Looking for off grid power options

[wbpino]

Hello,

For the last few weeks I have been researching the net for options regarding "off grid" power options for my RV.
I would like to hear from you regarding what makes sense in my particular setup.

RV - 2007 Tioga 28f  (No basement)

Goals- To be able to be off grid occasionally and not to depend on generator / shore power all the time. (particularly on long  X country trips
          when over nighting at Walmarts etc. or the occasional remote camping trip)

          To be able to have AC power while on the road so the kids and family can enjoy the TV / cook etc without having to run the genset. 
              We routinely do long  trips (10 - 15 Hrs drives) and  X Country trips to visit family in FL (we live in MT)


Power needs:  Priority needs :  Need to run 80W ( 12 V  @ 6.67 amps)  medical device at night estimated 6 - 8 hrs.
                        Occasional needs: TV & Sat setup at night  ( Approx 150- 200 W ) maybe 1-2 hrs
                                                      Charge  Laptop / Cell Phone / Sat phone
                        Infrequent needs:  Coffee pot ( 1200 W ) maybe 30 min / day in AM
                                                      Microwave (1000 W ) infrequent and may defer to use only w genset or shore power if needed.

Setup:
I was planning to dedicate one of the outside storage compartments to this project.  From what I have read so far seems that it may be best to add a battery bank for this instead of relying on the existing coach battery setup. 

My Ideas:
1. Add between 2 to 4 GC2 golf cart batteries somewhere?? and connect this to an inverter/charger ( 2000 - 3000 W)
2. Connect this setup to the existing charging system / genset/ shore power
3. Add solar panels in the roof ( 2 or 3 120 W panels if I have the space ) .  ? Maybe supplement the permanent solar with a portable panel as well for the those times of the year or camping setups when the sun is not @ 100%.

Thanks again for your ideas and input!

 

[Kevin Means]

Hello and welcome to the forum. Unless you run your generator while traveling down the road, you're going to need an inverter to power 120 volt devices. You should size your inverter to the size of your battery-bank. Your "priority" and "occasional needs" list will easily be taken care of by the additional batteries you mentioned for overnight use (and then some.) It really depends on how long you want to run on batteries alone, your total consumption and the size and condition of your batter-bank.

Our convection microwave and cofee pot will run off our batteries/2800 watt PSW inverter, but they certainly draw a lot of juice. I think you'd need at least about a 2000 watt inverter to run those devices but some pretty sharp electrical folks who hang out here will be able to help you more with that.

I'm a big fan of solar, because we do a  lot of off-grid camping. Three 120 watt panels, that were properly installed, would go a long way to keeping your batteries charge, as long as they were in direct sunlight (no shading at all). Even slight shading from a raised vent cover is enough to almost or even totally shut a panel's output down.

Kev

Kev

 

[Jeff]

Wbpino


What do you have for batteries now?


There is no question that 4 GC batteries will handle your needs but two deep cycle 12 volt batts could probably do as well. (I am referring to real deep cycle 12 volts with 200 amp/hour capacity, not the RV/Marine batteries usually installed in Class C and Class A gas RVs.) depending on your current setup this might allow you to keep them in place.


There are some 1500-2000 watt inverters that include internal automatic switching when connected to shore  power for a couple of hundred dollars or so but they do not include charging capability. If your current converter/charger is 50 amps or so it will take forever to recharge a 400-500 amp/hour battery system.


Inverters need to be located close to the battery system because of cabling size requirements for DC power bout should not be in the same compartment unless you go to sealed AGM batteries.

 

[Ken & Sheila]

Wbpino

Inverters need to be located close to the battery system because of cabling size requirements for DC power bout should not be in the same compartment unless you go to sealed AGM batteries.

Somebody forgot to tell Monaco this! Mine is 18 ft, hence my use of double 4/0 runs.

wbpino,Based on your projected use it would look to get at least 400 Amp/hrs of battery storage (4 CG = about 440 AH). The inverter should be a minimum of 1500 watts. To recharge to batteries you want a high amp charger (at least 100 amps) as you will typically be using at least 200 AH a day and probably more. The larger charger will replenish the batteries faster using the genset. If you existing converter is a typical 55 amp unit, then I would get at least 2000 watts inverter/charger with 100 amps of charging capacity. This will replace your converter. These inverter will also automatically switch the 120AC load from the inverter to genset or shore power when available.
We normally run the genset when we are using the  most AC power (microwave for dinner prep etc). This means while running the genset we are charging the batteries and powering the Microwave. It is just more efficient this way (less total gen time). Adding an inverter to handle the AC loads does require some planning and electrrical knowledge - or you will need to find a pro to install.
Our set up is a 2800watt/130amp Inverter/charger backed up by 550 watts of solar and 765 amp/hr battery bank. For just a overnight we don't use the genset at all, but the second + days generally call for 2+ hour of gen time depending on usage and solar. We do run a desktop computer for estimate 4-5 hours per day, residential frig (80 watts, part time -depends on heat and opening frequency) plus 3+ hours of TV time.

 

[joelmyer]

You can do this hard or you can do this easy.

Occasional Walmart's and remote camping trip - the easy way.

Need to run 80W ( 12 V  @ 6.67 amps)  medical device at night estimated 6 - 8 hrs. = 56 amp hours
TV & Sat setup at night  ( Approx 150- 200 W ) maybe 1-2 hrs = 20 amps x 2 hours  =40 amp hour
Charge  Laptop / Cell Phone / Sat phone - my daytime usage dry camping is 30 amp hours and that's mostly charging toys
You didn't mention lights and fan.  Put in LEDS if you haven't already.

Total is about 130 amp hours.  So you need 260 amp hours of battery.  You could fudge a little and get 2x6 volt 220 amp hour batteries - total 12 volts & 220 amp hours.

I use a 700 watt $40 inverter.  Install close to the batteries and run an extension cord for the things that need off grid power.
Crank the generator for microwave & coffee pot.

This should take care of you for a day or three.  For weeks at at time, add solar - solar watts about the same as battery amp hours.

Joel

 

[Gary RV_Wizard]

Nice & simple, Joel. That makes for good advice.

I'm dubious that there is adequate room or weight capacity to add 4 x GC2 batteries to a Tioga 28f, but I've not seen that model up close. A pair of GC2 will weight about 135 lbs and produce 220-230AH (when new) and that's probably a practical limit for this coach. That gives a usable 115 or so AH and the generator can pick up any extra loads.

There is no silver bullet in GC2 (6v) batteries - you need the same weight & size of lead plates to produce the desired amp-hours whether they are 6v or 12v. GC2 6v are merely the most cost effective way to get larger capacities.  12v deep cycles are specialty items and therefore usually highly priced. However, Sam's Club and Costco members may be able to get decent quality 12v AGM deep cycles at a reasonable price (around $1/AH). Residents of larger metro areas may also have a battery discount store that can supply private label AGM deep cycles at good prices.

 

[wbpino]

Thank you for the suggestions and replies to my post.

Just returned from a brief trip to Yellowstone where I had a chance to learn more about my rig and what I really need to work on and what not to do.  (I tried running my CPAP on one of the available 12V outlets and I bust have blown a fuse somewhere!!....  . Now trying to find where it may be hiding......)

My MH has 2 Duracell Golf car batteries  (215 amp hours) in the coach compartment and I have changed most of my inside lights to LED's.

I was planning to dedicate one of the outside storage compartments for this project and add a additional battery bank outside.  I am concerned about the distance between the coach and outside compartments. The wire gauge requirements to connect them may limit me using my existing batteries.  Will look for the AGM type since I don't want to worry about maintenance and leaks.

Exploring around the roof it seems I may not have too much space up there but I may be able to fit 2 of the 120W panels. I will supplement the system if needed with a portable panel on the ground that may also help with the sun exposure issues.

I have tried using some of the inexpensive inverters but seems that my unit will not run with a modified sine inverter so.... in search of a PSW inverter.  I think anything between 1500 and 2000W should be just fine.  Anyone has any ideas on which kind or brand of Inverter / Charger to look for?  Hear a lot about the GoPower units but have no experience with them. I would prefer to stay away from the Chinese stuff if possible.

Thanks again!

 

[Jeff]

I don't know what brand CPAP you have but my Respironics RemStar M Series ran great on a $40 500 watt car inverter until I installed a larger modified sine wave that runs our refrigerator now.

Many 12 volt outlets are really light wired to run electronics.

Many 12 volts cords have a fuse in the plug.

 

[SeilerBird]

If I was going to be running a CPAP all night I would be hooked up to shore power and not depending on a battery bank.

 

[Gary RV_Wizard]

I have tried using some of the inexpensive inverters but seems that my unit will not run with a modified sine inverter so.... in search of a PSW inverter.  I think anything between 1500 and 2000W should be just fine.  Anyone has any ideas on which kind or brand of Inverter / Charger to look for?  Hear a lot about the GoPower units but have no experience with them. I would prefer to stay away from the Chinese stuff if possible.

If "Chinese stuff" includes Taiwan your choices may be limited, though there is "Korean stuff" on the market as well. It is still likely that inverters sold by "American" companies were in fact made in China, Taiwan or Korea, or at least using circuit boards from those countries.

The Xantrex ProWatt (their less expensive brand) is available in a 2000 watt model for around $400 from online discounters. Here's one source:
http://www.donrowe.com/Xantrex-806-1220-PROwatt-SW-2000-p/806-1220.htm


I'm a bit surprised your CPAP won't run on MSW - they usually aren't that sensitive. What does it do (or not do)?

 

[Jeff]

If I was going to be running a CPAP all night I would be hooked up to shore power and not depending on a battery bank.

Tom even with the humidifier on the draw is 3-4 ampsDC so it isn't a big problem. The issue was leaving our 2000 watt inverter on all night, it draws 10+ ampsr of parasitic power.

 

[wbpino]

The main issue I believe is my current electrical setup.

Using the existing 12v outlets to power a 400 W modified sine inverter resulted in the machine turning on/off during and the inverting unit alarming  I did try a 750W unit with similar results.  I then got the Phillips 12 power adapter resulted in a blown fuse somewhere.  There is not power to the 12v socket and all the fuses I have found are intact, so there is probably an in line fuse somewhere I haven't found yet.

Maybe if I connected directly to the battery instead of the existing 12V lighter plugs that issue may be solved. If I am going to do that, then It may be best to set up thing to add some convenience to the camping /rv experience at the same time, so here we are................

I did speak with a rep from Phillips and they advised against using that type of inverter and using shore power or a PSW type inverter.
The unit I have has a humidifier ( which I can disconnect ) and a heated tube which may cause most of my issued since I suspect it is a power guzzler.

 

[Jammer]

Hi wbpino

Much depends on latitude, time of year, and cloud cover.  A setup that will work great in Texas in July won't work in December in Minnesota

That said, for ongoing off-grid operation, 300-400w of solar panels is typically considered about right although with a CPAP you would want to err on the high side.  Remember that, unless you're going to tilt the panels to the south, there is an output loss since they are flat.  Most parts of the country you use a 5 hour a day of solar for planning purposes.

Typically you will want at least 2 days worth of battery capacity (to 0%) if you are willing to use a generator fairly often, 7 days if you won't run the generator at all, in between is in between.  As others have pointed out, space and weight may limit what you can do

 

[Jeff]

I would bet the sink it is the wiring to the plug. Try running some heavier wiring from the power center or batteries.

 

[Lou Schneider]

Agree on the wiring being at fault. You're pulling 10 times as much current as at 120 volts, and you only have 1/10th as much voltage to play with.  This means 12 volt wiring has 100 times as much voltage loss at any given power as 120 volt wiring.

Excessive wire loss means it only takes a slight decrease in battery voltage to make the inverter think the batteries are fully discharged, so the low voltage shut down trips well before it should.

Try putting the inverter within a couple of feet of the batteries so the 12 volt wire length is kept to a minimum, then extending the 120 volt side to your CPAP.  You don't want the inverter in the same compartment as the batteries because of the acid fumes attacking the internal parts, but you could put it in an adjacent compartment and just run the wires through the intervening wall.  This should give you much better results.