I am a newbie and need serious sage advice and answers. Thanks

System

I will try to make my question(s) as short and concise as possible.

I just bought a small (16') camper.  I am going to do only dry camping in long weekends.  4 to 5 days.  There will be an extended stay of about 10 days along the way this summer.  I have settled on a 80 watt Sharp solar panel for refilling the battery as we use power for recharging with (300 watt inverter plugged into a 12 volt outlet in camper) small batteries for flashlights and laptop for games and movies on rainy days.   I will have a Group 27 battery to work with.

Through web research I know I need a Charge controller (mounted inside the camper) I have decided on the Solar boost 2000e.  They did a nice job marketing the MPPT technology and it is supported by several on line articles raving about it.  However, upon going through some of the other posts in this forum I am noticing that due to my small setup I may see no real benefit to a MPPT charge controller.  What would be a better option?  This may solve my delema as to having the charge controler wired in by a local dealer who features products from Go-power.  I just need the word from someone who has some experience.  I am getting to old to learn from my own mistakes!  I need to save time  :-D

my main question(s) are:

I do not want to mount the panel on the trailer as we will park it in the shade.  I want to have 20' foot cables and manually move the panel throughout the day to point it at the sun.  I have seen brackets with a kickstand on it to set it upright and adjust angles and such.   I have not seen in any wiring drawings how I connect and disconnect the panel for transport.  I imagine that there must be a kind of junction box that can be mounted on the outside of the trailer that the panel wiring can be clamped to or plugged into.  I have not seen this ever mentioned.  How can it be done?

Second is, how hard is it to wire myself?  I have approached a local camper service department and they Will not install (wire it) because they did not sell it to me.  liability issues they said.  I just do not know if I have the know how to do it and am frustrated.

Any and all help or advice will be greatly appreciated,

Thanks,

Rick

niel

Re: I am a newbie and need serious sage advice and answers. Thanks

rick,
i am not the rv expert here, but i can give some general input. for just the one pv i do agree not to go with the current mppt controllers. if you plan on another pv later on you could get the mppt anyway like those from bluesky. you will find the pv to give a max of around 4.5amps, but it will typically be less than this for the number of hours it'll get full sun and that will vary too by where it is you rv at. a straight pwm controller is good too, but of course get one that has a remote battery temperature sensor. this would apply to any controller you would want to get to accomodate the variations in voltage to properly charge your battery with temperature changes. the real problem with most of the mppt controllers is the amount of power needed to operate them even when there's no sun. bluesky does have a variety of mppt controllers and you could get one without a meter on it that is a major source of draw on the controllers. this could be replaced with an external meter you can switch on or off. my sb50 also powers a relay so that is figured into it efficiency as well.
you are going with the remote setup and that will be good for you in staying cooler by being in the shade, but you will have to keep an eye on it(thieves). the wiring can be calculated for whatever length you choose to make the run for. if you want you may have one of us run some calculations for you or do it yourself. start at the beginning of the following thread if you want to do this yourself.
http://www.wind-sun.com/smf/index.php?topic=1477.0
if you plan for more pv later on it may be easier for you to get a bigger pv now rather than another 80w pv later. i'm thinking along the lines of having 2 pvs remotely mounted as opposed to one. a kc130 would yield over 7amps and still have only one pv to mount.
the group 27 battery would probably be around the 80-100amphr range and could accomodate 2 of those 80w pvs for charging it, no problem. if you should deplete the battery to 50% (not recommended to be exceded) that means you have taken 40-50amphrs out of the battery and do understand that a single 80w pv will need a couple days at least to replenish what was used.
as to a connection outside i do not know if there is a standard outdoor connector used in the rv field for dc. it should be weatherproof though. maybe crewzer can give you the lowdown on it and much more as he is heavilly into rving with solar.

crewzer

Re: I am a newbie and need serious sage advice and answers. Thanks

I have settled on a 80 watt Sharp solar panel for refilling the battery

How did you settle on the 80 W Sharp PV module?

More later,
Jim / crewzer

System2

Re: I am a newbie and need serious sage advice and answers. Thanks

Mostly price and wattage. In all the searching on the web and through my local RV dealers everything else was about 65 watts and 200 dollars more. It is also the only one of it's size I can get through a brick and mortar store (Northern Tool).

I am anxious to hear what you may have to educate me on to make this all happen.

RW

crewzer

Re: I am a newbie and need serious sage advice and answers. Thanks

Rick,

The Sharp 80’s STC Vmp is 17.1 V. Since its PTC power rating is 70.24 W, typical output voltage at 20 C (68 F) ambient will be ~17.1 V x (70.24 W / 80 W) = 15.0 V. It’ll be even less at higher ambient temps.

Accordingly, I submit that in your case, there will be little -- if any -- "extra" voltage available to convert to additional charge current. Therefore, there will be little -- if any -- net benefit derived from the SB2000E MPPT controller. Also, note that although the Bulk charging stage may benefit from MPPT technology (especially on a sunny and breezy day in very cold ambient temperature and with a low battery state-of-charge), the Absorption stage does not.

A cost effective solution for you would be something like the Morningstar SunSaver SS-10L (~$70). It’s larger than you’ll need for a single 80 W module, but it’ll allow you to add a second module at a later date. My deck lights use a Morningstar SunLight controller, which has the same charge controller guts, and it’s worked flawlessly for several years with a Interstate SRM-27 Group 27 flooded-cell battery.

Anderson connectors are popular quick-disconnect high-current connectors. Here’s a link to one for #10 wire. I don’t know if the contacts are crimp-type or solder lugs -- you’ll have to check on that.

Here’s the type of wire you’ll need. #10 should be large enough for an 80 W PV module at 20 feet.

Wiring is fairly straight forward. You can download the controller’s user manual as a reference. The Anderson connectors would go in the wire between the PV module(s) and the controller. Make sure you include a fuse or circuit breaker between the battery and the controller. You can wire high-current loads directly to the battery (rather than via the controller), but make sure they’re fused as well.

Make sure you secure the PV module when you’re not around. :-(

HTH,
Jim / crewzer

System2

Re: I am a newbie and need serious sage advice and answers. Thanks


I like sharp products but their panels always seem to be a
little on the high side price wise compared to kc 85's and
others. i guess they need the money :roll:

brad

System2

Re: I am a newbie and need serious sage advice and answers. Thanks

Another question I thought of is, The sharp I am looking at has a Kit version of the panel and it is about $150 more than just the panel.  Would I be better off financially to get the wiring separately?  My time and effort are worth a little bit so if there is not a large cost savings....  I guess I am also interested if the kit has what I need or what they want me to need.

http://www2.northerntool.com/product/200306869_200306869.htm  $599 Kit

http://www.infinigi.com/sharp-ne80u1-watt-solar-module-p-84.html  $450 Panel only

Or Is there a panel/kit of equal or greater size for the same or less money?

For the Charge controller you mentioned is there a monitor I need/want to keep an eye on the battery charge?  If we use more that the panel can fill over a few cloudy days I need to know when to supplement with charging through the truck battery (running the truck for a couple of hours) or something.

One other thing for now.  I will be checking this string often and encourage anyone with any experience or advice for do it yourself wiring to add on to the post.  In my perfect world scenario Someone from my area (Rochester MN) will read this and point me in the direction of someone (dealer or private party) who I can hire to help me with this project before July.  Actually We camp around the St. Cloud and Alexandria MN are and would not mind having the work done up there.  Anyone??????

I just looked over the Kyocera 130 watt solar panel, KC130TM and am thinking I may have been to quick to dub Sharp as my pick.  More wattage less money.  if I go with a larger panel will I need different wire than #10?  Any other thoughts or opinions out there?

Thank you for your help and advice so far,

RW

BB.

Re: I am a newbie and need serious sage advice and answers. Thanks

Regarding wire size, use the link Niel provided above to calculate your one... A couple if points. Losses in a wire go at the square of the current. So, if you double the current, the losses to heat in the wire will go up 4x.

P=I^2*R (heat lost due to current and resistance).

I believe Niel has used ~3% as his recommended trade-off point between the cost of the wire and amount of heat loss. Sometimes though, you will just have to call it quits. A 6 gauge cord is not small.

The other issue is if you are going to be moving this panel around a lot, you will work harden solid wire. You might be better off looking at something like a heavy two conductor shop cord (sunlight rated) that also has strain relief in the cordage itself. The cord will be thicker than to TC (Tray Cable) solid conductor wires bundle tied together every foot--but it will last many times longer if it is handled a bunch.

Also, watch that the panel is not knocked over by people or wind. The typical panel is glass and will break pretty easy (may still operate, but the crack in the glass will probably cause early life failure). You might want to take a look at this type of thin film panel from Uni-Solar. It is not near as efficient as a high end glass panel, but it is cheap per watt and much less fragile. They will just be somewhat larger for the same output. They also work better in hot climates.

http://store.solar-electric.com/unus64wathfi.html

-Bill

niel

Re: I am a newbie and need serious sage advice and answers. Thanks

if you like to watch the charge on a meter get a controller with the current and voltage meters built into them. there are aftermarket ones available, but those on the controller tend to be more reliable and cheaper.(my opinion) if it were to be just a voltmeter you wanted and not the current then i'd say go with an aftermarket voltmeter, but the current is what you'd be more interested in.
as to which controller you pick is going to be up to you and having low amps from 1 pv is iffy for mppt controllers. this will be one you will have to decide on.
for the wire gage with more amps going through you most definetely will either have to shorten it up almost in 2 or go to a bigger gage of wire. you say 20ft, but you may need a few more feet going into the rv so i'll figure this at 25ft. btw a wire run is just the distance involved for the wire, but you have 2 wires involved(+ and -) so the total wire length is double that of the run length.
for 4.5amps at a 25ft run(50ft of wire) this is about 2.1% with #10 and is fine
for 7.39amps at 25ft run it goes out of tolerance by being 3.44% with #10, but at a 21ft run of #10 this is within tolerance at 2.89%. obviously if it's to be longer than 21ft at 7.39amps you will need #8 wire. this is in keeping the voltage drop percentage below 3% and if you would like you could make those percentages tighter tolerances by going to the next gage number. the wire should be more flexible by using stranded wire or risk breakage and more resistance points made in the wire that'll lead to failure quicker. the use of fuses and even a disconnect could be a good idea. minimumly put a fuse inline that could double as a disconnect by being pulled.

crewzer

Re: I am a newbie and need serious sage advice and answers. Thanks

Rick,

http://www2.northerntool.com/product/200306869_200306869.htm  $599 Kit

I’d pass on this “deal” and instead spend the additional $$ on exactly what you need for your intended installation.

http://www.infinigi.com/sharp-ne80u1-watt-solar-module-p-84.html  $450 Panel only  Or Is there a panel/kit of equal or greater size for the same or less money?

The Kyocera 85 is $449 at NAWS.

For the Charge controller you mentioned is there a monitor I need/want to keep an eye on the battery charge? If we use more that the panel can fill over a few cloudy days I need to know when to supplement with charging through the truck battery (running the truck for a couple of hours) or something.

Battery monitors like the Trimetric and the Link 10 are very useful tools, but you’d have to decide if they’re cost effective for your installation. A voltmeter would help monitor battery voltage. A compromise solution might be a Morningstar ProStar 15M controller with a built-in meter and LED charge indicator.

Note that the only accurate way to measure battery state of charge is when the battery is disconnected from both charging sources as well as loads, and has been allowed to rest for at least three hours.

I just looked over the Kyocera 130 watt solar panel, KC130TM and am thinking I may have been to quick to dub Sharp as my pick.  More wattage less money.  if I go with a larger panel will I need different wire than #10?  Any other thoughts or opinions out there

The KC-130 at $595 looks pretty attractive. The combination of PV module voltage, wire size, controller type and battery type is a delicate balance. While it’s true that higher current through the PV-to-controller wire will lead to a larger voltage drop, this may not be a major issue for a hi-voltage panel (KC 130 STC Vmp = 17.6 V) as the PWM controller will throw away any “extra” voltage.

I estimate that the mid-day voltage drop from a KC-130 through 40 feet of wire (20 feet for each polarity) would be ~0.33 V. Accordingly, the KC-130 should have no problem pushing the end-of-bulk stage battery voltage to 14.4 V, which is typical for flooded-cell batteries.

Finally, note that PV modules rarely produce their specified power, which is based on a very cold ambient temperature. Expect mid-day output power from a clean- and well aligned PV module on a sunny day to be ~87% of the STC spec. Essentially all of this power reduction will manifest itself as lower output voltage.

HTH,
Jim / crewzer