Is Xantrex C12 good for my small set up ?

TDIwestfalia
TDIwestfalia Registered Users Posts: 10
I have been doing a lot of reading. I just read Bob the solar guys entire web site. I may need a drink after that. I currently have a portable 100w Renogy panel. I replaced the wiring on it with quality 10awg that is 44feet long so I can park in the shade. The controller that came with it is adjustable but I already had to send it back once as it stopped letting me adjust the voltage which I need at 14.8 to get the Trojan SCS225 fully charged (130 a/h) It seems typical that most controllers that comes with a panel is usually junk.

Correct me if I am wrong. It seems to me the only affordable morningstars that have adjustable voltage settings are the tristars which are too big for my app. I will be adding one more 100w fixed panel to my roof for a total of 200watts. The C12 is fully adjustable and can do a true equalization manually I believe. Before I go ahead and get one of these are there any other quality 15a or less controllers that have adjustable parameters?


Thanks

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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?

    Okay, problem #1: 44 feet of 10 AWG carrying about 11 Amps @ roughly 12 VDC. Can you say "Voltage drop"? Looks like about 8% loss to me. Add panels out in hot (which lowers Voltage) sun and you may well have trouble coming up with 14.8 Volts regardless of charge controller.

    Unless you are willing to spend some significant money. This is one of those circumstances where where a very small MPPT controller may pay off. Put the two panels in series and feed them to a Morningstar SunSaver 15 MPPT http://www.solar-electric.com/mosumpsochco.html which can be programmed via PC to the right Absorb Voltage for your Trojan batteries.

    Yes, it's nearly 3X the money. But it eliminates the problem of V-drop.
  • TDIwestfalia
    TDIwestfalia Registered Users Posts: 10
    Re: Is Xantrex C12 good for my small set up ?

    44 feet is just on the one 100w panel. I calculate a voltage drop of about 3.3% on that. The one on the roof will have about 12 feet of 6-8awg. Nothing wrong with that is it ? I considered 8awg on the 44ft section but 10awg is so much easier to work with when setting up the portable panel.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?
    44 feet is just on the one 100w panel. I calculate a voltage drop of about 3.3% on that. The one on the roof will have about 12 feet of 6-8awg

    Okay, 12 feet of 8 AWG isn't going to present any significant V-drop for one panel running about 17.5 Vmp and 5.7 Imp.

    But that leaves you with another panel at the end of 44 feet of 10 AWG suffering about 4% Voltage drop just from the wiring. So here's the thing: as battery comes up in Voltage that second panel may go over Vmp before charging is finished and thus contribute nothing at the higher Voltages.

    This is not necessarily a problem so long as you realize you may still have only 1/2 power at Absorb level.

    As far as the C12 is concerned it's of the series of decent equipment Xantrex makes (unlike their newer bug-laden stuff) and can be adjusted as described. At roughly $78 it's not a bad deal either. For this application it looks like the best choice.
  • TDIwestfalia
    TDIwestfalia Registered Users Posts: 10
    Re: Is Xantrex C12 good for my small set up ?

    I appreciate the input. I may cut the 44 feet down to 25-30 and make an extension out of what I cut out just in case there's ever a time I need to actually go 44 feet.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Is Xantrex C12 good for my small set up ?

    The Renogy Panel has a relatively high VMP of 18.9Volts, I suspect you will be fine, so long as you understand the capabilities of PWM charge controllers, particularly if it's just one panel that far out, if you decide to have 2 that far out, I would combine them at the panels and run 8 gauge, but even then your likely to have enough voltage to properly charge and equalize the battery.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?

    The 18.9 Vmp will be a big help on V-drop. You're almost down to the magic 3% mark there.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?

    I use that same Renogy panel with the rebadged EPsolar pwm charge controller. I also use the C12 on other projects.

    But be careful with the long runs as noted above. Normally, one tries to place the controller as close to the batteries as possible to reduce voltage drop. The Renogy panel when first starting out can give one the wrong impression that the controller should be close to the panels. It is only this way for convenience, since the Renogy folding panel assumes you aren't going to run more than 15 feet max from the controller to the battery. They do have extensions available, but they are heavier gauge wiring. Still, the weakest part is the fact that the controller is near the panel, and not the battery as it really should be.

    So it would be ideal to run the C12 close to the batteries, and not mounted to the renogy plate. It's a tradeoff between convenience and efficiency.

    I like the Xantrex low end pwm line because the settings are so user-customizable, and very accurate if you use a reliable voltmeter on the test-points when setting things up should you wish. You didn't mention if you are also using the remote temperature-compensation sensor, and from where you are traveling, that would be ideal. At the very least it could just hang there being an ambient sensor. Heh, that's one thing the cheap EPsolar controller has over the C12. :)

    I like the C12's fully adjustable voltages, so I can stop the controller from going into float too soon when using agm's. Normally I set both the float and absorb voltage to the same value in the C12 to basically override the 1 hour timeout in absorb.
  • TDIwestfalia
    TDIwestfalia Registered Users Posts: 10
    Re: Is Xantrex C12 good for my small set up ?
    PNjunction wrote: »
    I use that same Renogy panel with the rebadged EPsolar pwm charge controller. I also use the C12 on other projects.

    But be careful with the long runs as noted above. Normally, one tries to place the controller as close to the batteries as possible to reduce voltage drop. The Renogy panel when first starting out can give one the wrong impression that the controller should be close to the panels. It is only this way for convenience, since the Renogy folding panel assumes you aren't going to run more than 15 feet max from the controller to the battery. .

    Thanks for the reply. I should have mentioned that the first thing I did was remove the controller and install it in the van less then 2 feet from the battery. I am still not happy with the wire I used for the run. I ordered it from this website and it is not fine stranded is pretty cheap feeling and stiff so it does not work well for a portable unit. Although marine grade 2 conductor wire is not sun resistant I think I am going to move to that as it is very flexible. After getting a working EP controller I am quite happy with it. It actually puts out 14.8v to my trojans when adjusted. I do a lot of camping...especially in the winter. I got this mainly to run an espar D2 diesel furnace. I will probably go with a xantrex C when I get the other panel mounted.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?

    Glad you got the controller close to the battery!

    Just note that with EPsolar, you should "trust, then verify". That is, just because the display shows 14.8v, doesn't mean it is actually driving the battery to those levels. It may simply mean that the battery is high enough in SOC that the display is showing your *target* setting, but it may not actually get there.

    As always, I recommend a meter you can trust, rather than a cheapo that *may* be in range. The absolute minimum for my tastes would be the Fluke 11x series, the 114 being the cheapest if you don't need inline amperage reading up to 10A. If you are doing current readings with a clamp-on meter anyway, this would be the cheapest. Or the 115, which does do amperage would be the next step up. Either way it is a matter of me trusting a Fluke more than ANY other manufacturer's voltage readouts. :)

    With the C12, you can easily preset the voltages with just the battery. Attach the negative lead of your voltmeter to the -BAT terminal, and the positive lead to the little solder blob next to the pots near the 9 o'clock position. Adjust pots to compensate, but remember that they are different values for compensation! Thus:

    HVD (absorb) starts at 13.0v (if you wanted 14.8 absorb, you'd set the pot for 1.8v on the multimeter)
    HVR (float) starts at 12.5v. (If you wanted 13.6v float, you'd set the pot for 1.1v on the multimeter)

    I found this very handy to be able to set up on the bench before putting it into operation in the field with the panel. The silkscreen markings gets close, but since I'm doing lifepo4 now, I really needed to be accurate. (in the field, attach the battery to the C12 first, and the panel LAST to make sure the logic gets set up properly.)

    Ideally, when running the C12, one should invest in the RTS or remote temperature sensor. At least the EPsolar comes with an ambient sensor, which amazingly you can adjust (like to ZERO temp comp for lifepo4, or run the C12 without, but I digress).

    Of course, this all assumes minimal loss runs, and with only 2 feet from the C12 to my battery with an 8 gauge wire, I'm pretty much in the ballpark at the battery end. :)
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Is Xantrex C12 good for my small set up ?
    I am still not happy with the wire I used for the run. I ordered it from this website and it is not fine stranded is pretty cheap feeling and stiff so it does not work well for a portable unit. Although marine grade 2 conductor wire is not sun resistant I think I am going to move to that as it is very flexible.

    A note about wire.
    Ordinarily fine strand wire is not used for hook-ups. The extra flexibility isn't required because once in place these wires don't move. What's more, fine strand is more likely to come loose from crimped connections.

    Many people use fine strand welding cable for battery hook-ups for example. It does not pass code, but it does work. Personally I would not use it for the reasons mentioned; it does not have to move about and the crimp connections are less certain to hold.