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1200w induction stove off 170Ah bank possible?

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  • 1200w induction stove off 170Ah bank possible?

    I want to run a 1200w induction single burner stove. 1200w is on max temperature, realistically I'll be running it around 600-900w. I'd be running it for no more than 15 minutes.

    My understanding is the following would be the consumption:

    Medium setting: 600w@50A but for 15 minutes, so drawing 600w for 15 mins @ 50A would be like 12.5Ah or 150wh but still at 50A.
    Max setting: 1200w@100A but for 15 minutes, so drawing 1200w for 15 mins @ 100A would be like 25Ah or 300wh but still at 100A...erg

    My bank is currently only 170Ah 12V AGM. I have a 2000w (4000w peak) pure sine inverter.

    I have 300w of solar through an MPPT controller and live in sunny San Diego. I'm also running a DC fridge that averages about 15w at 12v and charge a laptop and phone (maybe 100wh).

    Is this possible?

    I've heard of people doing it. I'm aware of Peukert's law but don't know off hand what the N rating is of my batteries (two 85Ah 12v AGM).

    My guess is it should work around 11am when the batteries are topped off, and that I'd be pushing the batteries pretty hard even with the stove on medium. And that running it at night when the batteries are around 90% might be pretty rough. Would my voltage drop below 11, 11.5, or 12v running at 50a or 100a for 5-15 minutes?

    I want to add a third battery but heard that a new one would die quickly because I'm adding it to old batteries (about 1 year old, generally drain to 60-70%).

    Thanks in advance, smart people.

  • #2
    Medium setting: 600w@50A but for 15 minutes, so drawing 600w for 15 mins @ 50A would be like 12.5Ah or 150wh but still at 50A.
    Don't bet on this, Don't know if they are all the same but the one I have uses the same power no matter the setting, but pulse's on and off on the lower setting like a Microwave. They may not all use the same power scheme though.

    Mixing new and old batteries would not be a good idea. Those old ones will pull the new one down to their level and they'll never charge the same.

    Comment


    • #3
      It is possible you might get away with it, but dangerous, very dangerous. A 300 watt panel con only support a 12 volt 250 to 300 AH battery. A 12 volt 250 AH battery can only support up to a 400 watt inverter. 12 volt systems should never go above 1000 watts and that is even pushing it.

      The only advantage you have is using AGM batteries and at 12 volts @ 170 AH can only support at most a 500 watt Inverter.

      Two things you need to watch out for:

      1. Most likely what will happen is your Inverter will trip off line from under voltage. The inexpensive single Induction Heaters are on/off controlled devices which means it will dray the full 1200+ watts in an on/off fashion at 50% duty cycle for half power. That is more than 100 amp of current and those batteries are not made to deliver 100 amps without significant voltage sag.

      2. The other more serious problem is fire from poor electrical connections and undersized wiring.
      MSEE, PE

      Comment


      • #4
        My system is in an RV, it is also powered by an alternator - I think it's 150A. I drive the RV on average every other day. It's not uncommon to see RVs with 800Ah banks and only 240W of solar.

        That said, is that getting me any closer to being able to run it? And if it actually draws only 400, 500, 600, 700W and isn't just phasing on and off at 1200W, could I rely on this stove for everyday cooking at 5-15 minutes a day or should I just scratch it and and go back to propane?

        It really sucks cooking eggs in the morning in a 95sq/ft RV that's already 90° and then turning on a giant flame....

        Comment


        • #5
          Originally posted by sdbuck View Post
          My system is in an RV, it is also powered by an alternator - I think it's 150A. I drive the RV on average every other day. It's not uncommon to see RVs with 800Ah banks and only 240W of solar.

          That said, is that getting me any closer to being able to run it? And if it actually draws only 400, 500, 600, 700W and isn't just phasing on and off at 1200W, could I rely on this stove for everyday cooking at 5-15 minutes a day or should I just scratch it and and go back to propane?

          It really sucks cooking eggs in the morning in a 95sq/ft RV that's already 90° and then turning on a giant flame....
          Cold cereal and milk for breakfast would not generate a lot of heat.

          Comment


          • #6
            Originally posted by sdbuck View Post
            My system is in an RV, it is also powered by an alternator - I think it's 150A. I drive the RV on average every other day. It's not uncommon to see RVs with 800Ah banks and only 240W of solar.
            Smart man, most do not do that. With that you really do not need any solar. 1 hour drive time will generate more power than the panels can do in a week. So the question becomes what voltage, AH, and battery type do you use? If you are running 12 volt 500 AH AGM batteries no problem. If you are running 12 volt 225 AH FLA batteries you might have a problem but an easy work around, start the dang engine up and cook your eggs with the Air Conditioning running. 150 amps from the alternator is more than adequate. Just be sure all your wire gauges are up to the job and properly sized.
            MSEE, PE

            Comment


            • #7
              Ha! Batteries are two 85Ah 12V AGM, both about a year old. When these are toast, I plan on going with 3 for 255Ah total. Any more and I'd exceed GVWR. Lifopo4 is too expensive, though I'd love being able to drain to 10% and charge at full amps to near 100%; between that and the weight savings, I could easily double my usable Ah without going overweight, maybe even quadruple.

              Are you saying that I should just cook with propane while running the AC? - not a terrible idea. I know cop cars and cabs idle all day without a problem, and they're gasoline just like me. My water temp stays around 110° when idling, so no problem there. I've read something about the EGR valve or other aspects of a gas engine that might not like idling at long periods of time, maybe some buildup or something, then again, cops and cabbies do it so I'm not sure.

              Or are you saying that at idle, I should be able to charge the batteries enough to not have too much of a voltage drop in the batteries from a 50-100A load? My alternator is 150A, but I'm assuming that's peak, somewhere closer to 3500rpm, not at a 900rpm idle.

              Clearly, I really want induction to work. Main reason is because my countertop is so small and the induction can be built in, and with the glass surface, double as counter space and looks really sexy. I've been looking into building a single propane burner directly into the countertop, but I've only seen one image in all my google searches that shows a gas burner built directly into the countertop (i.e. no stainless surround, just the burner protruding from a small hole cutout in the counter). Counter would have to be appropriate heat resistant material. Considering I'm looking for lightweight materials (it's in an RV), I don't know if Corian, Formica, or the typical alternatives to heavy Granite, Marble, and soap stone would act as heat shields and not start to melt...

              I also saw a diesel stove that was a smooth, glass surface, similar to an electric stove top, but I'm not going to convert my LP system to diesel - unless it's easier and cheaper than I assume. Still trying to find a glass-top-propane-built-in-single-burner....

              Originally posted by Sunking View Post
              Smart man, most do not do that. With that you really do not need any solar. 1 hour drive time will generate more power than the panels can do in a week. So the question becomes what voltage, AH, and battery type do you use? If you are running 12 volt 500 AH AGM batteries no problem. If you are running 12 volt 225 AH FLA batteries you might have a problem but an easy work around, start the dang engine up and cook your eggs with the Air Conditioning running. 150 amps from the alternator is more than adequate. Just be sure all your wire gauges are up to the job and properly sized.

              Comment


              • #8
                Originally posted by sdbuck View Post
                Ha! Batteries are two 85Ah 12V AGM, both about a year old. When these are toast, I plan on going with 3 for 255Ah total.
                Do not do that, just use 225 AH batteries to make a single string.

                Originally posted by sdbuck View Post
                Lifopo4 is too expensive, though I'd love being able to drain to 10% and charge at full amps to near 100%; between that and the weight savings, I could easily double my usable Ah without going overweight, maybe even quadruple.
                You would be dead wrong there my friend. A 100 AH LFP = 200 AH AGM. A 12 volt 100 AH LFP battery will cost you roughly $600 and last 2 to 3 times longer than AGM. Long term for your application is a lot less expensive than AGM. A good 6 volt 220 AH AGM a Concorde PVX 2240 cost $640 for a pair and will last 2 to 4 years. 4 CALB 100 AH LFP Cells cost $560 and will last up to 7 to 10 years. Drive 1 hour to fully recharge. Two 220 AH AGM weigh in at 135 pounds. 4 CALB 100 AH cells weigh in at 30 pounds and only take 1/3 the room. The CALB's can discharge at 300 amps easily without sag. Only 20 minutes, but would work. Don't let that throw you off because at 300 amps on the AGM only gives you the same 20 minutes sagging to 10 volts.

                Originally posted by sdbuck View Post
                Are you saying that I should just cook with propane while running the AC? - not a terrible idea.
                No Sir I am saying use your Induction Cooktop and if the Inverter trips from under voltage from the battery, just run the engine and let the alternator supply the power while also charging your batteries. If you get too warm cooking those eggs on the Induction Cooktop, turn on the AC if you want with the engine running.

                240 watt of solar panels for a few minutes around noon on a 12 volt battery only generates up to 18 amps. Your alternator can deliver 150 amps all day long if needed. On a really good day your 240 watt panels can generate maybe 1000 watt hours if they are in full broiling hot sun all day from sun rise to sun set. A 150 amp alternator can do that in 34 minutes in the nice cool shade with the Air Conditioning running.

                MSEE, PE

                Comment


                • #9
                  IIRC the 7 pin plugs are 15A max.
                  1150W, Midnite Classic 200, Cotek PSW, 8 T-605s

                  Comment


                  • #10
                    That's awesome! Thank you. Sounds like I could go induction as long as I plan on upgrading to LFP in the future. LFP would basically solve all of my issues (primarily weight and space) and like you pointed out, actually be much cheaper in the long run! SWEET.

                    Comment


                    • #11
                      I don't know what this means.

                      Originally posted by thastinger View Post
                      IIRC the 7 pin plugs are 15A max.

                      Comment


                      • #12
                        If I move to LFP down the road, I guess I'd also need a new charge controller. I have the MPPT Tracer 30A 3215RN and it allegedly doesn't support LFP.

                        I saw this LFP charge controller for $49. Seems suspiciously inexpensive.

                        Any other factors I'd have to consider before assuming I can switch to LFP down the road? These LFP batteries seems to be able to handle anything I could throw at them with their charge and discharge amperage ratings.

                        I'm assuming I'd by four of the 3.2v LFP to create 12.8v. at 100Ah, which gives me about 90Ah of usable energy, and I could just idle my engine if there's no sun...

                        Comment


                        • #13
                          Originally posted by sdbuck View Post
                          I saw this LFP charge controller for $49. Seems suspiciously inexpensive.
                          Never heard of it but for $50 something is wrong, certainly not a MPPT controller. Only controller out on the market specifically for LFP is a GenSun a 10.5 amp MPPT controller which means a maximum panel wattage of 140 watts on a 12 volt battery for $200. One could just simple use two of them, but there are other ways.

                          Originally posted by sdbuck View Post
                          Any other factors I'd have to consider before assuming I can switch to LFP down the road? These LFP batteries seems to be able to handle anything I could throw at them with their charge and discharge amperage ratings.
                          You can use some of the conventional controllers out there that allow you to program set point voltages via keyboard rather than pre-selected dip switches. LFP is somewhat tolerant of over charging, and does not tolerate any over discharge. All it takes is one over discharge and you gotta a brick on your hands. That is taken care of by properly setting your LVD value on your Inverter to 11 volts. A fully charged LFP open circuit voltage is 13.6 volts, and death is 9 volts. At 11 volts gives you access to 90% of the capacity.

                          Come back when you are ready and maybe by then Midnite Solar or Morningstar might have something for LFP then.
                          MSEE, PE

                          Comment


                          • #14
                            Originally posted by sdbuck View Post
                            I don't know what this means.
                            Means your vehicle isn't capable of delivering more than 15A to the batteries while you're driving unless you've upgraded the wires and connections.
                            1150W, Midnite Classic 200, Cotek PSW, 8 T-605s

                            Comment


                            • #15
                              Originally posted by thastinger View Post
                              Means your vehicle isn't capable of delivering more than 15A to the batteries while you're driving unless you've upgraded the wires and connections.
                              Vehicle is a 1997 VW Rialta, it's a motorhome. Comes from the factory with a 150A alternator that charges both the starter battery and the house batteries. So, there are 3 batteries total: 1 that runs the car, and 2 AGM that total 170Ah at 12V.

                              The alternator runs to a solenoid that let's me start the car or charge the car battery from my house batteries (AGMs) if the car battery dies.

                              The wires all appear to be 0awg - pretty heavy duty stuff. But if I remember correctly, I don't think I was able to charge my batteries from dead to full in a half hour of driving, nor do I recall idling really charging the batteries.

                              Guess I'll have to do more investigation.

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