Inverters

[OldDan1943]

Okay, I will start this off.
At one time, when one turned on an inverter, its output was "total" aka, 'hotel load.' If it is rated at 2000 watt inverter, turn it on and you have 2000 watt using it or not. That would mean, it makes a draw on the battery to produce 2000 watt and not in degrees to produce enough AC for the demand (to the max, of rated output as designed)????

 

[DavidM]

I don't know what "at one time" means, but every inverter I have seen draws current from the battery in proportion to the load it has to satisfy. If the inverter is rated at 2,000 watts which requires 170 amps DC, if the actual load is 1,000 watts then it will draw about 85 amps.

If there is no load some inverters just draw a few milliamps in stand-by and pulse a 120V output every few seconds to see if there is a load and if so they turn on. Others draw a fraction of their rated output with no load but sometimes that can be a few amps.

David

 

[OldDan1943]

David,
I mean historically.

 

[GregBrannon]

I still don't get what you mean. Can you give an example of your experience with an old-time inverter's performance versus those of today? And a one-word thread title is rarely sufficient to be useful.

Greg.

 

[OldDan1943]

I still don't get what you mean. Can you give an example of your experience with an old-time inverter's performance versus those of today? And a one-word thread title is rarely sufficient to be useful.

Greg.

First generation and maybe subsequent inverters.
I cannot give you a brand. I do recall reading about inverters and a reference to "hotel loads" meaning something one my call, 'full load'. No percentage based upon load. All or nothing.

 

[SteveK]

Dan, does this describe it. Hotel Load

 

[caltexflanc]

What you are talking about Dan was, kind of, the case around 50 years ago. I had a noisy little inverter in my van back in '72, which primarily powered a hifi system and a shaver. I could only use it when the engine was on; in conducting some measurements it sucked a bunch of watts (but not all) whether the hifi was on or not. Even cheapo inverters these days draw only nominal wattage at idle.

 

[High Wire]

Dan you’re talking about inverters back before semi conductors when it was a device that flipped DC voltage polarity mechanically. You might find one in the basement of the smithsonion museum. All inverters today are load dependent as others described.

 

[DrissZougari]

Gents,
There no such thing as described by Dan (Electrically impossible and it does not make any sense sorry!).

 

[OldDan1943]

Dan, does this describe it. Hotel Load

Simalar to a UPS and motor generator.

 

[twistedtree]

Okay, I will start this off.
At one time, when one turned on an inverter, its output was "total" aka, 'hotel load.' If it is rated at 2000 watt inverter, turn it on and you have 2000 watt using it or not. That would mean, it makes a draw on the battery to produce 2000 watt and not in degrees to produce enough AC for the demand (to the max, of rated output as designed)????

I don't believe this has ever been the case.

 

[twistedtree]

Simalar to a UPS and motor generator.

Those too consume power based on the load.


All inverters have an "idle load" which is how much power they consume when operating, but with no loads. It's equivalent to the fuel consumed by an engine when idling.


Then as you apply a load, the inverter will draw power from the battery equivalent to the load, plus a bit more. The "bit more" will be the idle load plus the conversion losses for the actual load power. This is a rough breakdown, but should be close enough to better understand it. Again, it's just like your engine. The more load, the more fuel you burn.


A UPS is an inverter, so works just like above. Same too for a motor/generator. The load on the motor is proportional to the load on the generator, plus the idle load and power for conversion losses.


Depending on the device, the idle load and conversion losses may be better or worse, but I can't think of any device like this where the power consumption is constantly maxed out regardless of the load.

 

[twistedtree]

The Hotel Load would be the power to run all the human amenities, as distinguished from the power to propel the boat, truck, or whatever. So on our boats it's lights fridge, TV, computers, heat, HVAC, fresh water and toilet pumps, etc.

 

[OldDan1943]

Okay, that part of the discussion has been answered.
Next, I opted for a stand alone inverter. Reason: if it dies, I still have the battery charger. Opinions?

 

[Swfla]

Dan, there's no right or wrong answer to inverters. If it makes you happy is all the matters. Most folks are buying units that automatically switch between, battery use (inverter mode), shore power, battery charger, solar. This automatic type system has been around for many years and works well. Victron is one example. But if you like the idea of separate systems and manually making choices, go for it.

 

[OldDan1943]

Dan, there's no right or wrong answer to inverters. If it makes you happy is all the matters. Most folks are buying units that automatically switch between, battery use (inverter mode), shore power, battery charger, solar. This automatic type system has been around for many years and works well. Victron is one example. But if you like the idea of separate systems and manually making choices, go for it.

I have 2 solar panels that sort of blend in with the existing electrical system.
If I want more than a 40amp charger, I only have to upgrade the charger. If I want to upgrade the inverter, I dont have to buy a charger too. Then I go back to my rational (perhaps feeble rational) if the charger craps out, I only need to buy a charger and the same for the inverter.
I will point out, I also have 2 independent rudder indicators and 2 independent depth sounders.
Also, I only a belt to hold up my pants, no suspenders. LOL If my pants fall down, so be it.

 

[roddy]

Think OldDan1943 is victim of poorly worded documentation on solid state inverters.
DC circuit and batteries, has to be able to support full load and is highlighted in most documentation which leads to interpretation errors.
All inverters input kw is relative to output kw.
1.
Rotary inverters were not efficient as there losses in air drag, cooling fan, bearings, slip rings and brushes, compound winding speed control circuits. Frequency control not precise, always needing tweaking if 50 / 60 precision needed. Expensive!
Big, and heavy. Inefficient at light loads not too bad at rated output. Tolerant of induction motor starting.
2.
Solid state units have progressed over the years to the point where they are reliable. Square / modified wave are efficient and tolerant of overloads and induction motor starting.
Sine wave most efficient, but not tolerant of overloads especially induction motor starting. Both have excellent frequency control.
3.
Most quality inverters today incorporate excellent battery chargers as process to invert or charge is similar.
If you have big battery bank 2 inverters allows quick charging especially if carbon or lithium batteries in your future.
Think high quality charger and inverter charger are similar enough in price to go for inverter charger.

 

[High Wire]

Next, I opted for a stand alone inverter. Reason: if it dies, I still have the battery charger. Opinions?

That is true. The typical inverter/charger uses the same diode package and cables for inverting as the charger as well as the control boards.
A stand alone inverter just needs its own cable connections to the battery. Which equals more cost and space on a bulkhead somewhere.

 

[roddy]

OldDan1943 mentioned his solar..
Have 620 watts of solar panels...
Have seen 3.6 kilowatt hours in one day under ideal conditions.
Average summer production is 1.6 kilowatts hours including rainy and foggy days, (including when on shore power when panels don't have load)
Lowest output during fog and rainy days 550 watt hours.
With separate 12 volt fridge and freezer, microwave and coffee maker use. We can go 4 days before batteries down to 50%
Going to add another 600 watts... Have used easy real estate. New real estate requires creativity.
Additional benefit is reduction of shore power consumption, as house load during daytime is carried by solar. Saving probably don't amount to much but least its something.