220v oven in van setup

JadesJades Registered Users Posts: 27 ✭✭
Hi all,

I just found a great deal on a nice 24” oven for my van. I like to cook, so the decrease in space seemed worth it.

I have a 200w 24v panel with 2 * 300amp 100amp/hour lithium batteries. Currently, I have a 120v AIMS pure sine inverter.

I’m wondering what I would need to do such that I could run the oven with my setup (hopefully, I wouldn’t need a different inverter, if that’s the case then I can track one down.

Also, the gas stove can run off propane but the igniter runs off of 120v…is there a way to reconfigure that to be 12v (is it that there’s a transformer to change it to 120v…or are these kinds of things setup to be 120v

Thanks much!

James


Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    edited June 27 #2
    From the manual:

    https://www.manualslib.com/manual/103476/Miele-H4780bp.html?page=69#manual
    Power supply
    The oven comes equipped with a 7.2 ft.
    (2.2 m) power cord with a
    NEMA 14-30 P molded plug ready for
    connection to a:
    208 V, 20 A, 60 Hz power supply.
    or
    240 V, 20 A, 60 Hz power supply.
    It looks like it is a split phase 120/240 VAC appliance... And no indication that it can be re-wired for 120 VAC only use (i.e., timer/controls could be 120 VAC, but the heating elements are probably 240 VAC.

    You might find the schematic on the back of the oven, or inside a removable panel and you can see if the over is native 240 VAC or not.

    Assuming the power ratings are accurate... 240 VAC * 20 Amps = 4,800 Watts

    If your batteries are 2 x 100 AH @ 12 volts (or 100 AH @ 24 volt battery bank):
    • 100 AH * 24 Volts = 2,400 Watt*Hours of stored energy
    Your oven probably draws upwards of 4,800 Watts--Or it would take 30 minutes to take your battery bank dead:
    • 2,400 WH stored energy / 4,800 Watt load = 0.5 Hours
    A 200 Watt panel in "pretty good sunny location" of 5 hours per day (summer), your expected harvest would be:
    • 200 Watts * 0.77 panel+controller deratings * 5.0 hours of sun per day = 770 WH per day
    • 770 WH per day / 4,800 Watt load = 0.16 hours = 9.6 minutes per day of a pretty sunny summer day
    Regarding the stove... It depends on the brand/model of stove--But a "basic" stove that uses an igniter for the gas oven is a 400-500 Watt @ 120 volt glow element... And it can be "on" whenever the oven gas flame is on (15 minutes to heat, and X minutes on every YY minutes cooking)...

    Your above loads are just way too large for your system as is--If you are planning on running from a 200 Amp solar panel.

    People with RV's have systems that run induction cook tops and even efficient A/C systems... But the solar is probably 500-1,000 Watt array, and the battery bank is probably 4-8+ 100 AH @ 12 volt batteries...

    If you can tell us more about your loads, location (nearest major city), and expectations (summer, weekends, or full time off grid--Any backup genset/power sources, etc.).

    For gas stoves, there are a few brands like Peerless (and RV stoves) that use zero or very little electric power to operate:

    https://www.warehouseappliance.com/category/peerless-premier-gas-ranges-with-ovens/

    Induction cook tops--They still use 1,800 Watts on full power (perhaps use 1/3rd that power for more efficient cooking/simmering and energy usage(?). So a largish solar system is still needed.

    And you did not talk about an electric refrigerator/freezer--Do you need to power one of this too? Lights? Water pump, etc.?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,358 ✭✭✭✭✭
    I don't see a wattage /amp rating for the oven.   Knowing how many watts it consumes and how many hours a day you will use it, is critical
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • JadesJades Registered Users Posts: 27 ✭✭
    Thanks for the info!

    This would be for full-time off the grid.

    I have a dometic energy efficient fridge that I think draws around 3 amps, a water pump, maxx air fan, some LEDs, and that’s pretty much it.

    I don’t use a lot of Energy, notwithstanding this behemoth oven.

    I actually have a 300w panel. Not an enormous difference compared with what you’re saying Bill (the person I bought the panels and batteries from was running AC and had 3*300w panels and 4 batteries…I sold two of the panels and two of the batteries). 

    I think Bill is right regarding the 20amps (is that per hour?). I would really only want to use it several times per week (if that)…but if it’s accurate that it would deplete the batteries in 30 minutes, then that would be impractical. If it could be used for an hour and the batteries would have -30-40% left, that could be doable.

    I live in San Diego now, so no shortage of sun. But do plan on traveling. On non-sunny days, I could absolutely get by without running it.

    I do not plan on having a backup source (generator or otherwise). 

    Another question: if the batteries are 3c and 100amp hours then isn’t that 300amps which would be more robust then something like a battleborn with a 1c 100amp hours?

    Re the stove, could I not just leave it unplugged and light it manually. Or only turn it on when lighting the stove?

    I’ll see what I can find out regarding possibility of 120VAC for the oven.

    Thanks much!

    James
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    If this is a "real" RV stove, I would be surprised if it needed 120 VAC and had "glow bar" igniters... I would have expect something more like this, with Pizo (or match) ignition and maybe a 12 VDC light for the oven pilot (I know nothing about the product--Just an example for research of stove+oven combination):

    https://www.amazon.com/Atwood-Dometic-Cook-top-RV-1735-BSPSX2-52938/dp/B08N5G2Y48

    You don't want to "play" with gas appliances and their safety systems. There are there for a reason--To prevent your vehicle from filling with propane if the pilot blew out or something else happened. A gas explosion is not something you want to have happen (and propane is heavier than air--So it tends to settle towards the floor and not rise to a vent fan).

    Details matter here--So for your existing stove a Brand/Model and/or URL would be helpful.

    For the Dometic Fridge--Again the model would be helpful. And need to know if 3 amps @ 12 VDC or 3 amps @ 24 VDC, etc... And is it a compressor fridge (12vdc/24vdc/120vac) or an absorption type (LPG/12vdc/120vac)?

    https://www.dometic.com/en-us/food-and-beverage/refrigerators/rv-refrigerators/dometic-crx-110s-136380

    A "typical" Dometic compressor fridge would draw around 600 WH per day (inside a "warm" RV.

    A 200 Watt panel mounted flat to roof on an RV in San Diego:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    San Diego
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a horizontal surface:

    JanFebMarAprMayJun
    3.30
     
    4.10
     
    5.21
     
    6.34
     
    6.42
     
    6.08
     
    JulAugSepOctNovDec
    6.28
     
    6.15
     
    5.28
     
    4.27
     
    3.61
     
    3.09
     

    As you can see--Even in San Diego--An RV mounted flat to roof panel does not do great in winter... Say you needed 1,000 WH per day (fridge+lights+water pump plus a little extra harvest to cover for cloudy days):
    • 300 Watt panel * 0.61 off grid system eff (Lithium battery) = 183 Watt "effective" harvest for loads
    • 1,000 WH per day / 183 Watt effective harvest = 5.5 hours of sun per day
    6As you can see--Even in summer you barely break 6.x hours of sun per day--And in winter only ~1/2 of that.

    Ampere is a "rate"... Like Gallons per Hour for pumping water (technically, Joules per second). Amp*Hours is an "amount" (like gallons pumped)... However, it is not the full description of energy usage... We need to also know the Watts and Watt*Hours... Sort of like pumping water--did we pump the water up 1 foot, or up 100 feet (higher lift, need more energy to move the water up).

    So... When dealing with only a single voltage system like a 12 or 24 VDC battery bank... Amps and Amp*Hours does work OK (assuming we know if 12 or 24 VDC system).

    However, when working with both 120 VAC and 12/24 VDC systems--We turn everything into Watts and Watt*Hours to make the math less confusing.

    AH = Amp*Hours = Amps * Hours (yea--obvious) -- But we need to know at what voltage
    Power (rate) = Voltage * Current
    Energy (amount used) = Voltage * Current * Time (hours in our case)

    I.e... A 3 amp refrigerator uses how much power and energy?
    • 3 amps * 12 VDC = 36 Watts
    • 3 amps * 24 VDC = 72 Watts
    • 3 amps * 120 VAC = 360 Watts
    Assuming the refrigerator runs 50% of the time (like 30 minutes per hour--Just to show the math):
    • 36 Watts * 0.5 duty cycle * 24 hours per day = 432 Watt*Hours per day
    • 72 Watts * 0.5 duty cycle * 24 hours per day = 864 Watt*Hours per day
    • 360 Watts * 0.5 duty cycle * 24 hours per day = 4,320 Watt*Hours per day
    So you can see--"Same Current' but different voltage assumptions--And we get very different answers on how much energy per day the refrigerator used per day.

    Regarding: 
    Another question: if the batteries are 3c and 100amp hours then isn’t that 300amps which would be more robust then something like a battleborn with a 1c 100amp hours?
    You need to look at "all" the specifications... A Battleborn 1C battery is designed to be (mostly) "fool proof"... They have circuity inside the battery to limit excessive charge/discharge current and running too hot or too cold of battery. They have internal MOSFET transistors (or similar) to turn off the battery is it is running in unsafe or damaging conditions.

    You can get cells that will be 3C discharge--But they may not have any protection circuits--And you would need to add a BMS--Battery Management System to make sure the cells are protected from operating outside their specifications.

    Also, a 3C battery may not have the same number of charge/discharge cycles as a 1C battery would--There are always trade-offs.

    For an off grid system (RV, Cabin, etc.)--There is not usually much use for battery bank you can discharge in 20 minutes (3C rate)... Watch TV for 20 minutes, then shut down. Run the oven or stove for 20 minutes, then shut down....

    Guessing--I suggest that you would like to run your "normal loads" for ~5 hours a day (or in the evening) during bad weather (no sun)... For a cabin that would be for ~2 days (10 hours total or 5 hours a night for 2 days). Having cells that could support 3C discharge may be great for starting a deep well pump--But not that useful for running a fridge, LED lighting, and an RV water pump. So 1C (lithium) batteries are still way more capable than what we normally use for Lead Acid batteries in a C/5 or C/8 typical max continuous discharge (5 hour rate, or 8 hour rate). The typical Lead Acid deep cycle storage battery is rated for C/20 hour discharge rate (20 hours of discharge)--And that works pretty well for Cabin and RV use.

    You really need to make an energy budget for your "desired loads" an how you operate them (i.e., Watt*Hours per day for each load)... Then design a system that can support those loads. It is almost always cheaper to conserve energy than to generate it. Getting very efficient appliances helps a lot.

    A 300 Watt panel in San Diego in December:
    • 300 Watt array * 0.61 off grid Lithium AC system eff * 3.09 hours a day (long term average December) = 563 WH per day
    • 600 Watt array * 0.61 off grid Lithium AC system eff * 3.09 hours a day (long term average December) = 1,127 WH per day
    • 900 Watt array * 0.61 off grid Lithium AC system eff * 3.09 hours a day (long term average December) = 1,681 WH per day
    The typical "useful" stored energy in a 200 AH @ 12 volt Li Ion battery bank would be:
    • 200 AH * 12 volts = 2,400 WH of "raw storage"
    • Derate for "safe and long life" operation = 90% full - 20% empty (high/low state of charge) = 70% "useful" capacity
    • 2,400 WH "raw" * 0.70 "useful capacity" = 1,680 WH of "useful" stored capacity (overnight discharge, 1 day without sun, etc.).
    In general, solar panels are historically "cheap"... And batteries (especially Lithium Ion) are quite expensive (yes, prices may be coming down some)... The first choice for a solar power system is to see how large of an array (how many Watts of panels) you can install. A large array does a better job of keeping your batteries "happy". Adding more batteries without more solar/other charging sources--Usually expensive, and still does not give you more energy per day...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 706jim706jim Solar Expert Posts: 436 ✭✭✭✭
    Electric oven off grid power fine, off of solar power forget it.
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 28th year.
  • JadesJades Registered Users Posts: 27 ✭✭
    706jim said:
    Electric oven off grid power fine, off of solar power forget it.
    So you’re saying there’s a chance:) What do you mean by “off-grid” vs “off-solar”? Generator vs battery?

    Bill, as always, you’re responses are thoughtful, informative, and appreciated. 

    I agree with the principle of conservation…wasn’t sure whether I could make this work. (My understanding is that it is efficient…just not propane…is that wrong?) Was a good deal and a sweet oven, but looks like I will have to resell. I see another oven only device (a Furrion) that is a good price that is propane.

    I installed a Daly BMS for the batteries and top charged before hooking-up…learning as I go. It has 1500 cycles, which seemed good and par for the course. 

    Re discharge rate: all good to know; I was just under the impression that the total capacity of the battery is amp/hours * discharge rate. Agreed, not much reason else to go for 3C…I mostly see these being sold for electric motorcycles…not sure why the person I bought them from (who also had a van) originally bought them. But are you saying that that isn’t the case is we’re just dealing with a 12v DC system?

    No, I don’t think the stove was made for an RV; I think it was probably made for a small apartment. Here is the model #KM 360 G. It’s a Miele.

    The model #for the fridge is CF-80-AC-120-U it says version B. Dometic. I can run it from a DC car adapter, so that’s what I do.

    I’ll have to go through and read everything again and will probably have more questions and will definitely have to get a better idea of budgeting, if only for the sake of gaining a deeper understanding of the system (I thought I might have some energy to spare in the bank) with this oven, though now that we’re getting into “luxury” items, I see that it will be a good practice. I’m a bit surprised that and oven takes so much energy…I know there are people who get by with space heaters (not a great idea, I know)…heating a larger, less efficient space, albeit at a much lower temperature. Obviously, I have much to learn!

    Thanks!

    James


  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Not to put words in Jim's mouth... Powering an electric oven from the grid (off the grid)--Easily done (just monthly power bills). Powering from solar (off of solar)--Not so easy.

    Anything can be done with enough time/money/effort... But to be cost effective, that is something else. An old engineering saying--You can have cheap/fast/reliable--Pick any two.

    So back to reality. If you were in a cabin/home in a sunny part of the world and had the land and money--Yes, you can build an off grid solar power system to run an electric oven... Solar panels have gotten cheap (prices may be going up some with sanctions against China and such). Batteries have always been an expensive part of off grid solar--And they are the things that have a limited life (cheap golf cart batteries--3-5 year life... Expensive traction batteries/possibly Li Lion, perhaps 10-15+ year life). Even power electronics (charge controllers, AC inverters, and your cell phone/laptop computer--10+ years is doing really well.

    So--Comes back to hardware costs (and labor if you pay somebody else)--$0.10-$0.40 per kWH from grid... For off grid, something like $1.00 to $2.00+ per kWH (these are really variable--Some folks have gotten down to $0.50 per kWH for their systems--Looking for sales, used fork lift batteries, managing systems to harvest/use kWH when sun is shining, etc.). For example--You bake one day a week--For an RV power system you can store 1-2 days of energy. If you make the system large enough to support one day a week load (large array, large charge controller, large battery bank, large AC inverter)--For the other 6 days a week--The extra power is "unused" and simply tossed away (batteries full, you are at work not using the power, etc.)... It costs money to build that very capable system that you only use 1 day a week to capacity (using your race car as a daily driver)...

    But if you look at your RV... Off grid electric costs are 5-10x the cost of utility power--Plus you pay much of the costs "up front" to install your system--And then more 3-8 years down the road for new batteries, and 10+ years again for new power electronics).

    For an RV--You are space (and weight) constrained... You only have so much roof top. You can only install so many batteries (Li Ion batteries are very interesting--High density storage and light weight--At the expense of $$$$). Figure out how many Watts of solar panels you can mount--Will you tilt them (more important at higher latitude--Towards Canada; and during winter with low sun angle). Where will you be--US southwest or Northeast in New York?

    In your case--You really have two paths you need to follow--Defining the appliances you want to use (specifications, use a Kill-a-Watt meter to measure actual energy usage, etc..). And how large a solar power system can you install in your RV... Once you do those two calculations, then you can design a paper systems (or a few paper systems) and see if your solar system would run your loads, and if your wallet has enough $$$$ to buy the parts and install.
    ll
    Large oven--more power just to heat, and leak heat through walls. Small toaster oven, less to heat, and even if not well insulated, there are less square inches of walls for heat to leak through.

    If you are interested in Electric power in your RV--Get a Kill-a-Watt meter (they are not that expensive)--And measure the energy usage of your toaster oven, microwave, coffee maker, laptop computer, etc. as you plan to use them in your RV and see how much energy you do use. "Do the Math" is my mantra. It only cost your $30 for a Kill-a-Watt type energy meter to get real numbers for your usage.

    https://www.amazon.com/s?k=kill+a+watt+meter&ref=nb_sb_noss_2

    There are DC versions of the same, if you have "significant" DC loads (LED lighting, water pump, vent fan, etc.).

    Efficiency is not the only factor--Scalability and suitability for your needs too... 2-4 diesel locomotives are very efficient pulling a 100 car train... But no where near cost effective when driving down to the store for a gallon of milk (walking, electric bike, econo-box car, pickup, etc.--Right tool for the right job).

    We have had a few requests over the years to help with designing a "green" Food Truck... I see food trucks in my area doing just fine with a 3 kWatt genset and 2-5 gallons of gasoline per shift. That is (very roughly) 8,000 WH to 20,000 WH (8 kWH to 20 kWH) per day... For an "on board" solar power system--Just no way to harvest/store that amount of solar electricity in the space of a food truck (fridge, fryers, grill, space for food/drinks/etc.).

    A "cabin/small efficient home"--You might get down to 3.3 kWH (3,300 WH) per day for a "near normal" electric existence (using propane/wood/etc. for heating, cooking, water heating...).

    1,500 Cycles sounds good... You get into questions of "what is a cycle"? Is it discharging from 90% to 20% or is it discharging from 90% to 75% and recharging... The usual answer is they are both "one cycle" in battery life... How long does 1,500 daily cycles last:
    • 1,500 Cycles / 365 days per year for full time off grid = 4.1 years of "cycle life"
    And if you charge over 90% or discharge under 20%--For lithium cells, they can have less cycle life. (not saying you will have 4.1 years of battery bank life--But that is what the specifications are telling you--Yours may last longer or die sooner--Have money in the bank to fix your solar system--You are the power company).

    And no--It is not "...the total capacity of the battery is amp/hours * discharge rate... Amps is already a "rate". So it is just Amps (Amperes). Like gallons per hour.... Amps*Hours ("*", not "/") is an amount 10 gallons per hour * 2 hours = 20 gallons pumped.

    Think of a 20 Gallon Water Tank... It holds 20 gallons (like 200 Amp*Hours). A smaller pump may discharge at C/8 discharge rate (run a sink, shower, etc.). A fire engine may discharge at 3C Rate for a short time (getting a pumper to the scene, connect to hydrant or backup tanker truck a bit later):
    • 20 gallons / 8 hour drain rate = 2.5 gallons per hour useful draw (great for RV water usage)
    • 20 gallons / 1/3 discharge rate = 60 gallons per hour useful draw (great for controlling a fire)
    • 20 gallons / 2.5 gallons per hour = 8 hours of "useful water"
    • 20 gallons / 60 gallons per hour = 0.33 hours = 20 minutes of "useful water draw until hydrant/tanker connected"
    For an electric bike/scooter/car... You may get 20 miles on flat level ground with a 100 lb driver... I live in an area with lots of hills, and prevailing afternoon winds--I may only get 5 miles on a scooter charge and I am (unfortunately) >> 100 lbs) (completely made up numbers for example). I certainly want a battery bank that can go up the nearby hill to school (high discharge rate for short time)... But I will not have 20 mile battery life (still air, cruising speed, flat ground).

    Your "stove" is just a cook-top:

    https://www.appliancesconnection.com/miele-km360g.html (I think this is your cook-top)

    And it is made for the home, and appears to be made for Natural Gas only.

    It has electronic (typically automatic spark) ignition. You can with an AC inverter (I would guess TSW/PSW type, not MSW). These do not use much power--And should work OK with just using matches...

    HOWEVER--It appears to be Natural Gas only--No propane conversion):
    LP Conversion    No
    Gas Type    Natural Gas
    For peace of mind: the gas shuts off automatically in the event of excessively long operation.
    With automatic burner timer/shutdown, appears that running without AC power could be problematic (will it even run without AC power)?

    And since made for home use--Probably not UL/NRTL rated for use in RV...

    I would not use this in your RV... Too many strikes against it.

    Your fridge/freezer is an AC/DC compressor type (not LPG):

    dometic.com/en-us/food-and-beverage/coolers/electric-coolers/dometic-cf-80-139581

    From an Amazon page, says energy usage is:

    https://www.amazon.com/Dometic-Electric-Powered-Cooler-Freezer/dp/B075J5TL77

    2 AH/H -- 2 Amp*Hour per Hour... When you do your math, that is 2 Amps (hour per hour cancels out)--Amps is already a rate.

    The 24 hour per day usage:
    • 2 Amps * 24 hours = 48 Amp*Hours
    • 48 Amp*Hours * 12 volts = 576 Watt*Hours per day (41F interior at 90F ambient @ 12 VDC power) 
    Not a "terrible" amount of energy usage... But just this one appliance would easily keep your 300 Watt occupied with only a little bit of "extra" power (depending on location, weather, etc.). Refrigerators are just "energy hogs"... They frequently are the largest user of energy for an off grid system (a full size energy star refrigerator 

    You are "not there yet" for living in your RV just yet... Most people overestimate the amount of energy a solar power system can generate, and underestimate their energy usage--Just how we are "wired".

    My wife has gotten hooked on Youtube and Camping Vans... Search for "Van Life" there and start seeing what people are doing (and for their recommendations). Note that some of these folks have spent a lot of time and $$ on their conversions--And many of them are very nice and seem to be quite "livable". 

    https://www.youtube.com/results?search_query=van+life

    Many have some relatively large solar power systems with induction cook-tops and even microwaves and the occasional toaster oven--And the larger systems frequently (usually?) are connected to the Van's alternator (or even a second dedicated alternator) to provide power during heavy loads/driving days/bad weather/parked under trees), or even have a backup genset.

    Just play with the kill-a-watt type meter on your present devices (home, van, fridge, computer, cell phone, microwave, toaster oven, etc.) and see what your "real" energy usage is... We are frankly quite spoiled with utility provided power. Making your power, and paying for the hardware and repairs/upkeep--Not a lot of fun for most people.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    To answer your 12 VDC question... The "standard" for RVs (smaller non-commercial) is a 12 VDC battery bus (lights, water pump, fan, 12 VDC adapters for cell phone, laptop, etc. converters)... My suggestion is that your actual power draw is around 1,200 to 1,800 Watts maximum.

    For a 24 VDC system... You can find some 24 VDC native stuff (LED lighting, RV water pump, some "truck" and "marine" accessories, etc.). Suggest maximum draw at 2,400 to 3,600 Watts

    For 48 VDC system... That is for larger home off grid power systems that are over 3,600 Watts or so draw.

    The above assumes that there will be a 2x surge draw (starting pumps, motors, tools, etc.) for AC inverters and DC loads.

    There are lots of issues between 12/24/48 VDC systems... But you really need to address your loads/power draw first--Then you can look at the "optimum" for your needs.

    There is also the design which supports almost no DC loads, and runs everything off of 120 VAC (North America) for cabins and RVs... Wiring is "standard" NEC wiring (breakers, boxes, ROMEX, etc.) from Home Depot (cheap and easy to get) (even ~240 VAC for larger loads and Euro RVs/Homes).

    The big think with low voltage... You need heavy wiring to carry significant loads any distance more than 10+ feet or so--And copper is expensive, and heavy wiring is stiff/hard to install. You can send a lot of 120 VAC power (1,000 Watts or more) 100 feet or more with a simple 14 AWG cord.

    And you look at your needs... If you have a need for 12 VDC appliances/common adapters--Then 12 VDC may be the bank you want.

    But if most of your stuff is 120 VAC--Then the losses of the inverter (5-15%)--Just a slightly larger solar array and battery bank can make up for those losses. And 120 VAC plugs (15-20 Amps) are a lot nicer than 12 VDC plugs (typical 10 Amps). And the power available from 120 VAC is >>> than 12 volt "car standard" plugs:
    • 12 VDC * 10 amps = 120 Watts
    • 120 VAC * 15 amps = 1,800 Watts
    Just to give you an idea of energy need "brackets":
    • 500 WH per day (500 WH per day / 12 volts = 42 AH per day) -- LED lights, cell charging, RV Water pump, Cell Phone charging
    • 1,000 WH per day (1,000 WH/12 volts = 83 AH per day) -- Add fan, efficient laptop computer, more lights
    • 3,300 WH per day (3,300 WH/12 volts = 275 AH per day) -- Refrigerator, clothes washer, some microwave/electric cooking
    • 10,000 WH per day (10,000 WH/12 volts = 833 AH per day) -- A normal energy efficient home with natural gas/propane for heating/cooking/hot water
    • 33,000 WH per day (2,750 AH @ 12 volts per day) -- Electric hot water, heat, cooking A/C
    • 500 WH per day * 30 days per month = 15,000 WH per month = 15 kWH per month (how home energy is billed)
    • 1,000 WH per day = 100 kWH per month
    • 3,300 WH per day = 100 WH per month
    • 10,000 WH per day = 300 kWH per month
    • 33,000 WH per day = 1,000 kWH per month
    The smaller systems (500/1,000 WH per day) work fine on 12 VDC

    The mid size 3,300 WH per day is 24 or possibly 48 VDC battery bank

    The larger systems (10,000+ WH per day) are 48 VDC battery bank.

    I was feeling bad--I had been throwing a lot of words at you--But I wanted to give you some numbers you can compare with a Kill-a-Watt meter/home energy bill and see that the "real numbers" are like.

    Energy usage is a highly personal set of choices... And what may work for me may not work for you...

    You really need to define your loads/usage first... The design a system that will run those loads. If you build the system first, then it may not run the loads you need (or may run them in summer in the South West), but not elsewhere.

    And the numbers above are just SWAGs (scientific wild ass guesses). But are a good start for you to aim at... Mostly propane loads for heating/cooking, 1,000 WH per day can work. Add a refrigerator, then 2,000-3,300 WH per day system--But you are getting larger and more expen$ive... May not be what you want/need. A 3.3 kWH per day system is not "small solar".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    One appliance I find indispensable offgrid is a multifunction rice cooker which has settings for baking bread, cakes as well as claypot and slow cook. Very efficient drawing 800W for a short initial period then intermittently uses 150W to maintain temperature, takes up little room which is at a premium in mobile applications, the one I have is this https://shop.panasonic.com/support-only/SR-ZG185.html picture below.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • 706jim706jim Solar Expert Posts: 436 ✭✭✭✭
    Just to give one example I've mentioned before:

    I used my Skil saw to shorten about 40 2 x 6's using my solar battery system. Surely saved a lot of work compared to sawing them by hand. A rough estimate of power used 1500 watts for maybe five minutes. Brew a pot of coffee about 1000 watts for ten minutes in fact more power used than cutting 40 boards. This is a good example of  how power can be efficiently used (the Skil saw) and not so efficiently used (coffee pot).
    In the case of the 220 volt oven it's not that you CAN'T make it work, but at what cost? Remember a thermal oven runs for a lot longer than a coffee pot.
    Island cottage solar system with 2400 watts of panels, 1kw facing southeast 1kw facing southwest 400watt ancient Arco's facing south.Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 28th year.
  • JadesJades Registered Users Posts: 27 ✭✭
    Thanks, all.

    Wealth of info.

    Maybe I was misreading this page on battery specifications at MIT: http://web.mit.edu/evt/summary_battery_specifications.pdf. If you look at C and E rates, I read that as amp hours * discharge rate.

    So I'm actually already in a Van, so a little late for the Kill-a-watt meter. Where I work at UCSD has a kitchen and a fridge, so I've been using that. I finished up the most important things first (bed) and have slowly been building it out. After I've finished oiling the counters and have them installed, I'll take some pictures. 

    So pretty familiar with Van Life. And yes, some people have certainly taken it to a whole new level. I'm trying to find the middle ground...make it beautiful and unique, but also build it myself. Mostly out of wood--I belong to a wood shop here in San Diego. If I were to do it again, I would've found a place to work on it before moving into it (and having storage). I've found that there are so many details, that it's really impossible to plan everything out. I've taken way too many trips to Home Depot. But I've enjoyed most of it. I originally bought a Dometic stove/oven, but I haven't hooked it up, and I'm not crazy about it. (It honestly just feels cheap). It's been a process to have less shit, but I want the stuff I do have to be nice (though I try to find deals as much as possible). Ultimately, I'm down for the experience, and I want to save up for a house down the road. I had a string of Volvo 240s and worked on those and realized that it gave me some satisfaction. I replaced the water pump on the Sprinter a few weeks ago and have a couple other things I need to do. I feel like having a greater connection to the energy one uses will bring the same kind of satisfaction. (Frankly, I'm so glad to be done with roommates and stupid expensive energy bills). I wish people would conserve more, but I also don't want to be the one offsetting absurd consumption. Now, I guess, will be the test of how much I use (without a 240V oven). 

    Tomorrow I turn 36. It's funny, growing up there was that Chris Farley SNL bit about the "van down by the river." LOL...I didn't think that would be me, but I honestly haven't minded it. I do look forward to finishing everything up and traveling...and someday owning a home.

    Since the fan, water pump, lights, diesel heater, I decided to make the system 12v. I thought about going with the inverter on all the time route, it just didn't seem to make sense (especially with the 8-15% energy cost). I also thought about a 24-volt system; but given that the fan and water pump were both 12v; it didn't make sense to use transformers on those. I use mostly 12ga and 14ga multi-stranded wire. I've done mostly 12v sockets for plugging in electronics, but it would be nice to have a 120V socket or two (do most people just use an extension cord for that and run it to a socket?)...I also check out some van life videos on that.

    Work has been a little crazy over the summer, but I need to start devoting time to the project each day. It's almost there. 

    So I spoke with someone at Miele today. They do offer a propane conversion kit for $30. I spoke with someone who knew nothing about ovens and was the go between from a tech and I, but she (via the tech) did assure me that the kit would work. It also outlines how to do the procedure in the manual; it seems to be replacing the jets and possibly the regulator.

    Regarding running it without the cord, I found this:

    So it seems like the options are to either run it without the cord or run it with the chord and use the inverter (which isn't a bad option, if, as you say, it doesn't end up using that much power).

    I do also have an insta-pot. Not sure how that compares with your Rice cooker, but it says it uses 1000W, so I take it that that is over the course of an hour (which would be crazy, if two hours of running the fridge is one hour of cooking). It functions primarily as a pressure cooker, so it probably uses more than the rice cooker you post, Mcgivor. It also can cook Rice in 12 minutes. Seems to be energy efficient.

    This post here suggests that the Dometic 80 CF fridge uses ~ 2.2AH per day: https://expeditionportal.com/forum/threads/dometic-cf-80-fridge-mini-review.47755/. I remember when I had batteries hooked up to the fridge when I first purchased them (using the inverter), they ran it for what felt to be about 2 weeks (super scientific, I know).

    I'm also familiar with the part you talk about, Bill, that runs from the alternator to the batteries and charges them (which is why, in another post, I thought it might be possible to go reverse, from the solar to the starter battery). Living in San Diego and working here, I've had a much greater need for the latter (vs the former), but perhaps it is something I should install, because there comes a point at which it becomes much harder to take a part the van to add something. And I plan to start traveling a bit, soon.

    Thanks much!

    James



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