Max solar panel for RV30 controller

[geordi]

Originally Posted by 757driver

Jim,

At 335 watts at high noon in the summer you are getting very good output from those panels. The output of 16 amps is about 67% of what the panels are capable of. That controller may be getting old and tired or perhaps your wiring is undersized. I would check into this prior to adding more solar.

We don't have enough information to know if 335 watts from those panels is good or not - we don't know what they are rated, only what they output. We are missing another key piece of info to evaluate them - the voltage or the amperage.

W=VA, and volts and amps can vary inversely to each other - watts never change.

My panels are 6.7 amp, 45vdc nominal, 340 watt each. I have actually seen the controller reach 1000 watts (only 20 watts off the sticker-max!) in Southern USA full sun... And this gives you all the info to evaluate my setup's efficiency according to the stickers. Obviously mine are quite good, at least now since they are still very new.

The "panel efficiency" rating is something of a misnomer and useless to the consumer, b/c the average consumer has no way of measuring the total number of photons landing on them from the sun. The panel rating is based on a foot-candle-per-foot-square rating measured in a laboratory with a controlled light source, and (for example) since the sun outputs X, the panel is judged to be 15% efficient if it can convert 15%X into electrons.

This efficiency percentage isn't practical information for the consumer... What are we to do, try and save up a cup of extra photons to pour on the panel when it is cloudy? LOL, I wish.

All we know is whether a 100, 150, 200 watt (or 340 watt) panel is producing that many watts at the controller... If it is, AWESOME! Getting the sticker-rating out of a system and getting it all the way to the batteries is dang hard!

[vsheetz]

You need to know what occurs within the controller when excess PV current is applied. Blows up, dumps the excess, stops passing current, other. See the manufacturer data for this info. Then you know how much margin you may have for oversubscription.

You need to determine the parameters if your installation to see what the real expected production is. For example, typically a 15% reduction from rated output can be expected if mounted flat. PVWatts software can be used to model thus.

[jacwjames]

One issue is that I have 2 different size panels. The original 80 watt panel installed by Monaco and 2 Kyocera 120 watt panels. So I actually 320 watt of solar.
The 1 panel is a BP Solar, 4.4 amp, and 18 Vmp.

The 2 Kyocera I replaced with new (under warranty) in 2010. They are rated at 7.45 amp, Vpmax 16.9 volt.

When I checked the panels I used blankets to cover up 2 of the 3 and recorded the amperage.

So I believe they are working about as well as I could expect.

Still would like to get to the 30 amp charging if at al possible.

[geordi]

Originally Posted by jacwjames

One issue is that I have 2 different size panels. The original 80 watt panel installed by Monaco and 2 Kyocera 120 watt panels. So I actually 320 watt of solar.
The 1 panel is a BP Solar, 4.4 amp, and 18 Vmp.

The 2 Kyocera I replaced with new (under warranty) in 2010. They are rated at 7.45 amp, Vpmax 16.9 volt.

When I checked the panels I used blankets to cover up 2 of the 3 and recorded the amperage.

So I believe they are working about as well as I could expect.

Still would like to get to the 30 amp charging if at al possible.

Ok... NOW we are getting somewhere on the knowledge. Mismatched panels create entertainment in setting things up, you *will* have to make a compromise somewhere and you may still need a different controller.

First things first: 30 amps is the OUTPUT of the controller. To get to that, you will need bit more solar in the front end, you need at least 360 watts of solar, 400 is better because of losses and inefficiencies, clouds, etc.

You have to connect these panels in a certain way, either in series or in parallel. Series (how I did my setup) adds the voltage of each panel together, but all panels will only produce the same amperage as the lowest panel. For your option, I don't think this is a good way, you lose too much.

Connecting each panel in parallel adds the amperage but the voltage will only match the lowest panel. So in this, you lose 1 volt off of the highest voltage (but lowest wattage) output panel (not a huge loss) but still get to add the amperages together. That means your controller should be seeing 19.3 amps at 17 volts, or 328 watts of power.

Now at a 12v nominal system, that means you get a maximum charging output from your controller of 27.3 amps, if there is no losses.

You haven't mentioned if your controller is an MPPT or PWM style. PWM is just an "onff" style, and about as technologically advanced as a hammer. You want MPPT, but no matter what controller you have... Mismatched panels induce losses. I also doubt that Monaco (or any other coach builder) will have bought the highest quality panels or systems... They want this as a gimmick to sell coaches! They don't really care if it provides useful power, just that they can SAY you have a solar system and you buy it from them because of the marketing. Honestly, you may be better off getting a third panel of the Kyocera ones you already bought, (maybe 2 if you have the roof space) and going for a better controller from someone like Victron. Why do I say this? Quality of the system and the size of wiring.

By going with "low voltage" but high amperage, you will need thicker wires, or you will have losses and possibly even fire risks. As I mentioned before, wattage never changes but voltage and amperage vary inversely to each other. So a standard 12 gauge extension cord for example is rated at 1800 watts carrying... Which under normal usage is 15 amps and 120 volts. AC or DC doesn't really matter for this calculation. BUT if you want that same 1800 watts at 12 volts.... You are asking that wire to carry 150 amps!

Just like the starter cables on the engine are 4-0 (four-ought) and rated to handle 500 amps momentarily... The lower the voltage the thicker your wire would need to be for the amperage. For a 19 amp load, you will need 8-gauge cables to avoid losses or heating in the wires. Adding another panel to raise that 19 amps even further, you might end up needing 6 gauge cables which are quite pricey.

Since you still need another panel anyway, matching what you have and combining them in series would mean your controller would see: 3x 16.9= 50.7 volts and 7.45 amps, WELL under the ratings for a 12 gauge cable. An MPPT controller would easily be able to step that down to the battery charge voltage and that 377 watts would translate to 31 amps of charging into your batteries.

A controller like the Victron 100:30 would be able to handle this task quite nicely for you. https://www.victronenergy.com/solar-...-100-30-100-50

Victron controllers also shed excess power, although since you would be so closely matched with 3 panels... I think it would be just about a perfect fit.

https://www.amazon.com/Victron-Energ...s%2C160&sr=8-9

[TajMahal]

Originally Posted by jacwjames

One issue is that I have 2 different size panels. The original 80 watt panel installed by Monaco and 2 Kyocera 120 watt panels. So I actually 320 watt of solar.
The 1 panel is a BP Solar, 4.4 amp, and 18 Vmp.

The 2 Kyocera I replaced with new (under warranty) in 2010. They are rated at 7.45 amp, Vpmax 16.9 volt.

When I checked the panels I used blankets to cover up 2 of the 3 and recorded the amperage.

So I believe they are working about as well as I could expect.

Still would like to get to the 30 amp charging if at al possible.

Here's a read about what happens when you start mixing different size panels. Good Luck
https://solarpanelsvenue.com/mixing-solar-panels/

[jacwjames]

All good information, Thanks.

One question though is I still have to get power from the controller, which is located above the passenger seat, back to the batteries located passenger side rear of coach. I'm guessing the distance has to be +30 ft (not sure the current routing). The wire is 8 awg. What is the maximum amperage I can push using this wire, one source I looked at showed ~20 amp

If that's the case it's a mute point getting a 30 amp controller unless I change my wire to 4 awg. Not sure how'd I'd route this.

[geordi]

Originally Posted by jacwjames

All good information, Thanks.

One question though is I still have to get power from the controller, which is located above the passenger seat, back to the batteries located passenger side rear of coach. I'm guessing the distance has to be +30 ft (not sure the current routing). The wire is 8 awg. What is the maximum amperage I can push using this wire, one source I looked at showed ~20 amp

If that's the case it's a mute point getting a 30 amp controller unless I change my wire to 4 awg. Not sure how'd I'd route this.

Yeah... That distance is not optimal. You may want to think about moving your controller as close as practical to the batteries. The higher the voltage, the longer it can go (through thinner wires) without losing energy. At 12v, you will lose a LOT of that power before it ever finds the batteries.

As far as sizing... I'm seeing that even the 8awg you have now isn't capable of 20 amp, more like 15. You will induce losses in the cable. Moving the controller to next to the batteries and using higher voltage will solve this. That's why a 12awg at 120v can handle 15 amps, but no chance it can do the same 15 amps at 12 volt!

My controller is actually mounted in the battery bay, and is only about 3 feet wire-distance from the batteries. I still used 4-0 welding cable though, b/c it is low voltage and silly high 80 amps. Although the chart that I have says for that length (under 6 feet), I could have used 4AWG, as 2-0 is rated for 200 amp service.

[vsheetz]

Originally Posted by jacwjames

All good information, Thanks.

One question though is I still have to get power from the controller, which is located above the passenger seat, back to the batteries located passenger side rear of coach. I'm guessing the distance has to be +30 ft (not sure the current routing). The wire is 8 awg. What is the maximum amperage I can push using this wire, one source I looked at showed ~20 amp

If that's the case it's a mute point getting a 30 amp controller unless I change my wire to 4 awg. Not sure how'd I'd route this.

Sounds liheca different, and larger, controller would do you the best. Place the controller near the batteries. Look at something like victron with bluetooth communications for monitoring.

[JohnBoyToo]

You know, I usually zone out when a thread gets too deep in the weeds regarding a subject as it usually is something I'll never have a use for... Just want to know enough to use something - and only curious about deeper knowledge on things I'm interested in...



But kudo's to a deep, but good discussion here - I read it all !


(I still may not use it as the DW thinks murderers are around every tree where we would boondock and/or if the site does not have a resort label, it's below her standards ) but still curious about upgrading the marginal oem solar Monaco put on our dip...

[jacwjames]

OK, so it appears as if the front controller and solar panels are limited out but still functioning and it would be difficult to redo to improve overall capacity.



Is it possible to just add additional panels near the rear of the coach and a second controller very close to the batteries.


One of the articles I read actually showed 2 controllers. Is there any special considerations if I decided to go this route?

[TajMahal]

Originally Posted by jacwjames

Is it possible to just add additional panels near the rear of the coach and a second controller very close to the batteries.
One of the articles I read actually showed 2 controllers. Is there any special considerations if I decided to go this route?

I have heard of people adding a 2nd controller and panels but have no info on anything else about it, good, bad, or indifferent. It would make sense to have 2 systems as if 1 fails, you still have some solar commin in to keep you going. Sorry I can't be of more help. Good Luck

[jacwjames]

Originally Posted by TajMahal

I have heard of people adding a 2nd controller and panels but have no info on anything else about it, good, bad, or indifferent. It would make sense to have 2 systems as if 1 fails, you still have some solar commin in to keep you going. Sorry I can't be of more help. Good Luck

I actually saw this in the article you posted earlier. 2 substantially different size panels and the solution was to have 2 different controllers.



Having a separate system does provide a safety net in case one fails.

[BillJinOR]

Originally Posted by jacwjames

OK, so it appears as if the front controller and solar panels are limited out but still functioning and it would be difficult to redo to improve overall capacity.



Is it possible to just add additional panels near the rear of the coach and a second controller very close to the batteries.


One of the articles I read actually showed 2 controllers. Is there any special considerations if I decided to go this route?

Yes exactly what I’ve done .. original 160 watts of panels by one controller and 800 watts of new panels down the back closet to the batteries with a new controller .. they will both work to add to the system. Along with the inverter/ charger they all just work together

[jacwjames]

OK, good to know. Sounds like this would be the most viable solution if I choose to add more solar.