wasted energy

PluckaPlucka Posts: 36Registered Users ✭✭
12 volt to "240 VOLT" [3000 watt 240 volt inverter] back to 12 volt energy consumption compared to 12 volt direct from 360 amp/hr lithium battery for 12 volt satellite tv short cable. Answer here  [                  ]

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  • BB.BB. Posts: 27,574Super Moderators admin
    A first approximation is that a 120 VAC inverter will have ~85% efficiency... Or, your solar array+battery bank will need to be:
    • 1/0.85= 1.17 or ~17% larger array and battery bank
    You also need to look at the 12 VDC devices that you are using... The typical range for a 12 volt lead acid battery bank runs from 10.5 to 15-16 VDC... Most "DC Car" adapters (laptop, etc.) run best around 13-14.2 volts or so.

    And, the typical "12 volt" power supply (wall transformer) is 12 volts +/- 10% (+/- 1.2 volts) nominally. Again, outside the nominal operating range of a lead acid system.

    The issue is that you don't typically "know" what a 12 volt appliance can accept for DC input. Some will be fine, and some won't be. If they are "cheap enough" to play with and see what works--Why not.

    My suggestion is that an AC inverter stabilizes the voltage for all of your loads. There are 12 volt to 12 volt converters (used by HAM radio and others) that can give you 13.8 volts nominal (or adjustable 12 volt switch power supplies)--But they are probably around 90% efficient too. (not much better than your properly sized inverter).

    And there is the last question--How far do you want to send this power... Sending 12 volts for much more than a few 10's of feet, you start needing to use some pretty heavy cable to avoid large(r) voltage drops.

    At 120 VAC, you can send 120 VAC 100's of feet on relatively light cable (16 or 14 AWG) with acceptable voltage drops.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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