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  • #16
    Think it cut my post off?

    I’m not sure even if such a wire exists, but buss bars are a good option. I might just opt for that.

    Also, I believe my battery set up is fine to pull like 9,000w. Not for extended periods, but for short bursts, right? I wouldn’t ever be running solely off batteries, I can kick the genny in the guts if there’s no sun.

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    • #17
      Please forgive me for stating the obvious, but the fuse or circuit breaker protects the wire AND everything else upstream of it. That includes connectors, the battery, the fuse holder, and anything else in the path. You can only make the wire and fuse so large before something else is the safety bottleneck.
      7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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      • #18
        Originally posted by bob-n View Post
        You can only make the wire and fuse so large before something else is the safety bottleneck.
        What do you mean by that?

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        • #19
          If the fuse is 1000 amps and the wire is large enough for 1000 amps, you would think that everything is fine. But what about the connector between the wire and the battery? Can that handle 1000 amps? What about the plates inside the battery? Will they overheat at 1000 amps?
          7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

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          • #20
            Originally posted by bob-n View Post
            If the fuse is 1000 amps and the wire is large enough for 1000 amps, you would think that everything is fine. But what about the connector between the wire and the battery? Can that handle 1000 amps? What about the plates inside the battery? Will they overheat at 1000 amps?
            Ahh, right. Totally on board now.

            I was reading another post on the forums and it was stated that there are optimized ratios for charging amps and the ah of batteries. Specifically, for my setup it would be best for me to have 10% of the total 15,000ah batteries, so 1,500a??

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            • #21
              Originally posted by Superdoom View Post
              ..............
              I was reading another post on the forums and it was stated that there are optimized ratios for charging amps and the ah of batteries. Specifically, for my setup it would be best for me to have 10% of the total 15,000ah batteries, so 1,500a??
              I believe that is generally true for lead acid batteries. Lithium batteries have a wider tolerance for charging rates but less tolerance for overcharging.

              NOTE: I reread your post and you originally said you were going to have 12 batteries (2v) in series. You also stated those cells are 1255 Ahrs so that is the total Ahrs since only volts add when in series. Based on the above rule you should have 125 Amps of charging current.
              Last edited by Ampster; 03-27-2020, 01:28 PM. Reason: Correct Ahrs of charging
              9 kW solar. Driving EVs since 2012

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              • #22
                Originally posted by Ampster View Post
                I believe that is generally true for lead acid batteries. Lithium batteries have a wider tolerance for charging rates but less tolerance for overcharging.

                NOTE: I reread your post and you originally said you were going to have 12 batteries (2v) in series. You also stated those cells are 1255 Ahrs so that is the total Ahrs since only volts add when in series. Based on the above rule you should have 125 Amps of charging current.
                Yes, and that’s what I’m still doing. That makes a lot more sense, thank you!! Now, is over 10% better, as in it will charge the batteries faster?

                EDIT: I ask, because I only have 100a in my current plan (slightly different PV circuiting from first post).

                I also thought volts were more important for charging?
                Last edited by Superdoom; 03-27-2020, 06:37 PM.

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                • #23
                  Originally posted by Superdoom View Post
                  I also thought volts were more important for charging?
                  One only needs the charging volts to be slightly higher than the battery volts in order to force the current into the batteries. At least that is the general concept. During different phases the voltage may change or remain fixed. If that is what you meant by important?
                  9 kW solar. Driving EVs since 2012

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                  • #24
                    Originally posted by Ampster View Post

                    One only needs the charging volts to be slightly higher than the battery volts in order to force the current into the batteries. At least that is the general concept. During different phases the voltage may change or remain fixed. If that is what you meant by important?
                    Word up, that’s what I meant by important. Right, that makes sense to me. Another fella earlier in the thread said my original plan, which had a PV array voltage of like 156v and 100a was no good because 150v was the ‘death voltage’. Ever heard of that? Maybe he just thought I was using a MPPT that couldn’t handle 150v?

                    In any case, that makes sense to me and that current is more important than volts because you only need the same volts as the batteries plus probably whatever the charger needs to run; but then you want the max current the batteries can handle, huh?

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                    • #25
                      Read post #5 in this thread again, you may have missed it.
                      > Death voltage = MPPT controllers are rated for a certain Max Input voltage and max
                      > output amps. An internal logger circuit records the max input voltage for warranty denial. 150V is a common max/death voltage.

                      Designing an array with 156V nominal, will give you a cool morning start up voltage of about 180v, well above most controllers input and sure to be an expensive replacement.
                      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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                      • #26
                        Yup, so that’s what I thought, Mike. You’re essentially saying most MPPTs aren’t rated for 150v, so it would be a bad idea to use that voltage? Victron makes an MPPT rated for 250v, and I could use that one. What I’m wondering about though is if voltage past 30v is really needed for charging a 24v battery bank? Ampster seems to suggest the current is more important, and I can see the logic behind that.

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                        • #27
                          Originally posted by Superdoom View Post
                          .......... Ampster seems to suggest the current is more important, and I can see the logic behind that.
                          If you look at my comment, was not referring to the current from the panels. I was referring to the current out of the charge controller or charger. You have to have enough voltage for the current to flow so they are both important. I also made a distinction between Lead Acid and Lithium because Lead Acid is more sensitive to not being fully charged.
                          Last edited by Ampster; 03-28-2020, 12:41 PM.
                          9 kW solar. Driving EVs since 2012

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                          • #28
                            Ohhh, I never even thought about that. I guess controllers have different output currents as well as voltages, huh? I will have to look into that... thank you! I just need something with like 125a output

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                            • #29
                              For 125A. you will need several controllers, each with their own array. The Magnum PT-100 handles 100A
                              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


                              • #30
                                Originally posted by Mike90250 View Post
                                For 125A. you will need several controllers, each with their own array. The Magnum PT-100 handles 100A
                                Yeah, I’ll have to look into which controllers put out the necessary amps to charge my batteries, because I’m unsure if they generally output the same amps that are input?

                                Also, would more amps than 10% be beneficial to charge the batteries? Like, if the MPPT puts out the same amps as in coming in, could I set up my PV array to put out the max amps so I charge the batteries quicker?

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