Powering my house with the MB - Page 2 - PeachParts Mercedes-Benz Forum

::matthew · #1 12-14-2008, 10:34 AM

and to think that MB never thought to put a PTO on the fronts of our cars.

strelnik · #2 12-21-2008, 08:23 PM

Quote:

Originally Posted by ::matthew

and to think that MB never thought to put a PTO on the fronts of our cars.

The German Bundeswehr in the days of the Warsaw pact had a 24V Unimog with a PTO in front to run a generator or a pump of some kind (maybe water pump?). Haven't seen one since 88 but sounds like it would be handy and easy to build

strelnik · #3 12-21-2008, 08:24 PM

Forgot to add: Model T cars were made that way too, but to run milking machines and cement mixers

babymog · #4 12-14-2008, 10:49 AM

I had a large diesel generator for a back-up genset at my house, started to realize that at 3GPH x $3/gallon, I'm looking at $9/hour in fuel, x 24hours = $216/day. I could stay in a nice hotel room, order room service, and let insurance pay for the lost food.

Anyway, with a stock alternator on a 240D, 45a, which is more like a 1200rpm output, not idle, you're putting out 45v x 13vdc = 585watts. Most of my inverters are high-end sine-wave units, IIRC around 95% efficient, the cheaper ones are typically less (some much less, and if a square-wave it will lose a great deal more efficiency running an inductive motor like a refrigerator). So, lets figure 80% efficiency from the 585watts = 468watts which is 4amps load at 117vac. It will likely have enough surge capacity from what's in your battery to start the load, but unless your total combined loads are less than 4amps continuous/average, you will drain the car battery until the inverter drops out on low voltage. The current drawn will also increase as the voltage drops so that even a 3a or 3.5a load will be greater than the output of your car's alternator, and the alternator will lose output as it heats up, and we're assuming the alternator is capable of its original rated output even though most aren't after some miles/years of use.

A lot of fuel and car use for a little output, but better than nothing I guess.

spark3542 · #5 12-14-2008, 10:49 PM

Quote:

Originally Posted by babymog

I had a large diesel generator for a back-up genset at my house, started to realize that at 3GPH x $3/gallon, I'm looking at $9/hour in fuel, x 24hours = $216/day. I could stay in a nice hotel room, order room service, and let insurance pay for the lost food.

Anyway, with a stock alternator on a 240D, 45a, which is more like a 1200rpm output, not idle, you're putting out 45v x 13vdc = 585watts. Most of my inverters are high-end sine-wave units, IIRC around 95% efficient, the cheaper ones are typically less (some much less, and if a square-wave it will lose a great deal more efficiency running an inductive motor like a refrigerator). So, lets figure 80% efficiency from the 585watts = 468watts which is 4amps load at 117vac. It will likely have enough surge capacity from what's in your battery to start the load, but unless your total combined loads are less than 4amps continuous/average, you will drain the car battery until the inverter drops out on low voltage. The current drawn will also increase as the voltage drops so that even a 3a or 3.5a load will be greater than the output of your car's alternator, and the alternator will lose output as it heats up, and we're assuming the alternator is capable of its original rated output even though most aren't after some miles/years of use.

A lot of fuel and car use for a little output, but better than nothing I guess.

You're off by a decimal. Your house genset would use more like 0.3 GPH, and that's even a a good load.

Run your genset on a WVO/RUG blend for about $0.16 per gallon and your cheaper than the grid.

babymog · #6 12-15-2008, 01:49 AM

Um, no. It is (was) a 42kva genset, would burn around 3gph with a good load. I sized it so it would run the pool, the Jacuzzi, the A/C, the motorhome, the 'fridge, the freezer, lights, entertainment, ... just like running on the grid only without it. Anything that can be done, can be overdone.

Quote:

Originally Posted by spark3542

You're off by a decimal. Your house genset would use more like 0.3 GPH, and that's even a a good load.

Run your genset on a WVO/RUG blend for about $0.16 per gallon and your cheaper than the grid.

turbobenz · #7 12-15-2008, 03:45 AM

Just for fun

1 us gallon of diesel fuel contains roughly 35,000,000 Calories

Which is 40.705 Kilowatt Hours

Imagine if your diesel engine, alternator, and inverter were even 50% efficient as a whole

I bet using a car as a generator is probably less than 2% efficient (someone want to do the math?), and a generator is probably around 5%. Not to mention voltage drop in your wires, which wastes a lot more than you think.

I have an old robin (subaru) 1 cylinder 5k gasoline generator. I was going to convert it to run on wood but, well, thats hard.

pawoSD · #8 12-15-2008, 04:36 AM

By far the cheapest form of power generation is a natural gas generator.....it costs like 3-4x less to run than a diesel or gas unit. Especially when sized for "emergency use", perhaps 3500-5000 watts. Plenty to keep important stuff working and still have some entertainment power. (Run fridge, furnace, etc...) + some lights (CFL) and tv's......and computer.

Also, essentially unlimited fuel source with no need to refill it.

Running off an inverter off the car engine at idle is super inefficient....and a good way to ruin the alt/battery if you use more than a few hundred watts.

Being a 240d, I sure hope you have it set to as high an idle as possible....

Graminal95 · #9 12-14-2008, 11:01 AM

KarTek, I used to work as an electrician and yep I have the breaker off for the furnace and disconnected as the neutral is actually ground and the inverter won't run hooked up to ground. But good comment there are quite a few linesmen that get zapped from dumb ass home owners and there generators. Its actually a bad idea to turn off the main if you have not done so in 5 or more years as they usually will not come back on.

The old girl is just idling away well a little higher then normal idle so about 1000 rpm although when everything is running it bogs down just a little.

I just rebuilt a 115amp alternator and installed a higher voltage (14.5V) regulator and its a real Bosch so its good for full output all the time. Right now I have the furnace, 5 circulation pumps, 3 lamps, 2 laptops, a box fan, modem and router for the internet and my cell phone charger. So close to the 1100w max for the inverter and the car, but she seems happy.

We don't usually get ice storms but this one is the worst I have seen. I was talking to some folks today and it seems there are no generators all the way down to RI!! So its a good thing the old girl is happy to work hard for me all night.

I was going to post this all last night but the phone line went down and I lost the internet. The inverter is hooked up to the battery and gets power from the alternator. I have yet to go out and see how much fuel is in the tank but it used about an 1/8 tank in the last 24hr run time so hopefully its not to much more then that today as well.

chasinthesun · #10 12-14-2008, 11:52 AM

Would 3 gallons a day be a good guess on usage for your 240d to run the load needed ? Ive heard of the old single cylinder Lister diesels get great efficiency while running off grid homes ,sounds like the 240 is doing the job. During Hurricane Ike I had my 300d charge 2 extra car batteries I had for tv and small frig usage off an inverter, 5 hrs at night and 5 hrs in the morning was the regular routine for 2 weeks .I know after a few days some comforts are greatly missed .Its a bit weird when power does finally come back on ,you really get a sense of relief for the small things like power to your home.
Their are some guys that travel the states just for selling generators in times like these .The sell off back of semi s was popular here in Houston for 3 straight weeks during that time ,at a 30 to 50% mark up no less .Mostly Chinese knock offs .The first news story broke about them selling for $1300 plus ,real crooks.

pizzachef · #11 12-14-2008, 12:11 PM

My wagon supposedly had been upgraded to a 115 amp alternator. Is there a way I can verify this from somewhere on the alternator? I'd like to be able to have a similar setup.

Squiggle Dog · #12 12-14-2008, 12:30 PM

I'd like to be able to do the same as well. The only thing I worry about is, isn't letting a diesel engine idle that long bad for it? Wouldn't it build up carbon deposits that would cause the engine to smoke, run poorly, enter the oil and cause the engine to wear? I'm no expert, that's just what I've been told.

Bio300TDTdriver · #13 12-14-2008, 12:38 PM

That would be my concern as well. That's why I asked earlier what RPM the car was running at. It might be OK if it were for a day or two and you gave it a few Italian tuneups the next time your drove it.

Quote:

Originally Posted by Squiggle Dog

I'd like to be able to do the same as well. The only thing I worry about is, isn't letting a diesel engine idle that long bad for it? Wouldn't it build up carbon deposits that would cause the engine to smoke, run poorly, enter the oil and cause the engine to wear? I'm no expert, that's just what I've been told.

Stevo · #14 12-14-2008, 09:59 PM

Quote:

Originally Posted by chasinthesun

Ive heard of the old single cylinder Lister diesels get great efficiency while running off grid homes

My little one "lunger" Lister runs about 6 hours on a gallon of fuel but thats only 2Kw through a six current transfer switch. Its enough to run the house, if more is needed (shop or deep well pump) I fire up the diesel Yanmar 5 Kw.

Pooka · #15 12-15-2008, 02:05 PM

Please keep us informed on how this goes. Running the house from the car that is. A list of everything you have would be nice, too.

I live in a home that was build in 1961. It has a medallion on the outside that proudly proclaims "Total Electric Living" so this is information I could really use.

The great thing about this is that it is a generator you can drive. You are not going to be driving much during an ice storm so you will not really need the 'car' part of your generator.

I think there is a horror story somewhere that starts out, "Some said it was a car, some said it was a diesel generator. In reality, it was both." I could be wrong about that, though.

Just think: I could power my house on WVO. I wonder if I could get an 'alternative power credit' with this?

Pooka