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High Amperage Drain on Lead Acid Batteries 1700 watt kettle vs 400 watt coffee maker

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  • #16
    Originally posted by Sunking View Post
    As for cable size as big as your wrist called a 750 MCM that cost $9 per foot.
    Sir, you jest !! (good to hear your advice here) 300A @ 12V only requires 0000ga cable (0.46")

    Of course, none of the inverters use heavy 300A cable inside them which is why you need a good insurance policy
    And you need a gorilla to bend the cable to fit, along with the giant tool to crimp the ends onto the cable. And it's a very special inverter that has terminals of the proper size to connect that big wire to.

    Here's some unnamed chart from the internet that supports my theory.

    amp chart table.jpg
    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



    • #17
      Originally posted by Mike90250 View Post
      Sir, you jest !! (good to hear your advice here) 300A @ 12V only requires 0000ga cable (0.46")
      Not so much jest. While I understand the tables you posted and where it came from has little to do with any wiring you can use and comply with NEC. The tables are true for equipment manufactures chassis wiring and utility power transmission with complete disregard for voltage loss incurred at low 12 volts. That has nothing to do with residential power and lighting wiring. That comes from NEC Table 310.15(B) using 90 degree cable insulation would require a minim 350 MCM which still does not address any voltage loss at 12 volt distribution. So I may be guilty of stretching it a bit, the point is the insanity of using low voltage for high wattage loads. Not only is it incredible expensive, but extremely dangerous doing so with that much current. Joe DIY Home Owner does not have the tooling, training, or experience to terminate such sized conductors properly.

      As you properly stated the first clue is something is not right is none of the 12 volt toy inverters sold can terminate a proper sized conductor or a massive surface area required. Example in any high current panels for commercial or industrial application using 350 amps would use Tongue type 2-hole terminals using Grade 5 3/8-inch hardware to secure it with proper torque.


      Here is a tip. If your application requires any wire to be larger than 6 AWG, your voltage is likely too low.

      Last edited by Sunking; 09-15-2020, 04:23 PM.
      MSEE, PE