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Old 10-26-2020, 09:11 AM   #1
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“Watt” would I need?

We are on our 3rd rig, a 29’ class C that runs off30amps/Generator. Our last rig had solar but we really don’t boon-dock, but with all these people crowding in the campsites, boon-docking is looking more like a Necessity!

So now I’m trying to figure out exactly what equipment I would need based on my usage. I happen to purchase a watchdog surge protector after my sure guard failed. The watchdog has a great app that tells you KWH usage. I can do the math, so far in 1 day of 45ish weather, with our electric space heater running, (not LP), we are well over 200 AH! We will be on the road for 6 apx months starting January and planing on staying south in florida with a trip out to AZ to visit my badly ailing father.

My question is; Has anyone out there that installed solar do this type of math to figure out their required Amp hour usage? Or use another method? I may want to run AC occasionally, but I can do that off the gen, but at night, if I’m in a warm climate, I wouldn’t run the gen, and especially if I was near anyone. I could use LP furnace more To take the chill out, (even though we don’t like it), and change the way we use the various systems in our RV. (We have LP fridge also.)

Thanks for any suggestions ahead of time!
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Old 10-26-2020, 09:55 AM   #2
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There’s lots of solar calculators on line. I like kwh to figure power usage needs because it’s easier - most appliances list watt usage and panels are rated in watts. Electric heat of course is a huge drain, so any reasonable solar installation will rely on using propane as much as possible.

For actual solar panel efficiency, figure you’ll get about 70% efficiency in a coach with panels mounted flat. The big thing for overnighting is your battery bank and you’ll get the best results from lithium batteries, but of course you’ll spend more too.

Start with something like this:
https://gpelectric.com/calculator/#gf_9
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Old 10-26-2020, 10:23 AM   #3
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Originally Posted by Johnynorthla View Post

My question is; Has anyone out there that installed solar do this type of math to figure out their required Amp hour usage? Or use another method? I may want to run AC occasionally, but I can do that off the gen, but at night, if I’m in a warm climate, I wouldn’t run the gen, and especially if I was near anyone. I could use LP furnace more To take the chill out, (even though we don’t like it), and change the way we use the various systems in our RV. (We have LP fridge also.)

Thanks for any suggestions ahead of time!
First of all, thank you for thinking of others when running your generator - I wish more people would do that. Yes, the calculations have been done many times and the short answer is you can forget about using electric heat or air conditioning without using the generator or being plugged in. A very few people have made A/C work with only solar/batteries after spending a LOT of money and they still have to use their A/C sparingly and pay attention to where they park their rig (to get sunlight).

I chose to cover my entire roof with solar panels, double the size of the battery bank and avoid A/C and electric heat altogether so that we can boondock more-or-less indefinitely. We use the propane furnace which covers the heating (blower fan is still a significant draw at ~7 amps) and a Magic fan which effectively pulls cool air through the RV and makes it bearable as long as nighttime temperatures are below ~70 degrees. We simply don't camp where it's hotter than that without being plugged in. Our generator is for emergency use only as I feel it ruins the camping experience.
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Old 10-26-2020, 10:37 AM   #4
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Some good points Uniblad - while I could run my AC off solar, it depended on parking in the sun which kind of defeated the purpose. I could also run the AC after sunset for several hours off my lithium (Nissan Leaf) battery bank, but around midnight I’d be out of power and it would still be hot (think Memphis in August).

So while you can do ok fighting the AC from Solar/batteries battle, it is pricey, complicated, and unless you have a lot of roof, you’re most likely limited to one AC unit.

I’m still contemplating what the system will look like on my new (to me) rig. I think enough solar/battery to keep the fridge running (residential fridges are counter productive here) for 3-4 days will do it. Either that or double my battery bank to about 20kwh and install an 8kw inverter to run both AC’s during the day (6kw would do it, but I like the Victron 48/8000) and then AC one overnight. Decisions, decisions....
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Old 10-26-2020, 11:29 AM   #5
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Regarding a lot of generator run time for folks with diesel Class A rigs:

We once camped close to a large Class A motorhome, and one morning I "thought" I could hear an extremely low volume humming sound coming from it.

I was curious as to what piece of RV equipment could be making that non-sound. I walked up to the front of it (that was facing out towards the campground loop road) so as to hear what might be making that faint almost indistinguishable sound - it was a diesel generator buried deep inside thel Class A's chassis spinning at 1800 RPM!

For the life of me I can't understand why a properly installed generator like that could not be run when drycamping (and emergency power outage hookup campground camping) anytime anywhere - even constantly - without annoying anybody - except for maybe an "anybody" with some kind of off the chart noise fetish.

To me, considering what a built-in RV generator costs, the (slight) sound of a well installed one is the Sound of Independence -> complete independence from the grid, the sun, the heat, and the cold.

Considering what our RV cost, we like to drycamp in it with that kind of independence.
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Old 10-26-2020, 02:12 PM   #6
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For "Dry Camping" or "Boondocking", managing your power expectations is a must. The less you use, the longer you can go without recharging.

To maintain your current more than 200 amp hour daily consumption you would need 400 amp hours of battery bank capacity. You would need to recharge every day by running your generator for at least 4 hours, assuming you have a big battery charger. The battery charger should be at least 40 amps and as much as 80 amps.

See battery manufacture specs for maximum charge rate. 12 volt AGM batteries may charge faster than 6 volt flooded cell gulf cart batteries. Check battery specs. Of course lithium batteries are a lot better.

You would also need a BIG inverter. A 1000 watt inverter is just not going to cut it. To run all your electric appliances without the generator, you would need at least 600 amp hours of battery and well over 3000 watt inverter. a 400 amp hour bank would not adequately support such a big inverter. A bigger battery charger is also needed to fast charge the bigger bank. It is better to use propane or diesel where you can.

Periodically you would need to fully charge the batteries for 14 to 18 hours. The full clean charge is needed to maintain battery capacity for many years. Recharging while driving can help more or less depending on RV engine charging ability. Driving for 6 hours will not fully charge the batteries.

Typical RV solar systems rarely achieve self sufficiency. Two or three hundred watts can add to generator output. Possibly it will reduce generator run time. Run the generator in the morning before sun light is strong. Use solar for long slow finishing charge.

A better solution is to reduce power consumption. Big ones are: use propan water heater, propane absorption refrigerator, and a 12 volt fan instead of A/C. A microwave is a high power device, but if you only run it for a few minutes a day, it does not amount to much. Still, using the propane stove top to heat things including making coffee can make a significant contribution.

I wish you good luck and happy trails ahead!
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Old 10-27-2020, 07:41 AM   #7
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Wow!, lots of food for thought! Thanks everyone for your input. I’m guessing running my AC off solar is not practical for me. I don’t want to dump that much money in to my rig, we are thinking of upgrading To a new rig once the ramifications of the pandemic go back to some type of normalcy, in regards to manufacturing and supply.

I’m thinking of my solar upgrade more as a backup plan when a full hookup campsite is not available for 1-2 nights. So the system I would want to install can be small and simple in design. I’m thinking either AGM or lithium. My one big issue is my battery tray under my step has limited space, the apx room I have is 8” high, 8” wide and 23” long to clear solenoid disconnect and wires. Besides my battery compartment I only have one small, outdoor compartment where the Pre-wire for solar comes in from the roof, to store batteries. But when I look at the battery sizes they all seem to big. Maybe those golf cart batteries are my best, bet but I don’t see them in AGM’s? Any suggestions on batteries for my situation would be helpful?
I’m also pretty sure my Converter/Charger might have to be changed if I use lithium, it might not even be able to do AGM’s!, I have to remove the panel and check.

As far as an inverter, now I’m thinking it would only be for the wife’s hairdryer, our microwave, TV, laptop a fan or 2 and our cellular hotspot. Like I said in my OP, running my gen during the day, where practical as not to disturb anyone Or nature is an option.
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Old 10-27-2020, 01:41 PM   #8
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Originally Posted by Johnynorthla View Post
Wow!, lots of food for thought! Thanks everyone for your input. I’m guessing running my AC off solar is not practical for me. I don’t want to dump that much money in to my rig, we are thinking of upgrading To a new rig once the ramifications of the pandemic go back to some type of normalcy, in regards to manufacturing and supply.

I’m thinking of my solar upgrade more as a backup plan when a full hookup campsite is not available for 1-2 nights. So the system I would want to install can be small and simple in design. I’m thinking either AGM or lithium. My one big issue is my battery tray under my step has limited space, the apx room I have is 8” high, 8” wide and 23” long to clear solenoid disconnect and wires. Besides my battery compartment I only have one small, outdoor compartment where the Pre-wire for solar comes in from the roof, to store batteries. But when I look at the battery sizes they all seem to big. Maybe those golf cart batteries are my best, bet but I don’t see them in AGM’s? Any suggestions on batteries for my situation would be helpful?
I’m also pretty sure my Converter/Charger might have to be changed if I use lithium, it might not even be able to do AGM’s!, I have to remove the panel and check.

As far as an inverter, now I’m thinking it would only be for the wife’s hairdryer, our microwave, TV, laptop a fan or 2 and our cellular hotspot. Like I said in my OP, running my gen during the day, where practical as not to disturb anyone Or nature is an option.
The battery compartment under our Class C's entrance step is close to the size that you show above - but maybe we have a little more height. We have a couple of Group 31 12V AGM batteries in there end-to-end, with some room to spare.

By the way as you might figure out from my post a earlier, when camping not on hookups we just fire up the built-in generator for the hairdryer or microwave - that's some of the uses it's intended for.
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Old 10-28-2020, 12:09 AM   #9
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The battery compartment under our Class C's entrance step is close to the size that you show above - but maybe we have a little more height. We have a couple of Group 31 12V AGM batteries in there end-to-end, with some room to spare.

By the way as you might figure out from my post a earlier, when camping not on hookups we just fire up the built-in generator for the hairdryer or microwave - that's some of the uses it's intended for.
What brand batteries do you have? And do you have solar?
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Old 10-28-2020, 09:14 AM   #10
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...
I don’t want to dump that much money in to my rig, we are thinking of upgrading To a new rig ...

I’m thinking of my solar upgrade more as a backup plan when a full hookup campsite is not available for 1-2 nights. So the system I would want to install can be small and simple in design. I’m thinking either AGM or lithium.
...
Maybe those golf cart batteries are my best, bet but I don’t see them in AGM’s? Any suggestions on batteries for my situation would be helpful?
I’m also pretty sure my Converter/Charger might have to be changed if I use lithium, it might not even be able to do AGM’s!, I have to remove the panel and check.

As far as an inverter, now I’m thinking it would only be for the wife’s hairdryer, our microwave, TV, laptop a fan or 2 and our cellular hotspot. Like I said in my OP, running my gen during the day, where practical as not to disturb anyone Or nature is an option.
There are gulf cart AGM's. Search on-line for ideas and sources.

I use a pair if Interstate Marine AGM's. They are group 31 and supply 100 amp hours each. A 40 or 50 amp charger would charge them quickly. Keeping the regulated voltage below 14.4 except for bulk charging depleted batteries is the main charger difference. Conditioning and equalizing are the thing to avoid. 13.6 is the best for long slow full charging. 13.2 or fully charged and disconnected is good for storage. Get manual for your make and model charger by searching on-line. Also contact mfg. for advice.

Flooded cell would likely be cheaper and would work fine for a year or two. Monitoring water level in tight spaces is going to be difficult.

Lithium would probably charge faster. Contact the lithium battery mfg. with the make and model of your charger. Some maintain a list of compatible chargers. Their websites may also have that info and may provide charging times and rates. No need to worry about periodic full charge. Install them inside the cabin. There are no hazardous vapors to worry about.

They cost a lot and last a long time. Not such a good investment for just a couple of years.

An inverter for hair dryer would need to be at least 1800 watts. That requires about 400 amp hours of deep draw battery to support. Same for microwave. The inverter may draw 150 amps of 12 volt DC while running a hair dryer and other little stuff.

Other stuff may work with 1000 watts and 200 amp hour marine AGM's. The inverter may draw 85 amps of 12 volt DC. I can run a hair dryer on "low" setting with my 1000 watt sine wave inverter. It pulls the batteries down a lot in a short time.

Inverters come in lots of flavors and can have lots to different functions. More functions and larger cost more. Installation for both 12 volt supply and 120 volt output require careful consideration.

At minimum it should be sine wave type. Modified Sine Wave is a thing of the past.

A quiet light weight inverter type 2000 watt generator would run all of these things and charge the batteries. High current devices like the hair dryer would be limited to one at a time.

I wish you good luck and happy trails a head!
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Old 10-28-2020, 09:41 AM   #11
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Old 10-28-2020, 01:06 PM   #12
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What brand batteries do you have? And do you have solar?
I have two of these Group 31 AGM deep cycle batteries, wired in paralllel, under our Class C's entrance step:
https://www.fullriverbattery.com/product/dc115-12/

This brand of batteries is popular in the marine world, so you probably won't find them where only car/truck batteries are normally stocked.

We do not have solar, as we're part-time RV'ers and want the location flexibility of not having to rely on hookups or the sun in order to charge our the coach batteries. We have five non-solar ways of recharging the RV batteries when not on hookups.

If we do add any solar capability for drycamping, it will most likely be these 200 watt portable suitcase solar panels with long cables so that the RV can be in the shade while the panels are in the sun:
https://www.renogy.com/200-watt-12-v...olar-suitcase/
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Old 10-28-2020, 01:26 PM   #13
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For the occasional boondocking we do such as the OP, we elect to bring the Honda EU2000 along. Yes, we could use the onboard Onan 7.5, and we do for occasional AC usage. We typically run about 200 AH use daily as well. (about 50% of capacity of our battery bank)
We do use LP for refer, hot water and furnace.
The Honda, run about four hours a day in late morning-early afternoon keeps up with everything just fine.
50' of extension cord with the gen in the bushes, the exhaust pointed away from everyone, and nobody hears it. Never had one complaint, even in a state park. We also installed a small 300w PSW inverter for the tv, laptops only. Much more efficient than running the RS2000 inverter for light loads.
Food for thought as opposed to potentially spending thousands on solar and additional battery capacity if you only need it occasionally. That said, solar still intrigues us. I like the portable idea also, as we prefer to park in the shade at our favorite non hook up spots.
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