Questions about adding solar panels

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Questions about adding solar panels

November 23, 2011, 10:08:13 pm

Greetings,

I've been putting together a strategy to add solar to my coach; am hoping those that have been there can answer a few questions. Planning to add four 135 watt panels, which seems to be what I need with a pair of 8D gel house batteries.

1. I spent about an hour on the roof with a tape measure. Still not sure on the layout. Seems to me I should leave room to access everything and be able to move around. This leaves me with a rather oddball layout. Wondering if it matters how close the panels are to each other, and will it matter if some run lengthwise and some across the roof.

2. It appears the easiest way to hook the panels up is with the combiner box on the side of the fridge roof vent, then down the back of the fridge bay into the battery bay below. Is there a better way?

3. Where did you mount your charge controller? Looks like for me it will be in the battery bay, as under the fridge will be the inverter and control modules. Am concerned about how hot the controller might get, though. If the batteries are charged and there is no draw, what happens to the solar energy? Does the current get dissipated as heat through a resistive load?

4. The MPPT controllers I looked at thus far indicate they may generate electrical noise when running in pulse mode. Has this proven to be an issue for anyone?

Thanks for any insight you can offer.

Steve

Re: Questions about adding solar panels

Reply #1 – November 23, 2011, 11:55:43 pm

We also like the Kyocera 135 solar panels (Affordable Solar $332) and have four mounted front to rear on aluminum angles bolted to panels, which are bolted to 2nd set of aluminum angles screwed to roof braces. Our roof layout is solar friendly as we have no roof AC units forward of kitchen. We wired (#10 cable) each panel to one combiner box (AM Solar $50) so we could series them or remove a panel within the combiner. We use #6 cable from combiner to a Morningstar 60-amp MPPT controller (Infinigi $610) mounted on bay wall with 50-amp circuit breakers on cables to and from controller. The breakers turned out to be very handy as we can easily disconnect our solar panels if desired

Two panels mounted end to end (2' x 10') are located near edge roof edge starting from just behind air horns. We recently added two more panels and found we could swap out the connector bus bars in the combiner for longer bus bars. Next time I would use the larger AM Solar combiner to start with. Our #10 cables are THHN from Lowe's run inside 1/2" Non-Metallic Liquid-Tight Flexible Conduit. We can access our solar controller's memory with our laptops as the controller is plugged into our computer.(Ethernet).network. We found our roof metal supports using an electronic stud finder from Lowe's.

Max amps displayed on our controller's remote kitchen panel has been 36 amps. The other day on an overcast day we got 7 amps, so clear skies make a difference. I recommend buying a solar controller with much greater capacity than current needs dictate for expansion and for very low batteries on a very cold day. Also MPPT increases will not run into a maximum limiting capacity. I am not aware of a lot of heat form our controller.

Re: Questions about adding solar panels

Reply #2 – November 24, 2011, 01:32:58 am

We set our four panels up on the passenger side of the motorhome. We now always park pointing the windshield to the East. Our refrigerator is on the north side in the shade. We tilt our panels up around December 1 and take them down about April 15. We drive everywhere with them up.

Regards,
Jon Twork

Retired, Unemployed, Homeless, Transients
1996 Foretravel U270-36 w/24

Re: Questions about adding solar panels

Reply #3 – November 24, 2011, 07:09:00 am

When I put my panels up on my 99. I ran the cable into the back cap and down into the engine compartment and thru the center channel into the battery compartment. I put the charge controller MPPT under the bed so that is the reason for that run. I could see it that way. I might do it differently in this coach and go down the fridge area as I have room under the fridge to put the controller but I can not see the side of the fridge if the slide is in so maybe the bedroom is still the best place.

Re: Questions about adding solar panels

Reply #4 – November 24, 2011, 10:31:09 am

Thank you all for the replies.

I guess the layout depends on the floor plan, and there are a lot of variations over the years. I've attached a crude drawing of my layout thus far; while I could pack the panels closer, I wouldn't be able to get to the front AC unit for maintenance.

Am planning to add a remote meter/display with the controller - my issue now is where to group all the panels together (power line monitor, inverter remote, solar controller remote, tank level display). Not a lot of places to put these, and getting the cables routed is a big part of it. There's always something.

Relative to heat generation, it sounds like putting the controller in the battery bay will work all right. Was going for a 45 amp controller, but I guess the 60 amp might be a good idea. I could only conceivably add two more panels, but then I wouldn't be able to move around or access anything up there.

Re: mounting the panels - do you need to attach to the roof rails? Given the limitations of where I can place the panels, this might be a problem.

Re: tilting the panels - some online vendors say it isn't worth it as the difference is insignificant, while others say it makes a big difference. Seems to come down to whether or not they sell a tilt mounting system. What are your own experiences with this?

And lastly, something that occurred to me this morning - what happens if the inverter is charging at the same time the solar system is? Wouldn't there be a conflict?

Thanks again for your help.

Steve

Re: Questions about adding solar panels

Reply #5 – November 24, 2011, 01:05:56 pm

My experience with solar panels has made me think that the ability to aim them is important. Perhaps not critical because you could probably put enough power on top of a 40-foot coach so that if it's parked in Arizona or Florida it would not be an issue. But one plus to a tilting mount is that you move the heat away from the coach roof. So that, if nothing else, would make me move to a tilting panel mount.

Craig

Re: Questions about adding solar panels

Reply #6 – November 24, 2011, 01:48:02 pm

I have 4@ 150watt and 3- 8d lifeline for 675ah. I have tilting and find it makes a big difference I have used them so far this trip ( am now in San Carlos Mexico) and they have given me all the power I need so far and take about 4 hrs to bring from 89% battery state back up to 100%. semi cloudy. I have 45 Morningstar controller and AM Solar said that as the panels very seldom work at 100% I can put at least another 1 to 2 panels on roof before needing to change to 60 model (I should have done that at first but did not think I would be going all solar then) I am also changing all lites to LED which as you know makes a big saving of power. So far happy and when we get further down south and set them in tilt for 3 months will know better how it all works but do not see any problems .
John

Re: Questions about adding solar panels

Reply #7 – November 25, 2011, 09:35:32 am

Thanks folks.

Re: inverter/charger with a solar charger - wondering what happens if the gennie is running and the sun is shining - found this (pertains to a residential install, but still applies I think) -

Quote

When using these more sophisticated battery-charging inverters with a solar array, you must take care to properly balance the battery charging setpoints on the inverter with the setpoints on the solar charge controllers. If not set correctly, the inverter will easily "over-power" the output from the solar array and provide all of the battery charging from the utility grid regardless of the available sunlight.

Going to contact both Magnum Energy and Morningstar to see what they can tell me on this.

Steve

Re: Questions about adding solar panels

Reply #8 – November 25, 2011, 11:23:09 am

That statement means that if you charging setpoints aren't right your solar panels won't charge the batteries at all; only the grid will. But when you have a generator you probably don't really care that the solar panels aren't charging... the generator is doing it anyway. When you turn the generator off the solar panel regulator will not see any need to charge the batteries (because they'll be fully charge by the generator) until the load sucks down the voltage levels.

What I'm trying to say is that you have a different priority when you are off the grid. If the generator is running anyway then having it charge up the battery bank is not an issue. But when you're trying to keep your electric bill down by using solar then you don't want your backup batteries to be charged from the grid; it costs you money.

Craig

Re: Questions about adding solar panels

Reply #9 – November 25, 2011, 02:51:46 pm

I believe that it is also recommended to have the panels 4" above the roof to benefit the cooling of the panels.

Re: Questions about adding solar panels

Reply #10 – November 26, 2011, 06:33:23 am

Thanks guys.

What I'm concerned about with both systems running is what happens to the power from solar panels if the generator is running. Both systems are trying to charge the batteries - so what ensues? The worry is one system backfeeding the other. Going to make some calls Monday. This is really bugging me.

Steve

Re: Questions about adding solar panels

Reply #11 – November 26, 2011, 08:01:35 am

The higher voltage wins. It drives the other off line.

Re: Questions about adding solar panels

Reply #12 – November 26, 2011, 09:23:14 am

Quote from: Dave Head – November 26, 2011, 08:01:35 am

The higher voltage wins. It drives the other off line.

Ahhh... that's what I thought. Thank you Dave.

From this is would seem that the inverter should have a slightly higher charge voltage setting, so the solar charger goes off line when the inverter is charging. That makes sense.

Couple more dumb questions - what happens to the solar energy the panels are generating when the charger is off-line? Is it converted to heat within the controller with a resistive load, or does the charger simply open the circuit from the panels? Don't the panels need to have a current path when active?

I've searched and searched, but can't seem find answers on the questions I'm asking here. Thanks for your help.

Steve

Re: Questions about adding solar panels

Reply #13 – November 26, 2011, 11:56:42 am

Quote from: Merle Hench – November 26, 2011, 09:23:14 am

Couple more dumb questions - what happens to the solar energy the panels are generating when the charger is off-line? Is it converted to heat within the controller with a resistive load, or does the charger simply open the circuit from the panels? Don't the panels need to have a current path when active?

The solar charger is solid state and samples battery voltage to determine their state of charge. Below a setpoint they allow current to flow from the panels to the batteries. Once the setpoint is reached they open the circuit and no current flows. At this point the panels are like a battery with nothing connected to the terminals. There will be voltage measured between the two terminals but no current; hence no power; hence no heat (except the heat caused by the sun shining onto the panels).

Current cannot "backflow" into the solar panels because there will be a diode in series with one of the output leads of the panels. This blocks reverse current.

The panels are always "active" when photons are impacting the cells but unless there is a completed circuit there is no current flow and, as before, no power... and no heat. Just don't touch the two leads together.

Craig

Re: Questions about adding solar panels

Reply #14 – November 26, 2011, 01:16:45 pm

I, like John Twork, have my panels tilted so that I park facing east.

I have sixteen 55watt panels (880 watts total).

I use a Bluesky 50 amp MPPT controller (very adjustable) which open circuits when batteries are charged and every few seconds to determine the Volts_Open_Circuit. Some older solar controllers "short circuit" the PV panels when batteries are charged, but most solar controllers today "open circuit".

I replaced the inverter/converter combo with a "pure sign" inverter and an Iota converter.
The converter has a switch in the kitchen which allows voltage to be 13.3 volts or 13.9 volts. The converter voltage is normally set to 13.3, so solar controller wins. On a cloudy day when plugged in, I set converter to 13.9.

Bluesky technical dudes told me that the converter could be run through the solar controller but that the converter could be damaged if not sufficiently protected from the higher solar voltage. Iota technical dudes indicated "No Issue" because Iota converters are protected. The solar controller and converter are simultaneously connected to batteries with no problems.

The panels are paired so 34 volts is coming off the roof (42 volts open circuit). Higher voltage provides lower line loses.

The solar controller, inverter, and converter are all mounted in the basement storage behind the batteries. The displays are mounted in the cupboard opposite to the fridge with telephone or ethernet cables between the display and the unit.

Be careful mounting electronic equipment in the same compartment as the batteries. Sealed AGM or Gel batteries will be good if you do not equalize. Flooded batteries outgas oxygen/hydrogen which will damage electronic equipment.

Re: Questions about adding solar panels

Reply #15 – November 28, 2011, 06:38:23 am

Thank you gentlemen. It's all clear now. Full steam ahead.

I'm considering ditching the installed converter altogether as it will be redundant, and I don't trust it to charge the batteries (AGM start, gel coach) properly anyways. I think I will be mounting the solar controller in the battery bay, simply to keep cable runs as short as possible.

Wyatt - interesting that you set the solar charge controller to take the lead. I was thinking that the inverter/charger should take precedence. I'll be calling both Magnum and Morningstar today to discuss this. Will let you know what they tell me.

Steve

Re: Questions about adding solar panels

Reply #16 – November 28, 2011, 12:17:49 pm

Merle:
The reason I set the solar controller as the winner over the converter is that works with my camping style. I boondock for weeks/months at a time in the desert with no A/C shore power while seldom using the generator (30 hours/year). I am very frugile with A/C power and have gone all LED lights. The inverter is only on when needed with a convenient switch in the kitchen and LED reminders showing when inverter is "on".
Works very well for me.

The five months I will be in California from Nov to May I will be in a campgound for 4 days at the Motorcader Christmas Rally in Palm Desert, and maybe for about a week in Yuma in February. My phantom load is 0.3 amps, down from the 6.5 amps when I purchased.

In my case, solar works so well at keeping batteries topped up that I do not even plug in the A/C power cord when parked in my driveway in Canada.

Re: Questions about adding solar panels

Reply #17 – November 28, 2011, 12:19:14 pm

now in Mazatlan last 2 days and not plugged in to shore power as panels are providing all the power I need. Sun shining from 7 am almost overhead 1/2 way thru day so not bothering to tilt them till I get south. Clear blue skies and 90+ deg. I will be disconnecting engine battery terminals once there so slightly less load on coach ones (trickle chge and phantom loads will be gone). I have shore power if needed but do not want to use it as last year myelectrical took a beating due to high and low volts at different times of day.very happy so far !!!!
Wyatt, I like you do not plug in at home as solar does it for me--charging and we are luckier than you as we are in the Interior (kinda like the desert-and have hardly any rain) so it really works well. I have only used my Gen for 4 hrs since I bought coach 2 yrs ago- so have to run it now and again to keep it operating.
John H

Re: Questions about adding solar panels

Reply #18 – November 28, 2011, 12:46:45 pm

Quote from: P. Wyatt Sabourin – November 28, 2011, 12:17:49 pm

Merle:
The reason I set the solar controller as the winner over the converter is that works with my camping style. I boondock for weeks/months at a time in the desert with no A/C shore power while seldom using the generator (30 hours/year). I am very frugile with A/C power and have gone all LED lights. The inverter is only on when needed with a convenient switch in the kitchen and LED reminders showing when inverter is "on".
Works very well for me.

Turning off the inverter is an important step as those critters can routinely draw 500 ma (and often more than that) at idle. Being able to do this conveniently (without opening up the battery compartment, for instance0 is also important. This is one of the major criteria for choosing an inverter in my opinion. That and the shape of the sine wave (which few offer, anyway). Most inverters simply say that idle current is less than .5amp; and any inverter that does not at least have this in their specifications is probably not to be trusted.

I love seeing someone who can get by fully on solar power alone. I spend a lot of time trying to convince people that it not only can be done but it's not all that hard nor that expensive. But it does take a little time (turning an inverter on and off, for instance) and management (tilting the panels if necessary).

You and John Haygarth are role models worth emulating! In our little 21-foot aluminum (Streamline - 1972 model) we could go over a week in SoCal with only 100watts of solar power. The big rig owners with their generators often would ask me if they worked. Thirty years after we first installed them people still don't understand them.

Craig

Re: Questions about adding solar panels

Reply #19 – November 28, 2011, 01:08:25 pm

I've been thinking more and more about solar.

Mostly as a way to ensure batteries are topped off as we seem to be spending more and more time far away from our motor home - which means having to rely on others to make certain batteries are not discharged (when we first got our current Foretravel it had brand new Lifeline AGMs because the RV Dealer let them die - and this was the second time this happened in this Foretravel). I assume a couple of panels would do that.

But going the next step and not rely on RV Parks in our Summer travels (we spend Winters in our "Park Model), and then rely on solar almost totally as Wyatt does is a lifestyle change for us.

But before we could even get to thinking about lifestyle I guess I'd like to hear more about "nor that expensive"

best, paul

Quote

I love seeing someone who can get by fully on solar power alone. I spend a lot of time trying to convince people that it not only can be done but it's not all that hard nor that expensive.

Re: Questions about adding solar panels

Reply #20 – November 28, 2011, 04:47:03 pm

When a controller is purchased/fitted for the new solar panels, make sure to check with the battery manufacture to see if the "conditioning" mode needs to be de-selected if it is the default setting. My house batteries have that in big print in the literature.

Pierce

Re: Questions about adding solar panels

Reply #21 – November 28, 2011, 06:19:44 pm

Quote from: Paul Smith – November 28, 2011, 01:08:25 pm

But before we could even get to thinking about lifestyle I guess I'd like to hear more about "nor that expensive"

As far as keeping batteries charged during your absence you could do that with one 50-watt solar panel (about $150 from Amazon) and a $30 regulator. You wouldn't even need to "install" anything unless you were worried about thievery or vandalism. Just put the panel where the sun will shine on it, aimed south, and towards where the sun will be about noon.

When it comes to outfitting a coach for full-time use with solar there are so many variables to consider. All-electric takes more power. Will you be using AC appliances and an inverter? Can you live without having air conditioners? Plan to use tilting mounts or not? How handy at this are you? It's much cheaper to do it yourself.

I think doing it yourself would be possible for under $2500 for three 200-watt panels. Depending upon how well you track down your stray loads and how efficient your inverter is and how diligent you are at parking for maximum solar input this would probably do the job as long as you use propane for your refrigerator. And, after all, we have generators that should be run at least once in a while to keep them lubricated.

Kits which include panels, mounts, wiring and virtually everything you need to put the panel up yourself will cost more. John Haygarth and others can probably give you a better idea of what they use and how much it cost them. Then you can also just have someone (hopefully reliable) can do it all for you.

I could be wrong but I think you could get away for under $10,000 for everything... installed. That's not cheap but they'll last a long time.

Living with solar does require some management. And usually it means you park in the sun, not in the shade. You need to turn the inverter on and off as you use it. You have to be aware of the battery charge because the regulator only protects batteries from overcharging; it will not make up for under-charging.

Craig

Re: Questions about adding solar panels

Reply #22 – November 28, 2011, 07:15:35 pm

I have spent $4000 on panels and wiring and controllers and they AM Solar set the controller to what Lifeline told them too (Battery maker). I use the inverter and make sure it is off when not needed and have installed the extra one (as per Barry's Mod site) for the tv etc up front and fridge as it uses less stand by power and is true sine. My DW is now into the mode and will tell me when she thinks I should change over to a different system ( source of power) I am not as far as Wyatt on the LED change but getting there as I am designing new fixtures for Bathroom vanity and now have a couple made that take the LED tubes I put in the ceiling. Once I have them finished (need staining) I will post pics, but I know they will save big time as DW uses them a lot (vanity lites). When I get home in March I will be doing more of it as here in Mexico LEDs are not available for what I want to do.
I do not expect to get back any investment I have made but it is nice to not be dependent on someone elses power esp' here in mexico. I guess we will not know if it has been worth it all till about 5 or 6 yrs and see how the batteries are doing, still fun though!!
Here in the sun it is only 5 hrs to totally recharge after going down 12% WHITHOUT tilting the panels which I know will be faster, but we have lots of time as we are on holiday!!!
John

Re: Questions about adding solar panels

Reply #23 – November 28, 2011, 09:25:49 pm

Very impressive gents. While I try to be frugal with power as well, I am installing a computer based music production/recording workstation in my coach. I've monitored power usage of this equipment; I'll be using anywhere from 40 watts (no computer) to an absolute maximum of 430 watts (very rare) plus the computer. So I expect to be needing to run the generator every few days or so, depending on whether or not I'm doing anything musically. I've also installed an electric fridge, which will require the inverter be on all the time. I can live without A/C, to a point.

. Would rather read a book or sit outside than watch TV - I think I'm the only person in America who has removed all the TVs and antennae from his coach.

I'll still be able to watch DVD movies with computer and monitor.

At any rate, I spoke to Don today at Magnum Energy regarding using solar with the inverter. My concerns are easily addressed - with the advance remote control and battery monitor, the unit can be programmed to start the generator based on state of charge, instead of the battery voltage. The battery monitor allows the unit to collect information on power consumed over time; when it calculates the battery charge has dropped to the selected setpoint, it will trigger the gen start module to start the generator, activating the inverter charging system (assuming it is not a "quiet time"). So even if the solar system is charging the batteries, if the inverter remote figures the batteries are low enough, it will start charging as well. Don recommended the same charge voltage level on both the solar system and the inverter. This may take some fiddling to dial in just right. The other cool thing you can do with the inverter advanced remote is to program the system to start the gennie to do a top up charge right before quiet time begins.

Costs break down as follows:

Magnum Pure Sine Wave inverter, 2800 watts
Magnum Battery Monitor
Magnum Battey Combiner
Magnum Auto Gen Start module
Magnum Advanced remote

Subtotal $2465

Two new main breaker panels $120
Additional breakers $28
25 ft of 10/3 cable $45
400 amp T style fuse and fuse block - $68
14 ft of 4/0 battery cable (7 ft red, 7 ft black) plus 12 terminals - $63

Subtotal $324

Materials to redo end of bed (had to cut most of the end out and reframe to mount the two new panels)
Sheet of 1/4 inch black melamine - $43
Oak trim $9 (no one around here has premade walnut trim

)
Misc hardware and materials $20

Subtotal $72

The rest I have yet to get:

Four 135 watt Kyocera solar panels
Morningstar MNPP solar charge controller
Remote digital display/control
Combiner box
Cabling

Estimated subtotal $2000

Total about $4861 (doing ALL the labor myself)

Steve

Re: Questions about adding solar panels

Reply #24 – November 28, 2011, 10:55:12 pm

So I'm Scrooge this time of year or most any other time and I don't want to seem tight just because I threw Bob Cratchit and family under the bus but prices have come way down on photovoltaics now. See the Forbes article at: Cheap Photovoltaics Are Eating Solar Thermal's Lunch - Forbes

For prices for the cells and accessories, look at: Solar Panels, PV Systems and Inverters Distributor If you want to do the frame yourself, the laminates have come down to 50 cents a watt.

We have two RV acquaintances that had their systems professionally installed. Both had problems with system after the install so DIY people, just take it slowly and you can save a ton.

Pierce

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