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.