using 400 watt solar kit w/ extra battery I already have....

You would be much better off not using the inverter to charge the RV battery. I lived in my motorhome for years without turning on my charger. I have a 415 rated watt solar system.

You could install the solar panels on the shed, then install one battery either there, or in the RV, and run the wiring to it. 12 volt wiring can run between the two batteries and charge it fine. #10 UV rated direct burial romex will work fine, you can buy it by the foot or in 25 - 50 foot rolls at Home Depot, Lowers, ect.

#10 will carry 30 amps, but for the most part, your RV power load will stay under 10 amps on average, so voltage drop should be insignificant. By leaving it at 12 volts, you will save a lot of power that might otherwise be used by the inverter and charger.

Say you had a 10 amp load in the trailer at 12 volts or about 120 watts of lights on. The charger would use about 150 watts to make that power. To supply that power from a inverter, then the inverter would be consuming about 180 watts - perhaps as much as 220 watts, depending on it's efficiency. So your inverter might be drawing 20 amps to put 10 amps into the trailer battery. Not what you want to happen.

I would really recommend putting both batteries as close together as possible, then run the solar wire from the panels, through #10 wire for each 200 watts, to the battery bank.

If you have a MPPT controller, and can wire all the panels in series so that it has say 80 volts input and 12 volt output (there are many controllers that will accept up to say 150 volts input and have 12 or 24 volt output, your choice) that would be ideal, but a MPPT controller is about 3 times as expensive as a PWM controller, and you might only collect another 50 watts per day using the much more expensive controller.

Panel prices are so low these days, you could find a 140 watt 12 volt panel new for $229, install that and a $20 20 amp PWM controller and get more energy than a $300 MPPT controller will get you. . .

SunElec.com has both controllers and panels for great prices. So if you upgrade, think about them. For RV's you want something with a aluminum frame. For homes, or your shed, frameless will work, but frames are easier to mount to.

Good luck,

Fred.

Guess I should have made it plain that I'm aiming for a rudimentary exploration of this concept, using what I already have, without killing myself or frying the RV. In a few months, I'll start all over with the house I'm building. I should understand solar power a little better then.

I figure it out a little at a time. Long as it won't electrocute me, I'll see what it does, and take it from there.

It all depends on what you are doing in the trailer. Living in it? Weekend cottage?

The OP asks can this work, with split bank etc, so answer is yes, but that way is not necessarily what most would recommend for the job.

Why does the OP want to have one battery at each end of the trailer instead of putting both together at the front? We don't know enough.

Best way is to ignore the converter unless you have a generator, combine four batteries (get two more) in one bank a the front, connect the inverter and plug the shore power into it (unplug the converter!!!) Use all 400w of solar on the big battery bank (might need two controllers if that is two kits, but the two controllers can be in parallel on the one bank.)

You can set up the solar panels tilted up facing South on the ground or on the roof of the trailer or you can build a "contraption" so you can turn them towards the sun a few times a day to keep it aimed.

Many ways to do it and they all work. But what is "it"?

The air conditioner is something I won't worry about til next summer! :)

400 watts of solar
400 watts is 3.5 amps at 120v output from the inverter
The a/c uses about 12 amps at 120v that's 1400 watts
Wire all the batteries together to the solar
Using DC into inverter to drive converter to make DC for the other battery is double conversion and a lot of wasted power, possibly 20% our more wasted in the process
There are one or two members that run a small 5 amp 600 watt, window a/c using a big battery bank and 900 watts or more of solar

(yeah, I meant the solar panels would be enough to keep that 2nd battery charged for at least awhile each day)

but I don't need some other kind of ground-wire connection, right? Just the positive and negative from the battery to the inverter. I will never understand all that about grounding.

Not quite--the 1500w inverter will need more of a battery bank to be able to run anything. Usually need four batteries to run a big inverter that runs bigger things like microwave, toaster, kettle.

Solar doesn't work at night and won't supply the inverter directly by day either. It just slowly resupplies the battery bank after the inverter runs it down.

So, I could set the 2nd battery on the platform (that's already on the back of the RV), hook it up to the inverter with the two thick cables (and a fuse), plug the RV power cord into the inverter? (with an adapter plug to take the 30-amp RV plug down to the "regular" outlet on the inverter?)

I'll assume for now that 400 watts worth of solar panels in the Texas sun :) will be enough to power the inverter and then through the converter to the other battery, if I'm visualizing this correctly.

You don't need a ground rod.

You can do that with the inverter on one battery bank with the shore power cord plugged into the inverter and the converter to charge the other battery bank. You can't have the inverter and converter on the same bank (loop-drains battery)

You can have the two solar sets each with its own controller. One can be on each battery bank. Or you can put both controllers in parallel on the same battery bank, or you can combine the banks and have all the solar on that (but now the inverter can't run the converter, but it might not need to if the solar can do it all)

What's missing as a way to run the converter to charge the batteries when there isn't enough solar for too long. Usually a generator does that.