Electrical needs calculations?

[ValerieP]

I think I might understand, but it’s fragile knowledge, so I would love input.
First, the Grape solar kit, is not going to be picked up- the beauty of ordering from Home Depot is that there is a lag between ordering and taking it home.
My ultimate electrical needs, which will probably never happen all at once is approx. 1100 watts.
Here’s where it gets tricky:
TV    amph 5x2.    50 watts pull at a time/2 hours 100 watts?
Battery chargers- 1.7 amph. X3= approx 30 watts- but runs for hours
LED lighting.  7x2 amph for 3-4 hours about 30 watts
Heater- once in a while 16 amph per hour 200 watts
Rice cooker upon occasion 48 amph over a 29 minute period 627 watts
Fan 4amph- 9 amph or 100 watts a few hours a day
Fridge 4-5 amph all the time- pulls 50 watts 

So I think if I were running all that at any given time, which I probably wouldn’t, I could pull 1137 watts, so I should have a 1500 watt inverter?
I think 2 125amph batteries would work
I think 300 watts solar would keep the batteries at above half.

Am I right, or even close?

 

[tx2sturgis]

I think 300 watts solar would keep the batteries at above half.

Keeping the batteries at above half is not gonna be good enough. You need to be able to power all of your loads AND return the batteries to full each day, or conserve power until they recover. 

Leave out the rice cooker (especially at night) and maybe cut TV usage and you might see some good performance. But cloudy days and low winter sun angles will also work against you. 

So what did you mean by the statement, "[font=Verdana, Arial, sans-serif]First, the Grape solar kit, is not going to be picked up-"?[/font]

 

[ValerieP]

I ordered the grape solar kit, but I think I need a bigger better inverter, so I’m going to return it when it arrives at my local Home Depot.
The rice cooker would be a once or twice a week thing.
Also, before I actually get the solar, I’m going to get the inverter and the batteries.
How do I charge the battery with my extension chord, does it plug into the inverter, or do I need something else?
I have to measure to see how much solar will fit.

 

[ValerieP]

It’s an extended bed, so I think I would have enough space for 4-100 watt panels and a fan?

 

[tx2sturgis]

How do I charge the battery with my extension chord, does it plug into the inverter, or do I need something else?

Unless you buy an inverter/charger you will need a seperate battery charger, or some hardware to charge them from your vehicle alternator, or a generator with 12v output.

 

[tx2sturgis]

It’s an extended bed, so I think I would have enough space for 4-100 watt panels and a fan?

Is this a van or a pickup with a topper?

 

[John61CT]

Nothing that produces heat from electricity is practical until you get *much* bigger energy inputs.

Cook rice in your camping pot over propane.

Best to try to avoid needing an inverter at all.

Your solar controller **is** a battery charger, you should charge other small batteries after your House bank is nearly full, direct DC - DC conversion, not through a wasteful inverter.

Best if you can give more specifics on each (remaining) load item, ideally with links.

 

[John61CT]

TV    amph 5x2. 50 watts pull at a time/2 hours 100 watts?

Stick to AH @ 12V DC for consistency. 100wH = 8AH

Is that from measuring with a Killawatt?

Best to get DC gear, and measure DC usage with a WattsUp or similar.

You using an antenna or streaming via Internet?

 

[John61CT]

Battery chargers- 1.7 amph. X3= approx 30 watts- but runs for hours

As above, comments and Q's.

For what devices specifically?

Best to find "car adapters" to suit.

 

[tx2sturgis]

Your solar controller **is** a battery charger,  

But only if she has panels connected. 

She said she was not going to have solar right away:

Quoting ValerieP:

"Also, before I actually get the solar, I’m going to get the inverter and the batteries. 

How do I charge the battery with my extension chord, does it plug into the inverter, or do I need something else?"

 

[John61CT]

LED lighting.  7x2 amph for 3-4 hours about 30 watts

Fan 4amph- 9 amph or 100 watts a few hours a day

Off 12V directly obviously.

Careful to select ones that work well over the whole voltage range of your system, or add a 12V to 12V DC converter / stabiliser

 

[John61CT]

Fridge 4-5 amph all the time- pulls 50 watts

DC compressor fridge right?

Cycles on and off depending, as needed.

Might be 30-70 AH by itself, need model maybe Watts Up.

Big load!

 

[John61CT]

I think 2 125amph batteries would work

Maybe, but barely, depends on avoiding heat/cooking and on the fridge.
The best battery value by far is Duracell (actually Deka/East Penn) deep cycle golf cart batteries, 2x6V, less than $180 per 200+AH pair from BatteriesPlus or Sam's Club.

IMO at this point I'm betting two pair would be better, could be three if you don't optimize as above.

 

[John61CT]

Biggest question is how are you going to get the bank back to 100% Full when 400W of solar isn't enough? e.g. cloudy weeks, camping in the woods.

Are you able to get to shore power for recharging every few days?

 

[ValerieP]

Is this a van or a pickup with a topper?

It’s a Chevy 3500 extended bed, van.

 

[ValerieP]

Yes, I do plan to plug in daily for much of the next 2 years, but not in the summer- then sporadically.

 

[highdesertranger]

I always say using electricity to heat anything is very inefficient. what heater are you planning on? also anything you run through an inverter, you must take into account the inefficiency of the inverter, 10% for the better ones but the el cheapo one could be as high as 30%. so you must add that to your power needs. that's why most advise to use an inverter sparingly and to use 12v native as much as possible. highdesertranger

 

[MrAlvinDude]

TV    amph 5x2.    50 watts pull at a time/2 hours 100 watts?

Is the TV powered by 110V?
Does it say 50 watts on a sticker?

Or as John61CT is asking: Is the 50 watt the result from measuring with a Killawatt 110V measuring device?

Either way, the power usage at 12V is calculated as: 50W / 12V = 4,16 Amp
So for each hour it is on it uses 4.16Ah.

If you plug it into your inverter (the device that takes 12V in and steps it up to 110V out) then the inverter also uses some energy to that stepping. It typically uses (looses) about 10-35% doing the step-up.

So, if the TV is supplied from 110V, coming out of the inverter, the draw on the batteries is likely to be 4.16Ah x 30% = 5.42Ah to run the TV every hour.

Battery chargers- 1.7 amph. X3= approx 30 watts- but runs for hours

You can use the 110V plug-in chargers, but you are much better off using one of those plug-in converters that plug into you 12V plug in your dashboard.

John61CT  also calls them: "car adapters".


If they give out  1.7 amp, this is most likely at 5V
Making it: 1.7A x 5V = 8.5W (maximum, only while the phone is charging)

I am not sure if 8.5W is a good point to go from,
but 8.5W at 12V is 8.5W /12V = 0.7A and when it has been plugged in it for one hour, is equal to 0.7Ah

So being plugged in for 5 hours makes 0.7Ah x 5h = 3.5Ah from the battery pool of energy

LED lighting.  7x2 amph for 3-4 hours about 30 watts

This is probable connected directly to 12V.

Do you have 7 LED lights?
And do you think they draw 2A each?
By the way, that is quite a bit of light from just one LED.

Heater- once in a while 16 amph per hour 200 watts

You have a heater that plugs directly into a 12V socket?
If so, you can do directly with a 16Ah number.

The watt numbers are mainly useful, when you check to see if a 1500W inverter is able to supply the energy needed for the appliance.


If it is a 200W heater, that plugs into 110V, then you hourly amperage draw on the battery is likely to be 200W + 10-30% loss in the inverter. For a conservative calculation, let us say 30% loss.

200W + 60W lost in the inverter,
is 260W / 12V = 21.7A or 21.7Ah for each hour it is turned on.


As John61CT points out, then you are much better off producing heat from and other source. Could be you propane stove, or a MrBuddyHeater, or...

Rice cooker upon occasion 48 amph over a 29 minute period 627 watts

Cooking by electricity is a not optimal, as it pulls very hard on the batteries.

If the cooker uses 48A when turned on, then a 29 minute use will use
29 minutes / 60 minutes an hour  x  48A per hour = 23.2Ah pf energy drawn from the battery.

Fan 4amph- 9 amph or 100 watts a few hours a day

If the fan is connected to 12V, then try to do the numbers in Ah.
The fan is 4Ah, and if it is run for 2 hours then 8Ah of energy is drawn from the battery.

If it is a 110V fan, then the calculation like those other ones where stuff runns off the inverter.

Fridge 4-5 amph all the time- pulls 50 watts 

What kind of fridge is it?
Most compressor fridges only run for a few minutes at a time.


A 4-5 amp fridge, could be one of those electric coolers, with no compressor, but a fan in the lid, and fan inside the lid.

Is it this kind of fridge? 

They are quite energy hungry. If it uses 5A per hour, and runs all the time, 
this is 5Ah x 24h = 120Ah drawn from the system in 24 hours. That is quite a lot! 


-----

Does these examples of calculations make sense to you? 

Do you see how the watt numbers mainly  to see if a 1500W inverter can run several appliances at the same time? 

And that it makes sense to convert the use from each device into amp hours (Ah)? 
Using Ah makes it easier to do a nightly calculation, or calculation of Ah needed between each charge. 

Like the fan uses 5Ah for lets say  2 hours = 10Ah from the battery pool, each day. 
The rice cooker uses 24Ah of battery pool each day
The TV uses 4.16Ah for, lets say 5 hours , is 4.16 x 5 = 20,8Ah from the battery pool

These three has then used 54.8Ah in one day. Or between charges. 

Does this example of calculating Ah from the battery pool make sense to you? 


Do you have other questions? 
Anything else we should try to explain? 
Or other calculations details that you would like to do one at a time? 


I hope this helps?

And I hope it is okay for John61CT that I sometimes use more words or rephrase? 
And basically say the same thing, just using my way of saying it. 
I find that John has already presented to me, much detail and many insights that I have greatly benefited from, even in this short time I have so far been active on this forum.

 

[MrAlvinDude]

Yes, I do plan to plug in daily for much of the next 2 years, but not in the summer- then sporadically.

Do you then need the batteries for much of anything, while you are plugged in? 

Are you also asking about a battery charger, so you can charge your batteries while you are plugged in? 
And then you might once in a while run off the batteries, like for a day or two? 

But in the summer time you plan to be able to travel, without being plugged in? 
And "how do you then make sure to have enough energy available?" Is that one of your questions?

 

[ValerieP]

I also conferred with one of my sons- he looked up a Xantrex 2000 watt inverter with a battery charger.
The fridge is a Whynter 62 qt dual zone. The heater would only seldom run- when we were in Maine, we ran it for a few hours just to take the chill off, so that would be it’s use- only once in a while. The rice cooker would be an extravagance, but I’d rather be able to use it if I wanted, rather than not be able to use it- but I don’t have to use it! I’m going to cook on a little propane single burner that uses cans of propane, I think. I used it for a couple of summers when we had the cargo trailer and it worked great.
I appreciate any and all advice! Some I understand, some I will have think about.
From Aug-May, I’m in Nevada and can plug in from 4pm-6am daily, unless we travel for a weekend, like last weekend, and I would have really liked to have had a fridge and more light!
I was only figuring 2 led lights for a max of 7 hours a day. I don’t have them yet. Right now, I have battery operated push on lights from IKEA, and a low light I plug in, in the evening.
In a couple of weeks, I’m driving to S Carolina, and my sons will wire the van so the battery will also charge when I drive.
I would like to add the solar before next May, but otherwise, I’ll be using it like I said previously.
I plan to go to the RTR for a few days, and hope to learn even more. While I’m there, I would arrive with 2 batteries fully charged and would like to be able to run the fridge and charge my phone for 4 days. I might have a TV by then, but I can live without it if it would run my batteries down too much. I also have a 2000 watt generator that I used with the cargo trailer, so I could run it for a bit to top off the batteries if necessary.
It sounds like I might be close to the right track.
Currently, I don’t have anything that is directly dc- but I won’t rule that out, and I appreciate the info-
I didn’t know about energy loss, nor did I know about start up surge, so I’ve learned some more. Apparently, the Xantrex 1000 watt has a 2000 durg for starting things and something so it doesn’t overcharge.
Whew- there are so many variables!