Reply
 
Thread Tools Display Modes
 
Old 01-28-2009, 11:17 AM   #1
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Introduction and questions

I discovered school bus conversions and skoolie.net about 2 weeks ago. Since then, the majority of my time has been spent reading about bus conversions, van conversions, RVs in general, electrical systems, solar power, wind power, water systems, biodiesel, diesel engines, and pretty much anything related. Also some things not so related, like kinetic sculpture racing and Burning Man.

I think that the school bus conversions are a fascinating bit of engineering. I have a few ideas that I'll have to run by everyone here, and I want to draw up some diagrams of water and electrical systems to see if I really understand how they work.

Although it's fascinating to read and think about, there are a lot of good reasons why I shouldn't attempt to do a bus conversion myself. Here, I'll be negative and list them all out:
  • I have a bad habit of starting projects, but not finishing them.[/*:m:3d9ijlga]
  • I've never driven anything larger than a big pickup truck.[/*:m:3d9ijlga]
  • I have essentially no experience working on vehicles or engines.[/*:m:3d9ijlga]
  • I don't know how to weld.[/*:m:3d9ijlga]
  • At the moment, I have lots of time but little money, and when I eventually decide to go back to work I'll have sufficient money but very little time.[/*:m:3d9ijlga]
  • I don't have any place to store or work on a bus.[/*:m:3d9ijlga]
The reasons in favor of buying a bus:
  • I want to.[/*:m:3d9ijlga]
  • I would have to learn some useful skills, which is always a good thing.[/*:m:3d9ijlga]
Not a very balanced pro/con list, is it? However, I recently thought of a perfect justification for buying a bus:
  • I'll be moving some time within the next few months, and a bus could easily cost the same or less than renting a moving truck. A bus with most of the seats taken out should be able to haul a whole lot of stuff.[/*:m:3d9ijlga]
All right! Now I have a rationalization that will let me seriously consider buying a bus!

So now I'd like everyone's opinion on a couple of buses that I'm looking at. These are on auction, so the price may end up being well beyond what I'm willing to spend, but it doesn't hurt to consider it.

The buses are 1982 and 1983 Blue Bird 84 passenger with 300,000 to 350,000 miles. They're the flat nosed, front engine variety. I've been thinking that I'd like a 10' garage in the back of a converted bus, which is why I'm looking at such huge ones. The buses have a 3208 Caterpillar Diesel engine, and an MT643 transmission. The engines have never been rebuilt, but the transmissions have all been replaced at least once with Allison OEM rebuilt replacements. They're being sold directly by a school district, so the maintenance should be good. They're in Tucson, AZ, so rust should not be an issue, though I guess that climate is hard on runner parts and batteries. That's 800 miles away from my current location, so inspecting them in person is impractical (maybe not if they were for sale, but I can't see traveling 1600 miles to do an inspection for an auction I may or may not win.)

I know that the MT643 transmission is a good thing. More durable and better gas mileage than the typical 545, right?

What about the 3208 cat diesel? I don't see many of those in buses, but they seem to be regarded as reliable engines in other applications. Is 300,000 or 350,000 miles with no rebuild a big concern?

What else is there to be concerned about on a 26 year old bus?

So, given that I can't practically inspect these buses, what would you say they're worth? The auctions for all three buses are currently at only $500, and two of them no bids placed at all, but there are still 2 days left. I'm guessing that at $500 they would be worth the risk, and maybe the same at $1000, but not too much above that. Does this sound about right?

It would be different if I could inspect them first, of course. What would these be worth if they were inspected and in good shape? Maybe $4000 or $5000?
Anomalous is offline   Reply With Quote
Old 01-28-2009, 12:25 PM   #2
Skoolie
 
Ray_WA's Avatar
 
Join Date: Nov 2008
Posts: 193
Year: 1991
Coachwork: BlueBird
Chassis: GMC
Engine: 6.2 liter diesel
Rated Cap: 24
Re: Introduction and questions

Greetings! Welcome aboard! I can't answer your questions about the value of those particular buses, but they are the kind you'll want to do what you want, that is, put a garage in the back.

As for starting projects and never finishing.... I can tell you what I did when I got my bus. I started getting rid of my other projects. I didn't just add my bus to a long list, I shortened up that list quite a bit and put the bus on top of it. I have also started getting rid of junk. Am doing a real house cleaning here!

Do you have a link to the auctions we can look at?

-Ray
__________________
Pack up your bus and bug out to the hills!
Ray_WA is offline   Reply With Quote
Old 01-28-2009, 04:19 PM   #3
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

I guess the link would be a good idea, wouldn't it? And a publicly listed auction isn't exactly a secret that I should try to hide.

http://www.publicsurplus.com/sms/auc...iew?auc=312853
http://www.publicsurplus.com/sms/auc...iew?auc=312858
http://www.publicsurplus.com/sms/auc...iew?auc=312851

It seems like most of the buses listed here are cheaper than on ebay or on the dedicated bus resellers' sites. There are auctions for a pair of transit buses which end in 45 minutes, and they're only up to $1500. I'm planning to watch those at the end, to see how much last minute bidding is normal for this place. One thing I like about this site is that they extend the auction time five minutes after every bid, so there shouldn't be any sniping like on ebay. It's a lot more like a real auction in that way.
Anomalous is offline   Reply With Quote
Old 01-28-2009, 07:57 PM   #4
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

I'm still hoping that someone can tell me what kind of reliability to expect from a Cat 3208 engine with 300,000 or 350,000 miles on it. That's my biggest concern at this point.

I've been doing some preliminary footwork just in case I end up buying one of these buses. I called a place near me that offers RV storage, and they said that a bus would be fine, and doing some minor work on it there is no problem. $100 per month for covered parking, and an extra $10 per month for utility electricity.

I also got a quote for insurance. First I tried the company I have my car insurance with. As soon as they heard "bus to rv conversion", they said "we don't insure bus conversions" and hung up on me. I tried GMAC next, since I have read that people here have had good luck with them. I got a very helpful person on the phone, who helped me get an approximate quote even though I'm missing a lot of information (such as what vehicle it is that I'm insuring.) They say $265 per 6 months for liability insurance, which doesn't seem bad at all. They also told me that it doesn't matter what the title and registration of the bus say; so long as I am using it personally rather than commercially, they will be happy to sell me RV insurance on it.

I've also been considering how to get a bus from Tucson AZ back to SLC UT. I can think of two different options:

1) Pay someone with a CDL to drive the bus 800 miles. This is simple, but likely to be quite expensive.

2) Rent a place in Tucson for 1 week that will let me park the bus there and work on it. Hire someone with a CDL to move the bus a short distance in Tucson. Ask them to give me a crash course in bus driving. Pull out all but 15 seats myself, so that it's legal (or closer to legal) to drive without a CDL. Also consider removing the stop sign, covering top lights, and covering or painting over anything that says school bus. Then hire someone to install a receiver hitch on the bus, and rent a trailer, so I can haul my car back along with the bus.

The second option is vastly more complicated, and I'm not very confident in my ability to drive a 40' bus towing a car 800 miles. It's likely to be a lot more affordable, though. It would be kind of silly to buy a bus for $500, then pay someone $1500 to deliver it.
Anomalous is offline   Reply With Quote
Old 01-29-2009, 12:18 AM   #5
Bus Crazy
 
Elliot Naess's Avatar
 
Join Date: Oct 2005
Location: Clearlake, Northern California
Posts: 2,272
Year: 1992
Coachwork: Blue Bird
Chassis: TC-2000 Frt Eng, Tranny:MT643
Engine: 5,9 Cummins
Rated Cap: 84
Re: Introduction and questions


Well, since I'm the Kinetic Sculpture Racing guy....

When I sum up your initial post, it seems clear that you should NOT buy a bus.

That said.... I know what it is like to fall in love, and sometimes... sometimes the only way back to sanity is to surrender, let the disease run its course, then pick up the pieces and calmly rebuild.
Two and a half years ago I absolutely HAD to have a vintage BMW motorcycle, so I bought one. Now it is for sale. I have ridden it once. Once. (Excellent bike.)

For the moving chore, you would probably be better off renting a truck. For one thing, when it breaks down along the road, you just "drop a dime".

I see that these are the All American model. As recently discussed elsewhere around here, the AA is the "deluxe" model, so this is good. Curved windshields, nice. More galvanizing -- good around that salty lake of yours.

The 3208 is a bit bigger than the usual B-series Cummins. The 3208 is what they used in the fancy Blue Bird Wanderlodge RV models. (So you are half way to a fake Wanderlodge here. ) I have no experience with these engines, but from what I have read, they are not very durable, and are poor candidates for rebuilding.

With the age and milage, and sight unseen, without a diesel mechanic's evaluation of the engine, I would say these buses are not worth much more than the $500 starting price, and driving one back to SLC right off the bat would be a bit risky.

They say the tires are "fair". This could mean anything. Six good used tires could set you back something on the order of $1.200.

On the positive side, they are selling several identical buses at once. That fact suggests that they are being replaced because they hit a certain age; not because the engine just went kablooie.

Since you ask.... No, I think these buses are too old, with too much miles, to be worth anywhere near five grand even if shown to be in sound condition.

Oh, and I go to Burning Man also.
__________________
Elliot
Millicent The Bus - roof raised two feet, toy-hauler tailgate.
http://www.skoolie.net/forums/f11/th...gate-1564.html
Elliot Naess is offline   Reply With Quote
Old 01-29-2009, 01:29 AM   #6
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Yep, Elliot, you are the one who caused me to spend a number of hours reading about both Kinetic Sculpture Racing and Burning Man.
Both events sound like something that I'd like to try attending some time, even if I only go once.

For the record, I think I'm currently in the middle of an insane phase. I graduated from college about 3 years ago, worked diligently for 2.5 years, then got fed up and quit my job. I moved to Utah to take hang gliding lessons. I didn't make a lot of progress in learning to fly before winter set in, so now I'm trying to decide whether to hold out until spring and continue the lessons, or go find another job somewhere. In another few months my savings will get uncomfortably low, so the decision will be made for me.

Back on topic: I just sent an email to the contact for the bus auctions, asking if they have maintenance records available for the engines, and if they could expand on what "fair" condition means.

I'm kind of thinking that for $500, why not buy one of these? If it breaks down, there's no huge loss. Either way, it would be a bit of an adventure.

The weird thing is that I don't really like adventures or doing anything out of my comfort zone; I have a tendency to sit around at home, staring at the computer, not going out for days or weeks at a time. Then I eventually realize that I'm stuck in a rut, and need to go do something. It's my hope that I'll eventually fall into a happy medium somewhere between comatose and insane.

Sorry for the introspection cluttering up the skoolie board. I'll probably regret being so forthcoming after getting a good nights sleep, but what I've written will not be any less true.

Anyway, let me post some technical stuff to make up for the other foolishness. There are a couple of ideas I've had about skoolie conversions, which have probably been done before, but I haven't run across yet in my reading.

My understanding is that most people hang things like water tanks, waste tanks, generator, and batteries in simple frames below the floor of the bus. They then insulate the floor of the bus. This may be a good idea for warm climates, but wouldn't you have trouble with things freezing if you stay somewhere cold?

Would it be practical to build enclosed bins under the majority of the bus, and put the insulation on the outside and underside of these areas? Then leave the bus floor uninsulated, so enough heat would end up below to keep the water, waste, and batteries from freezing? I understand that some commercial RVs feature heated basements, but I haven't seen much about this in skoolie conversions. If you used radiant floor heating with an uninsulated floor, that would certainly keep things below nice and toasty in the cold.

Another thing I've noticed about most conversions is that they make use of propane in one way or another. I don't really like the idea of carrying multiple incompatible fuel sources, so I'd prefer to use diesel for everything. Perhaps install a second diesel tank and a pump to transfer between the two, so you could have a reserve tank. Is there any disadvantage to this, other than the fact that it would probably be more expensive?

I've done a lot of searching, and it seems that there is diesel product for just about anything you could want to do. Probably use a tankless water heater for both hot water and for heating the cabin. I'm not sure whether it would be better to install radiant floor heating, or to run the hot water through radiators. You could use a heat exchanger connected to the engine coolant for heat while driving.

Diesel generators are obviously available. They cost a lot more than the gas ones, but from what I've read, they're supposed to last a lot longer as well. I put together a spreadsheet comparing various generators, and based on the manufacturers' specifications, diesel generators are also a lot more efficient in terms of kw/gallon (still more efficient even if you use kw/$.)

You can get diesel stoves, but I don't think I would bother. I'm thinking that a convection microwave and a couple induction cookers or hotplates would work fine for me. These would use a fair bit of electricity, but I plan on having a good sized battery bank, and the generator is always there if needed.

I guess they only thing you can't power with diesel directly would be the refrigerator. An efficient fridge can use so little electricity though that it shouldn't really be a problem. I've also read that the propane fridges have to be exactly level to work, which seems rather annoying. I've read a couple of articles about chest freezers converted into fridges using an extra thermostat, and they use an astonishingly small amount of power. I guess that finding the space for a chest freezer in an RV might be a problem, though.

So what do you think? Am I headed in a practical direction with these ideas?


Edit: Hey, I forgot about a question I meant to ask!

I have no experience with vehicles that have air brakes, but after reading about them a bit, they seem pretty neat. One question that occurred to me while reading: can you tap into the air brake system to do things like refill tires, blow away dust, and run air tools, or is messing with the brake system a no-no?
Anomalous is offline   Reply With Quote
Old 01-29-2009, 05:18 PM   #7
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Downsouth, I'm gratified to hear that I'm not the only one crazy enough to consider owning a bus without having all the fancy fabrication and mechanic skills that many of the other people here have demonstrated.

It's also interesting to learn that you have neighbors that don't mind a bus parked in the yard. It seems like the kind of thing that many neighborhoods would throughly dislike. I don't have that option at the moment, because I'm renting a couple of rooms in the basement of a town house. There is a back yard, of sorts... it's about 4 by 6 feet in size. I'll be moving within the next few months though, so if I own a bus, I can look for a place that will accommodate that.


The idea of putting water tanks inside the bus is interesting. That would keep things nice and liquid, but it would also cut down on the amount of storage space available. It would certainly be a great deal easier than trying to build a basement onto a bus that doesn't come with one, though.


I now have less than 24 hours left to decide if I want to bid on one of these $500 auctions. I think that if they remain at $500, Id be happy to take the risk of getting a defective bus.

However, if I buy one of these buses, is it possible to get the engine and transmission inspected somehow, to learn how much life is left in them? Or would I have to constantly live in fear that the bus could break down at any moment?

If I can know the condition, it doesn't matter so much what that condition is. If I pay $500 for a bus and it turns out that it's no good, then I'll just get rid of it again without putting a lot of time or money into it. If I can buy a bus and it's in a good enough condition to last another 50,000 miles, then I could go ahead with a conversion project. However, if there's no way to establish the condition and an estimated lifetime, then there's really no point in buying it in the first place.

I've been reading about oil testing, and it sounds pretty neat. Would it be worth while to change the oil and transmission fluid in a bus before driving 800 miles, then send samples off for analysis? (Assuming that the bus makes it through the trip.) Or is a 300,000 mile engine going to be be so worn that the test would be useless?
Anomalous is offline   Reply With Quote
Old 01-29-2009, 07:26 PM   #8
Bus Crazy
 
Elliot Naess's Avatar
 
Join Date: Oct 2005
Location: Clearlake, Northern California
Posts: 2,272
Year: 1992
Coachwork: Blue Bird
Chassis: TC-2000 Frt Eng, Tranny:MT643
Engine: 5,9 Cummins
Rated Cap: 84
Re: Introduction and questions


I could spend the rest of the day (attempting to) answering your questions, but I need to get to the Post Office before they close. But quickly... From what you are telling us, I say Go For It, but don't bid more than something like 550. More later.
__________________
Elliot
Millicent The Bus - roof raised two feet, toy-hauler tailgate.
http://www.skoolie.net/forums/f11/th...gate-1564.html
Elliot Naess is offline   Reply With Quote
Old 01-29-2009, 09:57 PM   #9
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Hey, no rush. I have a whole 19 hours left before I have to decide if I want to bid on one of the buses.

I'm still hoping to hear back about the maintenance history before the auction closes. The contact person at the school said that they forwarded the request to the transportation department, so I'm waiting for them to respond.

Elliot, your short statement is useful: it cuts right to the heard of the matter and advises me what to do. I would love to hear the reasoning behind that advice, if you don't mind spending the time to educate an ignorant newbie.

I'm thinking that if I do end up with a bus, I'll plan on spending a few days down in Tucson with it before I attempt the long drive. This would give me time to get everything in order and do some minor work. Not to mention that it's cold up here in Utah, but nice and warm down in Tucson. I would have to find a place to park the thing, but I'm guessing that worst case I can pay an RV storage place for one month's rent. If the prices are similar to the ones here, that would only be $100.
Anomalous is offline   Reply With Quote
Old 01-29-2009, 10:17 PM   #10
Skoolie
 
Ray_WA's Avatar
 
Join Date: Nov 2008
Posts: 193
Year: 1991
Coachwork: BlueBird
Chassis: GMC
Engine: 6.2 liter diesel
Rated Cap: 24
Re: Introduction and questions

Quote:
Originally Posted by Anomalous
I would have to find a place to park the thing, but I'm guessing that worst case I can pay an RV storage place for one month's rent. If the prices are similar to the ones here, that would only be $100.
Up here you can park in Walmart parking lots without hassle. Don't know about down there.

-Ray
__________________
Pack up your bus and bug out to the hills!
Ray_WA is offline   Reply With Quote
Old 01-29-2009, 10:43 PM   #11
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

I've read that many Walmarts allow overnight RV parking, but I think they might frown on parking a bus there and doing things like removing the seats or changing the oil. I suppose it couldn't hurt to ask, but I'm not going to count on being allowed to do maintenance in a parking lot.
Anomalous is offline   Reply With Quote
Old 01-29-2009, 11:08 PM   #12
Bus Crazy
 
Elliot Naess's Avatar
 
Join Date: Oct 2005
Location: Clearlake, Northern California
Posts: 2,272
Year: 1992
Coachwork: Blue Bird
Chassis: TC-2000 Frt Eng, Tranny:MT643
Engine: 5,9 Cummins
Rated Cap: 84
Re: Introduction and questions


Quote:
Elliot, your short statement is useful: it cuts right to the heard of the matter and advises me what to do. I would love to hear the reasoning behind that advice, if you don't mind spending the time to educate an ignorant newbie.
Well now.... You don't sound all that ignorant, so you probably know NOT TO place too much weight on so-called advice from some old bum in California.

As for the reasoning, you spelled that all out yourself -- I just summed up my impression of it for ease of reference.

If you buy one of these, it would make sense to have a competent shop examine the bus --since you, by your own admission, is no mechanic. You should ask for a basic safety inspection, which is a routine thing for commercial trucks and does not cost much. You are concerned about exessive wear in the steering, brakes, etc. You should also ask if they can evaluate the condition of the engine and the transmission; including oil analysis, which is not expensive. Oil analysis is most useful when you do it regularly so the results can be compared over time, but any analysis is better than none. And it could be very useful in a high milage engine, as they may be able to tell you if the bearings are worn thru to the backing metal. Look for a Caterpillar dealer, so you get a mechanic who is familiar with these engines.

I cannot say much about frost damage, since we don't have much frost around here. We get down in the low 20s some nights, then it warms to at least the 40s before Noon. Today (January 29), it was in the 60s. To protect against those frosty nights, I pour a couple of gallons of RV tank antifreeze in my tanks, and run it thru the fresh water pump and toilet. RV tank antifreeze costs just three or four buck a gallon in most auto parts stores. In colder climates, you need to do more, yes.

Refrigerators. Refrigerators draw a lot of electricity. My tiny RV refrigerator (which I have not inststalled yet) draws 10 Amps. I tested it with one 12 V deep cycle battery and inadvertantly left it overnight, and it killed that battery -- I mean, dead, buried, forever.

On the other hand, the propane feature in an RV refrigerator is said to be very cost efficient. I have no experience yet, but word is they use very little propane.

This makes sense, since RV refrigerators work on a different principle from house refrigerators. RV units work on -- strange as it may sound -- heat. A friend of mine found a discarded RV fridge at a recycling center, and the sun was shining on its exposed mechanism and... it was cold inside! Heating with electric resistance draws a lot of electricity. Heating with a propane flame, much cheaper. Yes, they need to be level so the liquid inside the cooling coils does not puddle. But I don't know the tolerance. I'm thinking of mounting mine in some sort of gimbal, so I can level it no matter how I'm parked.

Yes, you can tap into the air brake system for other purposes. Truckers do it all the time. But get a truck mechanic to show you where to tap in, and use proper hardware. Don't expect to get much use out of pneumatic tools though, as pneumatic tools draw a HUGE flow of air and the bus wil not be able to keep up.

That will have to do for now. You are doing a pretty good job of answering your own questions.
I suspect that nine out of ten skoolie projects are never finished. That's OK, so long as you are prepared to tow it to the scrap yard and give it to them -- as I did with my first bus (which cost $250,-).

Word is, many Wally-Worlds allow RVs to park overnight, because RV'ers are usually good customers. But don't even think of doing mechanical work in anybody's parking lot. Very bad for our overall reputation.
__________________
Elliot
Millicent The Bus - roof raised two feet, toy-hauler tailgate.
http://www.skoolie.net/forums/f11/th...gate-1564.html
Elliot Naess is offline   Reply With Quote
Old 01-29-2009, 11:39 PM   #13
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Lots of information, thanks!

I agree that propane refrigerators are an interesting and useful bit of technology, but I just don't like the idea of having to carry and refill propane!

Here's a link to the chest freezer to refrigerator conversion: http://www.mtbest.net/chest_fridge.html. This claims 0.1 kWh per day. A bit of searching turns up results from other people who have tried this; one person claims 0.264 kWh/day for a very large freezer, and another cites 0.125 kWh/day as their result.

It seems to me that 150 or 200 watts per day is pretty reasonable. That would easily be handled by a couple of large solar panels, or by running the generator once a week if you have a moderate sized battery bank.
Anomalous is offline   Reply With Quote
Old 01-29-2009, 11:50 PM   #14
Bus Crazy
 
Elliot Naess's Avatar
 
Join Date: Oct 2005
Location: Clearlake, Northern California
Posts: 2,272
Year: 1992
Coachwork: Blue Bird
Chassis: TC-2000 Frt Eng, Tranny:MT643
Engine: 5,9 Cummins
Rated Cap: 84
Re: Introduction and questions


Let's wait for some knowledgable electricians, but I'm worried about your "watts per day".

A Watt is a measure of energy flow at any given instant. Volts x Ampere = Watts.
My little Dometic draws 10 A at 12 V = 120 W. Continuously. Right? Wrong?
__________________
Elliot
Millicent The Bus - roof raised two feet, toy-hauler tailgate.
http://www.skoolie.net/forums/f11/th...gate-1564.html
Elliot Naess is offline   Reply With Quote
Old 01-30-2009, 12:35 AM   #15
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Yep, 10A at 12V would be 120 watts. Running constantly, that's 2880 watts per day. I doubt that the compressor would be running constantly though.

The chest freezer to refrigerator conversions are claimed to be up to 10 times more efficient than regular fridges. Part of this is because freezers are usually insulated better than refrigerators. The rest of the efficiency comes from the fact that a top loading freezer doesn't spill all the cold air out onto the ground every time you open it, unlike a normal fridge.

I'm pretty sure that my math is correct. I understand all the voltage / current / power stuff pretty well. The only part I'm skeptical about is the figures that people have recorded after doing a freezer conversion, which is why I used 3 different sources for those numbers.

Edit: it just occurred to me that RV fridges don't have a compressor, right? So my comment was a little nonsensical. Still, I would hope that they don't draw power constantly, no matter what they do with it. Logically, they have to regulate how much cooling they do in some way. Otherwise a fridge couldn't maintain a constant temperature while the outside temperature fluctuates.
Anomalous is offline   Reply With Quote
Old 01-30-2009, 12:43 AM   #16
Skoolie
 
Ray_WA's Avatar
 
Join Date: Nov 2008
Posts: 193
Year: 1991
Coachwork: BlueBird
Chassis: GMC
Engine: 6.2 liter diesel
Rated Cap: 24
Re: Introduction and questions

I've done a bit of research on the chest freezer to fridge conversions and I am quite impressed. There are also some very efficient production chest refrigerators you can buy, although they are very expensive. I will probably go with a homebuilt chest freezer conversion for my bus.

-Ray
__________________
Pack up your bus and bug out to the hills!
Ray_WA is offline   Reply With Quote
Old 01-30-2009, 12:47 AM   #17
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Just playing with numbers some more:

If I had unlimited funds and no concerns about weight, I'd like to have a bank of 6 250AH batteries. At 50% usage (to preserve battery life), that would give me 9000 watt hours of usable energy. It would also weigh 1000 pounds and cost about $3500 (for AGM batteries and charger.)

More realistic would be a bank of 3 200AH batteries. This would provide 3600 WH at 50% discharge, weigh 400 lbs, and cost about $1600.

Going for a really simple setup, we could use just consider one single 200AH battery. At 50% discharge, this would give us 100AH at 12V, or 1200 watt hours. If the inverter is 85% efficient (which is a very conservative estimate), we could get 1020 watt hours of 120V electricity (8.5 amp hours).

If a converted chest freezer uses 200 watt hours per day (which is also a conservative estimate if we can believe reports), this battery would run a fridge for a little over 5 days.

If we consider the RV fridge using 10A of 12V power constantly, that would be 120 watts. We don't have the loss from the inverter, so 1200 watt hours being used at a rate of 120 watts should give you 10 hours of running time.
Anomalous is offline   Reply With Quote
Old 01-30-2009, 02:44 AM   #18
Bus Crazy
 
Join Date: Jan 2008
Location: Adirondack Mountains NY
Posts: 1,099
Re: Introduction and questions

Elliot Wrote:
Quote:
Let's wait for some knowledgable electricians, but I'm worried about your "watts per day".

A Watt is a measure of energy flow at any given instant. Volts x Ampere = Watts.
My little Dometic draws 10 A at 12 V = 120 W. Continuously. Right? Wrong?
Yes.

Right - If it draws 10A at 12v then it draws 120 W.
Wrong - Not continuously (unless it's very poorly made or you always leave the door open). 120 W x 24 hours would be 2880 Wh (or 2.88 kWh) per day .

A load like a light bulb or fan left turned on WOULD be a continuous draw. Anything like a fridge that cycles draws the maximum only when it's running. Also, most (if not all) data plates list the peak instantaneous load, not the average. For example, if you got the 10 amps from a data plate, not from a meter, it might be 10 amps for a compressor start, and 5.5 amps when cooling. Add in a little draw between cycles if the control circuits are electronic.

The devil in the details on accumulated usage is how often and how long does YOUR fridge run? Everyone's mileage varies on this. How much stuff is kept in it? How often do you open the door? Are you always rotating warm food in, and cold food out, or just grabbing out a frosty beverage? Do you re-stock daily or weekly? Is the temperature outside the fridge 90 or 35? Some people gradually add jugs of water (like one per day) into the empty spaces in their freezers for thermal mass to hold heat, and to cut down on warm air exchange when the door opens. The goal is to reduce the number and length of the energy use cycles (but don't block the circulation of cold air).

The only way to tell what YOU use is with a run timer (think hour meter) or even better a watt-hour meter. If the fridge is 110 volts, an inexpensive Kill-A-Watt or Power Angel between the wall outlet and the load will display the accumulated usage for your personal equipment and style. If you have a DC system, a moderately-priced system meter like a Bogart TriMetric is very useful to show both usage and battery health.

[Note to self: Self, order that Kill-A-Watt you've been meaning to get, and go measure the freezer load.]
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Old 01-30-2009, 01:31 PM   #19
Bus Crazy
 
Elliot Naess's Avatar
 
Join Date: Oct 2005
Location: Clearlake, Northern California
Posts: 2,272
Year: 1992
Coachwork: Blue Bird
Chassis: TC-2000 Frt Eng, Tranny:MT643
Engine: 5,9 Cummins
Rated Cap: 84
Re: Introduction and questions


Thanks, Redbear! That certainly makes sense.
__________________
Elliot
Millicent The Bus - roof raised two feet, toy-hauler tailgate.
http://www.skoolie.net/forums/f11/th...gate-1564.html
Elliot Naess is offline   Reply With Quote
Old 01-30-2009, 05:39 PM   #20
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Introduction and questions

Well, no bus for me, at least not yet.

The buses went for $2550, $2450, and $2500. A similar one with a flat tire sold for $2485. Apparently 25 year old buses with over 300,000 miles are worth more than you might have thought.
Anomalous is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Introduction SustainableExistence Everything Else | General Skoolie Discussions 1 03-21-2011 12:37 AM
Introduction and looking for a bus. Abbott Everything Else | General Skoolie Discussions 1 09-16-2009 01:53 PM
Introduction/New Here eggman Everything Else | General Skoolie Discussions 7 08-21-2007 07:59 PM
Introduction & Questions nyrockingchairs Skoolie Conversion Projects 1 05-24-2007 03:43 PM
Introduction Slowpoke Everything Else | General Skoolie Discussions 15 03-05-2006 08:40 AM

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 08:47 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×