maria_bettina
Auburn, CA
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time2roll wrote:Amps x volts = watts. DC or AC works the same.
Always use 12 volts when calculating because that is where the power is coming from.
Otherwise need to plug into a 120v generator.
The 12 Volt Side of Life
This discussion has been eye-opening. !!!
I ended up calculating the DVD/TV draw, and it meshes with what I saw on the Renogy screen, ~3A. Which seems crazy high to me, but I gotta start thinking in 12 volts, which is clearly difficult for me to wrap my pea-brain around.
Thanks for the link. I will check it out.
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mbloof
Beaverton, OR
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maria_bettina wrote:time2roll wrote:Amps x volts = watts. DC or AC works the same.
Always use 12 volts when calculating because that is where the power is coming from.
Otherwise need to plug into a 120v generator.
The 12 Volt Side of Life
This discussion has been eye-opening. !!!
I ended up calculating the DVD/TV draw, and it meshes with what I saw on the Renogy screen, ~3A. Which seems crazy high to me, but I gotta start thinking in 12 volts, which is clearly difficult for me to wrap my pea-brain around.
Thanks for the link. I will check it out.
Your little inverter ought to be fine for the DVD player and TV. Keep in mind that DC power draw is DC power draw - depending on how much sun you get and how long you'll be 'out' away from plugging into another charge source it all adds up.
I had a Renology solar charge controller that would not only report the voltage and power the panels were generating but what voltage the battery was at.
The rule of thumb (off the top of my head, someone will correct me if I'm wrong):
10.5V = DEAD
11.5V = %50 - you should not discharge a flooded lead acid battery below this as it damages the battery/reduces the # of charge/discharge cycles you can use.
- Mark0.
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ewarnerusa
Helena, Montana
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OP, give yourself credit - you are understanding the AC to DC conversion thing and that you need the current * voltage to provide the watts! Also the reality that while electric heat is efficient, it is not practical in a small portable battery system.
I kind of went on a similar path when I first started using our camper. After installing solar and upgrading battery capacity I figured I should use it to operate a 12V heater to take the edge off at times. But I quickly abandoned it and tossed it into the bottom of the camper gadget pile. So recognize that even a 12V heater that eliminates the need for an inverter at all will still not be great if you are using the stock 12V plug in the camper. In my camper I have another 12V plug that I wired in using some relatively large wire (8 gauge I think?) and it makes a huge difference on how that little heater performs. It can run when plugged into the stock 12V plug, although it barely produces heat. When I run it plugged into my fat-wired 12V plug it puts out pretty good heat. But it isn't warming a room up. Of course it is only a 150 watt heater/DEFROSTER and defrosting a windshield sounds realistic.
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valhalla360
No paticular place.
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maria_bettina wrote:time2roll wrote:Inverter should draw power direct from the battery using #8 wire minimum. 250w is close to 25 amps at 12 volts.
If I bought a new inverter and connected it to the battery directly, I am still looking at 25A. Which is crazy. We have a 200Ah battery, so 4 hours of continual use (before I reach 50% battery charge)? But if that same 250 Watt heater was DC, that's a whole different story. Electricity is like magic. Totally boggles my mind! Haha
Watts are watts.
Divide by the voltage to get the amps.
DC can feed the heater directly or it can feed the inverter...of course the inverter isn't 100% efficient so it will use even more amps.
As previously mentioned, 250w is going to be upwards of 20-25amps depending on the exact voltage of the battery bank.
Heating takes a lot of power, even with a small heater. There's a reason, most RVs go with a propane furnace and only power the fan with electricity.
Heavy power demands (lots of watts) are typically done with 120v AC, with the exception of starter motors but they have huge cables and only run for a few seconds to compensate. At 10 times the voltage 120v AC, amperage is drastically lower. When powering an inverter, you want big thick cables from battery to inverter and you want them as short as possible because it's going to be a lot of 12v DC amps.
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time2roll
Southern California
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maria_bettina wrote:I ended up calculating the DVD/TV draw, and it meshes with what I saw on the Renogy screen, ~3A. Which seems crazy high to me, but I gotta start thinking in 12 volts, which is clearly difficult for me to wrap my brain around.
Thanks for the link. I will check it out. 120 to 12 is a factor of 10
As you drop a zero from the voltage... just add a zero to the amps. 3 amps 120v becomes 30 amps 12 volts.
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RickW
Sacramento CA
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maria_bettina wrote:
I have an uber safety conscious son who won't run the Little Buddy at night. I guess it could be worse. I could have a son who juggles knives or something. ![[emoticon]](https://forums.motorhome.com/sharedcontent/cfb/images/smile.gif "smile")
Yes, it's the breathing the frigid air that keeps me up.
Good for your son! I almost succumbed to CO poisoning in a TC as a teenager and am uber careful too.
If it is breathing cold air that is the main issue for you, find a way to warm just the air near your head when sleeping. Maybe one of the aforementioned small defroster heaters. Even a light bulb in a box and a small computer fan may work for you. You may also need earplugs to mitigate nearby fan noise.
Edit: A few years ago I built a small heat exchanger that brought in fresh air and retained 80% of the heat from the exhaust. It used 1-1/2 inch diameter plastic hose to put the incoming air where I wanted it. The fans and exchanger were in a standard plastic ammo box. The same style box, fan and hose could be designed with a light bulb in the ammo box to put warm air where you want it.
Hope this helps,
* This post was
edited 06/21/22 11:52am by RickW *
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Grit dog
Black Diamond, WA
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I won't expound on the safety of a Buddy heater, although, know they are safe. Biggest downside is they put moisture in the air and create condensation as a result.
Presuming your camper doesn't have a built in furnace.
Honestly, it's either not that cold if a little $20 cube heater does the trick, or your more resilient to cold weather than you're giving yourself credit for!
If you can deal with the condensation, I'd be more inclined to explain the safety features it DOES have and also that you have (or should have if any other gas appliances) a CO detector in the camper.
If you weren't aware, they have a tip over switch which cuts them off if...tipped over, or even jostled. And also have a low oxygen sensor which cuts it off in the presence of not enough 02.
While they don't have a specific CO sensor, the 02 cutoff achieves the same effect, as 02 replaced by CO in an enclosure will shut it off just the same.
Can confirm it works well, as they're only recommended to operate up to 7kft altitude IIRC. And I could keep mine running, barely, at a little over 8kft but it would randomly shut off (being a combo of density of the air at altitude mostly and likely a slightly higher CO concentration right at the heater itself) in an 8x12 relatively sealed up, uninsulated tin can cargo trailer. But it was around 0deg F and a Big Buddy running full tilt, vs much less heat needed for your scenario.
You can be 100% safety conscious and use a catalytic LP heater indoors. Just have to understand it, if it's worrisome.
And you'll want some ventilation an airflow anyway and won't be worried about sealing up the camper from cold air if you have a heater that works 10x better.
It is 100% easier to deal with than the battery/charge/inverter/solar/etc/etc of trying to power an electric heater in the middle of the woods with limited battery capacity.
Just food for thought.
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pianotuna
Regina, SK, Canada
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RickW,
I'm with you 1000% on CO. I won't run a non vented combustion heater--and I won't run a generator while sleeping, either.
My daughter is a CO survivor.
Regards, Don
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ScottG
Bothell Wa.
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maria_bettina wrote:stevenal wrote:Once the fuse blowing issue is solved, I expect you'll be dealing with battery capacity. Heating appliances will draw your battery down very quickly.
Yes, I am bummed. I don't know how to heat ourselves at night. Below 40-degrees and it's downright uncomfortable. We have a Little Buddy heater, but not for sleeping. We have Reflectix around the vinyl (we have a pop-up TC), but that's not enough.
Back to the drawing board.
Reflectix is for heat infiltration and isn't intended for cold. Details are on its packaging. So maybe find a better insulation material to put in its place and it could make a big difference!
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pianotuna
Regina, SK, Canada
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ScottG wrote: Reflectix is for heat infiltration and isn't intended for cold. Details are on its packaging. So maybe find a better insulation material to put in its place and it could make a big difference!
Aerogel may be a solution.
http://www.aerogel.org/
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