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Need 428 Ah at 48 V; 12 Outback 200 RE 12v 178 Ah OR 8 Rolls S-550 6v 428 Ah?

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  • Need 428 Ah at 48 V; 12 Outback 200 RE 12v 178 Ah OR 8 Rolls S-550 6v 428 Ah?

    xxx

  • #2
    I'd try to avoid building batteries into a house. I'd build a outside lean-to box next to the house for the batteries. If anything went wrong, I would not want it in the house.
    Powerfab top of pole PV mount (2) | 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

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    • #3
      You have your batteries figured at 100% dod. In RE they are generally figured at 50% dod to obtain the best cycle life and cost of replacement. You'll get to much voltage sag as you drop below 50% that the Inverter cannot deal with. So you need twice as many batteries as you figured.

      If you intend to sell power ( grid tie ) your going to need the double capacity to get the Inverter to work correctly anyway. You are pumping current into the battery bank as the Inverter is pulling it out. That takes capacity in the storage. It generally figured at 100 AH for every 1000w of Inverter.

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      • #4
        What size generator will you be using?
        MSEE, PE

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        • #5
          Originally posted by Bill NC
          Willy, I see what you're saying. All the array power has to go through the batteries, right? Would this be an issue when the batteries are fully charged? That is, if the system is usually operated in a grid tied function, and the batteries are kept charged for backup power in the case of a power outage, would not the system either offset current electric consumption or feed back into the grid? What would happen with an undersized battery component when the grid is down?

          Bill NC
          1) Willy, I see what you're saying. All the array power has to go through the batteries, right? Correct

          2) Would this be an issue when the batteries are fully charged? No, the charge controller will control the Voltage and current going to the batteries.

          3) That is, if the system is usually operated in a grid tied function, and the batteries are kept charged for backup power in the case of a power outage, would not the system either offset current electric consumption or feed back into the grid? If the " Sell " is turned on the Inverter will begin to sell once the trigger voltage is reached. Once the the lower limit is reached the the sell is turned off.

          4) What would happen with an undersized battery component when the grid is down? You stated that you wanted 3 days ( 429 ah ) of back up reserve. With no grid qualified the Inverter will act as any other Inverter, it will supply power until it reaches it's Low Voltage cut off ( 40-44 volts )and the batteries would pretty much be dead. Your panels would continue to charge the batteries and that power would either go into storage in the batteries or be consumed by your loads.

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          • #6
            You need a single string of batteries if possible. Why 24V instead of 48?

            For the battery storage, build a wood box and line it with the rubber shower tile underlayment. PVC collar and male/female form an ait tight seal on the rubber. Gravity vent works fine but not needed if you can locate the battery box outside the building (depending on temperatures).
            1150W, Midnite Classic 200, Cotek PSW, 8 T-605s

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            • #7
              80% dod is waaaayyyyyy too much for those batteries. I design down to 50% after 3 days, which means as long as thee is sun on a regular basis, you are only doing up to 20% dod on a given day. Those are expensive batteries to only get a few years out of with such a high dod. It's an expensive way to save a little up front money.
              Solar Queen
              altE Store

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              • #8
                Originally posted by Bill NC
                At the 72 hour rating of 524 Ah and two strings this would be 1,048 Ah. 343 / 0.3273 = 1,048 Ah. <33% dod. Batteries might just outlive me.
                Geez when is someone going to break the news to this guy and tell him what he needs to know, not what he wants to hear?

                You will not be discharging at the 72 hour rate, you will be discharging at a much higher rate. Batteries have both cycle life and calendar life. Whichever comes first. Float those batteries and never use them and you might if you are lucky and keep them at 75 degrees their whole life 7 year tops. Cycle them 45 to 5 years. Cycle them deeply just a few short years.

                If you have commercial power, last thing you want is a hybrid system. If you do use a hybrid system the batteries are only sized to last you a couple of hours for emergency loads only. After that the generator takes over. Not this fat boy, last thing I want to do is waste all that money and suffer with only emergency loads. I want a whole house generator to power my air conditioner, every light, every appliance, and every toy in the house. Let the neighbors suffer. I can do that at half the initial cost with Grid Tied and whole house generator with no God awful expensive battery replacement every few years and be a lot GREENER both environmentally and economically than your plan.
                MSEE, PE

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                • #9
                  Bill help me out. What is your discharge rate on the batteries. I canno thelp you unless I know that.

                  Here is the deal with the hybrid inverters. They have built in Automatic Transfer Switches inside the unit of 60 amps. That does not mean you can draw 60 amps at 240 VAC as that would be 14 Kw. It just means the copper inside is rated for 60 amps. From the Hybrid Inverter you run a feeder cable to a new 60 amp Breaker Box. A 60 amp breaker box can contain up to 8 120 VAC circuits. Then you have your electrician pull all th ecircuits you designate out of your existing breaker panel and reroute them to the new Emergency 60 amp breaker panel. Note I said EMERGENCY CIRCUITS. That does not include any air conditioner, cooking, hot water. etc. Just stuff small stuff you have to have. Largest load will be you refrigerator. Has anyone explained that to you, or have you figured that part out yet? If not you know now and rewiring your house is EXPENSIVE.

                  The smartest way to use a hybrid is with a small set of batteries, enough to run your Emergency Gizmos for a couple of hours. When they get low the generator comes on, picks up the load, recharges the batteries. When batteries are recharged, the generator shuts off and the cycle repeats until commercial power is restored.

                  Now here is my point. First I am not trying to sell you anything. I don't care what you do. But consider this. Since a hybrid system requires a generator plus batteries, plus a very expensive hybrid inverter, and a very expensive re-wring your house for extremely limited power usage during outages. Why not just install a conventional grid tied system with a whole house generator. Initial and operating expenses will be significantly lower. When and if power goes out, genny starts. and everything in your house has plenty of power like nothing ever happened.

                  You may think I am being tough on you, but I am not. I am giving you all your options and explaining each of them with pros and cons. Up to now all you have heard is 1 option from a sales person telling you what you want to hear. Hell I am not even in your country. WTF do I care?
                  MSEE, PE

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                  • #10
                    "I don't know what you are asking when you ask "What is your discharge rate on the batteries?" if "...my backed up loads total up to 343 AHs over 3 days." doesn't answer that question. I can post my load calcs when I get back to my office in the morning if that's what you are asking about."

                    I think what he's asking is more about the rate, how fast the power is being discharged in amps, as opposed to how much in amp hours. So you'll be using 343 ah over 3 days. But is your load consistent across the whole 72 hours, or are there high and low usage times during that day? Is it 343ah / 72 hours = 4.7A, which is closer to 100 hour rate, or is it going to be bursts of high usage, say 4 hours a day x 3 days = 343ah/12 hours = 28A, which is closer to the 10 hour rate?

                    Rate / Capacity / Current
                    100 HOUR / 466ah / 4.66A
                    72 HOUR / 441ah / 6.13A
                    50 HOUR / 417ah / 8.33A
                    24 HOUR / 361ah / 15.0A
                    20 HOUR / 350ah / 17.5A
                    15 HOUR / 329ah / 21.9A
                    12 HOUR / 312ah / 26.0A
                    10 HOUR / 298ah / 29.8A
                    8 HOUR / 280ah / 35.0A

                    Amy
                    Solar Queen
                    altE Store

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                    • #11
                      Bill what I am asking is how many amps will the batteries be supplying, Not amp hours but the actual amps and peak demand..


                      Battery Amp Hours is a numbers game. For example a 450 AH battery is rated on the 20 hour discharge rate of 450 AH / 20 h = 22.5 amps. But if we use that same battery and discharge it at 45 amps, the battery capacity is 360 AH. This is known as Peukert Law. Same battery loaded down with 115 amps is only a 230 AH battery. Far cry from the 450 AH spec @ 20 hour discharge rate.
                      MSEE, PE

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