Buying, hooking up solar and then an Inverter

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Well-known member
Aug 30, 2018
I want to install solar,  so here is what I have now...  ON a 28 ft dutchman
To run my generator I have to take the shore cable and plug it into a spot in the RV. Then I run the generator for 110 ....unplug it and no power ...

If Im NOt using the Genset. I have one house battery  ( which sits in its own little outside compartment)  The power goes to a converter which then lights the 12v lights and other 12v plugs.  There is no inverter , book says there is one, but how it works or where it may be I cant find it.

So ive decided I need 300 watts of solar, When i  hook them up
the panels will NOT be wired in series but parallel. As I understand it, if in series, one part of a panel doesnt get any sun. Then entire system stops working NOT just the panel in the shade.

I'll put a fuse between The panel and the controller, Im going with a 30 Amp controller which will handle what IM doing plus more panels if needed. and another fuse between the controller and the Batteries.  Im going to buy 2 deep cycle 12v batteries and mount them in a storage compartment .  Then run a wire from them to the 3rd battery. The 3 batteries will be wired so the system is 12V ( of course) .....

so first question,  can the wires from the controller, go on just one battery , or do I need to put one wire on one battery and one at the other end of the row of batteries one on + one on - ...????  ( its not  a stupid question if u dont know the answer)

at this point I'll have lots of 12v power  but...

Then the big question. I'll buy a pure sine wave inverter. connect it to the house batteries.  and then what???????

I can put in another 30 amp plug and when I want to use solar, I unplug from the generator and plug in the solar.  sure that would work
but can I connect it any place else so I dont have to  connect the plug each time I want to use it.

Last question, prices ive gotten
30 amp controller ,$175
300 watts of panels  ( going with Monochrystalline ) $329
Inverter $350
fuses n wire$ 20
two batteries  109 each
Price around $1100,  does that sound right?????

Hi rvwanderer1... Here's a few things to consider. There's nothing "wrong" with wiring the panels in parallel, because when wired in series, shading on one panel will affect the other panels. However, there are distinct advantages of wiring panels in series - most importantly, higher voltage. The higher voltage of series-wired panels will produce more amps when used in conjunction with an MPPT controller. You mentioned getting a 30 amp controller, but you didn't mention whether it's a PWM or MPPT controller.

An MPPT controller doesn't help much on smaller solar arrays, but they do help with larger arrays. MPPT controllers convert excess voltage to amps, PWM controllers don't. PWM controllers basically convert excess voltage to heat, and "toss it overboard." A 300 watt array could benefit from an MPPT controller, but only if the panels are wired in series. For what it's worth, we have six panels. Every two panels are wired in series, and then the three sets of series-wired panels are wired in parallel.

You didn't mention the number of panels you're planning to install, but if you're installing three 100 watt panels, for example, each panel will generate approximately 19 volts and about 5.3 amps. When it comes to RV solar, it's all about replenishing amps, so getting as many amps as possible out of your array, in the limited solar charging window (about 6 hours) is important. Do you plan on tilting them? Tilting your panels toward the sun can increase their output by 45%, or more.

Most RV solar installations don't have fuses between the panels and the controller. There's nothing wrong with doing that, but to ensure maximum safety, you'd need a fuse between each panel and the controller, if they're wired in parallel. However, there should be a fuse between the controller and the battery bank.

Speaking of batteries.... solar is a package deal (at least that's how it should be considered.) It includes; charge capacity, storage capacity and consumption. It's best to balance those things as equally as possible with, perhaps, a bit more charge capacity than needed (for cloudy days.) You said you were planning to install two more house batteries. That's a good plan, but make sure all three batteries have the same (or very near) the same AH capacity. Batteries with significantly different capacities will charge at different rates, and depending on conditions, could make it difficult for all three batteries to reach full charge.

If the original battery is a few years old, you might consider replacing it as well. As batteries age, their ability to store amps diminishes, and the time it takes to fully recharge, increases - even more so if they weren't maintained well. Keep the batteries as close to each other as possible, and use as thick a gauge wire as is practical.

The wires from the controller to the batteries should go to the positive terminal of one battery, and the negative terminal of the battery at the other end of the battery bank. That helps ensure as equal a charge as possible to all the batteries. Yes, the batteries will charge if you attach the wires to only one battery, but the charge won't be equal to all three batteries, especially if the wire run is long and/or inadequate. Truthfully, it won't be "equal" to all three batteries when wired as I recommended, but it will be more equal than wiring the controller to one battery.

You won't need to plug and unplug your power cord when your solar array is charging. The charge controller detects when another power source is charging the batteries (genset or shore power) and throttles back on its own. Installing an inverter is pretty straightforward, and won't have much of anything to do with your solar installation. The solar installation simply recharges the batteries. Just follow the inverter's installation instructions and you'll be fine.

I would highly recommend installing a good battery monitor. Among other things, they measure the amps going in or out of your battery bank at any given time, and enable you to tell - at a glance - the SOC of your battery bank. Voltage is a relatively inaccurate parameter to determine a battery's SOC. IMO, they're a must-have if you boondock - especially with solar.

Hello Wanderer!

I will not speak to the solar part, but your second paragraph has some incorrect assumptions.

Without an inverter, 120 power from either shore power or generator is required, as you said.  When you have 120V power, the converter changes this 120VAC to 12VDC to charge the batteries.  When no 120V power is present, the converter is completely out of the picture.  The batteries provide 12V power to the coach.

Personally, I would wire the CON verter output, INV erter input, solar output and battery pack all together.  This means the solar / converter charge all batteries and all batteries feed the inverter.
I am going to disagree with Kevin here on the MPPT vs PWM issue a bit, An MPPT solar charge controller will still out perform a PWM controller by a good bit even with panels wired in parallel, though it will generally do even better wired in series.  As to the single shaded panel issue, this can be partly compensated for by using bypass diodes.

p.s. as to handling automatic switching, you need to add an automatic transfer switch for the generator, as well as opt for an inverter with its own automatic transfer switch.
I have six 100 watt panels on my roof.  I paired panels in groups of 2 that are run in series and then the three pairs of panels are linked in parallel. I feel I have the best of both worlds with regards to not losing all power due to partial shading and taking advantage of higher efficiency with an MPPT controller with higher input voltages.
The solar panels I now pretty much understand.

when we get to the inverter I'm still lost........  On my boat, I just wired the inverter to the batteries.  Plugged in a cord that ran to a power strip and I had
110 for hair dryers etc. just about everything else on the boat was 12 v 

THE RV is different,  I want the inverter to power microwave tv  etc.  meaning I want the whole coach to be able to use the inverter....

How and where I make that connection , im completely lost.......Like I said, I could put in a plug, take the shore power cord and plug into the inverter 
but Id rather NOT have to go out side each time I want to use the inverter.

I may do that for starters but Iknow there is a better way. 
Autotransfer switch and subpanel so you do not power the hot water heater, air conditioner, fridge, and CONVERTER, on 120 volts AC fed by inverter.

Every outlet in my 5th wheel has electrical power going to it automatically from my inverter.  Since my inverter is only 1500 watts, I have to watch that I don't exceed this capacity by only running one high power item at a time.
There are SOME things you really do not want on the inverter.  The converter is NEVER connected to an inverter!!  A/C could completely drain your battery bank in just a few minutes.  Water heater is a big draw that runs well on propane.  Fridge is a smaller but significant draw that can run on propane.  Microwave is a big draw, and requires a bigger battery bank, but is certainly possible.  There was a recent thread on this topic.

The most simple way to wire an inverter is to run a wire from a breaker in your main panel to the inverter.  This goes to the auto transfer switch(ATS)  (built into the inverter?).  You also connect the battery bank directly to the inverter.  These are both INPUT sources.  If AC power is present, the ATS switches AC to the output wiring.  If no AC is present, the ATS switches the inverter generated 120VAC to the output wiring.

This common output wire goes to a new electrical sub box.  It then provides power through breakers to the selected circuits, which are removed from the main panel and relocated to this sub panel.

For the circuits still in the main panel, nothing has changed.
For circuits now on the inverter, if AC power is available (i.e. shore power), the ATS passes this power to the sub box and to the connected circuits.  If AC power is lost or not available, the ATS switches to the inverter to provide power to these circuits.

Hope this helps!

EDIT:  Here is that microwave thread.,117866.msg1069098.html#msg1069098

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