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Just_Jeff's avatar
Just_Jeff
Explorer
Feb 06, 2013

One large inverter or 2-3 small ones?

So as I get closer to adding solar (or at least a larger battery bank) to my RV, I have more questions than I started with! Big thanks to the folks who have helped me along so far.

I found a great place on the RV to install 4 x 6V AGM batteries. It'll require a frame mount installation, but it's open space right now and won't take away from the limited storage I already have. The new place is just behind the cab on the driver's side.

The current 1000W inverter runs only the cabover TV outlet, which is disabled when the engine is cranked. Interestingly, the inverter is mounted in the overhead cabinets on the passenger side...so there's a long DC wire between the battery and the inverter. Plenty to run the TV but I assume there's quite a bit of voltage drop over that.

I also want an inverted plug in the bedroom (rear of the RV) that's not disabled when running, and then maybe an outlet in the kitchen. What's the best way to do this?

Right now I basically see two options:

1 - Get a large inverter that runs the entire RV. This would be convenient for having all plugs available, having a larger capacity, could run the fridge short-term on AC if needed (for example), etc. Downside is that I think it should be mounted with venting which would slightly limit locations, and obviously the extra capacity would result in extra drain when I'm not using it all.

2 - Other option would be mounting another 1000W or 1500W inverter in the rear bedroom by the TV. Pros here are that I could conserve power by only inverting what I needed, it should be cheaper, and I don't have to worry about venting. Downside is that it's a long way from the battery, meaning a long DC run and resulting voltage drop. Would it be viable to mount the inverter closer to the batteries and make the long run an AC wire?

I'm also installing two 12v outlets in the bedroom for heated mattress pads and such, and another in the kitchen. That means with option two I could supplement with a small plug-in inverter if necessary.

What else should I consider when deciding?

As discussed in The Solar Plunge thread, I will likely add solar to this at some point...would that have any impact on where to mount the inverter?

Thanks in advance for all the help!

180 Replies

  • Just Jeff wrote:

    Mena - Do you run your fridge from the batteries/inverter, or do you manually switch the fridge to LP? Thinking battery bank capacity here.
    Manually switch to LP but I only run my fridge on LP so no problems remembering that. Unless you have solar, no battery charging will occur while on inverter power but you MUST remember to turn off your converter first. I installed a 30A RV plug in the same compartment that my shore cord is located so I can run my inverter on the road if I want to like BFL mentioned.




    The other end goes to a 20 amp plug that goes into my inverter.



    EDIT: Just noticed you have a MH so, yes, you'll get some battery charging from the alternator.
  • BFL13 wrote:
    Reposition the 1000w inverter you have now close to the new battery bank for best wiring (short,fat) Rig a way to plug the shore power cable into the 1000w inverter so it can be done while driving down the road. (turn off the converter when the shore power cord is in the inverter--you lose more than you are putting in if the converter is left on)


    Hrm...this is an idea. I'd just leave the existing wiring in, move the inverter closer to the battery bank, and run an extension cord through the over-cab area to that TV. That would be pretty simple.

    BFL13 wrote:
    ...if they get bored looking at the passing scenery and learning stuff.


    Yeah...I try to balance this. "But I can LEARN from my phone/computer/TV/PS3/XBOX/etc." "Yeah, you CAN...but DO you?" Sheepish look at the ground...

    Reminds me of something I saw once...
    - "What would you tell someone from 100 years ago who just appeared?"
    - "I hold in my pocket a device that lets me access the totality of mankind's knowledge, almost instantaneously. I use it to look at pictures of cats and argue with strangers."
  • Reposition the 1000w inverter you have now close to the new battery bank for best wiring (short,fat) Rig a way to plug the shore power cable into the 1000w inverter so it can be done while driving down the road. (turn off the converter when the shore power cord is in the inverter--you lose more than you are putting in if the converter is left on)

    Probably means run a 120v wire extension from the inverter to a new receptacle in the shore cord compartment.

    Now you can run the fridge on the 1000w while driving if you chose to not use propane for that (safety issue for many people--up to you) The alternator charging helps make up what the fridge uses, AFAIK--I have a trailer.

    The kids can then watch TV in the back while you are driving if they get bored looking at the passing scenery and learning stuff.
  • Thanks for all the info, guys. Looks like both options will work based on the few inputs so far. Anyone have a _strong_ opinion on why one is better, or would this end up as just a matter of style/choice?

    Easy wiring for Option 1 would be to get an inverter that accepts my 30A plug and just plug the shore power cable into it. That cable is currently very close to where the battery bank will be, so this would make installation very easy. When you plug the cable into shore power, does it still charge the batteries with this wiring?

    If I go with Option 2, I'll mount the smaller inverter inside the rig right above the battery bank, with the 120V lines running under the rig to an outlet in the kitchen and the TV outlet in the bedroom. This minimizes long 12V cables, and inverter draw compared to Option 1.

    Mena - Do you run your fridge from the batteries/inverter, or do you manually switch the fridge to LP? Thinking battery bank capacity here.
  • One big inverter to run the whole rig. I run my inverter whole house meaning I plug the shore cord into the inverter and turn off the converter.
  • RoyB's avatar
    RoyB
    Explorer II
    I found that large inverters draw a bunch of power... My 1500WATT AIM PSW Inverter will draw over 150AMPS if fully loaded. If you just have one 110AH battery it would only last about 15-20 minutes... Don't know what you four 6V AGM batteries will produce but if it is around 450AH then a fully loaded 1500WATT Inverter may only last a couple of hours...

    Just keep that in mind...

    I run all of my home entertainment items including HDTV and DVDs on a 600WATT PSW Inverter. I ran two 120VAC drops from this unit, one going to the home entertainment area and the other one going to the nite stand near the bed. Typically I will draw around 20AMPs from my 255AH battery bank using this inverter bewteen 8PM to 11PM then it will all drop down to around 1-2AMPS draw the rest of the night until 8AM the next morning when I can run my generator to re-charge the battery bank back up to 90% charge state in a three hour time period. Then I can do all of this all over again for the next day/night battery run...

    Check with others how many AMPS they draw using their high wattage Inverters...
    My game plan is to run the smaller wattage items from the Inverter and then wait until I have the generator running to handle the larger wattage items.

    Roy Ken
  • I would mount the inverter as close to the batteries as possible. The spec sheet for a 600w Samlex inverter calls out 8ga. wire at 1.5 meter, maximum. You will need larger wire for bigger inverters. If I didn't already know how deficient the DC wire was in most RV's I'd suggest a plug in 300w inverter for the TV in the bedroom. It would save time and expense. You just can't be sure how the mfg. decided to connect your DC receptacles. It may result in loss of the inverter or loss of the device powered. The better solution is to mount an inverter close to the batteries and pull a new length of AC to the desired location.
  • I would check to see what wire guage would be needed to provide adequate power from the battery bank to the chosen inverter.
    The reason I say this is it may be easier and cost less to have the inverter close to the battery bank, using a smaller guage wire to the ac outlet.
    Personally I would opt for a single inverter and use the smaller guage wire to the outlets.
    Ideally the inverter should be as close as possible to the power source.
  • I started with a large inverter to power the microwave. It powers just the one circuit plus an added GFI in the kitchen area. That was before solar and it idles at about 2 amps.

    I used a small inverter out of the 12v connector but it was inconvenient with all the plug in stuff. I debated connecting the big inverter to the outlets but decided on a small 300w inverter for the rest. Idles at 260 milliamps.

    I wired mine to separate circuits with separate transfer switches. Large inverter has a built in switch.

    Idle draw not such a big deal now with solar but I still like the pair. Works for me.
  • I vote for 1. Seems to me you should always vent an inveter.

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