Generator comparisons

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Thanks Lou.  That's what I was asking for. 
I also have a Craftsman (Generac) 4200 genny.  No need to run the numbers, unless your bored.  Used only in emergency situations.  Circa 1999 model, but still runs strong.  Fired up every year to try to prevent the need for re-flashing.
 
I'm glad I picked up the honda 1000 used from a dodge forum member. This confirms that I can use it for what I need (charge batteries and light loads) about 95% of the time I would run a genny, for the least amount of noise and fuel. The other 5% I have an Onan emerald 4 KW. It is considerably louder and burns more fuel.
 
That's also what I gathered from this discussion. It is always most efficient to use a generator that you will operate at the rated load where it is most efficient. Anything less and you lose efficiency. The variable RPM of the Yamaha just makes it a bit more flexible compared to a constant speed generator.
 
Someone help me out here...
Vassock's use of the word "variable RPM" pertaining to the Yamaha gennies has me a bit confused.  It leads me to believe that the Yamahas act like a variable speed electric drill.  Variable meaning operator can control the speed from zero revolutions to full speed, and everything in between, according to load required. 

If Yamaha's Smart Throttle is identical to Honda's Eco-Throttle, then the word "variable" may not be the word to use.
If like a Honda, a low load requirement equates to the Eco-Throttle keeping the RPM's at an almost idle.  A higher load requirement would increase the RPM's of the genny to full RPM's.  No "ramping up" of RPM's as load is increased and more demanding of the genny.  Once the load demand breaks the Eco-Throttle threshold, the RPM's go to full throttle.

I know of nobody who owns a Yamaha genny.  The reason I asked.
In addition, I hope Vassock isn't misunderstanding how these gennies work. 
I just wonder if Vassock is lead to believe that if the load increases just a little, the gennines RPM's go up just a little, as opposed to full throttle, if over the Smart Throttle setting?
 
All of the inverter generators operate like a variable speed electric drill, except the engine speed is automatically controlled by the generator.  When their eco-throttle feature is turned on, the engine slows down whenever there' a light load on the generator, then speeds up when a heavier load is applied.

If you do this on a conventional generator, the output is unusable at the lower speed because the output frequency is determined by the rotational speed of the generator.  Their eco-throttle setting is meant for uses like running power tools at a construction site, where there are long periods of time when no power is being used.

On an inverter generator, the engine turns a DC generator, feeding DC voltage into an inverter. The unit's output frequency is determined by inverter, not by the rotational speed of the generator.  This means the engine only has to spin the generator fast enough to develop the power needed at that moment, not at full speed all the time.

All of the inverter generators take advantage of this, allowing the engine to slow down when the generator is lightly loaded, then speeding up when a heavy load is applied.
 
Maybe I am not explaining myself clearly enough.  My bad.

I understand the workings of the Eco-Throttle.  I am the owner of my third Honda.  I love them.
However, I am unfamiliar with Yamaha generators.

What I am trying to say is even on my EU3000iS (2 years old), there is really only two speeds that the genny runs at.
1)  Low speed at no load/light load below Eco Throttle threshold.
2)  Full speed over Eco Throttle threshold.

There is no "medium" speed or 3/4 speed if load dictates only needing that much power.  If the load exceeds the Eco Throttle minimum setting, the genny goes to full power and RPM.

In my opinion, it's not the same as a variable speed electric drill.  My drill at home drills faster the further I pull the trigger in.  My Honda does not, and would not, gradually increase in RPM as load is increased from zero load all the way to full power.  With the Eco Throttle on, and the load reaches the Eco Throttle minimum setting, the unit automatically goes to full power in one step.  Even though full rated power may not be needed.  No options in between.  There is nothing "variable" about it.  It's either at the low RPM, or high RPM.

I was just wondering if Vassock was under the same assumption or I was missing something.  All I do know for sure is I would not call the Eco Throttle, and possibly the Smart Throttle, "variable".  Two speed?...yes.  Convenient and useful...absolutely!

I just wanted to clear the air in case Vassock was misguided by the word "variable".
 
My EU1000i doesn't step from low to high - there is a range in between where the engine speed will increase linearly between the two.

It's not a very wide range, but it is there.  Listening to the generator I can tell when it's approaching full load by the speed of the engine.

BTW: "idle" is about 50% of the full load RPMs.  The generator has to spin fast enough to create full voltage at it's output, but from there it doesn't have to increase until the power exceeds what the engine can deliver at that RPM.  I'd guess my EU1000i stays at the low speed up to about 60-70% output, then the engine ramps up to the higher speed.
 
I disagree.  My EU2000iS did exactly as I stated.  As well as my current EU3000iS. 
And my current EU3000iS must do better than 50% of full load at idle.  Put it this way...

On Eco Throttle on my EU3000iS, that puppy will run for almost 24 hours on a full tank driving a 10 amp smart charger for the battery bank, maybe a couple of interior lights during the day, TV after campfire hours, a check of who Letterman has on, then off to bed.

I have never heard my Honda's gradually increase in RPM's according to load demand.  Other than the increase in RPM when the load crossed the Eco Throttle minimum.  Then the genny would kick into high gear. 

All i can say.  I'm done.
 
It's variable, that variable being the wattage demand. However, since you have a gasoline engine running, I doubt it can perfectly match wattage demand. It probably has a few "sweet spots" of wattage demand where it is most efficient.
 
That said, thanks for all the info. However, I'm still trying to pinpoint the most efficient way to run a trailer using up to 200 watts of power at max and 150 watts average.

It would have 2 U2200 6v batteries working together to create a 12 volt current.

G - C - U2200 - I - UPS - PC

Generator, Charger, 2 U2200 batteries, Inverter, Uninterrupted Power Supply, PC.

Do I understand correctly that this set up would have the generator running power to the charger, which would charge the batteries, which would feed power to the inverter (12v to 120v), which would send it to the power supply, which would stabilize it and send it to the PC? I would run the generator when the batteries are low to recharge them. While it's running, I would be receiving power from the generator via the batteries even while they charge. When the generator is off, I would be running right off of the batteries. As soon as my UPS kicks in and warns me of lost power, that means the batteries are drained and I need to run the generator. For the sake of argument, here are the components:

Generator: EF1000iS
Charger: Schumacher SC-600A SpeedCharge High Frequency Battery Charger
Batteries: 2 x U2200 batteries
Inverter: Cobra CPI1000 1000W 12V DC to 120V AC Power Inverter with USB Port

Do I understand that correctly?


The batteries.

U2200 is rated at 232 amp hours. With 2 batteries, that's 232 amps at 12 volts. 150 watts / 12 volts is 12.5 amps per hour. So I'd drain 2 fully charged U2200 batteries (linked together to produce 12 volts) in 18.5 hours using that set up. Let's assume for the sake of argument that I use my PC for 6 hours per day everyday. In 3 days I will drain the batteries.

However, since I don't want to drain the batteries below 50% and since charging them above 80% takes too long, I'll only have about a third of that, so I'd need to charge the batteries each day. 4 hours each day at near peak power (700 watts) would drain about $2.50 in gas.

As opposed to just running the generator and directly powering the PC, which would use $1.16 per day.

Sounds like using those batteries is very inefficient although I'm sure my math is wrong somewhere. Although I guess I could use the PC while the batteries are charging, in which case I'll probably halve (4 hours on generator power, 4 on battery power) the daily cost down to $1.25.
 
You could get rid of the UPS and gain a couple of percent efficiency.  The charger - batteries - inverter form a UPS on their own, and the inverter will squawk (audible alarm) when the battery voltage gets down to critical levels - before it shuts down from low voltage.

And if you're running a modified sine wave inverter, it's unlikely a plug-in UPS would recognize it as valid power.
 
Lou Schneider said:
You could get rid of the UPS and gain a couple of percent efficiency.  The charger - batteries - inverter form a UPS on their own, and the inverter will squawk (audible alarm) when the battery voltage gets down to critical levels - before it shuts down from low voltage.

And if you're running a modified sine wave inverter, it's unlikely a plug-in UPS would recognize it as valid power.
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How much power will the charger eat? Is the 700 watts figure accurate? If so, that will bring total power consumption to around 850 watts which is very good since it's extremely close to the rated power output of the generator (900 watts). Research tells me that this is the most efficient way to run a generator. Assuming too much power is not lost in the actual battery charging process, it might make sense to have the batteries just for the sake of getting all I can get out of the generator while it's running and using it later since there are no generators rated at 200 watts. What I would appreciate is if someone examines my set up (I posted precise component models) and tells me if my calculations are correct.
 
Be sure that inverter is a true sine wave model as most UPSs won't work on a modified sine wave inverter.  Actually, with an inverter, you don't need the UPS as the batteries plus inverter are a UPS.  And you'll get better battery life without the additional losses of a UPS.
 
Ned said:
Be sure that inverter is a true sine wave model as most UPSs won't work on a modified sine wave inverter.  Actually, with an inverter, you don't need the UPS as the batteries plus inverter are a UPS.  And you'll get better battery life without the additional losses of a UPS.
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True, at this point the UPS is more loss. A question, vassock. Why not a big laptop? They are far more efficient than a PC, do not require an inverter (10% loss at the very minimum right there).
You can get a DC-DC power supply for a laptop and that is the least amount of loss in converting/transforming. They go to the coffee shop and use their power and internet, the benefits are quite extensive.
 
Do I understand correctly that this set up would have the generator running power to the charger, which would charge the batteries, which would feed power to the inverter (12v to 120v), which would send it to the power supply, which would stabilize it and send it to the PC? I would run the generator when the batteries are low to recharge them. While it's running, I would be receiving power from the generator via the batteries even while they charge. When the generator is off, I would be running right off of the batteries.
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The battery charger is not a big power draw. The reduction from 120v to 12v effectively multiplies the amperage by 10, so 20 amps of charging requires only 2 amps from the generator.

There is no "power supply" - just the normal 120v wiring in the RV. You plug the RV into the generator outlet and it powers the whole RV, including its battetry charging system. With the generator running, you can draw power direct from the RV's 120v circuits and you can also draw power from the batteries and inverter. The inverter output circuits may or may not be integrated with the rest of the RV's 120v system, depending on how it is installed. More integration means more expense and more convenience. If you just have your PC plugged to the inverter, you can leave it there and the inverter can run whenever the batteries have adequate charge.
 
Gary RV Roamer said:
The battery charger is not a big power draw. The reduction from 120v to 12v effectively multiplies the amperage by 10, so 20 amps of charging requires only 2 amps from the generator.

There is no "power supply" - just the normal 120v wiring in the RV. You plug the RV into the generator outlet and it powers the whole RV, including its battetry charging system. With the generator running, you can draw power direct from the RV's 120v circuits and you can also draw power from the batteries and inverter. The inverter output circuits may or may not be integrated with the rest of the RV's 120v system, depending on how it is installed. More integration means more expense and more convenience. If you just have your PC plugged to the inverter, you can leave it there and the inverter can run whenever the batteries have adequate charge.
Click to expand...

But given the set up I listed (the components), for how long would I have to run that generator to charge the batteries and how many watts will the charger draw? 100W? 200W? 700W?

I will likely be buying an old, used generator so I will be replacing all of the chargers/inverters.
 
What kind of battery charging set up can I make that would draw about 800-900 watts to charge the batteries? This is a generator efficiency-related question since generators operate at maximum efficiency close to their maximum output.
 
A good charger doesn't draw the same power during the entire charge cycle.  Your 800-900 watts is about 75A@12VDC which would only be output during the bulk mode.  When the charger switches to absorption mode, the current will slowly drop, until it switches to float mode, at which time it would output about 13.5V and minimal current, drawing very little power from the generator.  The charger needs to be sized for the battery bank AH and the generator for the maximum load it will see.
 
You also have to consider the Power Factor of the charger.

Power Factor is the difference between Real and Apparent power and can range between 0 and 1.  If the load is a pure resistance, the Real and Apparent Powers are the same.

If the load has inductance or capacitance reactance that makes the AC current and voltage fall out of phase with each other, the Power Factor becomes less than 1 which means you have to provide more power than if the PF was larger.

I've yet to see a converter with a Power Factor of 1, so you have to take it into account when matching it to your generator.

For example, if your converter draws 900 watts with a PF of  0.7, your generator has to supply 1285 volt-amps of apparent power.  It's working as hard as if it was supplying 1285 watts, but only 900 is making it to the load.

Wikipedia Power Factor
 
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