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Solar without batteries

Discussion in 'Off Grid Living' started by Kingfish, Aug 11, 2011.

  1. Kingfish

    Kingfish Self Reliant

    Ok the big question. Lets say I have a 2500 watt inverter that makes 120 volts AC from 24 volts DC. How many watts in 24 volt solar panels would I need to run direct into the inverter without batteries? This is to address the possibility that my batteries died and I could not replace them. Would a 2500 watt array be enough to feed a 2500 watt inverter during good sunshine? Can it even be done? KF
  2. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Yes and yes. But you would still need a battery, good shape or not, wired in for surge absorption. I guess that could also be done with a capacitor. You lose some power due to inefficiency of conversion, off hand I don't know how much the inverter uses internally. For a guess, about 10% more panels than watts needed on the 120v side to cover the inefficiency, then some more to cover panel degradation.
    forge1 and Kingfish like this.
  3. beast

    beast backwoodsman

    you can make a simple large capacity capacitor from aluminum foil and saran wrap
    Kingfish likes this.
  4. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    You should be able to buy a capaciter or two that , in the event of battery failure and no way to replace them could be used in place.....
    Kingfish likes this.
  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    There is NO NEED to duplicate Capacitor Technology, that can be purchased, Off the Shelf, for a few FRNS. Yes TinFoil and SuraWrap will make a capacitor, but modern Electrolytic Capacitors use an Electrolyte Paste that greatly reduces their Size to Capacity Ratio, and that formula is a very guarded Secret among OEMs. Remember the incident a few years back, where the Red Chinese stole an Electrolyte formula from the Japanese, thru Industrial Espionage. The chinese used that formula in Hundreds of Millions of Capacitors in hundreds of thousands of consumer, and their own Military Stuff. The only problem they had was, that the Japanese SNOOKERED them and they stole a FAKE Formula, and the Japanese just let nature run its course and didn't tell anyone. Well all the computers, Laptops, and other electronics, built use those Caps DIED in the first Year or two. It almost sunk Apple and Dell Support, as well as many other outfits worldwide. Taiwan also used a bunch of those Caps they bought from the Reds, at really good prices, and suffered along with the Koreans and the Malaysians, who did the same. Panasonic in Japan, couldn't fill the orders fast enough to fill the supply chain, and it was a world wide MESS.... ...... YMMV....
    forge1, Kingfish and Nadja like this.
  6. Kingfish

    Kingfish Self Reliant

    So, what you saying is just leave the batteries in even if they are worn out? KF
    BTPost likes this.
  7. beast

    beast backwoodsman

    yes you can buy better capacitors...
    but when TSHTF knowing how to make your own is a good thing
    they do burn out
    Kingfish likes this.
  8. Tikka

    Tikka Monkey+++

    Showed up in a lot of computer motherboards and not the cheapies.

    There are a few versions of the "how." Which is SOP with espionage. :D
    Kingfish likes this.
  9. TnAndy

    TnAndy Senior Member Founding Member

    Outback says their inverters won't work w/o batteries in the system ( though they don't say how good they have to be ).

    But from a purely practical standpoint, you wouldn't want to operate your system without them ( or a grid tie ) anyway because here is what would happen:

    To start with, you'll need 3 to 3.5kw to even hit 2500w output, based on what I see out of mine. By the time you factor in charge controller loss, and battery loss ( which I suspect would be greater if you had crappy batteries ), inverter loss, AND (the biggie) the fact your 245w panel (for example) is only going to ever give you 245w on the most rare of days ( great sun, perfect angle alignment, perfect temp ), you need to factor in AT LEAST 1/3 more in panel than you want in output.


    You only get electrical flow when you have something on the 120v side of the inverter requiring electrical use....say a fridge, or whatever.....otherwise your output is zero.....you just have backed up potential.

    OK, say you're actually managing to use 2500w in the form of 120v power....around noon on a good solar day....what happens if a cloud goes over ? Or you can't match load to inverter output ? ( You realize how tricky that would be ? )....THAT is the real reason for batteries.....a reserve pool of power to handle that management, and the fluctuations of your panel input ( which are a LOT, believe me.....early morning, late afternoon, you won't do anywhere close to your array KW ).

    SO, in conclusion.....yes, batteries really are a major part of the system. That is one reason I was so tickled to find the Absolyte GNP batteries I have in my system ( especially for the price I got them...ahahaha ).....20 year life batteries ( depending on the number of cycles of course ) in light use situations ( and maybe more ). Before you invest in batteries, you might also want to consider the Edison iron based battery.....only source right now seems to be imports from China, and they ain't cheap, but for a 50-100yr life battery, it might just be worth having at least a few on hand IF one anticipates the end of the world.
    forge1, Kingfish and BTPost like this.
  10. Kingfish

    Kingfish Self Reliant

    A 20 year Battery would last as long as my propane. Ill be researching these. Thank you. Again ,this forum just rocks. KF
  11. Kingfish

    Kingfish Self Reliant

  12. TnAndy

    TnAndy Senior Member Founding Member

    I have the 100G25 "blocks" ( 6v, 1200amphr )....which are really just 3 individual 2v cells in a case of 3 cells.

    Then there are 4 sets of these connected to make a 24v, 1200amp/hr battery pack.

    Unlike the typical battery, each cell has two sets of connection (pos/neg), but is an individual cell ( can be slid out of the metal case if you can handle 200lbs or so of weight )

    Here's one of 3 sets of these I hauled home I bought out in Kansas from a buddy that works at a cell phone company. His company was being bought out, and he was told to "get rid of everything in the warehouse for scrap"....which included 2 brand new sets of these, and one that was about 4 years old, which is when they pull them from service routinely, regardless of condition. ( and it checked almost at new specs )


    Scrap price ? 300 bucks.

    New price ? ( be seated, and have no beverages in your hand)

    About.......... 15,000-20,000 depending on where you shop.

    When he told me what he had, I said I'll be there tomorrow, and virtually walked out the door and got in the truck and drove 1500 miles.
    Sapper John, Kingfish, BTPost and 2 others like this.
  13. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Those are really nice Andy. You will need some power to fully charge them up. Maybe you should just giv'em to me. LOL super score
    Kingfish likes this.
  14. Kingfish

    Kingfish Self Reliant

  15. forge1

    forge1 Monkey+

    I wish you well with your solar project and will follow with interest.........Ross
    Kingfish likes this.
  16. TnAndy

    TnAndy Senior Member Founding Member

    Don't know anything about them. I used the Deka Flooded cell 6v initially, and that's what I put on my buddy's system few months back. That's the tall one with the rope handles in the PDF you listed. They weigh about 110lbs each, so you can handle them yourself or one stout boy, and run about 400amp/hr for a 6v version.

    Good battery (for the money), locally available here ( Deka dealer in town ), so shipping isn't an issue. About 250 bucks/ea. Expected life with light use is probably 7-10 years.

    As I said, if LONG term life is what you're after, you really ought to look at nickel-iron batteries ( Edison battery )

    nickel iron battery information

    US Supplier:

    Nickel Iron Batteries - A Lifetime Battery For Your Off-Grid System (or On-Grid Backup)!
    Kingfish likes this.
  17. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Kingfish, I got my Absolyte II Battery Bank, when the USCG upgraded a Remote Mountain Top Radio site. I spent one day of my time, helping the contractor remove three sets of these 48 Vdc @ 700 AmpHours setups, and the Three TEG (Thermal Electric Generators) and bought one Battery Bank 24 Vdc @ 700 AmpHour Bank and One TEG for $200 US, if I recall right. These kind deals are around, but you have to know someone, or just get very lucky. Being in the Comms Field really helps, as I knew most of the Telco Field Techs in the area. If you are looking for this kind of thing, you gota smooze around in that field.
    hank2222 and Kingfish like this.
  18. TnAndy

    TnAndy Senior Member Founding Member

    Yeah...it would pay to get to know somebody in the telecom field. My understanding is they have a cycle they replace them on, regardless of condition.....keeping service online being more important that price of batteries to them. Start nosing around and find who runs your local cell services.

    And, of course, if the SHTF big time, one of your first salvage operations might want to be that little shack at the base of a cell tower...... :D
    Kingfish and BTPost like this.
  19. Kingfish

    Kingfish Self Reliant

    Here is what I have so far from the Deka gel monobloc 6 volt 210 amphour. 300 bucks each. I would need 4 to have 24 volts. thats 840 amp hours per gang of 4 correct? KF
  20. TnAndy

    TnAndy Senior Member Founding Member

    Nope. That's 210amp/hrs at 24v.

    When you wire in series ( to up voltage ) the amperage remains the same.

    You get EITHER 24v OR 840 amp/hrs, but not both. Sorry.
    hank2222 and Kingfish like this.
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