically i have taken a painters rolling/folding scaffolding and cut the face off on a perhaps 70* angle.

  I found a bed frame in great condition and cut the fasteners off, measured and cut to the approx. length of 4 50w panels side by side + 1 inch.

   So now i have a frame with a 200w capacity. It has the standard bolts to resize the frame for differant beds (panels).

   I guess overnight i will be trying to draw up a design that will make it impossible to seperate the two sections without having access to a locked area behind the panels.

  Im thinking pins or perhaps even full locks... Bolts would work (except an impact wrench would be able to get them loose) as well i guess but the idea is that the genny can easily be taken down, folded and stored under a bed or closet.

    I thought about a sliding tray with a pin on each corner but i think its beyond my skill at this moment. Also, someone desperate enough might be able to figure out that by smashing a panel they could release the entire array and just rebuild the one panel after...

  I really need to take a pic because so far you cant really understand the folding problem.

   

[ghurd]

Carriage bolts! Round on top. Nuts in the locked area in back.

They should go in a square hole.  You have square drill bits, right?

G-

[juiced]

I was looking at the bold on the frame and they are almost what you describe.

  No i dont have square bits yet.. ill just drill and file. (budget has been excedded recently.. lol)

   I do have pics though! Gotta love 13 year old siblings with expensive electronics.

 

  Now, the rails are not the actual rails i cut but they will stay on with out a tack, so there they are :p

    The blanket will be replaced, likely by a high-white metal or if i cant get a good peice; plywood. A frame holds the panels and rests, secured by the bottom hooks + a lock. There is room for 2 battery banks. The sides will have sheet metal reinforced welds (6 mm iron bar blocker). The PV frame is adjustable so far.

   A hinged box will fit between the PV lock & and frame. You will need to unlock this box to unlock the frame. The box will give access to batt bank #1 and controls. I intend on the design to be largerly held together by.. (not quite friction fit) but one lock with allow all componants to be realease in order.

        The frame fits 200w as is. An additional frame section, perhaps 100w (or more, untill its not stable...) can be added by welding a special "slide-lock" cylinder into another piece of scaffolding and drilling a hole for the 'rams' to grab on and then fitting the add-on on top of the first, in the scaffolding holes.

  This section will also be accessable through the control bay.

  The frame has room for u-locks on either side for securing in an urban or remote location. Im also thinking about armoured glass.. but its heavy, light-ineffiecant and $$$$

      Now that there a pic and not a lucid dream to be talked about.. lol Lets hear it!!

    Thanks for all the support guys; hard to find a elec/tech/mech friend around here.

   Ill post pics of my neighbourhood soon to give you an idea of the inspiration.. lolol

[juiced]

As you can see. My frame is round and my bars are square.

   Welding (especially for a new guy) is seemingly quite difficult with these mismatched pieces.

  I read/figured out a few things. Angle, speed and depth are what i need to practice over and over. Bevel my joints with the grinder, work clean... Oh ya, and i tried to square the tube but all i have is a c-clamp, no torch.

       Now. I, on my second try got a triangle from scrap L and tube. The first fell apart! lol  The second i need to beat the piss outta with a hammer, while propped against concrete.

    So its semi-strong .. i guess? Im using a stick welder, 10% cycle.

 I dont mind screwing around untill i get it right before i touch my precious frame..

   Any advice?

[ghurd]

On re-reading, a 10% duty cycle welder may not get enough penatration. The ones I have seen at least. You need some amps. Maybe 90 or 100?  Someone may be better at it than me.   G-

[juiced]

I actually got that impression but i narrowed it down to lack of skill on my part.

  its a 15/20 amp machine and i must say; even with the supplied mask i woke up in the middle of the night with the worst case of burning eyeballs ive ever felt! Im a little sensitive to light; turns out these things spit UV like the sun.

  Someone told me earlier today that contacts can actually get fused to eyes... dunno if thats true but the pain was pretty intense.

[juiced]

Got most of the metal i need today.

  I have two 7/8 rods(actually, the tubing the bars go into is 7/8 and the rods are a millimeter smaller) ill be using as ancors/locks for the solar rack but im not entirely sure how to bend them the way i want; much like a question mark ' ? '. The reason for this shape easily lodges in the tubing. So i can put a weld or two down the inside of the tube.

  The metal is rebar. It was all i could find. I could alwas wait.. for a torch and differant metal but im kinda.. impatient like that sometimes. If i can not bend that metal how i want it, i might wait because by the time i can afford a torch i should be able to find a welding shop here.

Pictures tomorrow i hope!