How much Solar do you have?

[Every Miles A Memory]

We have 3 - 100w panels that feed 4 AGM 6-volt Lifeline batteries. These batteries then convert power through a Xantrex 2000w Sinewave Inverter.

The charge controller is one of the most important parts in the system. It keeps the batteries from overcharging and from sucking power out when the sun goes down.

Turns on and off automatically and in over 4 years time, we've yet to have any issues with the system other than the Xantrex Inverter freezing up a few times which meant i had to disconnect the batteries, let it sit for a few minutes and hook them back up....sort of an ALT>CTRL>Delete for the charging system if you will



What would I have done differently if I could have done it over again?

Would have gone up to a 3000w inverter because it would then run our A/C in the camper for short periods. Our 2000w will run it, but it doesnt like it.

Plus, I would have run two separate inverters. There are many times that we simply pull over for a few hours to take a nap or wait out a storm. If all we're doing is running the laptops and checking emails, there is no need to power up the big 2000w inverter. We have a 12v plug-in 400w inverter that we use when we're doing that for right now, but I hate cords strung through the camper, so having the choice to switch between the two and have them hard wired would be great!

When going with inverters, make sure you get a Pure Sinewave model. Makes a huge difference in the hum you'll get off the lights, cpu's and electronic equipment. When we run our little 400w model which isnt a Sinewave version, everything hums pretty loud

We have no affiliation with this company, but I refer them to everyone who asks AM Solar is who designed/built our system and they're a great company to work with. Just got a call from another traveler that I had recommended them to who couldnt get over home nice and out of their way they go to make sure you get exactly what you want.

[Bogo]

Perhaps take a look around the site and see the variety of vehicles people drive. 4 x 250w fits on even many small campers.

Yep. My eventual plan is 2 * 220W high efficiency panels on roof top mounts. That will fit on a RV back on a Toyota mini truck. That is all to power the refrigerator, freezer, lighting, and laptop with photo editing monitor. That last one is the power hog. An LED back lit monitor would reduce power needs allot.

[Bogo]

The charge controller is one of the most important parts in the system. It keeps the batteries from overcharging and from sucking power out when the sun goes down.

Different charge controllers can also greatly influence system efficiency. A simple one will only start charging when the batteries drop below x voltage and turn off above Y voltage. A really smart one will get the most out of your panels. Look for MPPT type charge controllers. They may mean being able to use a smaller solar panel or being able to do that much more with a given panel set.

A friend had 3 80W panels in parallel using a simple charge controller, then he changed to a MPPT controller and wired the panels in series. They now provide him around 25% more real charge going into the batteries. Also when the batteries are fully charged with the sun out, and something switches on, the charge controller provides power immediately to help supply the load rather than waiting for the battery to drop below X volts. Also he is seeing a much higher amount of charging on cloudy days as well as earlier and later in the day. He has Morningstar's small MPPT controller.

[dwh]

There is a drawback to wiring in series. With panels wired in parallel, if one gets shaded (or partially shaded) the other panels still put out full power. In series, if one gets shaded, it drops the output of the whole "series string".

MPPT is great, but you don't -have- to wire in series to get the benefit. The trick that an MPPT controller does is to down convert the voltage. A regular charge controller just connects the solar straight through to the battery. An MPPT controller has a converter so it can down convert the voltage.

So here's how the trick works: Basic electric math; 200 watts / 18 volts = 11.1 amps. Most "12v" solar panels put out around 18 (or more) volts. Connect it straight through to the battery and you get 11.1 amps to the battery. Now take that same solar panel but down convert the voltage; 200w / 15v = 13.3a. You get an extra 2.2 amps into the battery with the same 200w panel.

It's a neat trick. Sort of the electrical version of downshifting - same engine, lower gear, more torque.

To charge a battery, you have to supply a voltage higher than the battery, so the power will flow toward the battery. To fully charge a "12v" battery you have to push it up to 14.4v for a while (with most batteries, gels take different voltage), and you have to supply it at a bit higher voltage so the power will flow in the right direction. So any solar panel that puts out over 15v -when under load-* can be down converted by MPPT to do the extra amps trick.

There is no requirement to wire in series with MPPT unless your panels put out less than 15v under load, or if you need to charge a higher voltage battery, like 24v (because MPPT controllers only convert down, not up). So if you wire 2 18v panels in parallel, you'll still get the same amperage bump from MPPT as you would if you wired them in series and fed 36v to the MPPT.

You -can- wire in series if you want, but you get no additional benefit from the MPPT trick. You still get the trick but the volt/amps on the output side of the charge controller will be the same as wired in parallel. And if you do wire in series, you set yourself up for the partial shading issue.


* The voltage a solar panel puts when it is under load is called "Voltage Max Power". That's the "Vmp" rating on a solar panel. This is not the same as the voltage a panel puts out under no load - that's called "Voltage Open Circuit" or "Voc". The Vmp of a solar panel has to be higher than the voltage of whatever battery you are trying to charge. If it isn't, the power won't flow toward the battery.

[bstory]

Would it be bad form to ask whether anyone has used solar panels on their vehicles that didn't seem to stand up to being in motion all the time?

Some are certainly less expensive but I have been hesitating and thinking we had to save up for the Sunsei because they were designed for mobile uses and have a reputation for holding up well.

Kyocera? Sharp? Others?

We are thinking of just one panel 130 watt or above, depending on which brand and the cost.

[dwh]

Mostly it's all about the frame. A PV module (solar panel) is nothing but very thin wafers of silicon bonded to tempered glass and then vacuum sealed with a resin or epoxy backing. Then they take that and mount it in a frame.

For big architectural projects, the contractor might buy the modules with no frame because they are going to mount them with their own frame design as part of the building.

Some manufacturers offer the same PV modules mounted in different frames.

The frames are usually just aluminum channel, but there are some modules with beefy frames and some with sort of cheezy frames.

There are some modules where the silicon wafers are bonded to lexan or some other plastic instead of glass, and have plastic frames. I guess these have a little bit of flex to them, but it can't be much since the silicon wafers absolutely will crack if flexed.

There are also "thin film" modules, which are flexible, but not as efficient and probably not as long lasting.

A module made with tempered glass and mounted in a solid frame should hold up well. They are actually fairly tough and have regularly withstood golf ball sized hail. Just don't bend or twist them.

Personally, I wouldn't trust any aluminum channel frame to provide enough support for serious off-roading. I would build a stong frame to mount them to.


EDIT: If you look at the picture above, you can see that those modules are mounted in some nice hefty frames.

EDIT2: Another thing, if you look at that picture, you can see that the mounting tabs are positioned at the ends of the frames. Obviously, that could allow the centers to flex a bit (if the frames weren't as heavy as they are). In mounting modules on buildings, to withstand the greatest wind and/or snow and ice load, the mountings are generally not at the ends of the modules, they are usually about 1/4 to 1/3 in from either end. That keeps the flexible span as short as possible.