150 watt 12v Heater on Deep cycle bank... Will it work?

[spitta]

So, I've gone round and round with this and can't come up with the math.

I'm rebuilding a 13' Canned ham trailer. If I'm going to get my wife in it... it'll have to have heat. Heat takes a lot of power! I don't like propane. I don't like Carbon Monoxide or asphyxiating to death. Typically. So I would really like to go all solar.

Considering the wee little space I'm heating. The fact that we won't use it that often. And interior space limitations: I'm thinking of pulling the build in propane heater and just putting in 12v heater that I found that won't be great but won't kill us either. It draws 150 watts or 235.

Check on Amazon for Schumacher 1224 12V 235W/150W Ceramic Heater and Fan

If I did my math right... at 150 watt setting this draws 12.5 DC Amps. If I want to run it for 8 hours that's 100 amp hours? That means I need 200 Amps hours of deep cycle battery so I only discharge 50% and it would need to recharge the next day for 6.5 hours with my 135 watt panel and my PWW charge controller.

Did I get all that right? I'm lost and confused in the spreadsheet I created!

And also, all my calculation are totally theoretical. In the real world ... does this pan out?

Help! Oh wise ones!

ONE MORE THING: I read that it's better to tie two 6 volt deep cycles together rather than two 12v deep cycles... but that you don't get anymore amp hours? I totally don't understand the benefit then... please to explain.

[Sunking]

You are not going to like this one little bit... I just got facts

You want to run a 150 watt heater 8 hours per day in Winter right?

150 watts x 8 hours = 1200 watt hours.

If you use an expensive MPPT controller (40 amp $350) the panels need to generate 1800 Watt Hour in Winter with low Sun Hours or let's say 3 hours which is average in the USA

If you use a inexpensibe PWM Controller (40 amp $175) the panels need to generate 2400 watt hours in Winter with low Sun Hours or let's say 3 hours which is average in the USA.

Assuming MPPT controller and 3 Winter Sun hours your panel wattage need to be 1800 watt hours / 3 Sun Hours = 600 watts = $1200

Assuming PWM controller and 3 Winter Sun hours your panel wattage need to be 2400 watt hours / 3 Sun Hours = 800 watts = $1600

To add misery to your pain and suffering it would be very foolish to discharge your batteries 50% per day. 1 cloudy day and you freeze. To do that with only 1 day reserve time requires a AGM battery which is 100 to 200% more expensive than a Flooded Lead Acid FLA battery. Smart money is a minimum 4 or 5 day reserve capacity using FLA battery. So if you use a mere 1200 wh day you need 4800 to 6000 watt hour battery. At 12 volt capacity that means 400 to 500 AH battery. That weighs 300 to 400 pounds and cost $900 to $1300.

So to shake and shiver 16 hours per day (8 hours with questionable heat for a 24 hour day) constantly monitoring a solar off grid system you are looking at minimum of $2500 up to $4000 plus all the other stuff to make it actually work.

FWIW 1200 watt hours of electric heat = roughly 4100 BTU's or 12 cents of electricity if you buy it for 10-cents per Kwh which is national average.

1 gallon of LPG contains 91,000 BTU's and cost roughly 4 dollars. So if you have 1-gallon of LPG and use only 4100 BTU's/day means you have 91,000/4100 = 22 days of the same heat equivalent as the solar system you want. Assuming a 120 winter cost of LPG is $150.

Whatcha going to do?

[spitta]

Lol... what are you talking about? You're my dang hero. You had me at "...I don't care what you like."

So, you're saying I'm better off with bottle of whiskey and warm floozy. I gotcha. Well, I guess I'll look into a vented cat heater. I hear the non-vented are dangerous.

Update: So does this sound reasonable... I have 135w solar panel, cheap pww, controller...

If I tied 2 6v deep cycles to that would that run..

3 LED Dome lights. A DC Fan rated at 1.4 amps on HIGH... I assume low is like... .8 amps, a Flojet water pump... once in a while, possibly a few hours of laptop?

[inetdog]

So, I've gone round and round with this and can't come up with the math.

I'm rebuilding a 13' Canned ham trailer. If I'm going to get my wife in it... it'll have to have heat. Heat takes a lot of power! I don't like propane. I don't like Carbon Monoxide or asphyxiating to death. Typically. So I would really like to go all solar.

Considering the wee little space I'm heating. The fact that we won't use it that often. And interior space limitations: I'm thinking of pulling the build in propane heater and just putting in 12v heater that I found that won't be great but won't kill us either. It draws 150 watts or 235.


And also, all my calculation are totally theoretical. In the real world ... does this pan out?

Help! Oh wise ones!

ONE MORE THING: I read that it's better to tie two 6 volt deep cycles together rather than two 12v deep cycles... but that you don't get anymore amp hours? I totally don't understand the benefit then... please to explain.

If you take two 6 volt 200AH batteries and connect them in series, you get 12 volts, 200AH.

If you take two 12 volt 100AH batteries (about the same size as the 6v 200AH ones) and connect them in parallel you get 12 volts at 200AH. Basically the watt hours (volts time AH) will be roughly the same per volume of battery and weight of lead (for similar battery design, like both FLA, deep cycle).

Dereck has provided the math for solar PV.

Solar PV is not the way to go for heating. If you really are committed to solar in some form for heating, look at solar thermal panels, including a lot of DIY options. You will still need some electricity for fans and maybe pumps and a propane heater for backup on days when the panels just cannot cut it.

[Sunking]

Update: So does this sound reasonable... I have 135w solar panel, cheap pww, controller...

Nope 500 watt minimum and 400 AH battery. Dig deep in your pockets if you want to go solar.