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Old 09-22-2020, 12:59 PM   #1
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Help With Getting Started

I really need some help with figuring out the electrical system for our skoolie.
I have no idea how much power we'll need, let alone what we'll need for it.

The first step is to calculate how much wattage we'll need in a day, but we have no idea. See, we don't have the appliances yet, or know how many lights we'll have, what kind of security system we'll use, etc. My fiancée and I have rented cheap rundown places our entire lives, so we aren't homeowners with anything to reference from.

We have a list of what we would use in the skoolie, but we don't know how to calculate, because we don't know how often those things will be used every day.

One thing we do know is that we want to draw power from shore, solar, and the alternator.

How do you calculate and prepare for something when everything is a giant question mark? How did you guys know where to go and how to start?

Thanks
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Old 09-22-2020, 01:20 PM   #2
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I’m having the same situation over here. Plus I’m driving with a fridge and freezer with no power to them 😞
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Old 09-22-2020, 02:10 PM   #3
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To answer the question somewhat vaguely, a simple approach would be to acquire a measuring device (kill-a-watt meter, etc) and try it on a few appliances, set some baseline expectations. Appliances also typically state their ratings, which you can use to get an estimate on energy cost using well known formulas. When you add solar to the mix, you now have to start talking about generation and capacity, not just total appliance consumption.

It sounds like you need more of an actionable plan on how to estimate your needs, kind of hard to deliver without knowing a little more about what you hope to accomplish.

Quote:
Originally Posted by TheOwlSpirit View Post
I really need some help with figuring out the electrical system for our skoolie.
I have no idea how much power we'll need, let alone what we'll need for it.
There's so much to this if you're not already somewhat familiar that sometimes it is hard to convey the needed information in a forum post or two. If you would like to have a more real-time conversation (over chat or phone) to kickstart your knowledge, I'd be happy to oblige. Then you can follow up here with specifics as needed.

There's some great users here able to articulate information in an easy to consume way, just want to make the offer in case you're feeling stuck. PM me if you are interested. Duckstuff, that includes you as well. In the mean time you can also start by elaborating on your use case- what kind of devices you hope to power, when you hope to power them (during the day where you may have full sun versus at night), etc. The more we know about what you hope your build will look like, the better we can address the potential energy needs.


Best of luck.
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Old 09-22-2020, 02:11 PM   #4
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I think we have all started out in the same boat as you guys. I really don't know what my power needs will be with my finished product. I do plan on being able to run 3 roof top A/C units, so my philosophy is bigger is best. I am starting with a 50 amp shore connection because 30 would be too small, and 50 is the biggest typical set up. I plan to eventually add solar, but not until I'm essentially done with everything else and know what my power needs will be. The key to doing it this way is to build in the ability to add these things as I go. I built in a 6500 watt generator because it was what I already had, but made it possible to replace it with a 12,000 watt 50 amp unit down the road. If the current one is sufficient, I'll leave it there. We plan on traveling and being hooked to shore power most of the time, with very little boondocking, so I may never add more than a small solar system just to keep a small battery bank topped off. Or, I may not add solar at all. For me, getting into the bus and traveling will be the key to deciding what our end needs will be. I anticipate months of traveling at a time which will have different needs than my wife who thinks a few weeks at a time will be enough.
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Old 09-22-2020, 02:32 PM   #5
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I am definitely stuck and could use all the help I can get, so I appreciate your offer! I guess I'm shy to share what appliances we want to use, because I don't know if it's too much to expect, or if we're being too "extravagant". I just don't want to get laughed off a forum for choosing a larger fridge than what I've typically seen in skoolie photos, etc.
Obviously some of the power draws that we want to have will be used when we're connected to shore power, as I doubt something like a gaming computer would last long on a solar grid.

But see, I don't know enough! Some people make it sound like you can do a lot with a solar grid, others make it sound like you need to have the bare minimum always.
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Old 09-22-2020, 02:48 PM   #6
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Quote:
Originally Posted by TheOwlSpirit View Post
I guess I'm shy to share what appliances we want to use, because I don't know if it's too much to expect, or if we're being too "extravagant". I just don't want to get laughed off a forum for choosing a larger fridge than what I've typically seen in skoolie photos, etc.
Well.. I used a full size residential fridge in my rig. Some would call that extravagant, but I'm definitely not the only one doing that, and it indeed does run off of solar quite easily.
ima_7ddda4b_20%.jpeg

Even the ice maker works, as of yesterday. (Click to animate)
ice_dispenser.gif

Also: microwave oven, coffee maker, induction cooktop. All I've ran off solar. I've even ran heat off of solar, although I need upgrades to make my system truly ready for that.

And you know, some people are going to laugh, let 'em. What you can power is limited first by your wallet, then by how much space you have for panels/batteries/etc, then by your imagination.

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But see, I don't know enough! Some people make it sound like you can do a lot with a solar grid, others make it sound like you need to have the bare minimum always.
Those are different people with different wants and needs, different expectations. It sounds like you're trying to set your expectations and that's a good place to start, but don't get stuck there and don't let others decide that for you. There is such thing as expecting too much, I don't see that happening in your case.

I sized my system for a conventional residential electric dryer. That's 4000W continuous, just about the definition of insanity. There's very little you cannot run with the right setup.
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Old 09-22-2020, 02:51 PM   #7
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You can't have too much battery or solar or inverter.
If you are wanting to figure out how much all that costs, budget thousands of dollars should have you covered. Your piece of string is long enough.
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Old 09-22-2020, 03:02 PM   #8
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That makes me feel so much better, thank you.
With our current expectations for the bus, it will definitely be on a residential level as we're going to be living in it full time. Some of the appliances we want to power are fridge, gas range (has a convection oven) along with its ventilation, dishwasher, washing machine, and then various countertop appliances that will obviously not be used all at the same time (Instant Pot, Dehydrator, etc.).
Other things include a gaming computer, TV, consoles, etc.

I know, it's a lot of power. That's why I'm feeling shy asking about it, because the list seems like a lot.

Our current lifestyle is generally pretty power-conscious, however. We turn off everything that we're not using (lights, unplugging the toaster oven, the computer gets unplugged every night, etc.), and our power bill isn't very much, even with everything we use. I have high hopes that we can make this work, even if we have to save money for a while longer to have the right set up.

I just reeeaally don't want to screw it all up.
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Old 09-22-2020, 04:06 PM   #9
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That makes me feel so much better, thank you.
With our current expectations for the bus, it will definitely be on a residential level as we're going to be living in it full time.
This is reasonable, lets itemize your stuff, estimating how much time these will be running each day:

Quote:
Originally Posted by TheOwlSpirit View Post
Some of the appliances we want to power are
  • fridge - 24/7
  • gas range which has a convection oven along with its ventilation - 1h / day
  • dishwasher - 1h / day
  • washing machine - 2h every other day
  • Instant Pot - 2h / day
  • Dehydrator - ???
  • gaming computer - 4h / day
  • TV - 4h / day
  • consoles - 2-3h/day

So now we need to figure out how much each appliance consumes over that time period. Like I said, you can get a meter:
https://www.amazon.com/Poniie-PN1500...dp/B07VPTN8FZ/

You'd plug your fridge into it, reset the counter to zero, and then wait 24h. The reading in Wh or kWh is what you want.
For the gaming computer, do the same thing. Plug it in via the meter (along with the display) before you use it. After you are done, turn it off and check the meter. The Wh reading is an estimate of what you will use in a day.

Then you add it all up.

Lets do some theory math: Lets say the average draw (it kicks on as needed, most of the time it is off) for the fridge is 80W. Well, to find out how much it would use in a day, multiply 80W times 24 Hours = 1920Wh (Watt-hours).

That means for the fridge, you need to generate at least 1920Wh (well, plus about 10%-30% in losses) during the day to power the fridge. Now lets ask: Would a single 100W solar panel be enough?

To answer this, I've found that I make around 4 times the size of my solar array in energy per day. So 100W * 4 hours on average (sunrise to sunset, not always in full sun) = 400Wh. So not enough. Well, what would be enough for that one appliance?

1920Wh / 4h = 480W. So right around 500W, you will be generating enough energy during sun to offset your costs for the whole day. This is roughly how I estimate my generation needs.

Now of course there is such a thing as night, when you will not be making any energy. During this time, your fridge needs to use batteries to operate! I like to take half of the rated daily usage to figure this one out: 1920Wh / 2 = 960Wh of usable storage. If we are using 12V batteries:
960Wh / 12V = 80Ah (Amp Hours). Multiply this by two (Lead acid batteries, only around half of your capacity is usable) you have 160Ah.

So to conclude, to power just the fridge that draws 80W on average, a 500W of solar and two (common size 12V 100Ah AGM batteries would be sufficient to keep you going . Again, plus around 30% in panels/batteries for a nice comfort zone. That's actually fairly modest!

But then comes a rainy day: What do you do then? Well, if it rains for weeks you're outta luck. Very hard to combat long periods without any reasonable amount of solar input. But what you can do is say "I want to be able to last three days without good sun". So you'd take 1920Wh, the daily usage, triple it (5760Wh over three days). With a 12V battery bank, this means you'd need 5760Wh/12V = 480Ah of usable battery capacity. Again as lead acid batteries can only use half their rated capacity, you'd need ten 12V 100Ah batteries to get through. But seldom even with bad weather do you make nothing- usually you can at least offset some costs even on a somewhat rainy day.

Now this is all very rough math that I'm sure if I read enough times I can find some fault in, but the process is pretty straightforward:
  1. Either measure, or estimate daily usage for an appliance.
  2. Add a little percentage on top of that to give yourself some safety.
  3. Figure out how much time in the day that appliance will need to run at night, this will determine your battery needs each night.
  4. Your panel sizing is pretty simple- combined daily usage estimates of all appliances + around 10-30% will bake in enough safety to allow you to not only use appliances during the day, but recharge.
  5. Your battery bank should be sized based on how many days you want to be able to last without decent solar generation (with larger arrays, you will still make a good amount even in bad weather).

Quote:
Originally Posted by TheOwlSpirit View Post
I know, it's a lot of power. That's why I'm feeling shy asking about it, because the list seems like a lot.
It does add up...

Quote:
Originally Posted by TheOwlSpirit View Post
I have high hopes that we can make this work, even if we have to save money for a while longer to have the right set up.

I just reeeaally don't want to screw it all up.
So here's the thing: If you design your system to scale, you can start small and move up as needed to accommodate yourself, without having to redo everything. If you make room for panels on your roof, you don't have to install them all at once- put a couple up to start, play with it, see how it works. You don't need a gigantic battery array at the very beginning, start with just enough to get off of the ground and add batteries as your needs increase (they will, over the course of the build).

With the right system design, you can start small and flexible for cheap, but not have to redo much at all. My system went through 4 or 5 iterations, increasing in size and capabilities each time. There were a couple times I needed to change components (charge controller, inverter), most of the time I could get away with adding components. And I timed changing components in a way I could repurpose them for other tasks.

You don't have to build a full system up front, you can start with the basic components, add onto them and not waste much if any money. In fact, that's probably the best way to learn about the components and how to maximize their usefulness to you.


Sorry for the long post. If you'd like to talk it through, feel free to PM me and we can exchange details. Maybe the above is enough to get you on the right track. Let me know if you have any questions.
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Old 09-22-2020, 05:31 PM   #10
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Argh! I wrote a response to this, but my session "timed out" and I lost the entire post. I'll try to write what I can remember.

The math for all of this is where I get so, so lost. I like number crunching and figuring things out, but electricity is a whole other beast.
I don't have the appliances for me to get the wattage for, but I was able to write down their Amp and Voltage requirements based on their information online.
I thought I'd try to figure out the wattage myself, but the numbers don't make sense. Here's the formula I found:

Watts = Amps x Volts

So, I tried to use this for the info I got on the fridge:

15 Amps x 115 Volts = 1725 Watts

That's a lot, seems like. It doesn't seem like I'm doing this right, so I'm very confused and somewhat frustrated.
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Old 09-22-2020, 05:53 PM   #11
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Argh! I wrote a response to this, but my session "timed out" and I lost the entire post. I'll try to write what I can remember.

The math for all of this is where I get so, so lost. I like number crunching and figuring things out, but electricity is a whole other beast.
This is because there's a few overlapping concepts at play that you're confusing. Let me demonstrate.

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I don't have the appliances for me to get the wattage for, but I was able to write down their Amp and Voltage requirements based on their information online.
Amp and Voltage _requirements_, lets remember this.

Quote:
Originally Posted by TheOwlSpirit View Post
Here's the formula I found:

Watts = Amps x Volts

So, I tried to use this for the info I got on the fridge:

15 Amps x 115 Volts = 1725 Watts
The fridge calls for a 15A circuit. This is a description of the kind of power source it it needs to operate safely. What it is not, is an approximate average power draw under real world conditions.

Quote:
Originally Posted by TheOwlSpirit View Post
That's a lot, seems like. It doesn't seem like I'm doing this right, so I'm very confused and somewhat frustrated.
It doesn't seem right because it isn't right! And good on you for being skeptical, you're correctly identifying bad data. If you think "that can't be right", it probably isn't. This is something to applaud you for, not something for you to be frustrated about.

I measure my usage pretty carefully, lets look at my AC-side meters:
power_meters_25%.jpg

(The reason there are two meters is because common residential electrical has two phases / "legs" of 120V each, as to power both 120V AC and 240V (120V + 120V) AC appliances. Lets focus on the top meter. The bottom one we have two gaming laptops and a 4K TV running)

The top meter is the leg with my fridge on it, and as you can see, it is currently consuming 67.8W, or drawing 0.98A, a far cry from the 15A circuit it calls for. Sometimes it jumps to 180W (or more), most of the time (on average) it sits there around 70W.

Average power draw is what matters, and this is given either in amperage or more commonly, wattage. Your math isn't wrong, the information is technically not wrong, it just isn't the information you are looking for. The manufacturer can provide this, and often these figures can be found on the internet. Stick with averages in general.
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Old 09-22-2020, 06:09 PM   #12
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Notably one of the "RVLIFE" ads on the site has this link:
https://www.doityourselfrv.com/portable-freezer-fridge/

This is one of the more efficient chest-style fridge/freezers, and you can see in the datasheet its specific power draws. While mine idles at 80W or so and goes up, these tend to truly top out at their ratings (60W on "Max" mode, they may shoot up to 200W momentarily when starting the compressor). Two amperages are specified, this is because the unit can run both at 12V and 24V. It says it can run 120V, this is however via a power brick that produces either 12V or 24V, which is why neither amperage corresponds with the 120V use case.

Its kinda hard to tell all of that until you've looked at lots of such datasheets. Even then sometimes a figure can be confusing if the proper context isn't provided.



EDIT:
... or they just mess it up.
The datasheet is actually wrong. Leave it to China to confuse AC and DC voltages.
leaveittochina.png
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Old 09-22-2020, 06:46 PM   #13
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I really appreciate you taking the time to explain this to me.

I asked a Samsung customer service rep. on the wattage for a stove, and he just gave me the requirements. Lol. I tried to get him to tell me what amount of power it pulls, and he just told me that it depends on how much I use it, and what I use it for.
*facepalm*

I may have to try again. However, it does have an ENERGUIDE sticker that says the fridge does approximately 770kWh/yr, but I'm still unsure about what that would mean for me.
I didn't get so lucky with the other larger appliances, but some of the countertop ones had watts listed.
For instance, a dehydrator simply states "600 Watts" in the specs below. If that means the instant wattage, I'm not sure.

I am determined to get this right!
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Old 09-22-2020, 07:11 PM   #14
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I asked a Samsung customer service rep. on the wattage for a stove, and he just gave me the requirements. Lol. I tried to get him to tell me what amount of power it pulls, and he just told me that it depends on how much I use it, and what I use it for.
*facepalm*
Well, when was the last time you asked? Not many customers are seeking this information out, which is part of why it is hard to obtain. If this is an electric cooktop/stove, those are 240V and can use anywhere from 1100W per burner to 3000W per burner. If you can send me the actual model number I can give you guesstimates and show you how I got my figures. Heat is typically very expensive in terms of energy costs, this is why propane is an easier option for baking.

We use an induction cooktop, which draws around 1200W while heating. Its fine because we're not using it hours upon hours at a time, usually between 10 minutes and a half an hour. A crock pot/slow cooker is a lower energy alternative- they don't try to heat things fast, but rather keep them very warm. They draw up 70W - 250W so you can run them for hours at a time.

Quote:
Originally Posted by TheOwlSpirit View Post
I may have to try again. However, it does have an ENERGUIDE sticker that says the fridge does approximately 770kWh/yr, but I'm still unsure about what that would mean for me.
Ooh, you got a nice average. 770kWh (770,000Wh) per year, right? How many days are there in a year? 770,000Wh / 365 = 2109Wh per day on average. 2109Wh over 24 hours is 87.87W, which is your average draw.

Quote:
Originally Posted by TheOwlSpirit View Post
For instance, a dehydrator simply states "600 Watts" in the specs below. If that means the instant wattage, I'm not sure.
Well, if it is instant wattage, multiply that by how long it will be on. 1 hour = 600Wh.

Since we can't tell, we should probably measure it directly- if you already have the appliance this is the most reliable option. EDIT: Looks like 600W - 800W is the instantaneous measurement, and these can run for upwards of ten hours. Running this during the day if possible seems to make the most sense.

If you cannot find specifics for your make/model appliance, search in general terms, "how much power does a dryer draw". Now with the case of dryers, conventional dryers will draw upwards of 4000W. Heat pump dryers are much more efficient, and can draw as little as 1000W. The technology in use matters.

Some of this is simple searching : "how many watts does a crock pot use". Other figures require quite a bit of sleuthing to nail down. Typically, DC appliances will be good about listing. Also, good efficient models of an AC appliance will provide a yearly rating like above, that you can extrapolate your daily usage from.
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Old 09-22-2020, 07:18 PM   #15
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The conversation with the Samsung rep. was last night. Haha

I can start PMing you instead with the model number and whatnot if that's easier. I'm still learning the ropes of this website
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Old 09-22-2020, 07:58 PM   #16
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The conversation with the Samsung rep. was last night. Haha
I meant "most consumers aren't asking for this".

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I can start PMing you instead with the model number and whatnot if that's easier. I'm still learning the ropes of this website
I don't mind either way really.
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Old 09-22-2020, 08:45 PM   #17
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Can you link the gas stove/ convection oven you have? I have been wanting something very similar but haven’t found anything so far that I like.
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Old 09-22-2020, 08:56 PM   #18
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Sure, Duck! This is the one we've been keeping our eyes on: https://www.samsung.com/ca/support/m...X60T8511SG/AA/
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Old 09-22-2020, 08:57 PM   #19
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Actually, this link would be better for info: https://www.canadianappliance.ca/pro...60T8511SG.html
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Old 09-22-2020, 11:32 PM   #20
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I tried to direct message you. I’m not sure if it worked. The email function on this platform is not what I’m used to.
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