Basic Questions on Solar Install

[freetheheal]

I'm finally getting rid of the generator and looking to install solar. Right now I have a 2000W inverter and 450AH of lead acid batteries. I'm looking at installing (3) 175W panels and an MPPT charge controller. I'd like to run my idea by the forum and make sure I'm not missing something.

My run from the panels to the charge controller is about 25'. From what I've found I should wire the panels in series and run a 10 gauge wire. I'm looking at the Renogy Rover 60 mppt controller and that can handle up to 140V which is well within the parameter of the open circuit voltage of the 175W panels which is 24.3V per panel and allows room for additional panels down the road if the need arises. Does anyone see an issue with this or something that I'm missing?

From the charge controller to the batteries I am going to run 8 guage wire (5') with a 60amp fuse.

And between the solar panels and charge controller I was going to mount a 10amp fuse (the solar panels optimum operating current is 8.62amps).

Does this seem like a good plan so far? Am I missing anything? Thank you for your input and help.

[BFL13]

Parallel keeps the voltage down, which can be good when the controller has a lower voltage limit--the total of all the Vocs plus a bit for "margin" if in series.

Parallel or series has no effect on the controller to battery wiring gauge of course--about the same amps at "12v".

[pianotuna]

freetheheal wrote:
What does everyone think about wiring the panels in series? Should I be concerned about a shadow cast onto the panels from the covers if the panels are in series?

My system is in series/parallel because of a #10 prewire. Going to a 33 volt input got my line losses down to less than 1%. It also means that charging starts earlier in the day, and lasts longer.

My panels are unusual because they have bypass didoes for each cell.

If doing series it is important to not have shade on the panels.

[pianotuna]

I'd wait six months to dump the generator.

[Freep]

Lwiddis wrote:
“Dumping” the generator isn’t the best plan IMO. If you have a generator available, you won’t need it. If you don’t...

That really depends on the rig, how you use it and your preferences and lifestyle.

We have a truck camper and we boondock a lot. We've used the gen maybe 4 times in the last 5 years. It's loud and obnoxious and we generally don't stay in one place for more than 2 days. If the weather isn't good for solar, we go where it is.

We hate the generator and are looking forward to dumping it.

Right now I'm preparing to build a new LifePo4 battery bank and I should be able to put a decent charge in the battery from running the engine of the truck if it ever gets too low but I doubt that will happen. I'm moving up from 2 100ah lifeline AGMs to a 270 ah lifepo4 battery which means a change from 100ah usable to about 250 ah usable.

If this goes well, I'll probably dump the gen, add 300 more watts of solar and expand the bank to 540 ah.

[2oldman]

My 6 panels are in series. Yes, shadows will degrade,somewhat, but a little shadow isn't going to kill the entire string.

There are times in winter when my panels are tilted where I will get shadows from the other panels and the a/c cowling, but that's temporary as the sun moves (ok, the earth moves). I have enough wattage to make up for any shadow loss.

Series is great for no combiner and smaller wire. Just need to be careful with that higher voltage. It stings!

[time2roll]

Series is less connections and no combiner box to cause trouble.
All plug and play with MC4 for easier installation.

[BFL13]

I can only say about what I learned in real life playing with my three 100w panels in my ground mounted set-up. I could easily swap back and forth putting them in series or parallel with an MPPT controller and with them in parallel I could swap between MPPT and PWM controllers, leaving all wiring as is. So I did.

I was also able to see how shading part of one panel affected the array by watching the shadow cross the panel and the Trimetric monitor when in series or parallel. So I did all that to see what really happens. the shadow did not conveniently do just one by-pass section at a time, but was at an angle that would get part of two sections, eg.

In full sun I got the same amps to the battery no matter which way I did it, series or parallel, and PWM or MPPT. MPPT did a little better in the shoulder hours, but I never saw the fabled better low light with them in series and a higher voltage. It is a good theory, but in low light solar is near useless anyway, so whatever.

On shading, it was better to have them in parallel. However it didn't matter much in my case because the shading was late in the day with the sun at a low angle. By then I already had most of the solar I was going to get that day.

In this case with the panels on the roof and shading from vent covers and the A/C shroud, and even the TV antenna, it could matter for more of the day with the sun higher. So parallel is my vote!

Note that you can use taller "legs" to mount the panels so they are not as low compared with the height of the vent covers. You can test for shading ahead of time by using cardboard "panels" at different heights and positions on the roof. If you can't escape shading completely, you can learn which way to park to get the most sun, if you have the option of which way to park.

[freetheheal]

What does everyone think about wiring the panels in series? I had talked to Renogy about it awhile back and they recommended series because I needed to run about 25'-30' from the solar panels to the charge controller. These will be mounted on top of a travel trailer and between two vents that have large covers on them so they can stay open in the rain. Should I be concerned about a shadow cast onto the panels from the covers if the panels are in series?

[BFL13]

That one is perfect. No confusion there!

[Boon_Docker]

BFL13 wrote:
Those wire gauge calculators drive me crazy. You have to figure out if they mean for both wires (round trip) or just one way distance for one of the wires. Some calculators make that more clear than others. That one is unclear IMO. You want the total length for the round trip. It also helps if it is clear they mean copper wire.

I find this one to be a good voltage drop calculator.

[BFL13]

If the controller can take fatter wire, it is an easy decision. If it can take #8 as its fattest, you still have the choice of using a short piece of #8 then joining that to a fatter longer wire to the battery

[pianotuna]

#4 would be my choice for controller to battery bank.

[2oldman]

freetheheal wrote:
Is 8 gauge good for running from the controller to the batteries?

I think #8 might be a bit close for a maximum of 40 amps, but it may not reach that very often. I'm assuming this is a 12v bank.

[freetheheal]

Thanks again for the input. Is 8 gauge good for running from the controller to the batteries? This will be about 6'.

[BFL13]

Those wire gauge calculators drive me crazy. You have to figure out if they mean for both wires (round trip) or just one way distance for one of the wires. Some calculators make that more clear than others. That one is unclear IMO. You want the total length for the round trip. It also helps if it is clear they mean copper wire.