inverter help please!

[ruthi]

Didn't want to take away from seayfams thread, but, it reminded me that I need to get some info on what we need. We want to get an inverter. Our alternators are 12 volt, so, I guess it would need to be 12v? We have two central air units, Coleman basements, and we are wondering if there is anyway we can get enough power to run 1 air unit? We have a large house style fridge also. Any ideas on how big of an inverter it would take to run that, and what kind would be best? Or, am I just dreaming? We are usually driving at least every 3 days, and sometimes every day. How much and what kind of batteries are we talking about? I know there are those of you out there that have experience with this kind of stuff. We have to totally depend on our gen.set for our power for weeks at a time, and with the cost of fuel, we need to figure out a way to not have to run it 24/7. HELP!! confused. Thanks y'all

[robertglines1]

My opinion: a huge battery bank= 1200$ plus maintenance+ 4000watt inverter pure sine wave.3500$ Plus switching gear 500$ will last running air a few hours. not a day. someone else here can do math for running time. or tell how big your bat bank will have to be. first hot day you will need both and have to run gen set any way. Looks like $5 grand to get  started. plus continuing maintenance and loss of most of a bay. $ 5grand can buy allot of fuel.  Others please correct my response about size of battery bank and efficiency(time will run AC and Ice Box) plus you will have to run gen set several hours a day to charge Batteries also.

[happycamperbrat]

Ruthi, would a swamp cooler work for you instead of air conditioning? They have them for vehicles and buses that run on solar power....

[Geoff]

I can tell you what works for me-- A 12v Trace pure-sine inverter rated at 2500 watts, a 7kW generator, and four golf cart batteries for the house system.  The only way I can run the air while camped is either off the generator or shore power.  If I am driving the inverter will run one roof air for a while, then I start the generator and run two roof airs while driving.  The inverter and batteries will keep my apartment 120v refer going for 2 days easily, but I also use an electric coffee pot and microwave/ convection oven so I usually end up running my generator an hour or two every day.  It is nice not having to start the generator everytime I need 120v while camping.

[belfert]

Ruth, I know you have a truck alternator at 12 volts.  I don't know that you have enough power to run an A/C unit.  Most folks using the alternator have a 270 amps at 24 volts which is around 6,000 watts.  Even if you had 270 amps at 12 volts you drop down to around 3,000 watts.  You probably have something like 150 amps at 12 volts.

I remember talking to you or Ken about an inverter and the answer was you guys just run the generator all the time.  I believe Ken didn't think it was useful to charge batteries since he would have to run the generator to charge them.

An inverter and batteries should run at least $2,000.  I figure at $4 a gallon and half a gallon an hour you could run your generator about 1,000 hours.  Your best option might be an inverter with auto start for the generator.  That way if you don't need heat or A/C at night you can turn off the generator and run the fridge on inverter.  If batteries get low the inverter will start the generator.

[ruthi]

Brian, yep, that was our original plan, but then, that was before the fuel started getting crazy. Kinda make you think again about it. I figure around 340 dollars at least to run gen 24/7 at fuel 4 dollars. I guess looking on the bright side, it is still better than hotels. I realize there is no cheap solution, yes that would be nice. Just like everyone else, looking at the long term. I dont know if there is anyone else who uses their bus the way we do, so , it is different circumstances for us for sure. Thanks for the ideas.

[jjrbus]

If you want to research it a bit, this is the best book I found.  It may be available at the local library.   JIm

http://www.amplepower.com/products/living/index.html

[bevans6]

I would look at adding a 125 amp 24 volt alternator, at least, and going to a 24 volt inverter to reduce current levels.  Use an equalizer to draw off 12 volt for house needs.  Battery bank in the 230 ah at 24 volt range will run one AC unit for an hour or so at a lunch break and run the house loads including fridge over night.  The alternator will produce enough to charge your batteries on the road and run one roof-top AC.

That to me is the minimalist way to get an AC unit to run on the road.  It will support that, and all other non-constant high current loads in a typical house decently.  It won't run AC units parked for very long at all.

Brian

[Geoff]

I like the way you spend money!  I did just the opposite:  I got rid of the 24v, 270 amp 50DN handgrenade alternator and installed a belt-driven 12v 160 amp truck alternator which is big enough to run one roof air with my Trace SW2512MC inverter.  And I have the same end result-- the inverter is not going to run the roof air while parked and on battery power for very long.   

I would look at adding a 125 amp 24 volt alternator, at least, and going to a 24 volt inverter to reduce current levels.  Use an equalizer to draw off 12 volt for house needs.  Battery bank in the 230 ah at 24 volt range will run one AC unit for an hour or so at a lunch break and run the house loads including fridge over night.  The alternator will produce enough to charge your batteries on the road and run one roof-top AC.

That to me is the minimalist way to get an AC unit to run on the road.  It will support that, and all other non-constant high current loads in a typical house decently.  It won't run AC units parked for very long at all.

Brian

[TomC]

When I first bought my Trace 2500 watt MS inverter/charger, it had the capability to stack-able to use two to get 5,000 watts.  I thought also to run my A/C's through the inverter.  When I asked the gal that sold me the inverter about this, she simply asked "do you have a Diesel generator?", I said yes, and she said "then just run the A/C's on the generator."  Hence, I just bought one inverter from her! I've always thought of the inverter as a intermittant source of electricity-like to run the microwave, toaster oven, coffee maker, bathroom heater, primary water heater (so I can have hot water going down the road), T.V., Stereo, etc.  As a result, I've not had any problems with my inverter by overloading it with a continuous heavy load like the A/C.  Believe me-you'll be much happier (but burn more fuel) and have less headaches and costs in the long run by running your electric A/C's off shore power or generator only.  Good Luck, TomC

[ruthi]

Tom, I am sure that is true, but, shore power is never an option for us, so, we keep pumping that fuel. 

[artvonne]

  Roof airs, basement airs, etc., the most common way we cool an RV is primarily based on cheap readily available fuel.

  I wonder what kind of inginuity would result with fuel at $6-$7 gal. Better insulation for starters, less glass. More efficient generators, batteries, inverters, compressors.

  That last one? DC motors today are the most efficient, but DC roof AC units are only now coming into the market place and they are $$$$$. Takes a long time to pay for itself, and they never will if you dont use them enough. But if everthing was DC you could gain efficiency by not have to convert/invert energy.

  I wonder how a bunch of diodes like they use in those electric coolers would work. Like in the floor, cieling, walls, etc.. Solar panels on the roof, diodes, LED lights, there are probably many things we could think a lot differently about.

[ruthi]

Art, I am glad we insulated as much as can possibly be done. Also, we only have 3 windows in the bus, figured that should help. Dont know what would work for us because of the way we use it.

[belfert]

The issue with fancy DC stuff to minimize power use is the majority of RVs only go from power pole to power pole.  There is no real incentive to save on power when the site includes electricity.

When a potential RV customer looks at an RV they are usually more concerned about cost/financing, floorplan, and interior colors than how much power the air conditioning uses.  They would rather pay $650 for a rooftop A/C than $1,300 for something that save on power use.  If there were two indentical RVs on the lot and one cost $650 per rooftop more which would most customers choose?

The power efficient stuff costs a lot in large part to fairly low demand, at least in the USA.

Those of us on this forum are not average RV customers.

[artvonne]

Those of us on this forum are not average RV customers.

  That is an understatment. Ive seen things on these Bus forums that borders on mindboggling. Both good and bad, LOL.