Power inverters. How many Ah do they use under load?

[jsbush]

How many Ah would say a 3000watt power inverter which is under load use?

 

[Rubycon]

At 12V (rare) your draw is going to be close to 290 Amperes!

Most 3kW units are going to be running at 24 or even 48V.

 

[FoBoT]

none, amp hour is a measure of battery capacity
W= volts x amps

 

[jsbush]

yeah but those invertors produce 3000watts of AC power, it doesn't draw 3000watts of DC, lol. You'd need 6 batteries just to run it for an hour if that.

 

[bobsmith1492]

Originally posted by: jsbush
yeah but those invertors produce 3000watts of AC power, it doesn't draw 3000watts of DC, lol. You'd need 6 batteries just to run it for an hour if that.

If it's producing 3000W of AC power at the output, it will draw MORE than 3000W DC at the input - basic laws of physics, energy can be neither created nor destroyed (except in special cases, i.e. matter-> energy conversions).

 

[slpaulson]

Originally posted by: jsbush
yeah but those invertors produce 3000watts of AC power, it doesn't draw 3000watts of DC, lol. You'd need 6 batteries just to run it for an hour if that.

Where do you propose this 3kwatts is going to come from if not from a DC source.

It's going to draw more than 3kwatts from whatever the DC source is.

 

[jsbush]

Originally posted by: FoBoT
none, amp hour is a measure of battery capacity
W= volts x amps

Uhhh ok.

I just want to know how many Ah does a 3000watt inverter draw.

 

[slpaulson]

Originally posted by: jsbush

Originally posted by: FoBoT
none, amp hour is a measure of battery capacity
W= volts x amps

Uhhh ok.

I just want to know how many Ah does a 3000watt inverter draw.

It doesn't draw amp hours. An amp hour is how long a battery will last if an amp is drawn from it.

You need to figure out how much current it will draw, then look at how many amp hours your battery is to figure out how long it will last.

 

[Rubycon]

Originally posted by: jsbush


Uhhh ok.

I just want to know how many Ah does a 3000watt inverter draw.

To plan for a specific application you must have a desired run time and demand. If your load is 3kW you don't want a 3kW inverter unless it's conservatively rated.

Trace is a good make and you can find some info here.

 

[FoBoT]

none, Ah = amp hour, that is a measure of battery capacity, it has nothing to do with an inverter

an inverter will draw X amps at Y volts based on the load, if you are saying the load is 3000 W , then you need to either specify the volts or the amps, since you seem to want to know the amps, even though you keep saying "Ah", then you need to specify the voltage and plug it into the formula to get the amps

 

[Rubycon]

Be careful around electricity.

 

[jsbush]

Originally posted by: cRazYdood

Originally posted by: jsbush

Originally posted by: FoBoT
none, amp hour is a measure of battery capacity
W= volts x amps

Uhhh ok.

I just want to know how many Ah does a 3000watt inverter draw.

It doesn't draw amp hours. An amp hour is how long a battery will last if an amp is drawn from it.

You need to figure out how much current it will draw, then look at how many amp hours your battery is to figure out how long it will last.

Thats what i'm trying to figure out. How current it will draw.!

 

[jsbush]

Originally posted by: FoBoT
none, Ah = amp hour, that is a measure of battery capacity, it has nothing to do with an inverter

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

 

[slpaulson]

Originally posted by: jsbush

Originally posted by: cRazYdood

Originally posted by: jsbush

Originally posted by: FoBoT
none, amp hour is a measure of battery capacity
W= volts x amps

Uhhh ok.

I just want to know how many Ah does a 3000watt inverter draw.

It doesn't draw amp hours. An amp hour is how long a battery will last if an amp is drawn from it.

You need to figure out how much current it will draw, then look at how many amp hours your battery is to figure out how long it will last.

Thats what i'm trying to figure out. How current it will draw.!

Ok, so what is the inverter going to be powering? Is it truely a 3000W load? How many volts is your DC source?

 

[Rubycon]

Originally posted by: jsbush

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

That is incorrect. Batteries are rated at C/10 rate. You will fall short of expected runtime at C rate unless the manufacturer specifically rates that way.

Also in the link I provided above there are data sheets that have the information you need.

 

[jsbush]

Originally posted by: MS Dawn

Originally posted by: jsbush

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

That is incorrect. Batteries are rated at C/10 rate. You will fall short of expected runtime at C rate unless the manufacturer specifically rates that way.

Also in the link I provided above there are data sheets that have the information you need.

http://www.optimabatteries.com/publish/...arine/marine_terms___calculations.html

 

[mugs]

Originally posted by: jsbush

Originally posted by: FoBoT
none, Ah = amp hour, that is a measure of battery capacity, it has nothing to do with an inverter

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

He's right. You want amps, not amp hours. And what the hell are you trying to do with a 3000 watt inverter? Power a clothes dryer with your car?

 

[uberman]

I have a 1,000 Watt Triplite inverter I've used a lot. 12 VDC to 110 VAC at 1,000 watts you're looking at 80 amps. Efficiency has not increased so much, meaning the amperage use is still similar.

I've spent many hours thinking about going solar and that's what I found out.

I've lots of experience with them and many tools for installs such as 1/0 wire crimpers. What is your intended purpose? What are you going to power? And for how long?

 

[slpaulson]

Originally posted by: jsbush

Originally posted by: MS Dawn

Originally posted by: jsbush

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

That is incorrect. Batteries are rated at C/10 rate. You will fall short of expected runtime at C rate unless the manufacturer specifically rates that way.

Also in the link I provided above there are data sheets that have the information you need.

http://www.optimabatteries.com/publish/...arine/marine_terms___calculations.html

What is going to happen is the voltage of the battery is going to drop as your inverter continues to draw a current. When the voltage goes down the inverter will need more current than it did before, which will cause the battery's voltage to drop further.

In other words your run time will be worse than the Ah rating would indicate, because your inverter will require some constant power from the battery, not a constant current.

Plus the efficiency of your inverter will probably be worse at lower voltages.


Let's just say for example you really are using a 3000W load, and your inverter is something like 90% efficient no matter the input voltage and you have a 48V battery that for the sake of argument is going to stay a constant 48V.

Your inverter would be drawing (3000*1.11)/48 = 69.38A. That's a ****** ton of current.

I don't really know off the top of my head how to calculate the effects of the battery's voltage drop when you want to figure out how many Ah you need to get a desired run time, but I'm sure somebody here does.

Just because you have a 3000W inverter doesn't mean it's going to be using that much power though. You will be using roughly the amount of power the device being powered uses, plus some extra power because the inverter is not 100% efficient.

 

[bobsmith1492]

Originally posted by: cRazYdood

Originally posted by: jsbush

Originally posted by: MS Dawn

Originally posted by: jsbush

No.
Example:
Lamp that draws 5 amps x 4 hours = 20Ah

so if I want to run that lamp for 4 hours i need 20Ah.

That is incorrect. Batteries are rated at C/10 rate. You will fall short of expected runtime at C rate unless the manufacturer specifically rates that way.

Also in the link I provided above there are data sheets that have the information you need.

http://www.optimabatteries.com/publish/...arine/marine_terms___calculations.html

What is going to happen is the voltage of the battery is going to drop as your inverter continues to draw a current. When the voltage goes down the inverter will need more current than it did before, which will cause the battery's voltage to drop further.

In other words your run time will be worse than the Ah rating would indicate, because your inverter will require some constant power from the battery, not a constant current.

Plus the efficiency of your inverter will probably be worse at lower voltages.


Let's just say for example you really are using a 3000W load, and your inverter is something like 90% efficient no matter the input voltage and you have a 48V battery that for the sake of argument is going to stay a constant 48V.

Your inverter would be drawing (3000*1.11)/48 = 69.38A. That's a ****** ton of current.

J

.... but easily handled via copper busbars and 1/4" bolts.