Running AC off Batteries
Many folks get confused by amperage draws when comparing a load at 120VDC vs. the same load at 12VDC.
OHM's Law says that power (watts) is equal to volts X amps. Any appliance has one rating for power measured in watts. A typical blower motor for a roof A/C uses about 300 watts.
At 120VAC, this translates to 300/120 or 2.5 amps. That same 300 watt load at 12VDC is 300/12 or 25 amps. The additional draw is probably inverter inefficiency.
If the compressor kicked in, the Magnum would be showing over a150 amp draw AT THE BATTERIES.
You can safely figure a 10:1 ratio to convert amperage loads from AC into DC. A significant number of folks have been opting for the Magnum MSH3012-M Hybrid inverter/ charger when they have been installing solar and lithiums, as this combination allows them to operate their roof A/C solely from their battery bank for 2-5 hours, depending on the size of their lithium pack and all day with a single 2000 watt generator.
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