A Frame Campers: Where Are You Mounting An Inverter?

[Evan H]

Hi guys,

I have a solid 12V system going, but want to get at least a poor-man's simplistic 110V system via an inverter.

Currently I have 2 AGM batteries wired in parallel, with 200AH. I'm running 200 watts of solar via an integrated Renogy suitcase with charge controller.

I'm thinking I'm going to go with a 1000W inverter. We just need to charge laptops and occasionally some small power tools, and maybe a small blender once a day.

I appreciate the need to get the inverter as close to the batteries as possible. From there, I just want to simply run an extension cord for now instead of going direct into one of the outlets, unless someone can convince me otherwise. I'm not much of an electrician, but I'm learning as much as I can.

I have a Flagstaff T12RB. Has anyone mounted an inverter in these things and have any suggestions on where to mount?

Attached are photos of my exterior battery bank, passenger side storage (a likely candidate for inverter) and the driver's side compartment with converter (an ideal location, but very cluttered). Both of these compartments are located just inside of the battery bank, with a wire length of 2-3 feet (guessing).

Thanks in advance!

[moose074]

Not able to provide much insight however interested I. Any answer as looking for way to power cabin

[cpttimerstraint]

I mounted mine in the front passenger side storage compartment. I added a separate plug on the front of the dinnette bench.

[Evan H]

Thanks, that’s what I was envisioning. Do you have any photos by chance??

[Big Vic]

As close to the battery as possible and with heavy cables. I mounted mine in the front storage about 18" from batteries.

[jimmoore13]

Consider....you seem to have plenty of room.

Look into a 1000 watt inverter with built in transfer switch. Illustration, not recommendation: https://smile.amazon.com/AIMS-POWER-...6380EB7556203A

This can hide more or less anywhere, and, if wired correctly, it will draw from the battery when there's no shore power, and it will draw from shore power when there is power.

There's no reason you can't route 120 volt wire through steel conduit under the coach to essentially any location, to make wiring easy.

Ideally, you'd want this somewhat accessible (under a hatch or in a cabinet) so that you can shut it off to save parasitic draws when you don't need it. Or install a remote switch next to the outlet(s) you feed from this thing.

It also needs to be REALLY close to the battery bank if you don't want to wire the thing with 00 welding cable. If you're sucking 1200 watts, that's 100 amps!!

I'm sure you know the math, but this calculator is handy.
https://www.rapidtables.com/calc/ele...alculator.html
And since the source is ultimately nominally 12 volts, the voltage is always 12.

So, now you begin to see the problem with this plan. If you have two batteries, each with 100 AH, totaling 200 AH, you get to use about half before recharging. If my assumption is correct, you have 100 usable amp hours.
That means that a big load, like a micro or coffee maker, can inhale your battery bank in an hour or two depending on the watts of the appliance! Obviously, you wouldn't be that foolish, but you're talking about a very big straw sucking from a very small cup.

My suggestion? A small - 400 to 600 watt - inverter can be used occasionally for short periods, but there is no substitute for a generator. For $499 or less you can get a 2KW Predator inverter generator from Harbor Freight that's 95% as good as a Honda (says Consumer Reports year after year no less). https://www.harborfreight.com/2000-w...xoCSgkQAvD_BwE When you need 120 volts, run the genny. The inverter would be handy during quiet hours.

As for charging phones, etc., far easier is to pick off 12 volts somewhere in the coach, "splice" in a 12 volt cigarette lighter socket and plug in a car charger (again illustration only: https://smile.amazon.com/Charger-Ada...NsaWNrPXRydWU= )

None of this up to 120 volts and back down again monkey motion for charging phones...simple, efficient, easy.

So, a case history:
My PUP had a 100 watt Windy Nation panel on the roof and a single group 24 battery. With careful power management, I went to bed every night (sunny Colorado) fully charged. I had a 400 watt inverter I used to run a 360 watt electric blanket for precisely 15 minutes to take the chill off the bed (during quiet hours). That's a 30 amp draw for .25 hour = 7.5 to 8 amps. The rest of the battery was dedicated to furnace (about 5 amps on a 50% duty cycle on cold nights = 20 AH over 8 hours), spark for hot water and fridge, water pump, parasitic loads and that's it. All lights were LED portable lanterns or a propane mantle lantern. A typical group 24 can deliver about 35 USABLE AH. As you can guess, I pretty much used it all overnight, and then the sun took over.

You have more...assuming 100 usable AH. But not a whole lot more when it comes to inhaling battery with 120 volt draws. My new rig has 400 watts of Renology solar on the roof and 2 x 6 volt golf cart batteries delivering about 110 or so usable AH. I will, again, install a small inverter...hopefully with a built in transfer switch. It will be as close as possible to the battery bank, and then I'll run a 120 volt circuit to the rear of the coach where my bed is to, once again, run the electric blanket...maybe for 30 minutes.

But a generator is the way to go for 120 volt power. And with each run of the genny, it's simultaneously able to push up to about 30 amps of charge at the battery bank during bulk charging....as it would in the morning when you're making coffee. If the batteries are somewhat drained, your genny can add 7 to 8 AH in 15 to 20 minutes run time...all the while making coffee and heating muffins in the microwave. That's the equivalent of 30 minutes to an hour of peak sun (Noon) of solar charging with 200 watts of panels.

You don't seem to be short on space, but my PUP was very tight. I mounted the inverter on the front interior wall--under the bed. The red wires above and to the left of the battery box fed the inverter on the other side of that wall.

But I had no room for the charge controller, so I installed it in a weather-proof plastic electrical (sprinkler control) box. The white box is on the driver's side over the tongue (to the right of the propane) in the photo. It's larger than expected to allow for rain-proof ventilation and all the wiring. Worked great. An inverter would go in one of these, and then you plug a 12/3 extension cord into the inverter, feed the wire to where you want it, and install a box and outlet wired to the cord. You can open the sprinkler box to turn the inverter on and off. Again, if you can't find space. Big advantage? VERY close to the battery.

Good luck with your project.

P.S. The facts of life about batteries. They suck as energy storage devices.
Compared to a 5 gallon propane tank, they are nothing. You can lookup all this info and use Rapid Tables calculators to do the math.

1 gallon of propane = 91,500 BTU/hour
1 tank holds about 4.5 gallons = 411,750 BTU/hour = 120,672 watts/hour
Use the calculator above with 12 volts = 10,056 AH (yes ten thousand)
So one tank of propane = 100 of your battery banks!
You probably have 2 tanks on the tongue of your A-Frame.

The math on gasoline begins with 114,000 BTU per gallon.
Use gasoline to provide the energy to make electricity for 120 volt loads.
OK, I'm done.

[jimmoore13]

PPS. I wasn't done. You can't wire anything with 2 or 3 feet of wire. Your battery terminals on the pair are at least a foot apart to start with. Plan on 5 or 6 feet minimum when it's all said and done. Wire routing requires slack and a bit extra just to accomplish the installation.

Calculate your amps, check the tables for wire gauge and length, and try to go up one size, because at these high amperages, losses can be considerable with "just-barely" wire and you pulling out of a very small finite supply. You'll probably need a minimum of #8 AWG (at 12 volts) for 500 watts, and so on. Use the calculator to determine amps, and then work from there. Also remember that most inverters are rated for "surge" watts...eg the startup of a microwave for example. Surges are brief, but tiny wire means pathetic surges. High current turns skinny wire into heaters.

https://i.pinimg.com/originals/57/22...a7d6387eac.jpg

[jimmoore13]

PPS. I wasn't done. You can't wire anything with 2 or 3 feet of wire. Your battery terminals on the pair are at least a foot apart to start with. Plan on 5 or 6 feet minimum when it's all said and done. Wire routing requires slack and a bit extra just to accomplish the installation.

Calculate your amps, check the tables for wire gauge and length, and try to go up one size, because at these high amperages, losses can be considerable with "just-barely" wire and you pulling out of a very small finite supply. You'll probably need a minimum of #8 AWG (at 12 volts) for 500 watts, and so on. Use the calculator to determine amps, and then work from there. Also remember that most inverters are rated for "surge" watts...eg the startup of a microwave for example. Surges are brief, but tiny wire means pathetic surges. High current turns skinny wire into heaters instead of conductors. The wire you see from my battery to my inverter is every bit of 5 feet.

https://i.pinimg.com/originals/57/22...a7d6387eac.jpg

[Evan H]

Wow, thanks for so much detail! I'm going to need to chew through this.

My thoughts on inverter size, and please tell me if I'm mistaken: If I get a 1000W inverter but am routinely only pulling 500 or 600W for short periods of time, is there any harm in overkill if I turn it off when not in use?

However, maybe it's too much. Here's what I plan to run:

- Charge laptops and phones, tablets, etc
- Run small blender 1x daily. ~250 W
- Charge tools occasionally. I'm a climber and I bolt routes, so I need to charge a 36V battery for a rotary hammer drill from time to time. Charges to full 2AH in 35 minutes on charger.
- Electric toothbrush every other day or so. Very low wattage?
-No microwaves, coffee makers, AC, etc. Nothing on perpetually. Furnace and fridge run on propane after started.

Also, if I'm not wired into the converter, do I really need the transfer switch option? I'm rarely going to be using shore power, and I just figured a poor man's extension plug off the inverter would be good enough, and I can simply turn the inverter off whenever I need to plug in to shore power. No?

Cable gauges: What are folks using to connect batteries? I got 20in 6AWG to connect batteries, but I'm already thinking I should go to 4 or even maybe 2. How about to inverter, assuming I can get it within 2-3 feet of batteries?

Does anyone have some good photos? That would be really helpful for me.

[Big Vic]

I suggest using 2-0 copper welding cable which is rated for 150 amps and is very flexible and easy to work with. It comes in red and black on Amazon. You will also need the appropriate connectors from the cables to your battery and inverter.

I installed my inverter as close as possible to the batteries using a 150 amp fuse between the batteries and the inverter on the positive lead. The 120v cable or extension cord coming from the inverter into your RV can be longer without significant amperage drop.

[emm-dee]

A 1000 watt continuous/2000 watt surge pure sine wave inverter usually has 40 amp fuses so 8 awg up to 7 feet should work just fine. And, most of those inverters have an on/off and some are available with remote control.

[Big Vic]

Here is some info on inverter battery cables

https://invertersrus.com/battery-cables/

[jimmoore13]

Originally Posted by Evan H

<<snip>>
- Charge laptops and phones, tablets, etc
- Run small blender 1x daily. ~250 W
- Charge tools occasionally. I'm a climber and I bolt routes, so I need to charge a 36V battery for a rotary hammer drill from time to time. Charges to full 2AH in 35 minutes on charger.
- Electric toothbrush every other day or so. Very low wattage?
-No microwaves, coffee makers, AC, etc. Nothing on perpetually. Furnace and fridge run on propane after started.

Also, if I'm not wired into the converter, do I really need the transfer switch option? I'm rarely going to be using shore power, and I just figured a poor man's extension plug off the inverter would be good enough, and I can simply turn the inverter off whenever I need to plug in to shore power. No?
<<SNIP>>

The Rapid Tables calculator and a serious effort to calculate your 12 volt loads and durations are your friends. That means "everything" right down to the CO/Propane detector, the parasitic loads from the entertainment system (e.g. display), and so on all the way up to the furnace and water pump. (pumps draw 3.5 to 7.5 amps if only for short periods. Do you use the lights? They count. How about the fantastic fan. Don't forget that small amounts of power are consumed to spark the fridge and hot water heater to life. It all counts.

120 volt loads are huge...if brief.

And the draw is only half of the formula. The goz-zin-ta is just as important. What is your panel array realistically pushing into the battery? In sunny Colorado, somewhere near max specs is realistic in sunny weather. I could reliably get 30 AH of charge/day out of my 100 watt panel. Where in the world are you? Hazy, cloudy weather will reduce the performance of your 200 watt array. But, as I said, I could count on 30 to 35 AH of charge on one panel under close to ideal conditions. Double that for you, and you are running a substantial deficit. You have a 100 AH tank, but you can only replace about 60 to 70 AH per day. Perhaps get another panel set and run them in parallel? I have 400 watts of solar to keep my 110 AH "tank" full...again in Sunny Colorado.

Every device you use will have a data panel on it...in watts or amps...including the chargers. I just checked my bench at home, and my 20 Volt LI charger for my drill draws at least 3 amps. Let's say it takes 3 hours to charge your battery, that's 9 AH...OUT OF 100...actually out of the 60 or so your panels can supply. You say your battery is full in half an hour or so? Perhaps. None of mine charge that quickly.

And don't forget inefficiencies. The rule of thumb is to toss in an additional 5 to 10% for various inefficiencies and unanticipated draws along the way...including that big ass inverter. A nominal 1000 watt inverter will eat slightly more wasted power than a smaller one...not a ton for sure. But you have a 100 unit bucket, and every single one counts...especially when you'll only replace 60 of them with your solar array.

Don't get me wrong. I made it work with a group 24 (35 to 40 AH max), and my battery held up for 5 seasons...even after abusively draining it dead once (before solar).

You can't realistically charge a 36 volt LI battery on a generator, unless you just love the sound of a generator. But you can replace one hell of a lot of AH with a genny first thing in the morning while the battery bank is low. Do as much of your 120 volt stuff as possible while on genny...surly brush your teeth. Let the generator run for about 1 hour, and it should push about 20 AH or so back into the battery while you're doing all the other morning chores on shore power. If possible, this includes beginning (or accomplishing) the charge cycle on your 36 volt LI battery.

If you have this attitude, you'll make it work. The attitude: "I have a small canteen of water, and I must cross this desert. I'll be very frugal with water consumption and monitor the supply closely." When you adopt that attitude, and then when you seriously do the math, you'll make it work.

Good luck.

P.S. The beauty of an inverter with built in transfer switch is that, when properly installed, you can use it to feed existing circuits in your rig. Installed near the converter, you can take a "house circuit" from the converter and move it to the inverter. Then you supply the inverter with 120 volts from the converter and 12 volts from the battery bank and voila, the device automatically chooses shore power if available and only uses 12 volt power if shore power is not available.

I prefer manual, because every AH counts, and I only turn on the inverter when I'm ready to use it. But the big rigs that have residential refrigerators are fully automated.

LAST THOUGHT. When boondocking ALWAYS run the fridge on gas...NOT auto. Why? Every time you fire up the genny, the fridge switches to 120 volt. The fridge is a BIG load...a giant heater to evaporate the coolant. If you're running the micro, and the fridge kicks on, and then you run the water (remember 3.5 to 7.5 amps for the pump), all those load can add up to overload the generator. My tired old (7 seasons) genny struggles if the fridge is on it, too. Save the genny power for other things. Force the fridge to run on gas.

[Evan H]

Thanks for all this helpful info everyone!

Jim, FWIW I too am in sunny Colorado, but we plan to live out of this thing and travel for a while (in a post-COVID world). In general, we will spend much of our time in the sunny west.

The 36V battery is an outlier for sure. I'd be charging that very occasionally, and not at all for weeks at a time. That is definitely not a daily power need.

I guess my biggest newbie question comes down to whether or not a 1000W inverter is overkill if I'm only routinely pulling half of that (give or take). I just want to have "cushion" for the times I need to pull more power, i.e. the 36V battery, etc.

I am coming to understand the limitations of the battery/solar configuration, but I feel it will be adequate for our "typical" daily power needs.

[jimmoore13]

Originally Posted by Evan H

<<SNIP>>
I guess my biggest newbie question comes down to whether or not a 1000W inverter is overkill if I'm only routinely pulling half of that (give or take). I just want to have "cushion" for the times I need to pull more power, i.e. the 36V battery, etc.

I am coming to understand the limitations of the battery/solar configuration, but I feel it will be adequate for our "typical" daily power needs.

I think the difference in efficiency losses between a 1000 watt and a 500 watt will be relatively insignificant, especially if you operate it manually and plug in directly to it. More is better might apply here.

I don't recall you mentioning a generator. I hope you'll plan to tote one. It will save your bacon more than once.

Enjoy your adventure.

If you're boondocking, you'll appreciate an off-road map book for each state. You may already know, but every goat path in CO is numbered and marked with signs. This book shows all of them. Similar books exist for many states. In the mountains, paper beats GPS any day. Much of this terrain is accessible with a small RV in tow. My wife and I have explored MANY of these trails in our box-stock 2006 RAM 1500 4-door 4WD. You seldom need 4WD, but it's great especially when towing up steep, gravel roads.
Many of the hospitable roads have lots of dispersed camping here, there and everywhere. Don't be surprised if you encounter a fifth wheel toy hauler 10 miles in off the beaten track.

[Evan H]

Originally Posted by jimmoore13

I think the difference in efficiency losses between a 1000 watt and a 500 watt will be relatively insignificant, especially if you operate it manually and plug in directly to it. More is better might apply here.

I don't recall you mentioning a generator. I hope you'll plan to tote one. It will save your bacon more than once.

Enjoy your adventure.

If you're boondocking, you'll appreciate an off-road map book for each state. You may already know, but every goat path in CO is numbered and marked with signs. This book shows all of them. Similar books exist for many states. In the mountains, paper beats GPS any day. Much of this terrain is accessible with a small RV in tow. My wife and I have explored MANY of these trails in our box-stock 2006 RAM 1500 4-door 4WD. You seldom need 4WD, but it's great especially when towing up steep, gravel roads.
Many of the hospitable roads have lots of dispersed camping here, there and everywhere. Don't be surprised if you encounter a fifth wheel toy hauler 10 miles in off the beaten track.

Thanks Jim.

I think I'll go with the 1000W inverter unless anyone can convince me otherwise. I'll do the remote switch and keep it simple with an extension chord to power 1-2 devices at a time, sparingly. I'll probably use 4AWG cables to connect both batteries and inverter, with a 150A fuse between the inverter and battery. Maybe overkill, but safer than sorrier (?).

I don't have a generator, at least not yet. I'm hoping to trial our system on some shorter trips and see how it goes. If we're coming up short, I'll obviously consider one. I know several folks with similar (if not more modest) setups who have lived on the road for 3-5 years without one, so I know it can be done. That's my hope.

As for the maps, you are correct for sure. I am a big believer in offline Google Maps (downloaded over Wifi and available later without using data), but they are lacking in backwoods areas.

Thanks again everyone! You guys are a helpful bunch.

[jimmoore13]

If you are going without a generator, you won't know your state of charge without a battery monitor.
This thread features a good one.
https://www.forestriverforums.com/fo...ne-169187.html

As for "going without a generator" as a condition...
When you fire up a genny or plug into shore power, if your battery bank is low, the converter cooling fan will scream for an extended period of bulk charge before it shuts off as the charge rate drops. That's no battery monitor, but it gives you a clue about the state of charge. If you have a genny, you'll no doubt use it daily, and if you've been in the sun all day and you fire up the genny to run the micro for a few minutes, the converter cooling fan should not come on. If it does, you're in trouble with charge status. It's OK if it comes on in the morning...after a night of furnace and other loads in the dark...but in the early evening, your solar should have you topped up enough to need very little charge, so no cooling fan.

I'm putting a battery monitor on my new rig, with 400 watts of solar and 2 x 6 volt golf cart batteries. The converter cooling fan is not an accurate measure...just a crude warning. If you are going without a charging backup (genny) and your solar supplies less charge than the batteries need, you'll want to know the state of charge. Draining the batteries too low will kill them.