Need help with inverter size

[RVPhD]

I plan to boondock in my small RV. Right now I do not have an inverter but I plan to install a small one to allow me to use my 30 inch TV and my Dish Satellite system (antenna and Wally) at night. Question: How many inverter watts do I need to support these two items? I will not use the microwave or any other 120v appliances. How much battery power would I need if we use the TV for 3-4 hours per day and we charge the batteries using our 4000 watts generator and a 200 watt portable solar system? Your help and comments are welcome!

[RVPhD]

I plan to boondock in my small RV. Right now I do not have an inverter but I plan to install a small one to allow me to use my 30 inch TV and my Dish Satellite system (antenna and Wally) at night. Question: How many inverter watts do I need to support these two items? I will not use the microwave or any other 120v appliances. How much battery power would I need if we use the TV for 3-4 hours per day and we charge the batteries using our 4000 watts generator and a 200 watt portable solar system? Your help and comments are welcome!

[formerFR]

1,000w inverter, or a simple 1,000 'power inverter' found at most W*mt battery section or any auto parts store would certainly suffice...easily.

a TV and receiver are only going to be pulling about 2-3 amps each, at most, so 6amps total on the high end...which equates to 6ampx120v = 720watts

they even have several 750watt power inverters to choose from...
I've done it many times with ours, even with a fan also plugged in.

[tomkatb]

Find the wattage required on both units. On the literature.

Add them together. About 75 watts

The small inverters that plug into a 12 volt plug would be enough. I would think about a better unit wired in. More efficient. You could run higher need units if necessary. Drills vacuum cleaner. DVD.

Total wattage divided by 12.5 will give amps used per hour. Then look at the available amps in the battery. One 12 volt is typically 50. So about 10 hours or so.

[LTDunltd]

A 350 watt inverter will give you ~3 amps on 120 VAC.
Make sure you get one with low battery shutdown, and install a fuse on the battery power leads.

[cavie]

for the inverter all you need to do is add up the wattage of the things you want to plug in and use at the same time. It will be listed on a tag or printed on the unit. go bigger than you think you need. Wife will love you if she can use her hair dryer!!

[Bama Rambler]

You don't say which RV you have so we don't know how many batteries you can fit on it, but I would recommend getting as many, and as large as you can fit.

If I were serious about boondocking, I'd personally install 2,000 watt inverter, and maybe larger.

[RVPhD]

Originally Posted by Bama Rambler

You don't say which RV you have so we don't know how many batteries you can fit on it, but I would recommend getting as many, and as large as you can fit.

If I were serious about boondocking, I'd personally install 2,000 watt inverter, and maybe larger.

I have room for two car-sized batteries. Thanks for your reply!

[MR.M]

need to find out what the wally receiver and dish use . the receivers are more then you might think . my guess is an 800watt inverter will be more then enough

[TitanMike]

Take a look at the Bestek True Sine Wave inverter they offer in 300 watt size. Amazon has them. While a cheaper MSW will work, you might end up with "noise" in sound and unsteady picture on TV.

The 300 W True Sine Wave unit sells between $25 and $29 online (Walmart, Amazon, etc).

[formerFR]

portable antennas are powered by the Receiver, so no additional power needs there, and if the OP has the normal 'home' 3lnb open-faced antenna, then also no power needed.

[jimmoore13]

This handy calculator will tell you how much power your appliances will draw (inverters are rated in watts which is "power"), and it will tell you how many amp-hours you'll consume from your battery at 12-volts.

Two sample calculations.

1) If your TV draws 3 amps at 120 volts, and your Satellite equipment draws 2 amps at 120 volts, that's 5 amps total. From the calculator, 5 amps at 120 volts = 600 watts. You'll need about a 750 watt inverter for that load. Use the numbers on the data plates on the devices to get actual amperage (or power) draw. If both have watts, just add the watts together.

2) Now, at 12 volts - the power draw through the inverter FROM the battery - if you pull 600 watts from your 12 volt battery, the calculation is 600 watts and 12 volts = 50 AMPS from your battery bank. That's 50 amps per hour of TV watching!! (note that the math is really simple...if you draw 5 amps at 120 volts, you'll draw 10X that number at 12 volts...and your ultimate power supply is 12 volts, so there's no free lunch here.) You'd better have a damned good battery bank to support that.

A basic RV battery is a 12-volt group 24, which has a rated capacity of about 80 AMP HOURS (AH). But you only get to use half of that without damaging the battery - 40 AMP HOURS. One hour of TV will exhaust your battery and may even damage it. You say, "small RV", and I think Group 24 or Group 27, which only adds about 10 usable AH at most.

2 x 6-volt golf cart batteries in series will have a maximum rated capacity of about 225 to 250 AH. Again, you get to use half. So you have roughly 125 AH to work with, and, after lights, furnace, water pump, spark for hot water and the fridge, parasitic loads like the CO/Propane detector, you might have 100 AH available to watch TV - 2 hours. And that assumes you'll fully recharge the battery bank tomorrow so you have 125 AH available at bedtime. Even with solar, you're going to listen to that generator run for a LONG time.

Do your own math to verify the numbers for your specific equipment, and allow for about a 5% to 10% efficiency loss through the inverter. So your 600 watt load might be more like 650, which equates to 54 AH for every hour of TV.

None of this is a big deal on shore power, but flooded cell batteries absolutely suck as power storage devices, and hitting them with 120 volt loads through an inverter is a bit like blowing a hole in a dam...the power just GUSHES out. Furthermore, pulling 50 to 55 amp loads out of a battery bank drains them much faster than they are designed for. The AH ratings on batteries are based on a projected 20 amp load.

Just for perspective. If you compare the energy stored in a group 27 battery vs. a tank of propane, the difference is staggering. Using round numbers.

• One gallon of propane yields 91,000 BTU.
• Your "5 gallon" propane tank contains 455,000 btu (round numbers).
• One tank of propane = 133,000 watts of power.
• One tank of propane = 11,108 Amp Hours of energy from a 12 volt source.
• If you have a big 12 volt battery, you have 50 AH.
• Batteries suck as energy storage devices...especially cheap lead/acid batteries.

Here's a great resource about all things battery.

If you're bound and determined to watch TV in the boonies, here are several recommendations.

1. Get 12 volt entertainment gear. It tends to be more efficient. Most new RVs have 12 volt TVs.
2. Upgrade your battery bank to 4 x 6-volt golf cart batteries and about 600 watts of solar.
3. Or go all out and get Battle Born LiFePO4 batteries...about a kilobuck a battery, but very high performance. Don't forget to upgrade your converter and solar charge controller to be compatible. It's just money.

Perhaps it's better to tune into the campfire or only watch TV when you can run the generator.

[boondocking]

A 300 watt inverter would do you just fine. Led TV's draw very little current. My 60" TV draws 160 watts max, typical power 60 watts.

[Scottmarm]

I was in the same situation last year. After considerable research I ended up installing a 2,000 watt pure sine wave inverter. With all the appliances at your disposal and a system to recharge your batteries, why would you not want to use them? If you boondock for many days i'd cut down but if you're only there for a couple of days, why not enjoy all of what you RV has to offer. Once you see the benefits of not having to start the generator to get a cup of coffee, or to use the microwave to heat up a lunch you won't regret your purchase.

[Theo]

As jimmoore13 indicated in his first point, there is a bit of a "price" to pay for using an inverter to supply 1 amp at 120V from a 12V source. An inverter will suffer some loss when converting a 1 amp/12V DC input source to amps/120V. Manufacturers state this as the inverter efficiency and it is less than 100%. The inverter efficiency percentage can be from <=80% for inexpensive models to somewhere in the 90% range for top of the line models.

Jim's first point uses an inverter efficiency percentage of 80%; thus, the example's 750w inverter is pumping out only 600w after its efficiency percentage (80%) takes its toll.

So, don't forget to factor-in the inverter's efficiency percentage in your calculations.

[TitanMike]

Originally Posted by Scottmarm

Once you see the benefits of not having to start the generator to get a cup of coffee, or to use the microwave to heat up a lunch you won't regret your purchase.

For years I've made "One Cup of Coffee" by just heating water on the stove and using a simple cone filter on top of the cup to make the single cup. No microwave or generator. As for lunch, or dinner for that matter, microwave rarely gets used. Food cooked the old fashioned way tastes far better.

Generator gets used mostly for A/C or to charge batteries on a day when the Sun is taking a day off

[unyalli]

This would do nice. https://www.amazon.com/Samlex-SSW-60.../dp/B004OU3A5Y
Mount inverter as close to batteries as possible. AC cord can be any length.


- Jeff