TV watching with separate inverter?

**Extreme** · 01-19-2021, 03:05 PM

Okay so lets say we have 2 acid 12v batteries fully charged while dry camping in your new 2500RL 30 Amp rig.
Regardless if they are charged that day with a Solar set up or a handy Generator, this part doesn't really matter for the question.

What if I connect the TV to a seperate small inverter (behind the TV) and have the inverter pull power directly from the rig via plug outlet to power the tv.
The question is how long could someone watch TV in this manner? What small inverter would you recommend?

How do I figure this out, can I do this without setting up a full inverter change on the rig?

Oh and how would this "watch time" compare to 2 full charged 12v 100 Amp Lithium batteries at night?

Thank you in advance.
EXTREME the "Ultra Newbie"

**xrated** · 01-19-2021, 03:49 PM

I'm not 100% sure what you are asking, so here goes with an explanation....that you may or may not know. An typical inverter will need a 12VDC power source to "pull" or draw power from, which in the case of an RV would normally be your battery or batteries, depending on what you have installed in your rig. An inverter would then take that 12VDC power in and convert it to 120VAC. The requirement for the size of the converter would be such that it's output (120VAC) would be enough to supply the television's power requirement....whatever that is that is listed on the tag on the television. And of course nothing is for free, so the amount of wattage into the inverter (read DC volts x amps = wattage) would need to be sufficient. Let's work it out backwards for this example. Let's say the television (TV) draws 3 amps of 120VAC to operate. That equates to 360 watts of power. In order to get 360 watts of power out to the TV, the inverter would have to be supplied with 360 watts of power to supply that amount. And remember, I'm not trying to calculate any of the losses involved in the DC to AC inversion. So to calculate the input power/wattage you would use this formula. 12V (the battery voltage) multiplied by some number = 360Watts of power. So 360 divided by 12 = 30 amps of DC power into the inverter. So in that instance, counting losses incurred in the power transformation, plus any possible inrush current factors when the TV is turned on, I would probably say at a minimum you would want to be looking at a 400W inverter. The DC circuit would need to be able to supply just under 35 amps to the inverter. That would require 10ga wiring from a battery source, possibly 8ga wire, depending on the length of the wire in the circuit from the battery to the inverter.

**Extreme** · 01-19-2021, 04:26 PM

While I know the TV will work fine on Shore power.
Do you think its really unrealistic (no matter how you have it set up) to get 2 Acid or 2 Lithium batteries to supply power to a 400 Amp inverter to run a TV for 3-4 hours while dry camping? Taking into account the 8ga wiring and anything else this can or worms would require?
I wife really wants this but I'm not willing to spend $$$$$ to get it done.
Let alone rewiring parts of the rig to make it happen.
By the way thanks for opening my eyes with all the information you supplied.

**TwoElkhounds** · 01-19-2021, 04:53 PM

You are better off mounting the inverter as close to the battery as possible and running an extension cord to the TV. That way you can reduce the current by a factor of 10 (120VAC /12VDC). You can then use just a standard 14AWG extension cord between the inverter and the TV. You still need the larger wire between the battery and the inverter, but the run will be short and loses minimized.

To determine the size inverter you need, just look at the wattage rating of the TV you intend to use and make sure the inverter is at least 25% larger to account for loses and provide some margin.

DAN

**Extreme** · 01-19-2021, 05:07 PM

Originally Posted by TwoElkhounds

You are better off mounting the inverter as close to the battery as possible and running an extension cord to the TV. That way you can reduce the current by a factor of 10 (120VAC /12VDC). You can then use just a standard 14AWG extension cord between the inverter and the TV. You still need the larger wire between the battery and the inverter, but the run will be short and loses minimized.

To determine the size inverter you need, just look at the wattage rating of the TV you intend to use and make sure the inverter is at least 25% larger to account for loses and provide some margin.

DAN

That sounds really doable.
Do you think a dual Acid or Lithium batteries would run a TV for 3-4 hours?

**xrated** · 01-19-2021, 05:38 PM

A true Deep cycle battery will be rated in AH....or amp hours....vs. a battery made for a car/truck/engine starting type environment. Let's say you found a FLA (Flooded Lead Acid) battery that was rated at 100 amp hours. What that is basically telling you is that the battery can supply 100 amps for one hour.....or 50 amps for two hours....and so on. As I've already stated above, a 400 Watt inverter is going to require approx 33.333 amps (I rounded to 35 in my previous post). So you would think that something like that would provide right at 3 hours of TV time. The catch though, is that you should never discharge a FLA battery more than about 50%.....so now we cut it down to 1 1/2 hours of TV time. Add in another 12V 100 AH battery in parallel and you now have 200 AH of power. And again, never run them down to more that 50% usage before recharging them. Now you are looking at maybe getting that 3 hours of TV time. But....and there's always a "but"....you will have other devices going also...maybe a few lights, the refrigerator running on propane, but being supplied with 12VDC for the control of the fridge, maybe the water pump for a short time, etc. Only you will know what you are going to use or not use from the battery supply, and all of that is assuming fully charged batteries in new/good condition.

I'm certainly NOT trying to discourage you, but you also need to know the ins and outs of what you have, it's capabilities, and the thoughts of knowing that if you deplete most of the battery, your done until you hook up to shore power or you fire up the generator to operate the converter and recharge them. Does that mean you will have little to no battery left to keep the fridge going overnight....how about power to run the furnace if needed? Those are all things to consider, along with the thoughts of batteries and boondocking or dry camping. And again, I don't know exactly the wattage rating of the Television as far as wattage consumption, but that and all the items I mentioned above...lights, pump, fridge, furnace, etc....needs to be figured out beforehand in order to have a fun and uneventful outing.

**Extreme** · 01-19-2021, 05:43 PM

Thanks....but I think I'm getting a headache.
Time to take a break from all this RV overload.

Your help is truly appreciated.

**xrated** · 01-19-2021, 05:49 PM

Sorry, I didn't mean to somewhat overwhelm you, but I also don't want you to go blindly in and think that you have a workable solution, spend money, and then have a failure to get what you need to really get the job done.

**Extreme** · 01-19-2021, 05:59 PM

No problem but to be honest its a whole lot easier buying a car than trailer.
It seems like if you don't have a working understanding of the electrical system and explain "every step" of what you want, than this house of cards falls apart!
I just wish I could go to our Service Department state what I want to to achieve, get a price and have it done in a reasonable period of time.
But I'm afraid that unless I have the dealer install what I want PRIOR to buying the rig, I'll be coming back later to install options with no leverage.
And these service departments out here take a LONG time to get work done.
Seriously this industry really is screwed for Customer satisfaction.
Sorry I just had to vent..................

**TwoElkhounds** · 01-19-2021, 06:48 PM

Everything xrated outlined is true, but you shouldn't let it overwhelm you. I watch TV using an inverter and battery all the time. Just did a quick look online and it looks like a typical 50" TV will draw around 200W to 300W of power, so less than what was stated above. Keeping the volume down will also help.

So keeping it very simple. Get a second battery and a 500W or more inverter, you might just want to get 1000W one since cost difference will be minimal. Hook the inverter up at the battery and run an extension cord to the TV when you want to watch TV. Watch the voltage on the batteries and try to keep it above around 11.5V. If you go below that, it is not a big deal, you are just using up some battery life. Not the end of the world. The inverter will automatically shut down when the voltage gets too low, usually around 10V.

Another note, if your battery is old, you will want to get two new ones. Never mix old and new batteries. Don't bother with the RV dealer, any competent auto mechanic can install the batteries and wire up the inverter if you are not comfortable doing this. Just take the trailer down to their shop and avoid the RV dealer altogether. If you have a friend who works on cars, then all the better.

Down the road you might want to upgrade your battery bank to provide more energy. But for now, it sounds like you just want to maybe watch a movie or a game here and there and that is easily achievable.

DAN