Announcement

Collapse
No announcement yet.

Newb Questions on 24v 2000w System

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Newb Questions on 24v 2000w System

    [SIZE=14px]I've inherited a solar project with the following components sitting in a box in front of me.[/SIZE][LIST][*][SIZE=14px]Victron Smart Solar Charge Controller 150V 70A Tr[/SIZE][*][SIZE=14px]4 HQST 100 Watt 12 Volt Polycrystalline Solar Panel[/SIZE][*][SIZE=14px]Giandel 2000W Pure Sine Wave Power Inverter DC 24V to AC120V[/SIZE][*][SIZE=14px]Uxcell New BIG-Size Voltage Converter Regulator DC/DC 24V Step-Down to 12V 40A 480W[/SIZE][*][SIZE=14px]Victron Battery Protect 12/24V-100A [/SIZE][*][SIZE=14px]ANJOSHI Circuit Breaker 50amp 50A-300A 12V-24V DC[/SIZE][/LIST][SIZE=14px]I want to use LiFePO4 batteries at 24v for off grid but confused on how many and best configuration to optimize the above components.
    Obviously more panels are needed and the charge controller manual says it can handle up to 2000w at 24v but this puts it at 83a yet it is rated at 70a. Will this be safe?

    Sorry for the font in the original post. I wrote it in Office, pasted it here and preview showed it fine.[/SIZE]
    Last edited by tripseven; 07-09-2019, 11:56 AM.

  • #2
    What I've learned is that you first have to know how much power you are going to want the system to meet by measuring how much power everything draws and working out per 24hrs what you'll need to cover. Killawatt meter is useful for this.
    Then you are going to want to size your 24V battery according to your power needs - are you going 100Ah or 150Ah or higher? Or does a 24V battery just not cut it for what you'll need? Then once you know what size of battery you're going to be using you can calculate the number of panels needed to charge it at the optimum rate.
    Then you start looking at the other equipment you have and deciding whether it's better to sell and buy new or whether you can use it. For example, the 24V inverter is 2000W - I understand this is approaching the max limit for a 100Ah battery at 24V - and may even be dangerous (see the sticky about relationship between inverters and PV size https://www.solarpaneltalk.com/forum...-size-tutorial). So there are a few things there to think about.
    Others here will be able to correct me and point you in the direction you should be looking.

    Comment


    • #3
      Thanks for the reply DavidH. I understand your approach to build system around my needs but this is a different situation where I get to keep ~$1300 of pre-purchased components if I install system on a friends toy hauler. That in mind, I'm trying to justify the purchase of missing components...especially the batteries and panels since they will be the $$$ gobbler.

      My energy needs go well beyond what this system can handle as I live on a mini-farm if you will. I can use this system to power LED bulb in chicken coup, thermo controlled heat lamp in coup, heat tape for water line in coup, elec fencer for hog pen, elec gate opener etc.

      My thinking is to shell out the extra cash for [SIZE=14px]LiFePO4 batteries for longevity and more bang for the buck. This is where I question how much battery I need to power this system safely at its potential while keeping in mind battery life. Knowing that 2000w will be the max panels for this 2000w inverter[/SIZE], what kind of battery bank am I looking at to max this system safely and get good battery life?

      Comment


      • #4
        Well, Battleborn states the following regarding their LiFePO4 batteries compared to lead acid: "You can charge a Battle Born battery up to 5 times faster, although we only recommend that you charge at 50% of the capacity to extend the life of your battery." https://battlebornbatteries.com/long...fepo4-battery/
        So if you have a 24V 100ah LiFePO4 battery its capacity is 2400W - I understand it as the recommended charging is 50% of that = 1200W. So really you are probably looking at a 1000W PV array or x3 350W panels to be on the safe side. A 24V 100ah battery is probably going to be x2 12V 100ah in series for you which is going to set you back around $1500-$2000 - going from prices on Amazon.
        Say you get x3 350W panels at $180 each - $540 plus tax. Then you'll probably need a battery management system for the LiFePO4 if the battery doesn't come with one.

        So the 2000W inverter might be fine with the battery (hopefully someone else can confirm) but if you think about it you don't want to be using anywhere near that capacity for a continuous load as it could pretty much drain your 2400 watt battery in an hour. So just make sure you've used a kill-a-watt meter and know what loads your stuff is going to draw and only use a max load that the system can handle.
        Last edited by DavidH; 07-10-2019, 02:57 PM.

        Comment


        • #5
          Originally posted by DavidH View Post
          A 24V 100ah battery is probably going to be x2 12V 100ah in series...get x3 350W panels...

          So the 2000W inverter might be fine with the battery (hopefully someone else can confirm) but if you think about it you don't want to be using anywhere near that capacity for a continuous load as it could pretty much drain your 2400 watt battery in an hour.
          Thanks, that gives me something to work with! What gives me pause is reading through threads and sticky's it seems that doubling the inverter rate to that of panels is a no-no safety-wise. Unless I understood SunKings sticky wrong, it seems that inverter wattage should be close to the same as panel wattage. I can see 2x 12v LiFePO4 batteries in series for 24v. Would it not be feasible to add another identical bank to that in parallel to double the AH? My thinking here is to double the array size to ~2000w to achieve the potential of components in hand.

          Comment


          • #6
            You could buy two more 12V 100ah LiFePO4 batteries and have them in parallel with the first two but you really gotta ask yourself if you want to spend another $1500-2000 just to be able to use an inverter that is worth like $300?
            If you actually had a 1000W inverter there instead of a 2000W inverter would you be definitely wanting to sell it to upgrade to the 2000W one?

            There are also 150Ah batteries available - I've no idea what the price is but your total capacity for x2 12V 150Ah LiFePO4 in series would be 3600W. This would allow an input of 1800W (charging at 50% capacity) and you could probably get away with x6 350 panels (2100W input) as they'll never output at 100% - mostly at 300W and even then only for a very short period of the day when sun is highest. But again maybe the store where you purchase the panels could help you out with that. You will want to check the Voc of a single panel - just to make sure you never get close to the total voltage of 150 that your mppt charge controller is limited to - but 3 in series and then another 3 in parallel should be fine. You could even check the price of 200Ah 12V LiFePO4 batteries - two of those in series and you'll have 4800 watt capacity to play with.

            It might be easier to sell the 2000W inverter and use the cash to buy a 1000W inverter (with a new warranty) and maybe have some left over to put towards wiring or the battery management system. But if you have the money and want to do it, then I don't think there's anything stopping you. The one thing to maybe read into is the disadvantage of putting batteries into parallel. Typically the advice is to go series wherever possible but this may differ with LiFePO4 batteries.
            Last edited by DavidH; 07-10-2019, 09:30 PM.

            Comment


            • #7
              Originally posted by tripseven View Post
              ...... Unless I understood SunKings sticky wrong, it seems that inverter wattage should be close to the same as panel wattage. ......
              it's a guideline to wring as much performance out of a system and to keep it balanced. An overly large inverter can easily deplete a battery bank past the point of the next day solar harvest not being able to recharge the batteries. As long as you know this risk, and that the idle losses of too large of inverter can add up rapidly, it's a guide to be considered, not a rule to be unbroken. But you need to understand the reasons for the rule, and why you benefit from ignoring it.

              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

              Comment


              • #8
                Great info, thanks! Would it be feasible and safe to run 8x LiFePO4 3v 200ah in series with 2000w of panels with components I already have? The batteries I'm looking at are here. Or with BMS here.

                Comment


                • #9
                  Originally posted by tripseven View Post
                  Great info, thanks! Would it be feasible and safe to run 8x LiFePO4 3v 200ah in series with 2000w of panels with components I already have? The batteries I'm looking at are here. Or with BMS here.
                  I cannot answer that. Safe depends on doing [B]everything [/B]right, and I cannot control how the pack is charged & treated. Maybe someone else will chime in and voice their opinion.
                  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

                  Comment


                  • #10
                    @Mike90250--I understand your reservation to answer my question directly so let me ask a different way. If you were to put together the above system, in your opinion, how would you control how the pack is charged & treated?

                    Disclaimer: No one will be held liable for any opinions given throughout this entire thread and all responses will be treated as opinion only!

                    Comment


                    • #11
                      I would for sure get them with BMS with RAM & data logging
                      Decide on high & low voltages for the pack
                      decision - top or bottom balance ? (I've not done this myself, I use NiFe batteries)
                      Configure chargers to proper voltages, absorb time = 1 minute
                      Configure inverter to proper disconnect voltage
                      Research, Research, Research !
                      Insure pack stays above 40F, below 105F
                      Make sure vendor will be around in 5 years
                      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

                      Comment


                      • #12
                        Perfect, thx Mike! That gives me a ton of research and decisions to make. Starting to look more like $1300 in freebies will be earned rather than "free" ...especially since I would be the one installing/sealing all the panels on top of the toy hauler.

                        Is there a reason you use NiFe over LiFePO4 batteries?

                        Comment


                        • #13
                          Originally posted by tripseven View Post
                          ......Is there a reason you use NiFe over LiFePO4 batteries?
                          no LFP batteries 8 years ago. None I could buy in the right capacity. The price was still astronomical.

                          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

                          Comment

                          Working...
                          X