I had a thought today. Generators use X fuel/hour, no matter how many watts are being used. What if you were to incorporate a battery bank, and have the generator start the engine as needed to top that off or if you need more power, in much the same way a hybrid car uses the batteries to power the wheels and only burns gas as needed.

Does anyone know of anyone who makes something like this? Or should I be getting myself to the patent people after doing some homework?

It's a good thought, but there are some errors in your idea. The generators use fuel according to the load, similar to a car, which is why always specify runtimes at a specific load. More load, more gas being used. The newer generators (I'm thinking specifically of the Honda EU series with the eco-throttle), automatically adjust the engine according to the output. In that way, they are able to save gas if the electrical load drops off.

Also, recharging a battery is not 100% efficient, so you will lose some energy there. I think it really depends on the conditions you use the generator for, it might be useful under certain conditions. Actually, you might want to search on something like that, I think it might already exist.

just did a quick search, i think this is similar to what you were looking for

http://www.cumminsonan.com/rv/products/ec/

As ducktapeguy said, the load varies. If you see a "runs up to xxx hours" on a generator, that the the amount of time that a tank of gas will power a night-light. If you plug in a fridge, the generator will require more power to turn, and your gas consumption will go up.

Hi Ironraven,

State of the Art portable generator technology is available here at
http://www.voller-energy.com/products.asp#
The future Voller VE600 could be very interesting.

Several companies make back up power supplies that are basically batteries. They come in all sizes, from sump-pump backups to whole-house backups. They look to be a lot more expensive than a generator.

I imagine you could rig a generator to provide power to the backup unit and have a sort of buffer that would eliminate power fluctuations to the generator. Don't know if this means that the generator will operate at peak efficiency (max MPG if you will) or if it would just pump out the maximum amps until the battery was recharged.

http://www.emergencypowersupply.com/

Ironraven, check out some of the solar energy sites. If you are going to use batteries then you will be using an inverter to make house power. And there are inverters with a generator starting function,

http://www.xantrex.com/web/id/45/p/131/pt/18/product.asp

Scroll down to features.

Of course you need a genny with auto start.

As far as needing more power, load sensing, i don't think that the generator would start and spin up fast enough to drive a instant heavy electrical load. For instance if the inverter is large enough to run the well water pump but not the washing machine and the water pump. When you turn on the washing machine and then the water pump comes on to fill the washer the inverter will overload or blow a fuse in the seconds before the generator comes up to speed. Hope that made sense.

Load does vary, yes, but with ones I've worked with it isn't very much, they run pretty much full bore all the time. How much change in fuel consumption is there if you are just powering a couple of 50W lightbulbs vs full on household use? I'm thinking something that when you have no draw, you burn no gas. For commercial purposes, this isn't as effective as a normal generator and I accept that, just like I accept that hybrid cars have no advantage if you spend all your time on the highway other than the extra mass means a Prius wins if it gets attacked by a Hummer. (There are photos of that accident online.)

What got me thinking about this is my folk's generator- they need a few lights, a pump for the well, and every so often the fridge kicks in, but most of the time when it's running, it's only feeding that couple of 50W bulbs and sometimes a water pump. It's the smallest that they could find that didn't seem like it would die if it was run for more than six hours, but it still feels like it's wasting gas most of the time.

And yes, I know that charging a battery isn't as efficent as putting the power in. But at some point, you are under the minimum of what the generator's output is. And this is the kind of thing where if you put a small waterwheel generator under your storm gutter, or a couple of solar panels...

If I was really worried about fuel consumption, I would just buy a diesel generator. Then can run almost twice as long on the same amount of fuel.


Speaking of generators, my buddy just put a natural gas generator in his house that's pretty cool. It runs off the regular natural gas house line, but can be switched to propane tanks if the need arises. I bet it could even be switched to regular gas with a bit of work.

Generators run most efficently loaded 75 to 90 percent of rated capacity. When you are running at low loads the losses from just running it wastes fuel.

I don't know if anyone makes a specific unit that combines a battery bank but it has been recommended for a long time to combine the two. That way you can properly load the generator by charging the batteries while running light loads.

While batteries and inverters aren't 100% efficent you gain in the long run.

The best way to use such a setup is to only run the genny when you are want to run heavy loads. Short term runs rather than continuious runs. I.E.The refrigerator, water pump, furnace and the like. Also to charge up the batteries. Then you shut off the genny. Then you draw continuous light loads from the battery bank. Things like the lighting system or radio.

Such a duel system can greatly stretch your fuel supply since your heavy load period are relitively short duration. And to operate best you need to schedule operations to sequentially perform them in a block.

I think under your circumstances your idea might work. I was thinking the ideal conditions that type of setup would be an extremely low current draw over long periods of time, or intermittent loads, where as you said, the electrical load is so small that the energy to run the engine overwhelms the energy to run the generator.

Here's the spec sheet for the Honda i was talking about

http://www.hondapowerequipment.com/eu1000.htm

Looking at their fuel consumption, it looks like running at 1/4 load is roughly 2x more efficient than running near full capacity. And if you assume a charging efficiency of 70%, and an inverter efficiency of around 85% (just rough estimates), somewhere there probably is a break even point where it would make sense to set it up that way. it's kinda late in the evening for math, but I'm pretty sure someone can figure out exactly where that point is.

Now that I'm more awake, I see I made some errors in my previous post. Looking at the Honda generator specs, you are NOT 2x more efficient at 1/4 load, you just get roughly 2x more runtime. If you calculate it out, you are actually about 2x more efficient in terms of energy/gallon running it at full load.

So what this means is that the advantage to a battery/inverter setup changes. You will probably not see much of an advantage under small, constant loads (like a continuous 50W lightbulb). Either way you are using a set amount of energy, either straight from the generator or from the battery bank. Using the generator, you are operating at a less efficient part of the power curve, so you waste gas there. However, using a battery bank will allow you to run the generator at peak efficiency (full load), but any gains in efficiency will probably be offset by the ineffeciency of the battery/inverter setup. Of course this all depends on the charging efficiency and inverter efficiency, I'm using an estimate of about a 60% efficiency for those types of systems. Under those conditions, I don't think you'll see much of a gain.

Where your idea will really shine is during intermittant loads. If you're running a few lightbulbs continously, and need to power a pump, refrigerator, A/C, only occasionally, then you will see an advantage. If we assume your peak load is about 5kw, instead of needing to run a large 5kW generator continously to power only 100W most of the time, you can run a smaller 500W generator to power the small loads and use the batter/inverter as a buffer to handle the peak loads. Then you will see the efficiency gains from running a smaller enginer rather than a larger one. Again, this all depends on your continous and peak loads.

These are all assumptions and rough calculations, so I wouldn't put a whole lot of faith into it. I'm just rambling off the top of my head.

Raspy, you are describing exactly what I'm trying to. Thanks.

AC at a 120V is hard for me to describe. 20V at 5amps is a LOT from my usual perspective. :P Silly little electronic bits.

And I think that intermittent loads is what most of us who have a household generator have. We have them when the lights go out, and that's about it.

What kind of loads to people put on thier gennies when they are using them? Not contractors, but house hold usage. If we can show a need, something like this might get built...

From memory, my folks would be:
5-8 bulbs in the 50-60W range
1 spotlight bulb, not sure of the wattage, on a motion sensor
water pump
fridge and deepfreeze

And that's about it. Maybe a television, but thats unlikely.

Personally... I've got a camp stove, I've got batteries, and no place for a generator. No electricity, no big deal. Unless BSG is on and I'm missing it, then there might be casualties. :P

I originally bought mine to run my well pump when the power went out. Now that we are on county water, the only time I start it up is when the power goes out and my sump pump is running like mad. It is absolutely amazing how fast the water level rises in my basement when the power goes out during a storm.

When I installed the switch box in the basement, I hooked up the well pump to two switches, the sump pump, and the kitchen wall sockets. This kept me in water, the basement dry, and I could run the toaster oven / coffee pot / electric skillet / refrigerator / etc. I really need to rethink what is hooked up since the well pump is gone and I have two extra circuits available. I had a marine battery & inverter to run the wood stove fan, but should probably look at adding that circuit to one of the switches.

Dragging the gen set out and hooking it up is a pain, especially when the weather is bad. Dragging it through 10" of snow to hook it up......... It only gets hooked up if the basement is in danger of flooding. Otherwise, I can live without it via other backup means.

The system that I use for my shelter option:

The generator will be run 2 times per day (for 2-3 hrs) to run the refrigerator & freezer after I break food out for the next 12 hr period. I'll also recharge my batteries during that same time.

I use a 300 watt invertor to supply battery power for the T.V, computor, cable box, & lighting during the majority of the time. No, I don't run them all at the same time 24/7. If EMP hasn't already destroyed the electronics, the plan is to make periodic checks for news, Civil Defense announcements, and weather reports; and run some lighting.

I also have a bicycle powered magneto that will put out 110VDC to recharge batteries.

I am playing with an anemometer to trickle charge the batteries. It will probably only be practical for recharging the small dry cell batteries.

My biggest problem at the moment is to keep my shelter cool in the summer months.

What about just putting a large-ish UPS[1] on the generator output? Get a higher-end UPS that will tell you the state of charge, and run the generator as needed.

eg: http://canadiantire.com/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443289558&FOLDER%3C%3Efolder_id=1408474396673606&bmUID=1182542683289

Alex

[1]Uninterruptible Power Supply: Typically used by people who have experienced the sinking sensation of watching a 10-page document disappear when the computer abruptly dies in a power failure, and who are seeking to avoid feeling that sensation again.

A little side note about rechargeable batteries: They have a limited number of recharge cycles. After a couple of years living in the woods you'll realize that your batteries wouldn't hold the charge anymore...

There are much more serious solutions for storing the energy do exist. The fly-wheel systems for example (the best if you're considering building of a concrete bunker).

Hope it's OK to revive this old thread...

I just bought a Honda EU2000i generator for my work, and I also like the idea of having it available for emergency service similar to what ironraven is looking for.

It's truly an incredible machine, and the more I learn about it, the more impressed I am. (There's a yahoo user group dedicated to only this model).

This unit seems to be the most practical method for providing intermittent fairly large power needs (fridge, etc.) and also coast along providing minimal power with minimal fuel use the rest of the time. At full rated output of 1600w (it surges to 2000) it uses its 1.1 gal of gas in 4 hours. When you're not using it full blast, it throttles way down, and uses its 1.1 gal over the course of 15 hours. At $3.20 a gallon, that's 23 cents an hour. It's all handled automatically, and provides the power through an inverter, so it's super clean and stable power.

I brought it home, and called wife outside to hear me fire it up. She didn't want start it, for fear of waking napping kid with nearby open window. (We were talking in hushed voices for that reason.) I started it anyway, and she was duly impressed. It then it sunk in we were still talking in our hushed voices, and could still hear each other perfectly over the generator running under full load at our feet. So to make a long story short, it's a quiet little sucker. Basically a loud hum.

FWIW,

Dave

No doubt Honda and Yamaha are the best portable generators ever made.

That's not entirely true. A given generator will have a minimum running fuel consumption at idle, but generally more fuel is used under loaded conditions. If this is not the case for your generator you should investigate its throttle settings. Systems designed to incorporate battery storage capacity into your home electrical system are commercial available (http://www.oksolar.com/abc/solar_systems_sta.htm) or you can put one together yourself with a charge/genset controller, interter, and a battery bank. Just get ready to fork over lot of cash...

I do this to run my tv and computer during storms. its also a good way of isolating your electronics from power surges. just keep in mind that ups systems are not linear loads like light bulbs or heater elements. They have current draw patterns that small gernerators don't like to supply. We installed a large backup genset at a local gas company office and had to take several of their ups' offline to test the generator. The genset's manufacturer recommended that the maximum ups load be not more than 20% of the generator capacity.