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  • #76
    Sunking no answer yet?

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    • #77
      Here are some real life costings from a real life off-grid system with a LFP battery. The system in question is the one detailed by steveg in post #444 in this thread "[SIZE=12px]LiFePO4 - The future for off-grid battery banks?[/SIZE]"

      The battery in this system is a 300Ah LFP battery which powers a 7kW(20kW peak) inverter. The cost of this battery using extrafu's figure of $1.30/Ah is $6240 (16*300*1.3). Even if we add a decent BMS for $500 which according to Sunking we do not need we end up with $6740.

      I would think the absolute bare minimum size FLA battery to run a 7kW(20kW peak) inverter would be 1000Ah as steveg has suggested. The cost of this battery using Sunking's $244/kWh is $11,712 (48*244).

      On top of this to charge a FLA battery properly we need a charge rate of C/10 so we need at the very least a 5kW generator/battery charger. Steveg only has a 2kW generator and probably only needs a 1kW charger to charge his battery. Steveg's LFP battery can also be left at low SOC for extended periods so he doesn't need to run the generator for nearly as much time as if he had a FLA battery.

      On top of this the 4.6kW solar array that steveg has would probably be too small to charge an FLA battery because of the C/10 requirement and due to the overall efficiency of an FLA battery being around 85%-80% rather than the 95% of an LFP battery.

      Then there is the fact that steveg's battery is maintenance free. Doesn't generate any acid fumes, doesn't have to be topped up with distilled water on a regular basis and is very much smaller and lighter that a 1000Ah FLA battery.

      Simon

      Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
      BMS - Homemade Battery logger
      Latronics 4kW Inverter, homemade MPPT controller


      Off-Grid LFP(LiFePO4) system since April 2013

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      • #78
        Originally posted by karrak View Post
        Here are some real life costings from a real life off-grid system with a LFP battery. The system in question is the one detailed by steveg in post #444 in this thread "[SIZE=12px]LiFePO4 - The future for off-grid battery banks?[/SIZE]"

        The battery in this system is a 300Ah LFP battery which powers a 7kW(20kW peak) inverter. The cost of this battery using extrafu's figure of $1.30/Ah is $6240 (16*300*1.3). Even if we add a decent BMS for $500 which according to Sunking we do not need we end up with $6740.

        I would think the absolute bare minimum size FLA battery to run a 7kW(20kW peak) inverter would be 1000Ah as steveg has suggested. The cost of this battery using Sunking's $244/kWh is $11,712 (48*244).

        On top of this to charge a FLA battery properly we need a charge rate of C/10 so we need at the very least a 5kW generator/battery charger. Steveg only has a 2kW generator and probably only needs a 1kW charger to charge his battery. Steveg's LFP battery can also be left at low SOC for extended periods so he doesn't need to run the generator for nearly as much time as if he had a FLA battery.

        On top of this the 4.6kW solar array that steveg has would probably be too small to charge an FLA battery because of the C/10 requirement and due to the overall efficiency of an FLA battery being around 85%-80% rather than the 95% of an LFP battery.

        Then there is the fact that steveg's battery is maintenance free. Doesn't generate any acid fumes, doesn't have to be topped up with distilled water on a regular basis and is very much smaller and lighter that a 1000Ah FLA battery.

        Simon

        Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
        BMS - Homemade Battery logger
        Latronics 4kW Inverter, homemade MPPT controller

        Karrak

        Please stop cherry picking individuals systems and picking them apart. We understand you have had good success with your off grid system and battery but IMO (and others) very few people have the knowledge (building their own BMS & inverter) and money to use to build such a system let alone find a way to justify the cost of living off grid.

        So I am ok with you providing details of your system information along with advice to other would be off grid people but you are in the minority of those that either need an off grid system or desire one. So please stop puffing your chest and bragging about your batteries as being the only way to go when off grid is the direction.

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        • #79
          Sunkıng also forgot to say that if u require lots of power like 30 minutes at C1 u will toast ur brand new trojan and kiss good bye ur warranty. If u r totally offgrid like me and u power evrything in ur house like an induction u would need at least 15 kw inveter that need 300 ampere at least. Also remeber pukert law which sunking didnt mention. if u had to cover my power 50/100 KW u can do it with 19 winston 1000 ah.if i had to cover the same power with lfa i u had to buy 10 times the capacity in lifepo4. But of course sunking didnt mention this neither....

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          • #80
            Originally posted by Barba View Post
            Sunkıng also forgot to say that if u require lots of power like 30 minutes at C1 u will toast ur brand new trojan and kiss good bye ur warranty.
            And if you size your residential battery bank to support less than an hour of your load - you would be foolish indeed.
            Last edited by jflorey2; 05-24-2016, 02:57 PM.

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            • #81
              I do sometimes go at C1/C2 maybe once week, so there is no need to spend 100 k in somethings u never use. Because every day I use 20/30 % in SOC. If I had a very big LFA the risk of never recharging becomes more a reality then a possibility, so PSOC maybe 6 months per year with ur brand new Trojan will last maybe a winter.
              With lfa u have to think that way. With lifepo4 u can make it possible with hi power at much less money.
              I run C2 in the weekend for like 10-15 minutes. It has been working out for me for the last 6 months more or less.
              Couldn't be happier.

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              • #82
                Originally posted by Barba View Post
                Sunkıng also forgot to say that if u require lots of power like 30 minutes at C1 u will toast ur brand new trojan and kiss good bye ur warranty.
                [B]You are full of crap and a fool as Jeff pointed out[/B]. If you knew anything about Golf Carts which use exclusively FLA batteries like Trojan have 300 to 600 amp controllers and will not harm the batteries. Yes you can pull 600 amps from a FLA 200 AH battery. Will not harm them one little bit. You are really making yourself look stupid. Even a small 12 volt automotive battery of 80 AH can easily supply 800 amps or 10C called Cold Cranking Amps. In fact a FLA will handle it better from a thermal management POV because of Thermal Mass.A lithium battery will burst into flames long before a FLA gets warm to touch.

                In Fact Trojan and Rolls even list 1C capacity rates. The difference between FLA and LiFeP04 is Mr Peukert Law and Internal Resistance which I can only assume you have no clue what that means.
                Last edited by Sunking; 05-25-2016, 10:19 AM.
                MSEE, PE

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                • #83
                  U cannot pull c1 or c2 for 10-15 minutes.!!! A cart can pull 500-600 A, yes but for few seconds not minutes. Ur trojan can probably last at C1 15 minutes at C2 can last 5/6 at C3 will probably short their plates and void ur warrenty.even if u dont harm them how will u recharge a 10000 ah or 20000 ah battery? Ur stupidity doesnt know limits!

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                  • #84
                    I will politely ask karrak, Barba, Sunking and anyone else to please stop the name calling and arguments in this thread. It is distracting and unprofessional.

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                    • #85
                      Originally posted by Barba View Post
                      U cannot pull c1 or c2 for 10-15 minutes.!!! A cart can pull 500-600 A, yes but for few seconds not minutes.
                      [B]You are Ignorant. [/B] You can draw 10C from any Pb battery until exhausted and completely discharged. Do that with most Lithium batteries and they catch fire. Pb batteries have 10 times the thermal mass of lithium. A FLA can be abused and still be recharged and used again and again. They just won't last long if you do that routinely.

                      If you really knew anything about batteries you would know Pb batteries are the default choice for UPS systems because they are designed for a 15 minute or 4C discharge. Every Telecom FLA battery is made to be discharged at rates in excess of 1C.

                      Even thick plated deep cycle batteries can be discharged at 10C with no thermal damage and survive just fine. You are completely ignorant on the subject and do not know what you are talking about.

                      I will give you a clue. SPECIFIC POWER expressed as Watts / Kilogram.

                      Lithium Ion = 150 to 400 w/Kg
                      Pb = 100 to 300 w/Kg

                      That means they are roughly equal. If you take into account equal capacity in [B]watt hours,[/B] a Pb battery has higher Specific Power. That means a 100 WH capacity Pb battery can deliver more power than a lithium. Do the math and learn something. A 100 wh Pb battery will weigh roughly 2 Kg, and a lithium will weigh .5 Kg.

                      If we use the lowest Specific Energy and really bias the model to lithium favor; A Pb means the Pb battery can deliver 100 watts x 2 Kg = [B]200 watts continuously.[/B]

                      That same 100 wh lithium at using the highest Specific Power is .5 Kg x 400 watts = [B]200 watts.[/B]

                      Wanna try apples to apples realistic comparison? Say the lowest or highest of both? Example a Pure lead AGM up against nano particle Lithium Polymer. How about the opposite low side; a Deep Cycle FLA up against a LiFeP04? . A Pb wins every time.

                      You just do not know what you are talking about.
                      Last edited by Sunking; 05-25-2016, 12:33 PM.
                      MSEE, PE

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                      • #86
                        Dear sunking the problem is not the power is the pukert law. If i need 50/100 kw i would need a lfa battery as big as my house that would cost me a fortune.
                        Second point a battery as big as this has another pronlem. If i discharge it completly it will take me a month at the best time of the year to recharge it.If i do it in the winter it will stay discharged for all the winter and it will get toasted. U know better than me that C1 or C2 u can short the plates in a short run. The best thik plate lfa battery recomands not toreach C2 for more than 5 minutes on a row. After that ur beautiful plates will go like a banana. I have been there before u
                        Last edited by Barba; 05-25-2016, 02:29 PM.

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                        • #87
                          I am done with the back and forth in this topic so I am closing it.

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