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Old 02-18-2016, 11:50 AM   #1
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Running AC off Batteries

Just viewed this video from Gone with the Wynns where they ran their AC off their lithium batteries with their full solar deployed.

My question is, why did the Magnum monitor show such high amp usage. With just the fan running prior to compressor start it show 27amp then when the AC kicks it ramped up to over 70amps. Most RV ACs are connected to 20amp breakers.

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Old 02-18-2016, 12:35 PM   #2
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The high current was DC current @ 13 volts from the batteries not AC draw @110 volts AC of the AC unit.

Yes it can be done but at a very high cost
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Old 02-18-2016, 02:17 PM   #3
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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.

Lew Farber
RVIA/RVDA Nationally Certified Master Tech
ABYC Certified Master Marine Electrician
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center*AMS Lithium Batteries
Lifeline AGM Batteries**Magnum Inverters
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Victron Solar Components and Inverters, Zamp Solar Panels, LiFeBlue and Battle Born Lithium Batteries, Lifeline AGM Batteries
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