wire sizes?

FreeBrrd
FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
in Solar Beginners Corner #1
Just want to be real clear. It's been a while since I did electrical work ;)

The #2/0 & #4/0 are just for interconnects between batteries??

If I have one Deka 8A24 to a Morningstar 10 to a Kyocera 65, all of my wiring can be #12 2 conductor outdoor cable, no conduit, etc. ?? If it is almost in living area, should I run it inside conduit or something?

All of the loads are less than an amp so no fuses?? I'm using all computer mods - 4 or 5 fans, some led lights, and a couple of cold cathode lights. Finally quit working on computers and now I'm going to live in a computer case.:D

Rocker switches with leds must use some power for the leds, but I guess it's real minimal. With my tiny system, everything makes a difference. I can always disconnect them. It'll be nice if I can afford another panel before next summer's heat.

Thanks all

other advice, comments appreciated
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    Re: wire sizes?

    I am not quite sure I understand your questions... But here goes...

    Typically, the interconnects of the battery are heavy and go to a common +/- bus bar / common interconnect point. These leads only need to be heavy enough to carry the maximum amount you expect to feed/draw from the battery... Too heavy, and you end up just wasting money... To small, the add resistance, voltage drop, and eventually can overheat if enough current is drawn.

    Regarding fusing--fuses are to protect the wiring. Lead Acid batteries can output huge amounts of current into dead shorts--more current than you can get from your home's AC wall outlet (which is limited by the pole transformer).

    So, typically, you would add one appropriate sized fuse from the bus bar to to your load (14 awg wire, 15 amp fuse, 20 awg wire, 20 amp fuse, etc.)...

    Many times, because of the voltage drop, you may need heavier cables to lessen the voltage drop from the battery to your load... Fuse wise, it is your choice--you can leave the larger fuse to protect the large wire diameter--or use a smaller fuse because you know that you will not exceed the lower current of the device (x1.5 or so to prevent false blowing).

    Fuses are not there to protect your radio, lights, etc.... It is to protect the wiring from overheating and catching your home on fire.

    Typically, your battery negative bus is grounded to safety ground--and you would only put the fuse in positive distribution lead... As close a practical to the battery (not 100' away near the load--again because you want to protect that whole run of 100' from getting a short and starting a fire).

    If you are wiring outside--typically you should use metal conduit--squirrels, rats, etc. can easily chew through your exposed wiring and cause shorts. Although--many people do run exposed wiring--just make sure it is UV rated for wet conditions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #3
    Re: wire sizes?

    Sorry I wasn't very clear. and this isn't a real typical application I don't guess. Sort of a microRV.

    I have one Deka 8A24 AGM battery connected to a Morningstar 10amp controller connected to a single Kyocera 65Watt panel. The controller only accepts up to #10 wire. The voltage / amperage on mine requires #12. What I am asking here is if I need anything larger to the battery? It doesn't seem like I should need a buss bar or anything else in between the single battery and the controller.

    Do I need a buss bar for a single battery? Do I need other than the #12 or #10 that goes to the controller coming off of the battery? Can the wiring to the battery be the single 2 conductor instead of 2 single conductor wires?

    I was going to put in a little fuse panel as power distribution, but did not think the fuses were needed here. Being computer mods, the wiring to the fans & lights is really small, no idea of #.

    The wiring will be in the wall. This is all on my 5' x 7' camper which I will be living in for the next ?? years. If I use the outdoor wire, do I need anything else with it run in the wall with reflectix insulation - probably plywood sheething on inside & outside. I had been thinking split loom until I realized that the wire is a single 2 conductor instead of 2 wires. Seems like the outside stuff has pretty thick insulation around the two wires. I will probably put some other kind of barrier between the battery area and the living area - I got a nice battery box, but I think something like plastic sheeting that keeps fumes, etc. out as much as possible. Of course, I also have truck exhaust, etc.
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #4
    Re: wire sizes?

    Actually, now that I read the product information all the way thru:
    http://store.solar-electric.com/12-2-tc.html
    "This is the standard wire for all outdoor applications. It is commonly used for wiring solar panels, and from the solar panels to the charge controller and batteries. Water and sunlight resistant. UL approved for use without conduit. Also known as type TC (tray cable). Complies with NEC article 340 and 690 and is rated as sunlight and moisture resistant. "

    pretty much answers my first question
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: wire sizes?

    freebird,
    you will not need anything special for the battery such as a buss as you only have the 1 battery.
    as to the fuses, use them for any connections to the battery because even a simple led drawing in milliamps has no bearing on an accidental short circuit that the battery will push huge amounts of current through your wires. the fuse panel should be at the battery or at least a fuse that could prevent a short across the wires from damaging your wires or battery that will not pop with your proposed loads. fuses located farther away would then act like a sub panel.
    now for an rv with 1 pv, i don't suspect you'll need heavier wires than #12 or #10 unless you intend long wire runs where the voltage drop will become significant. you can check the voltage drop calculator in the sticky located in the general solar section for that. you would need an xls (excel) program for that.
    the battery will not normally gas as gassing an agm will mean it is overcharging and that ruins agms so just make sure the voltage limits set by the battery manufacturer are not exceeded and you won't need to worry about battery gassing.
    there may be a small problem with voltage variations with temperature if your controller has the battery temperature sensor built into the controller as the sunsaver line does. the sensor belongs on the battery as it is supposed to track the battery temperature and not the controller's temperature.
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #6
    Re: wire sizes?

    so I should put a fuse inline between the battery & controller at the battery?

    The rated PV input is 10 amps. Maximum array short circuit current rating is 12.5 amps. The rated PV input current and the rated load current can both be exceeded by 25% (which would be 12.5) for up to 5 minutes. So my fuse should be around 12.5 amp or am I figuring apples & oranges? 10 amp would be too low, but would 15 amp be too high?

    (This is sort of funny. My dad was with Square D company his whole working life, but he doesn't have time to help me with this). I sure appreciate you folks and the folks at Arizona Wind & Sun.

    for temperature sensor, would it be best than to put the controller close to the battery also? No reason not to as far as I can see.

    thank you.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #7
    Re: wire sizes?

    Check the manual for the solar charge controller you want to use--they usually give the fuse rating and minimum wire gauge... If you are using a minimum of 14 gauge wire--then 15 amp fuse would be just fine.

    Technically, the solar panels also need a series protection fuse--check their data sheet. Normally, you don't need the series fuse unless you have more than two panels (or series strings) in parallel... This is to protect one shorted panel from getting too much current from the other panels in the string powering the short.

    Battery temperature sensor is really the ideal for long battery life and best charging practices... Because it is physically mounted on the battery--it is more accurate.

    Without a BTS, you should mount the charge controller in/near the battery space so that it is in the same temperature space... However, since the charge controller moves current from the panels to the batteries, it will get hot--and its internal temperature compensation sensor will cause it to drop its output voltage with respect to the battery (and not charging the battery as fast or to 100% charge level because of the self heating).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #8
    Re: wire sizes?

    I'm using #12 awg wire per requirements for my current, etc.

    Spec sheet for Kyocera 65 does not mention fuses.

    Morningstar Sunsaver doesn't use external temp sensor. Do you think it makes enough difference to get more expensive controller. I would love to get a MPPT controller, but they are out of my price range right now.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: wire sizes?

    yes, they do as it is the short circuit current rating they often show as Isc multiplied by i believe 1.5 and rounded up to the next common value. they usually say the value of the fuse to go with most pvs in their specs. the kc65 isc is 3.99a x 1.5 = 5.985a and you round that up to the next commonly available fuse value.
    for one pv into a controller a fuse imho is optional, but from the controller to the battery you better have a fuse there at the battery because the battery can still send lots of amps into the wires during a short.
    for the fuse ratings bb was refering to, most times you will see ratings like 15a for #14 wire or 20a for #12 wire are common for utility ac use, but if the current is smaller on your pv system a smaller value fuse can be used to accomodate it as many dc systems use oversized wires to overcome resistive losses. know that the fuse will not be larger than that ac spec.
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #10
    Re: wire sizes?

    So a 10 amp fuse between the panel at the panel & the controller, a 15 amp fuse between the battery & controller at the battery, and what ever fuses needed between controller & loads.

    I think that about does it. Tomorrow I can buy the materials for my camper. In two weeks I can order the solar stuff.

    No idea yet just exactly when I get to move in, but I'm really sort of looking forward to it - less responsibility & more mobility - freedom!!

    Thanks all for the help. I've already recommended this forum & Arizona Wind & Sun to a couple of folks looking to add solar. I research all kinds of stuff online and this is probably the best site / forum I have run across for anything.

    I'll report back on how well the cold cathode lights work. They seemed pretty bright when I plugged them into my computer, but I couldn't tell about using them for doing stuff. Couldn't tell too much about color either. They seem like they should be as good as most leds. They don't seem very delicate either. Nothing much to break except the wire.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #11
    Re: wire sizes?

    10a into the cc and 10a out of the cc at the battery. the current out of the cc won't be larger than the input current unless you use an mppt cc so 10a in 10a out.
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #12
    Re: wire sizes?

    thank you

    now to mounts

    I have selected panel, controller, battery, battery box, wire, fuse holder & connectors between battery & controller, wire & fuse holder between controller & panel (not sure of connector at panel), fuse box for loads, switches for loads, fans & lights. Think the mounting hardware should be all that is left.

    Better than tinkertoys or legos:D
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #13
    Re: wire sizes?

    have you decided to leave the pvs on the rv and park in the sun or remote them so you can be in the shade? some may do both if they have need of that much in pv. they need to be very physically secure to travel and an adjustable mount would be best, but it is difficult to be able to adjust for all directions off of the top of the rv as you never know which way you'll be parked. also theft is a real concern so some consideration for that must be realized. i would recommend you look back at some past posts concerning rv mounts and antitheft topics.
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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #14
    Re: wire sizes?

    I just asked the NAWS folks about the security bolts. They did not feel that they were necessary for a vehicle that doesn't sit, but I figure that it doesn't hurt. I won't have the option of removing the panel. Right now it's just the one. With only 28 square feet of living space, it all has to be used as best as possible. The panel would have to be stored on the roof anyway. Also, as it is illegal to sleep in a vehicle, it is supposed to be 'stealth' and needs to be ready to move. I don't hardly think my homebuilt camper will be very stealth. I'm not even taking off the motorcycle racing decals or my logo across the windscreen. Also I plan on painting my door bright red to match the truck.

    I'm going with the UniRac Flush RV Mount with the security hardware and probably carriage bolts for the roof side. I was thinking about adding a truck rack around the roof so that I could carry stuff like lumber and also to hide the panel a little without shading it, but I'm about out of money and need to spend all of my time packing. I just bought my first bit of lumber this morning to start building the camper. The lumber yard happened to have some Cedar 2x6's on sale. Ripped to 2x2, they will make great studs.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #15
    Re: wire sizes?
    FreeBrrd wrote: »
    The lumber yard happened to have some Cedar 2x6's on sale. Ripped to 2x2, they will make great studs.

    Park in sun, add water, and you have a sauna !
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • FreeBrrd
    FreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    #16
    Re: wire sizes?

    I just bet two little black kittens would love that. They love running water, they are going to miss that, but hot steamy... don't think so.

    I can see this if I'm working (I'm a union carpenter apprentice):
    Park in the sun, put a chicken in the solar oven, maybe a loaf of beer bread. See how many carpenters want to have lunch with me. No cookies though. I had a guy ask me if I shouldn't be home baking cookies instead of being a carpenter:roll:

    I can't wait to get a chance to try the solar oven. I got new black camping cookware (so it's light and has removable handles). I also have a flat water container that can live on the roof to provide hot (or warm) water at the end of the day. The 5gal black jug would be too heavy, but this little one holds about a gallon and is about 1.5 inches high when on it's side. Better than heating it over the alcohol stove.
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