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Unread 04-08-2014, 03:44 PM   #8
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Join Date: Jul 2009
Location: Baltimore, MD
Posts: 498
Check the motor’s nameplate for its current draw. Multiple the number of amps by 120 to get the number of watts the motor draws. My guess is you will end up with something around 1500 watts. That is the first minimum requirement for the inverter. That is a lot of watts for a car inverter.

Then you need to guess at what the motor starting surge is. Not likely the motor will list it. Depends on the motor details, but could easily be 3 times as large. Inverters usually don’t have much surge capability. A big surge could damage the inverter or the inverter could limit the current to where the motor won’t start. Then again, since the motor is started without load, it might work.

Looking at the other end, that 1500 watts has to come from your battery. At 12 volts that would be 125 amps without considering inverter losses. Call it 150 amps from your battery. That means the inverter needs to be connected with very heavy cable (think welding cable). 150 amps is way beyond typical cars alternator capability. Think about the battery being discharged very quickly. Then I would be worried about how long that battery would last before failing, possibly in a nasty way.
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