General RV Solar Questions?

[Lexicon7]

I'm planning to add a couple of new high end Kyocera 140 panels and build up a new system out of them. Currenly I have what my old 95' Squire 400 came with which is a substandard and smaller panel with an ACS Specialty Concepts Controller. This unit has one red light and no digital readout. It does keep the single 12V house batt charged and that according to Lances typical (and also probably substandard) idiot light array monitor.

I have no experience on solar but have been researching for a year or so and doing a lot of reading and on line window shopping. My thoughts are to begin the learning process by adding a better charge controller and an inverter since there does not seem to be one now.

I am aware that panels must be matched but I an considering (roof space allowing) leaving the existing system for "house" use and adding the new system with a huge inverter and of course components to match.

That being said, I need to determine the power coming from the existing charger before doing anything. Is this correct?
Also, how exactly can I do that to get a legit reading?
I assume I can get a reading in the fuse panel where the lines from the existing controller enter. Is this correct? I have a good meter so this should not be a ploblem, just correct procedure to get started?

Any assistance greatly appreciated. Morgan

[Lexicon7]

OK I will get measurements in the morning. Thanks again...

[pianotuna]

Hi,

All RV's by definition are a "small space". The last thing you want is a cord to trip over. By all means test with a cord--but for routine and regular use cords are murder.

Lexicon7 wrote:
WestEnd.. OK now I got it, thanks.. I think for a space this small I may be overthinking it... as you say, just use the "multi-plug" extension..

[Almot]

Lex, I'll say it again - stop thinking. Start doing. First things first (inverter isn't "first"). Take a measuring tape and go on the roof, see how many 100W or 120W, or 140W panels you can fit. Then start a new thread like "what controller for me, what wire gauge" etc.

Like Don said, big 24V panels are cheaper per watt, but they are usually 200W or larger, they are heavy enough to need a second man to lift them onto the roof, and they require more expensive controller (which is usually more efficient as well).

First things first.

[Lexicon7]

WestEnd.. OK now I got it, thanks.. I think for a space this small I may be overthinking it... as you say, just use the "multi-plug" extension..

[westend]

Lexicon7 wrote:
WestEnd ::: sorry to say, I am having difficulty following you on the "house" power / inverter issue I brought up... I like that site and have come to respect the Xantrex name...
For shear convenience, you think it would even be worth it? I suppose I could just rig a 4 place junction box on the end of a living area length extension cord... Can't wait to get out of here and start putting all this to the test. I'm sure I'll never stop tweaking stuff..

I was posting about using a transfer switch to power your receptacles when away from shore power. In the situation of a truck camper, it is probably more convenient (and less expensive) to just plug a multi outlet surge protector into the inverter and mount it somewhere convenient. That is how mine is now but I will be installing dedicated receptacles (a couple) that run just with the inverter. Then again, if I get an urge, I may just use the 15 amp transfer switches. It's about how clean an installation one wants and the convenience of not shifting plugs.

[Almot]

Redsky, I agree to disagree.

I "think" Lex has done too much "thinking" and it's time to stop thinking and start drilling holes already :)... People will soon stop reading this 10-pages topic. Measure how many panels of what wattage will fit on that roof, and go for it. $200 battery monitor will not generate you any energy.

And, I don't know what controllers with rating 30A or larger have terminals sized for #12 wire. Rogue 30 has #4 terminals, Morningstar 45 has #2 (I think). It could still be necessary to use splices to transition from #4 terminal to a thicker #2 controller-battery cable, but the panel-controller wire in RV systems is rarely thicker than #4.

[Almot]

Lexicon7 wrote:
RM2510 Dometic.

Just what I thought.

It's a 2 way LP/110V, with 12V needed in LP mode.

51"x13" solar panel is about 60W. Or less, if this is amorphous type. 60W panel could harvest 15-20 AH on a sunny day. Enough to run control board of the fridge. So if you don't do anything else in camper, and don't burn much lights, your battery stays full with this tiny panel already. The previous owner wasn't that stupid. I doubt it is wired "directly" to battery, there could be a tiny nondescript box of cheap controller somewhere, size of a cigarette pack. Or they've skipped the controller. With panel 50W and larger it's better to have a controller.

Meanwhile, Don has managed to write a "concise guide to solar off-griding" in less than a page ;). Good stuff. Read it.

[pianotuna]

Hi Lex,

Many folks use that meter--however it doesn't count amp-hours. Watt meter

I don't see the point of a Victron or Trimetric.

It may be better to use a Kiss principle when designing a solar system.

It is always better to have too much capacity than not enough. Full timer's need far more capacity than part time folks.

Wire size is determined by the kind of controller. The kind of controller is determined by the raw voltage of the panels. High voltage panels are significantly cheaper than nominal 12 volt panels (which are, in point of fact, 17 volts and up). Once you reach a panel voltage of over 21 it becomes prudent to go to an MPPT controller.

I full time and I run mostly on electric power (water heating, fridge, and cooking). Therefore I need a large solar system.

When I did NOT full time, my existing solar system was more than adequate for a seven to ten day trip.

Running a generator is more expensive than going to an inexpensive campground. Solar is a one time cost.

[Lexicon7]

Redsky, I'm all about books. Will order that one and thanks for all the great info.. I have been a bit puzzled over wire sizes since the article I read when I began my solar studies said use very large gauge.
This little device was recommended to me and even to install one on each line both coming and going but the wiring on it looks to be very small.
I know enough about elec to know that jumping around, especially down in size is not a good idea and as you say, RV's get so much voltage drop which nobody needs...

Here's the link in quiestion ::: http://www.ebay.com/itm/181110318783?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[Redsky]

Someone thinking of solar should first do two things, install a Trimetric so they can measure their average demand and know how much of a battery bank they need and how much solar output to restore the bank back to 100% during the day. Second is to read the excellent books by Bill Mohler

The Complete Book of Boondock RVing: Camping Off the Beaten Path

and if you need more information:

RV Electrical Systems: A Basic Guide to Troubleshooting, Repairing and Improvement

Most folks, including myself overkill it. Many go for 97-99 percent efficiency which only means a difference of 10-20 minutes in charging time. After installing my setup I found that it was double what we actually need.

I now recommend starting with a digital charge monitoring device and spending the $200 to know what your actual usage is at any given time. The most I was ever able to draw down my 220 AH battery bank was 22%. That took the two 6 amp output solar panels all of about 4 hours to bring the bank back to 100%. On an average trip, winter of summer our demand is less than half that amount and within 3 hours the batteries are fully charged.

The 1 Watt per AH of battery is a rough guide that works. A 100 AH battery provides 50 AH of usable current as you do not want to regularly draw it down past 50% DOD. A 100 Watt panel should provide 5-6 amps output and be able to restore the 50 AH used in 8 hours with a good charge controller and that is plenty good enough.

A good source for information and kits is Amsolar.com in Oregon. Their kits seem expensive except many of the part for which you may need only the two can be purchased elsewhere only in larger quantities so you do not save money and spend more time trying to find alternatives. They can also modify a kit so if you need a longer panel to C-box cable they can simply cut it however much longer you want it to be.

Controllers are not made for the RV industry but for house and commercial uses and so they usually have bus connections for small 12ga wiring as that is all that is needed for a normal installation with 10-20 panels wired in series. For an RV with much lower voltages larger gauge wiring is advantageous but if you need to downsize it with jumpers to get it attached to the controller this will double the space needed - fine if you have it and a royal pain if you do not.

[Lexicon7]

Almot, miss typed that.. RM2510 Dometic.

[Lexicon7]

Almot, the fridge is a Dometic RM3510 and the panel is 51" X 13" to the outside of the frame. It looks like the connectors go straight up into the panel and I can not see any junction box. I guess it's a pretty good little panel. I really need some monitoring for that batt.
Also, I will get the ah calc done so you'll know what I'm trying to do.
thanks...

[Almot]

Lexicon7 wrote:
... I am leaving it on gas. After further review, it seems that the "absorbtion" system uses electricity.
If this is true it must be on the house circuit. Either way, if the cheesy little Lance issue "colored light array" system has any credence, my batt is full and I've never seen it any other way!

Lexicon7 - it would've streamlined your learning curve if you had told anything about nameplates. What fridge, what solar size (the tiny one that you have).

It could be that your fridge is a regular LP absorption unit that needs a little 12V current for circuit board. Since it needs very little of this current, your existing small solar is able to keep the battery from depleting while in storage, i.e. when not running any other loads. Those control circuits are drawing from 5 AH to 15 AH per 24 hours, depends on the fridge model.

No, I would not give much credence to OEM light array on the wall that says Battery Full. It's likely between 50% and 100% full. An easy way to determine this is to put $5 multimeter across the contacts just before sunrise, when solar is still Off and all the loads are Off, including fridge.

[Lexicon7]

Forgot to mention: not sure if I miss spoke when I said I'm running fridge on LP exclusively.. What I meant was that I have the peremptory Gas/Elec selector switch and I am leaving it on gas. After further review, it seems that the "absorbtion" system uses electricity.
If this is true it must be on the house circuit. Either way, if the cheesy little Lance issue "colored light array" system has any credence, my batt is full and I've never seen it any other way! I'll be hooking up the little Wagan Tech 600 Inverter in a few days and plan to remove the batt for the first time to hydrometer test it and most likely top it up. It is not sealed of course. Looks like it's an EverLast 94 as printed on the batt top...