Small RV system - need help

For 5 years, I've used a small hard-sided pop-up camper with two 12v batteries.  The batteries have gotten to the point where they are not holding a charge, so sprung for 2 larger Trojan deep cycle (they fit in the battery boxes with no room to spare..)

For remote camping, I have a single 75W Siemens panel, and a cheapo old Lyncom 7 amp charge controller.  After reading here, I see things I did wrong - namely undersized wiring - but easily correctable.

Also, I want to add another panel, a permantly mounted UniSolar 65 watt on the A-frame. This will show how much I have to learn:
Can I wire 2 dissimilar panels in parallel to the charge controller?

Since I'll be doing rewiring, I would like to get a more up-to-date charge controller, preferably one with a display to keep an eye on battery condition.  I see the SB2000E mentioned a lot, would this be overkill for my needs, or is there something even better available now?  Thanks for your help,

John F

Comments

  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    Re: Small RV system - need help

    John
    Yes you can wire to different panels in paralel but it is not very efficient to do it that way. It would be better if you got another seimens that has the same voltage as yours especially if you are going to get an mppt controller. Wiring 2 different panels together will cause the panel with the higher voltage to be drug down to the voltage of the lower panel. Thus reducing the overall output of your system.
    Larry
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    The Trojans (T-105’s?) are great flooded-cell batteries. However, they require a fairly high absorption charge voltage (14.8 V), and the equalization voltage spec is 15.5 V. These voltages are difficult for “12 V” PV modules to deliver in the hot ambient temperatures typically associated with camping.

    http://www.trojanbattery.com/Tech-Support/BatteryMaintenance.aspx

    The output voltage from an array of parallel modules will be close to that of the lowest rated module. Since the Unisolar’s Vmp is 16.5 V and the Siemens’ is 17.0 V, adding the Unisolar panel will increase power but reduce charging voltage. Factoring in the additional voltage reduction associated with warm and hot ambient temperatures, I doubt that the expanded array will be able to deliver much above 14.0 V at full current in the Summer.

    Accordingly, I suspect that the combination of the high charging voltage required by the new batteries and the lower output voltage potential of the larger array will keep the batteries from ever being fully recharged by the PV array. If the PV array is the only charging source, then the batteries will likely suffer an early demise due to deficit recharging and resulting sulfation.

    A work-around might be a good quality four-stage external charger for use at home to recharge the batteries after a trip and keep them correctly charged while they’re waiting for their next camping adventure.

    The combination of the two modules will deliver ~8 A. This will likely kill the old solar charge controller, so you’re right to be looking for a larger controller. However, don’t be seduced by MPPT controller’s claims of 30% power boost, as these gains are rarely realized in small systems used for summer camping.

    So, what’s the solution?

    I need to think about this a bit. More later…

    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Good guess on the T-105's, but wrong.  They were simply too tall to fit (the batteries are located under each of 2 seats inside the Chalet pop-up, and the taller battery boxes they would have required wouldn't clear.  So, I got 2 Trojan SCS225's (12v) wired in parallel between the 2 battery boxes with the following specs:
    Capacity (minutes)
    @25 Amps:  225
    5 Hr Rate (AH):  105
    20 Hr Rate (AH):  130

    I know these were more expensive and less robust than the T-105's, but I'll keep a close eye on them.  The camper does have a built-in converter (Magnetek 6700) I can plug into AC at home to charge the batteries between outings.  The converter output is 20 amp, I measured charge voltage at 13.7 (batteries were already charged.)  Ususally I plug it in for a day before outings, then rely on the PV for recharging during outings.  This time of year we run the propane heater at night, use the lights sparingly (approx. 3 hr/day, I think they are 17 watt 12v bulbs), and of course the water pump runs maybe 30 min/day.

    Looks like the ProStar 15 would work, I'd like the display option to help keep an eye on battery condition without checking with my meter all the time.  I'll also rethink the permenent mounted UniSolar and maybe use another panel I can move around (if I can fit another one in the storage area), or mount it on the A-Frame portion of the Chalet if I can't.  Problem with that is that I can't always orient the camper to the sun direction, or trees provide too much shade - yes, I guess the next panel will have to be movable as is the only one I have now.

    BTW, we normally camp mostly in the fall/winter/spring in the Southwest.

    So, I should pick another panel with 17.0 v at load like my current Siemens, right? 
    Edited: Hmmm, looks like the Evergreen 120 is a pretty close match voltage wise. Could that be connected in parallel with my older SP75 without losing too much output? Seems like a 75+120 would allow me plenty of margin for cloudy days...

    Thanks for any other help you can provide,

    John F
    LV, NV
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    My crystal ball clouds up every now and then… :oops:

    The Trojan SC225’s are fine batteries. But, they’re still Trojan flooded-cell batteries, so, unless you have other instructions from Trojan, I recommend you follow the charging and maintenance procedures in the link I provided earlier.

    The ProStar 15M is a very good PWM controller, but its range of output voltage selections is limited. For the Trojan batteries, I’d suggest you consider a TriStar 45 (with the optional meter and remote battery temp sensor) and use battery setting number 5 or 6.

    http://www.morningstarcorp.com/products/TriStar/info/TS_DataSheet.pdf
    http://www.morningstarcorp.com/products/TriStar/info/TS_Manual.pdf

    The Magnetek charger is not a particularly good model. As you found, the battery charger voltage is ~13.8 V, That’s too low to fully charge a battery, and it’s too high for a long-term float voltage. I had a similar model in my old camper, and I stopped using it.

    http://www.parallaxpower.com/6700/MagneTek%206700%20series%20Owner%20Operator%20guide.pdf

    The Evergreen 110, -120 or Kyocera 130 will work with your SP75, although they will lose a bit of their output voltage. The cooler days of the Fall, Winter and Spring in the SW will help moderate the array’s hot weather voltage reduction.

    HTH,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    OK, I've read everything you recommended, and now I know .01% of what you do. Looks like the TS-45 is what I need. I'll even be able to properly maintain the batteries without buying a charger, as there is plenty of sunlight here in LV to hook up the panels monthly even if we don't camp.

    With the info provided by the TS-45's LEDs, looks like I can even do without the digital meter. I will order the temp probe, though. Without the external temp probe, there is no temp eq? This unit will be mounted close to one of the batteries (sealed box, vented).

    Did I mis-read the TS-45 specs on PV input voltage, does it mean I could hook 2 panels in series? I'll be getting either the Evergreen or Kyocera. Even if parallel, the voltage loss will be minimal.

    Thanks for all of your great info and help,

    John F
    LV, NV

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    I believe the TS controllers require the optional remote temp probe to enable temperature compensation. The TS controllers do not have a DC-DC step-down capability, so you'll have to wire your "12 V" PV modules in parallel for charging your "12 V" battery bank.

    Enjoy!
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Jim / crewzer,

    I know you are right about the Magnetek being a less than satisfactory converter, many Chalet owners have changed them out for more suitable ones.

    I'm thinking (and correct me if I'm wrong) that if I swap out my old solar controller with the TS-45, and add a panel, I should be able to properly maintain my batteries whether I'm camping or at home.

    Now, for the extra panel - I have no more storage room in the chalet, so it will have to 'sleep' on the bed inside the Chalet while traveling, and be pulled out when we reach our destination, so size is no longer a factor.  I got the Siemens SP75 years ago because of its width - it was able to slide into one of the outside accessable storage areas.  So, now, do you think I'm correct that the Koycera 130 would be the best 'bang for buck' and a good match for the SP75, or do I not even need that much capacity for my needs given the batteries I've got (outlined in messages above)?  More is always better, right? <g>

    EDITED:
    Actually, now that I look at them again, the Kyocera 85 looks to be a closer electrical match to my SP75, and should fit my usage needs (and save a few bucks in the process, and be easier to haul out of that little trailer door...) What do you think?

    Thanks again,
    John F
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    A key consideration of your system design is having sufficient current to recharge the battery bank on a regular basis. 5% mid-day charge current is a typical working spec, and that would mean 13 A (bulk stage) for your 260 Ah battery bank. That would require a 12 V array rated at ~225 W STC.

    Increasing your array’s size from 75 W to 160 W will deliver ~9 A mid-day, assuming the panels are aimed south and tilted up at ~ latitude. That’s ~3.4% of the bank capacity, and it should just enough to charge and maintain your batteries when the camper is parked at home. You’ll want to check the system every once in a while, the batteries will still need occasional maintenance, and you may have to tilt the PV modules up at home as well.

    So, adding just an ~85W module should be OK. And, don’t forget that the well maintained- and fully charged batteries can be a very useful backup power source at home in the event of a utility power failure.

    Good luck, and enjoy!
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Ordered the Kyocera KC85T panel (from Northern Arizona W&S, of course...)

    They did not have the TS-45 in stock, and were not quite sure when they would get them, so ordered the TS-60 (looks to be the same physical size according to Morningstar data sheet) as well as the RTS (controller will be mounted close to the batteries, but as far as I could determine, there is no 'built-in' temp comp without using the RTS.) Who knows, maybe someday I'll need the extra capacity for a small cabin system.

    I'm going to start prewiring and mounting for the new controller, will have to start from 'scratch' to use larger wire than I'm using now. Since I'll never run the trailer converter at the same time im using PV, I'll just wire the TS-60 straight to one of the batteries, which is already run parallel with the other battery.

    Then, convert the connector I'm using for the SP75 for parallel operation with another panel, and I'll be set. I'll let you know how it works out, and thanks for your help.

    John F
    LV, NV
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Small RV system - need help
    barshnik wrote:
    I'll just wire the TS-60 straight to one of the batteries, which is already run parallel with the other battery.

    Arghhh !! Somewhere, does someone have a photo or sketch, of how to diagonally connect batteries, to spread the load more evenly ? There's got to be verbage about it too
    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 ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    Mike makes a very good point about battery wiring. Take a look at this link for how a pair of 12 V batteries should be wired in parallel ("12 V battery bank" section, upper left diagram): http://www.solarseller.com/battery_bank_wiring_diagram.htm  The charger/load connections are made diagonally opposite at the battery bank to equalize charge- and discharge currents through the batteries and connecting cables.

    Otherwise, it sounds like you're good to go, and I hope you'll keep us posted on your progress and results. If you're ever over near Callville Bay, please give 'em a wave. I did a LOT of houseboating and powerboating out of there from 1982 through 1992.

    Regards,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Thanks, Jim, one more thing to rewire as the trailer mfgr. did not do it this way. Easy enough, though, and it does make sense rather than PV controller pos. & neg. both to one battery, with seperate wires linking the two batteries. I may as well rewire the Magnetek this way while I'm at it (before I get rid of it altogether...)

    The years you were around Lake Meade are about the same as when I was sailing around in a small sailboat, before the lake level plumetted and what was left was filled with crazy power boats and jet 'personal watercraft'.

    Again, thanks for your help.

    John F
    LV, NV
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Wow.  Now I'm confused about this battery wiring diagram for parallel operation.

    Assuming good connections and CLOSE to same length and gauge for all wires, it seems to me that there should be no difference, electrically speaking, between running a pos. and neg. to each battery from the charging source; and running a pos. to one battery, a neg. to the other battery, then tying the pos. and neg. of the 2 batteries together. 

    Why are the 2 methods not electrically identical?  I'm obviously missing something here...

    EDITED: I've thought about this, and am convinced that if all wire lengths were identical, there would be no difference in the 2 methods. However, in my case, the run to one battery is about 6' longer to one battery than the other. 10 guage wire is used, so this difference in length could make a difference.

    Wiring per the diagram, I can sort of understand, WOULD make more sense given that one battery is a longer run than the other.
    EDIT ENDED:

    John F
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Small RV system - need help
    barshnik wrote:
    Why are the 2 methods not electrically identical? I'm obviously missing something here...

    milli-Ohms : 0.01 ohms @ 30 Amps = .3V drop

    The resistance in the 00 gauge cable, and 2 terminals, at 20 & 30 Amp loads, means one battery is more isolated, and the other battery does more work. If wired on the diagonal, the drop is spread more evenly across all the batteries.
    Each cable clamp connection to the wire, and to the battery, has resistance. Very small, but it becomes important under heavy amp loading. just a few amps for trickle charge will eventually top off a battery, but during bulk charge, one battery will end up shortchanged.
    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 ,

  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    When I first wired up my 6, L-16's, I didn't know as much as I should have, so hadn't wired them wired diagonal. One day, checking things out with my Fluke meter, wondering if they needed to be equalized, I was quite shocked to see the voltage differences. It wasn't much, I knew I'd be in trouble unless something was changed, so thought about it and tried diagonal. Problem cured.
    For most of us, life is a continuous learning experience.
    Wayne
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    <<When I first wired up my 6, L-16's, I didn't know as much as I should have, so hadn't wired them wired diagonal. One day, checking things out with my Fluke meter, wondering if they needed to be equalized, I was quite shocked to see the voltage differences. It wasn't much, I knew I'd be in trouble unless something was changed, so thought about it and tried diagonal. Problem cured.
    For most of us, life is a continuous learning experience.>>

    Yes it is. I have been forced to think about this (it's that damn crewzer's fault). I'll be rewiring diagonal, even though there is only a 5' difference in run length to the 2 batteries using 10 guage. Funny, I asked 2 different electricians I know about this, and neither had any idea what I was talking about. I believe they've quit learning, or thinking.

    According to the voltage loss charts, I'll have to limit my 14 guage runs from panels to controller to about 8', and there is no flexible outdoor wire I can find locally that is larger guage without going to 3 wires, thus wasting one. I really want to use a flexible wire to the panels. My (Lowes, Home Depot) choices are: 14x2, 12x3, 10x3. Any way I look at it, 3 conductor is a waste of 1. I do have some 12 guage 2 conductor speaker wire that is very flexible, but I'm afraid not durable.

    John F
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Small RV system - need help

    there doesn't have to be a waste of the 3rd wire. put them all together as one solid wire, then get another 3 wire romex run for the other polarity. i've done this in the past. 3 #12 wires in parallel have a touch more resistance than a single #7 wire. 3 #10 wires in parallel have a touch more resistance than a single #5 wire. when using something like 10-3 this has 4 #10 wires in it so you could have 2 pairs of #10 paralleled wires. 2 #10 wires in parallel have a resistance similar to a single #7 wire and 2 #12 wires in parallel have a resistance similar to a single #9 wire. see the patterns? :?
    amending here i forgot to mention that for those not willing or wanting to use all 3 wires in a romex bundle for one polarity and using another 3 for the other that you could just double up on one of the polarities if you wish. that is, like 1 #10 wire for + and 2 # 10 wires for -. it will cut the resistance in half of only one of the lengths of wire in the wire run.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Small RV system - need help
    barshnik wrote:
    I do have some 12 guage 2 conductor speaker wire that is very flexible, but I'm afraid not durable.

    Check out Malibu Light power cord, designed for 12V, long runs, and fairly flexible and durable for outdoor lighting use.
    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 ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    John,

    You can get very good stranded wire at you local Home Depot. Got to the tall wire spool rack and ask the associate for custom lengths of the following wire:

    "600 V UL-listed type MTW or THWN-2 or THHN or Gasoline and Oil Resistant II or AWM" (all of this mumbo-jumbi is printed on the wire insulation). He/she may just refer to it as "THHN"

    It should be available in at least black, red (either will do for +) and white (for -). They typically carry it in on the spools in sizes 10 AWG, 8 AWG and 6 AWG. Just figure out the length you need, add a few feet, pick the size and get what you need... they'll price the wire by the foot.

    HTH,
    Jim / damn crewzer :wink:
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Do I want to use the same 'diagonal parallel' method of wiring the PV panels as I did for the batteries? Thanks,

    John F
    LV, NV
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help

    Not required for the PV modules. Just put the one with the higher Vmp spec at the end of the wiring (farthest from the controller).

    HTH,
    Jim / damn crewzer :wink:
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    But it won't hurt?  My plan is to run a single heavy wire to the pos. of one panel, a single wire to the neg. of the other panel, and tie the pos. & neg. of the two panels together.  So, I'll have two cables running out of the trailer.  Is this not good?  Thanks,

    In this case, it doesn't matter which panel has the pos. wire to the controller?

    John F
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Small RV system - need help
    barshnik wrote:
    I do have some 12 guage 2 conductor speaker wire that is very flexible, but I'm afraid not durable.

    Arc Welding cable is durable and flexible, and made to handle hundreds of amps
    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 ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small RV system - need help
    My plan is to run a single heavy wire to the pos. of one panel, a single wire to the neg. of the other panel, and tie the pos. & neg. of the two panels together. So, I'll have two cables running out of the trailer. Is this not good?

    John,

    The "diagonal opposite" wiring recommendation for the batteries make sense because we're trying to maintain the batteries at equal voltages. For your two-module array, you want to place the lowest voltage module closest to the controller, as this will minimize the voltage drop between the modules and the controller input.

    You'll be better off running a pair to wires from the controller's PV inputs to the (+) and (-) terminals of the module with the lower Vmp rating, and then paralleling from that module to the (+) and (-) terminals on the module with the higher Vmp rating.

    HTH,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Makes sense. ONE more stupid question, please -

    If I use 10x3, is there any advantage to doubling up either the pos. or neg. (rather than using just 2 out of the 3 wires)?

    And I thought I knew a little about electricity...

    John F
  • System2
    System2 Posts: 6,290 admin
    Re: Small RV system - need help

    Yes, definitely do double up whichever side you want. If the positive run is longer than the neg., then double up the positive. Or, the neg., if it's the longest. Either way, the doubled up line will have one half the resistance it would if run single.
    Wayne
  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    Re: Small RV system - need help

    I'm not an electrician, but I believe you should be using UV-fade-resistant wire (USE-(something)) for your outdoor wiring. I couldn't find that at home depot, but an electrical supply place should have it.

    John