Gone Solar!

After a good bit of research (see http://www.wanderthewest.com/forum/showthread.php?t=1332) and two weekends, the PV panel is now mounted and running.

We got a 120W Mitsubishi panel and a MorningStar SS-10L-12 charge controller from Alter Systems. There are other good vendors out there, but what is important is that you get a reasonably efficient PV panel (12% or better) and an MPPT (Maximum Power Point Tracking) charge controller. The MPPT type charge controller optimizes your power under less than optimal conditions (ie, when it's not high noon in SoCal). It's well worth the extra bucks, since it can increase the power out of the PV panel by 25% at lower light levels. You don't need an "RV kit", just the PV panel and the charge controller. Check with the vendor to make sure the charge controller is appropriate for the PV panel (current rating, etc.)

You pick your PV panel wattage based on usage. Take the current output of the PV panel (6.7A for our 120W PV panel) and multiply by 8. You get more in the summer and less in the winter, but this is a good working number for 3/4 of the year. Now, for FWC, figure 4 amps each for the roof fan and heater fans. If you use LEDs for lighting (see http://www.wanderthewest.com/forum/showthread.php?t=1070) they hardly count (.3A). For incandescent, 1.5A per bulb or 6A if all interior lights are on. For us, we add two laptops at 5A each. Now multiply the current for each device times the hours you expect to use it in one day in summer and one day in winter and take the larger of the two results. This came to about 58 amps/day for us. Our PV panel, at 6.7A for 8 hours, comes to 53 amps/day. (Ok, we also have a 1KW Yamaha generator (similar specs to the 1KW Honda but cheaper) so if we mis-calculated or for winter time in the Pacific Northwest coast.)

We mounted the panel to the front bar of the FWC roof rack with two 1 foot stainless steel piano hinges. If you already have the PV Panel connector on the roof (I think FWC does this standard, now) you need a molded two-connector automotive plug (see http://www.delcity.net/delcity/servlet/catalog?parentid=8771&childid=84009&page=1&tabset=1&pageitem=1&new=y for picture). Make sure that the exposed connector is the negative output from the PV so that when you unplug it, it won't short to the chassis. This should also be the black wire, which, on the Eagle, is under the wooden cover between the front of the camper and the front of the kitchen unit on the drivers side. But buzz the wires it out just to make sure!

Connect the PV panel to the charge controller and the battery to the charge controller. It is best to place the charge controller near the battery so that the voltage drop from the charge controller to the battery is minimized. Also, place a fuse on the positive side for both the battery connection and the PV panel connection. This is to protect both the charge controller and the PV panel. Since it was a 10A charge controller, we chose 10A fuses. The charge controller basically takes the output of the PV panel, which can range from 20V to 12V and 6.7A to a lot less and optimizes it to 12.6V (or so) and whatever current is being produced. We did not connect any load to the charge controller because the electric distribution panel is on the other side of the camper and the wiring would have gotten quite complicated with the converter and alternator connections. The advantage of connecting the load is that the charge controller will disconnect the battery (which means the "loads" will be turned off) when the battery is too low, thus protecting the battery from being over discharged (and potentially killed). If you install an inverter (12V DC to 115V AC), you may want to connect it to the load connections on the charge controller.

Having killed one battery by discharging it completely, I intended in the future to install a battery cut-off switch. Also, we used 10 gauge instead of 12 gauge braided wire (and braided wire is so much easier to route than single strand) to minimize voltage drop.

An aside about voltage drop for the non electricians and engineers. The goal is to get as much power to the consumer devices in the system as possible. Wire size is like a hose diameter and current is like the water. The narrower the hose, the more energy (voltage) it takes to push the same amount of water (current) through the hose. That means that the narrower the hose, the less energy there is at the device. In electrical terms, the resistance of the wire is part of the load and the wire and the load act as a three resistance voltage divider. Since current stays the same and since the power at the device is current x voltage, the higher the voltage at the device the more power. The $1 or so difference in wire cost buys about 1 watt of PV panel power. The difference between a 120W PV panel and a 123 PV panel is about $40.

To support the PV panel, we glued rubber pads (adhesive cement) to the roof and attached rubber feet to the PV panel. The hope is that either can be replaced as they wear, without ever damaging the roof or the panel.

Tying down the panel during travel is not a final solution. The bungee cord is a bit minimal. I'm looking for rubber loops with twin hooks, but other suggestions are most welcome. The loop attached to the roof latch are just figure eight loops, with one end under the screw.

I also put shunts on the negative side of the battery and the PV panel (0.1 Ohm) and attached sense lines from them and the positive side of the battery and PV panel to test probe connectors. A $10 Radio Shack DMM lets me see the voltages and currents for both the battery and the PV panel - far cheaper (and a bit less battery draw) than the optional readouts for the charge controller and the battery (OK, the shunts were free, otherwise, buy the readout LCDs).

Forgot to add that the total weight added of about 27 lbs is still manageable when lifting the front of the camper, but a few years down the line, my back will probably "encourage" me to come back to look at the various roof lifting devices that have been posted.

Nice write up

I'm getting ready to go solar and based on my own research, I have to agree that an MPPT (Maximum Power Point Tracking) charge controller is the way to go. I really like your hinged panel idea. I've been thinking of going with a pole mount for maximum efficiency and so I could be parked in the shade and have the panels in the sun, but that means more stuff to carry in the camper and more time required to setup camp. After seeing your solution (which is obvious once someone else thinks of it), I may very well copy your design.

Nice writeup and install. Definitely a nice reference if I ever decide to go that way.

one suggestion

Great job. Very clean install. I will be very interested in how the adhesive mounts work out. Keep us posted.

I suggest that others considering solar think carefully about whether or not to make the panel tiltable. Fastening the panel flat is simple and secure. Tiltability adds more complexity to the install and may not be worth it depending on where you live and camp. Here is a link to help you decide: http://quantum-sci.com/solar/insolation.php

Update

We've had the solar for almost a year and our only regret is that we didn't do it sooner.

I've added a photo showing the front hinges. The half of the hinge that is not visible is mounted to the back of the solar panel. The sides of of the solar panel are channel aluminum, with about a 3/4 inch lip to which the hinges are bolted with three bolts. When I drilled the holes for these bolts, I placed a block of wood in the channel slot so that when the drill broke through it hit the wood instead of continuing on into the back of the photovoltaic matrix. I don't remember the reason for not mounting the hinge to the side of the solar panel, but when mounting to the back, make sure there is about 1/16" between the edge of the panel and the center of the hinge so that the panel will swing freely. As I mounted the panel, it will not swing past about 45 degrees, but then, we don't intend to go so far north (or south) that greater angles would be needed.

One other item to point out on the mounting is to position the rubber pads over the roof ribs.

The rubber pads have held just fine and they and the rubber door stops show almost no wear.

We found that the small bungee was not adequate for rough roads, so we now have a bungee on each side that hooks to the jack plate for travel. We also found that high winds (30mph and above) can bounce the panel, making for a less than ideal sleep, so we still use the small bungee when camped if there will be high winds.

Incidentally, the pictures also show part of our forward hydraulic system. We found that the doors of the Tacoma are precisely aligned with the drip from the Eagle roof. In any kind of rain, opening a window or door would bring a stream of water into the cab. The bead of (formerly) white silicone caulk and the plastic gutter strip have pretty much taken care of the problem.

Thanks

Thanks for answering my shameless plea. A picture really is worth a thousand words.

Portable Solar??

Thanks for sharing your solar installation Jack, it looks pro.

Did you run across any portable installations around the same wattage you used when you were doing your research?

I don't know if it's practical or not, but I'd like to be able to transfer solar from camper to boat to cabin using the same panel, controller, etc. just hooking up to wing nut connectors at the battery terminal.

I don't know if it's practical or not, but I'd like to be able to transfer solar from camper to boat to cabin using the same panel, controller, etc. just hooking up to wing nut connectors at the battery terminal.

Just one set of connections is probably a bit of wishful thinking if you are actually installing the wiring to run though the camper instead of setting up a portable panel when you arrive at camp. However with some additionally strategically placed quick disconnects I'd think you could disconnect the panel as a whole and the controller as a whole (leaving the wiring through the camper and such), then just have the same wiring set up where ever you want to reconnect.

Good Words

Pods8 & Jack,

Thanks for the good words.

It sounds like I need to go back and study-up on installation of solar so I understand the need for the 6 wires to the camper instead of two. I'm sure that between a little closer read of Jack's install and some of the other solar threads I'll sort it out.

I was equating the solar panel to an old car generator and the controller to a regulator (like on the '56 Chev I had when I was in HS ). IF memory serves there was a wire to the battery and another to ground. I should have guessed that would be too easy

Happy Trails!

Pods8 & Jack,

Thanks for the good words.

It sounds like I need to go back and study-up on installation of solar so I understand the need for the 6 wires to the camper instead of two. I'm sure that between a little closer read of Jack's install and some of the other solar threads I'll sort it out.

I was equating the solar panel to an old car generator and the controller to a regulator (like on the '56 Chev I had when I was in HS ). IF memory serves there was a wire to the battery and another to ground. I should have guessed that would be too easy

Happy Trails!

According to Jack you have 2 wires going between the controller and panel so that part IS simple. The controller apparently has 6 (I'm guessing 2 would be the panel, 2 battery, the other two I don't know off hand maybe voltage sensing?) so that is the one that would take a bigger disconnect. Not saying you couldn't use a trailer harness or such but as Jack mentioned if the controller costs you $50 it might be easier just to get two because you'll likely have at least a few bucks in fittings.

Simple is good.

Pods8,

Thanks for the clarification on the 6 wires. I was under the impression there were 6 leading from the controller to the camper.

Having separate controllers may be necessary, but if it isn't it would be nice to have the option of using the PV panel other places that don't have controllers...not a big deal though.

Jack mentioned voltage drop being lower between PV panel and controller than between controller and battery (makes me think the panel must put out AC). If the drop between controller and battery is substantially more than the same distance between panel and controller it seems like having a controller separate from the PV panel and located either close to or in the camper would be best.

It looks like a portable panel or panel/controller combination could be made to work pretty easily. Now all I have to do is get the crow bar out and pry open my wallet so I can extract a $1000 bill to make it happen.

Happy Trails!

Jack mentioned voltage drop being lower between PV panel and controller than between controller and battery (makes me think the panel must put out AC). If the drop between controller and battery is substantially more than the same distance between panel and controller it seems like having a controller separate from the PV panel and located either close to or in the camper would be best.


I'm not fully versed in solar but the panel is definitely putting out DC. I believe the voltage drop issue arise because of the following: The controller is used to seeing varying voltages out of the panel and is designed to convert to a certain charging voltage (ie its going to correct out of spec voltages). After the controller any voltage drop means that much less the battery will see without anything correcting the situation. This would be motivation to keep the controller close to the battery or use a large enough gauge wire to negate the issue.

The six charge controller wires are: 2 to the battery, 2 to the PV panel and 2 to the load (camper lights, fan, etc.).

You can skip the last pair (the load) and connect them directly to the battery. However, the advantage of connecting the load through the controller is that the controller protects the battery from being discharged too much. Your battery's life depends upon the number of discharge/recharge cycles and the depth of discharge. Completely discharge your battery a few times and you can expect to spend the cost of 3 charge controllers ($150) on new battery.

Here's what voltage drop is all about. All wiring has some resistance and this resistance causes the voltage to get lower and lower the farther away you are from the voltage source.

The charge controller can't measure the voltage at the battery - only at its own terminals going to the battery. The battery charges best at about 14 Volts (depending on battery type). To charge the battery, the charge controller keeps the voltage going out a little above 14 Volts with however many Amps as are available from the solar panel (the more sun, the more Amps). If you have long narrow gauge wire to the battery, the voltage at the battery may be 13 Volts or less. The voltage drop also varies with the amount of Amps. If the charge controller puts out 14 Volts at 5 Amps and you find that the voltage at the battery is 13 Volts, when the charger puts out 14 Volts at 10 Amps, the voltage at the battery will be 12 Volts! What is happening is that some of the energy coming out of the charge controller is going into heating the wire - not very much, but enough to make a difference.

As pods8 pointed out, here are two solutions: short wire length and/or use heavier gauge wire. There are wire tables that show the voltage drop per foot at a given amperage, but I'm sure 25 feet of 10 gauge wire will handle 10 or less Amps.

Got drop...not load.

Pods8 & Jack,

Got the voltage drop issue cold now, thanks.

I got the two wires to the PV panel, 2 to the battery (since I have the house battery and truck battery connected together with an isolator between (stock FWC factory install) I ass/u/me it would effectively be "2 to the batteries") to charge it.

Not sure about the load deal.

I'm guessing the connection between the battery and the load must be shut off (manual switch installed maybe) so that the load runs solely from the PV panel/controller and the battery charges with what's left...I need to go study-up again and see if I can find where the wires from the controller to the load connect at the camper.

Not sure the load connection will be a big issue for us. I check the factory installed battery monitor on a pretty regular basis and it's only been out of the green once in about 2 1/2 months living out of the camper. Guess we could try just the battery connection without the load to start with and if it develops into a problem, deal with it then.

I did a little more looking at past threads and found a couple on smaller portable chargers and also found the LaQuinta Hikers "under the cabover" permanent install.

The under the cabover might work as a "storage" spot for a portable PV panel too (with our 48" overhang we might fit two in there) but with it sliding to the side instead of front for easier put/take.

lqhikers dual 75w install gave me thoughts of trying 75w to start with and adding another later if necessary...I'll have to run the numbers on the stuff we use and see if it looks close or not.

Thanks for all the good words...it's helped me understand the solar hook-up a LOT better than when I started looking at it.

Happy Trails!

lqhikers dual 75w install gave me thoughts of trying 75w to start with and adding another later if necessary...I'll have to run the numbers on the stuff we use and see if it looks close or not.


Pricing of 130+ watt panels makes larger panels more interesting. I would recommend starting with a 130 watt panel (10 pounds more than an 85 watt, maybe $150 more).

Les,

Do you have any idea what kind of power you are getting on an average day?

And you can still get all sorts of panel sizes, including 75w.

Thanks,
SB

Needed a Project???

Les,

Thanks for the information on dual batteries and the single panel. I think that's the direction I'll head, right down to the Costco batteries. I do want to investigate mounting two gel cells on their sides in the space where our one battery is now, so I don't have to eat up any more storage space...but Costco has gel cells too

The thing that puzzles me though, how do you get to the elevated position in life where you can say "...I needed a project."!! I got em stacked up 12 deep in the aisles and Susan keeps more coming every day.

Happy Trails!
D

Duane,
I solved the dual battery space problem by mounting them under the truck. My Dodge longbed has enough room between the frame and the side of the bed for 2 Optima blue tops. Servicing wouldn't be that easy but these batteries don't need much attention.

Dick