Inverter myths?

[Macblaze]

Originally Posted by sailorboy1

30 watts divided by 12.5V DC is 2.4 amps. So if at 0 amps 120 volt AC uses 30w of power you are losing 2.4 amps DC to do nothing but be in standby waiting for an AC load. If you left that on all day that’s 57.6 amp-hours. That’s a lot of wasted power !!!!

So it isn't 30W / 120V = .25A? That's what the spec seemed to imply? I am ok if I am wrong but i'd like to know how to read these things.

[Kelkara]

Originally Posted by Macblaze

So it isn't 30W / 120V = .25A? That's what the spec seemed to imply? I am ok if I am wrong but i'd like to know how to read these things.

What you are missing is that the load is on the OUTPUT 120V side of the inverter. By definition, with no AC load there is no current on the 120V side of the inverter = 0.0A. That is true for both the big and small inverter.

What you are asking about is the current on the INPUT 12V side of the inverter ... you are consuming 12V current to make that 30W of waste heat. What the spec is saying is that it will need 2.4A of 12V just to give you 0.0A of 120V.

[Macblaze]

Originally Posted by Kelkara

What you are missing is that the load is on the OUTPUT 120V side of the inverter. By definition, with no AC load there is no current on the 120V side of the inverter = 0.0A. That is true for both the big and small inverter.

What you are asking about is the current on the INPUT 12V side of the inverter ... you are consuming 12V current to make that 30W of waste heat. What the spec is saying is that it will need 2.4A of 12V just to give you 0.0A of 120V.

Thanks.

[john61ct]

Originally Posted by sailorboy1

The problem with plugging DC devices that use AC and then convert them to DC is that lots of times they don’t like the way boats DC varies. On my boat the voltage of house battery varies between 12.1-14.9V. So don’t just think you can cut off the plug “brick” and connect directly to the batteries.

No of course not. dcdc converters, if nominal 12V 13.8V is normal.

[sailorboy1]

Do whatever you want it’s ok with me

[DotDun]

30W sounded high to me, so looked at the Magnum 2812 manual, with the search feature enabled, if the AC load is less than 5W, the unit goes into search mode and pulls <8W from the battery. When an AC load greater than 5W is discovered, the inverter turns on and that is when the battery load is minimum 30W. Search mode enablement can be adjusted from 5W to 50W. Search mode disabled and inverter on pulls minimum 30W.

[Macblaze]

Originally Posted by DotDun

30W sounded high to me, so looked at the Magnum 2812 manual, with the search feature enabled, if the AC load is less than 5W, the unit goes into search mode and pulls <8W from the battery. When an AC load greater than 5W is discovered, the inverter turns on and that is when the battery load is minimum 30W. Search mode enablement can be adjusted from 5W to 50W. Search mode disabled and inverter on pulls minimum 30W.

I'll have to check that. I do no if there is no load, the remote reads "Searching" so I am going to guess that means Search Mode is enabled.

Reading the manual...who knew.

[StuM]

Originally Posted by Macblaze

I'll have to check that. I do no if there is no load, the remote reads "Searching" so I am going to guess that means Search Mode is enabled.

Reading the manual...who knew.

But note that search mode still draws up to 8W, compared to the small inverters "(at 12V) <0.3 A" which is < 4W.

And as soon as you are drawing any real load (5W is very little), you have that parasitic 30W kicking in.

[Macblaze]

Originally Posted by StuM

But note that search mode still draws up to 8W, compared to the small inverters "(at 12V) <0.3 A" which is < 4W.

And as soon as you are drawing any real load (5W is very little), you have that parasitic 30W kicking in.

Noted.

[smac999]

the magnum draws 2-3 amps just being on.

so it'll be 3a + .89% of your load.

vs like 0.2a + 85% of your load.

the load needs to be pretty big before the magnum starts to win

[smac999]

Originally Posted by DotDun

30W sounded high to me,

the xantrax 2000 draws 4-5a on. the magnum is actually a pretty low one.