How much power do you really need?

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How much power do you really need?

Postby haha49 » Thu Jun 09, 2016 1:53 pm

I'm looking into building a teardrop this summer so I was wondering how much power do I really need. I want to go with solar I was thinking 2 or 4 100w panels I would stack them under each other and have 2 roll out from under the other panel that way I could have power when parked and when moving it's just 2 panels. I'm also unsure of how much battery power I need as well I know more you pay better they get which is fine I have a large budget for panels and batterys just limited space.

The stuff I wanted to power is the following.

12v
Fridge freezer combo (car one)
Tv
Small 235watt 20amp electric heater
Fantasic roof vent
Usb devices (cellphone gopro batterys ect)
4 to 6 led lights (not all going to be on)


110v
blu ray player
Toaster oven (small) Might just get a dutch oven and use gas instead.
Laptop
Lipo batterys (for rc plane can be 12v or 110)
Last edited by haha49 on Thu Jun 09, 2016 6:21 pm, edited 1 time in total.
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Re: How much power do you really need?

Postby tony.latham » Thu Jun 09, 2016 4:55 pm

Your title, "How much Power do your really need?" can be answered by figuring out how much power each of those appliances uses.

I can say this: Forget about 12V heat (with the exception of the cheap 12V electric blankets). And forget about a toaster. Those will eat your battery's lunch.

Figure out how many amp hours each of your items uses, add them all up for a given day/night and go from there. Blue Ray, TV? You won't know until you look up the specific model's usage.

My Fantastic Fan uses about 3 amp hours. LED lights are hard to measure and insignificant.

Tony
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Re: How much power do you really need?

Postby GuitarPhotog » Thu Jun 09, 2016 4:59 pm

Small 235volt 20amp electric heater


Must be a typo somewhere here. Do you mean 235 Watts?

If so, you are going to need to limit the use to short periods of time or have lots of battery capacity. That heater will draw 20A per hour, or 20AH. If you have a 120AH battery, you will be able to run the heater for 3 hours (60AH) before running your battery down to the 50% point, below which it is advisable that you do not go.

In general, it is not practical to either heat or cool using 12 VDC battery power. Both require more power than most affordable batteries can easily provide.

All the rest of your stuff is negligible in comparison.

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Re: How much power do you really need?

Postby haha49 » Thu Jun 09, 2016 6:31 pm

GuitarPhotog wrote:
Small 235volt 20amp electric heater


Must be a typo somewhere here. Do you mean 235 Watts?

If so, you are going to need to limit the use to short periods of time or have lots of battery capacity. That heater will draw 20A per hour, or 20AH. If you have a 120AH battery, you will be able to run the heater for 3 hours (60AH) before running your battery down to the 50% point, below which it is advisable that you do not go.

In general, it is not practical to either heat or cool using 12 VDC battery power. Both require more power than most affordable batteries can easily provide.

All the rest of your stuff is negligible in comparison.

<Chas>
:beer:


I wanted to use it in the winter so I figured some heating would be not a bad idea I don't have very big power demands. Didn't want to go propane due to the small space and that would be 1 less thing to setup in it.
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Re: How much power do you really need?

Postby noseoil » Thu Jun 09, 2016 8:52 pm

For heat take a look at what some people are doing with a basic propane water heater, small heater core & 12 volt pump from a Prius. It practically heating with a pilot light. Depends on how cold it is, how much heat you need, how long the cold lasts & how much insulation you have. You might consider covering the walls floor & ceiling with carpet.

We get by with a group 27 AGM battery & 100 watts of solar, but no fridge & no heat. As Tony said, run the calcs for peak demand & use, ad 20% for slop & size both the solar & battery with a reserve.
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Re: How much power do you really need?

Postby Shadow Catcher » Thu Jun 09, 2016 10:11 pm

We have a 185W high voltage panel and power a Waeco refrigerator, TV/DVD, Recon weather radio (SAME technology), 300W Morningstar inverter, chargers for cells, laptop, Nooks. Fans are two three speed Antec computer case fans (MUCH less power draw). When off grid we do not use resistance heat for anything, heater is either Espar diesel or the water heater heater, coffee is a French press cooking is gas cook top or gas grill.
We have gone eight days in a shaded camp site and ended up with 64% SOC.
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Re: How much power do you really need?

Postby haha49 » Fri Jun 10, 2016 12:27 am

Didn't pick the fridge freezer and other stuff so hard to calculate for what you don't have yet. I found a propane furnace that bolts under the trailer 63000 but draws 1.2 amps. The insulation I plan on just plywood and the pink insulated hard foam r2p I think it's rated same thickness as standard plywood. I'm building for 1 person so not hoing very wide 4x8 or 4x9. So far planing for a raised floor to put the heater under. For indie it will be fiberglass and carpet. For bed I will just get a custum bed made I can make sheets for it. I was thinking backpacking type of gear for cooking might have to consider a propane tank as well for heating and cooking. I plan on buying a tow car and using it for more space wanted to travel the whole of canada at least that's the plan artic first never been up there also wanted it go skiing trips in winter cheaper then a hotel the amount for hotels for my trip plans make a trailer cheap even with buying a car to tow it. I do have winter camping gear ie sleeping bags so I've done the sleep in a tent in winter thing used a 3 season tent didn't snow so it worked out fine lots of clothing is the trick and cover your head. Artic no heater hell no you pee and it turns to slush inside you not fun in winter
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Re: How much power do you really need?

Postby Esteban » Fri Jun 10, 2016 2:01 am

haha49, It is a little hard to clearly understand what you wrote. It seems you want to use your teardrop for winter time camping in Canada. If I were in your shoes I'd do my best to insulate your teardrop as best as you can to help keep heat inside and to reduce condensation on cold surfaces.

Readily available rigid foam board insulation varies from about R 3.5 per inch of thickness up to about R 8 per inch. Foam Board Insulation R Values By Todd Fratzel on Insulation will provide you more information to choose what type of foam board to best meet your needs.

Expanded Polystyrene Foam has an R value of 3.6 to 4.0 per inch of thickness.

Extruded Polystyrene Foam (XPS) has an R value of 4.5 to 5.0 per inch of thickness.

Polyisocyanurate and Polyurethane (Polyiso) has an R value of 7.0 to 8.0 per inch of thickness. It often has a foil face too.

You also might choose to use the more efficient Model 7350 13 speed Fantastic (Fan) Vent that uses much less power than all the other 3 speed Fantastic Vents.
Steve - SLO, CA
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Re: How much power do you really need?

Postby haha49 » Fri Jun 10, 2016 7:19 pm

Esteban wrote:haha49, It is a little hard to clearly understand what you wrote. It seems you want to use your teardrop for winter time camping in Canada. If I were in your shoes I'd do my best to insulate your teardrop as best as you can to help keep heat inside and to reduce condensation on cold surfaces.

Readily available rigid foam board insulation varies from about R 3.5 per inch of thickness up to about R 8 per inch. Foam Board Insulation R Values By Todd Fratzel on Insulation will provide you more information to choose what type of foam board to best meet your needs.

Expanded Polystyrene Foam has an R value of 3.6 to 4.0 per inch of thickness.

Extruded Polystyrene Foam (XPS) has an R value of 4.5 to 5.0 per inch of thickness.

Polyisocyanurate and Polyurethane (Polyiso) has an R value of 7.0 to 8.0 per inch of thickness. It often has a foil face too.

You also might choose to use the more efficient Model 7350 13 speed Fantastic (Fan) Vent that uses much less power than all the other 3 speed Fantastic Vents.


cellphone typing sucks... Hate auto correct auto fill in crap.

I'm just going to use the hard pink foam at the store It's not much R valve but some is better then none. I plan od using plywood on the bottom foam then rasing the bed for storage and putting the heating under the bed. It also makes running lines for propane or diesel easyier. Debating between propane and diesel up north both are a pain to get but do able. I wanted a toaster over to cook thinks like a small pizza but I could do that in a dutch oven wanted to save on fuel by doing it that way instead of the dutch oven. It seems that you can get some nice diesel stoves for cooking I might go that route it takes more space then propane but you can haul more fuel for the space and weight for diesel. I'll just end up installing the tank under the bed if I go that route. For propane it would be on the hitch up front.

So really my power demands have shrunk abit. I still want a 12v fridge/freezer (car one) Cellphone, laptop, and cameras. I can do that all in the car just one at a time while it's running. So what 12v fridge freezer works well and has low power demands for the size? Still unsure on how much power I need it seems like it might be a simple 300w system. Wont be running everything at once anyways. I want the battery to be charged up so I can run the freezer all night the lights power draw is tiny 7w each don't use lights allot so that's like nothing. It's hard to figure out if you haven't picked the gear.

Now diesel or propane for heating and cooking. I don't plan on heating water I'm going with a simple jug of water from the store with a manual pump that clips on top. simple cheap and easy. For shower I'm going with a backpacking shower I can just heat water up and hang the bag. Extra water will be hauled in the car. The sink is going to be a plastic container because I don't want to waste the space putting a sink in. So next question would be how many amp hours for a standard 12v fridge freezer (car one) to run 24hours none stop. As well as how much solar to make up for cloudy/rainy days.

found this info
Code: Select all
http://www.australiandirect.com.au/buying/portable-fridges/portable-fridge-power-consumption-guide/10

For an example: Estimating an average from just the current draw of your Evakool portable fridge, and not taking into account any of the above factors. If the current draw of your Evakool Fibreglass 110L fridge/freezer is 5 Amps (60 Watts) while the compressor is running, then on a average day cycling 50% of the time you would be consuming approx 60 amps (720 Watts). ((5A x 50%) x 24hrs = 60 amps)
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Re: How much power do you really need?

Postby Esteban » Sun Jun 12, 2016 4:32 pm

A 110 liter fridge/freezer would be huge.

Truckfridge.com sells three ac/dc chest type fridge/freezers that might meet your needs.

Step up in price (and quality) and you can choose from several sizes of ARB fridge/freezers.
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Re: How much power do you really need?

Postby haha49 » Mon Jun 13, 2016 7:51 pm

Esteban wrote:A 110 liter fridge/freezer would be huge.

Truckfridge.com sells three ac/dc chest type fridge/freezers that might meet your needs.

Step up in price (and quality) and you can choose from several sizes of ARB fridge/freezers.


I know it's huge but might as well use its power draw since smaller is less margin of error. Seems like I could get by with 20amp hours worth of batterys so how much solar to fill them up. I know you buy 100amph you only get 80.
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