Does the formula Amps= Watts/Volts apply when a 110V AC appliance is being powered through an inverter?
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Its the same formula but you have to apply an efficiency factor. When you go from 12V to 120V there is a lost of power that turns into heat. Check your inverter for this factor. For example if you microwave is 1500w/120V = 12.5 amps at 80% efficiency factor it will draw 15.63from your battery (ies). V49
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This is easier to do by example:
Let's say you have a TV that uses 240 watts of 110 AC. That means that it will draw 240watts/110VAC = 2.18 AC Amps (note that these volts and amps are AC, not DC: You use a different meter setting to read them and they are actually RMS values as both the voltage and current are really sinusoidal functions of time).
So, what does this mean for your batteries supplying 12 volts DC to your inverter? Well, inverters are not perfect so let's assume yours is 85% efficient (some are better, some worse): This means that the DC power consumption will be more than the AC load is using since some power is lost in the inverter. So, continuing the example, the DC load will be 240 watts/0.85 = 282 watts. The inverter is wasting 42 watts (that's why it gets warm) and your TV is getting it's 240 watts.
So, on a 12 volt DC system, your inverter will be drawing 282 watts/12 VDC = 23.5 DC amps which is why we have such honking big cables in a 12 volt system as compared to the wires used in household wiring!
This is easier to do by example:
Let's say you have a TV that uses 240 watts of 110 AC. That means that it will draw 240watts/110VAC = 2.18 AC Amps (note that these volts and amps are AC, not DC: You use a different meter setting to read them and they are actually RMS values as both the voltage and current are really sinusoidal functions of time).
So, what does this mean for your batteries supplying 12 volts DC to your inverter? Well, inverters are not perfect so let's assume yours is 85% efficient (some are better, some worse): This means that the DC power consumption will be more than the AC load is using since some power is lost in the inverter. So, continuing the example, the DC load will be 240 watts/0.85 = 282 watts. The inverter is wasting 42 watts (that's why it gets warm) and your TV is getting it's 240 watts.
So, on a 12 volt DC system, your inverter will be drawing 282 watts/12 VDC = 23.5 DC amps which is why we have such honking big cables in a 12 volt system as compared to the wires used in household wiring!
AC amps not the same as DC
DC power consumed: 1500 watts/ 0.80 = 1875 watts
DC current: 1875 watts/ 12 VDC = 156.25 amps
Which is why my 1500-watt inverter has cable as thick as my thumbs connecting it to my battery pack!
Actually, a 1500W microwave on an 80% efficient inverter will draw a LOT more than 15 amps:
DC power consumed: 1500 watts/ 0.80 = 1875 watts
DC current: 1875 watts/ 12 VDC = 156.25 amps
Which is why my 1500-watt inverter has cable as thick as my thumbs connecting it to my battery pack!
Math genius
Good try, guys.
OK, now try going to a real reference source, like this: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Inverters.htm
Good try, guys.
OK, now try going to a real reference source, like this: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Inverters.htm
Re: AC amps not the same as DC
Time to find a less costly way to heat your food and to entertain yourself.
1st you buy an inverter
2nd you buy a microwave cooker
3rd you buy a TV and antnna
4th you buy bigger batteries
OR you could cook on fuel and read a book.
Time to find a less costly way to heat your food and to entertain yourself.
1st you buy an inverter
2nd you buy a microwave cooker
3rd you buy a TV and antnna
4th you buy bigger batteries
OR you could cook on fuel and read a book.
A more logical progression
would be:
buy more batteries to stay out longer
buy a battery monitor to track you battery use and health
use less battery power
stay out longer
fuel for food, your choice
would be:
buy more batteries to stay out longer
buy a battery monitor to track you battery use and health
use less battery power
stay out longer
fuel for food, your choice
The simple answer to the question posed is "yes." The complicated answer is that it requires the specific draw-downs of each component/connection/wire guage, etc., ad infinitum, of the electrical system to be factored in. Stick with simple wherever possible.
Yes, the electrical formula is the same. When you switch values from 12V to 120V there is a factor of 10. A 120V appliance that uses 2 amps will use 20 amps at 12V. When using an inverter the efficiency ratio is from 85 to 90% so consider you may use 22 amps at 12v to power that appliance. Electrical motors will usually require 2 to 5 times its running power to start so for refigeration compressors, fans and pumps the inverter should provide enough reserve power for starting.
Food on board
Any time you start moving heat around you want to consider using fuel. Using electricity for heat is VERY costly.
Gads I wish I could use gas for the reefer or AC.
Any time you start moving heat around you want to consider using fuel. Using electricity for heat is VERY costly.
Gads I wish I could use gas for the reefer or AC.
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