Charge controller help!

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rockyinnm
rockyinnm Registered Users Posts: 6
Super newbi, first post. Have small 50 watt RV system, had a very simple ASC sealed controller--EVERYTHING working fine!!
I installed a Xantrex C12 controller, yesterday, it worked fine during the day, did what it was supposed to do--but come night, it discharged the battery!! Like it needed a blocking diode??
I know that it should NOT, could I have a faulty controller???
thanks for any help, Rocky

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Charge controller help!

    You are correct... With virtually any solar charge controller, you should not install a blocking diode. The controller is supposed to prevent any self discharge by the solar panels.

    If there were no other loads left on--The perhaps you have a bad C12?

    I use a Grid Tied solar system--so I have not used an off-grid charger for any of my needs--But the C12 should be pretty bullet-proof.

    Check your wiring. Did you pout anything on its "Load" output or use the "Timing Function" to turn off loads?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rockyinnm
    rockyinnm Registered Users Posts: 6
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    Re: Charge controller help!
    BB. wrote: »
    You are correct... With virtually any solar charge controller, you should not install a blocking diode. The controller is supposed to prevent any self discharge by the solar panels.

    If there were no other loads left on--The perhaps you have a bad C12?

    I use a Grid Tied solar system--so I have not used an off-grid charger for any of my needs--But the C12 should be pretty bullet-proof.

    Check your wiring. Did you pout anything on its "Load" output or use the "Timing Function" to turn off loads?

    -Bill

    Thanks BB for the reply!!
    I made darn sure that the (2) wires for solar went to solar, and the (2) wires for batt went to battery, nothing on the load terminals!!
    I left nothing on to discharge battery!!
    Yes, a simple-should be, change out!!
    I may have got a bad C12--why me!!!-lol:grr
    This AM, it is working perfect, but this PM???
    I will see if I can return, as it is only a couple of days old!!
    Rocky in NM
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Charge controller help!

    If you can measure the load current back through the C12--from their specifications:
    Consumption at night (typical): 0.003 A
    Consumption with load disconnected (typical): 0.003 A

    If you see anything over 0.01 amps or so (10 milliamps)--then the C12 has a problem.

    Only other things I can think of:
    • Battery is pretty much dead (shows voltage while charging, when charging goes away, battery has virtually zero capacity to support any loads)--But I assume that the battery is working OK for you otherwise.
    • Poor electrical connection from battery charger to battery +/- bus points. With the sun up and charging--what is the voltage at the charge controller vs the battery bank... At most, you should see only 0.1 volts or so different. If you see more, there is a bad connection/cable somewhere.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Charge controller help!

    if you still have the other controller and you know it works then put it back inline and see if this changes anything. this could help point to the problem.
    are you very sure the c12 is sending a charge to the batteries during the day? could you be draining off the daily gains leaving the appearance that it has a phantom load?
  • dmiller
    dmiller Solar Expert Posts: 68 ✭✭✭✭
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    Re: Charge controller help!

    From reading past threads I've noticed that Solar Guppy usually pops in about now solving your cc install problem with his special fish wisdom. So there is still hope.

    The C12 has dip switches?
  • rockyinnm
    rockyinnm Registered Users Posts: 6
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    Re: Charge controller help!
    dmiller wrote: »
    From reading past threads I've noticed that Solar Guppy usually pops in about now solving your cc install problem with his special fish wisdom. So there is still hope.

    The C12 has dip switches?

    Again, thanks to the folks trying to help a newbi--
    as said earlier, this should have been an easy upgrade--take off old cheap, non adjustable controller, put on new adjustable controller!!
    Yes, conroller putting out 14.6v to battery this AM-(bulk)-then went to (float) 13.5v and it is holding that voltage now!!--(my settings)

    Here is another question??--I have the LVR set at 13.4v--and the LVD set at 11.5--I really do NOT know what they should be???
    Checked voltage in controller at PV terminal 18.2v--it's in direct sunlight in NM.
    Batt. termnals 13.5
    Maybe I got a bad egg--murphy does seem to hang with me-:confused:
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Charge controller help!

    LVR (Low Voltage Reconnect) should not really matter... As I understand, the LVR is associated with the LVD (Low Voltage Disconnect) for loads connected to the "LOAD" terminal.

    If you are not using the LVD, then LVR does not matter.

    Basically, if you run the battery "dead"--the C12 turns off the LOAD terminals. You can set the LVR level (or set to manual) and when the battery is partially recharged, it will turn the loads back on automatically.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rockyinnm
    rockyinnm Registered Users Posts: 6
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    Re: Charge controller help!
    BB. wrote: »
    LVR (Low Voltage Reconnect) should not really matter... As I understand, the LVR is associated with the LVD (Low Voltage Disconnect) for loads connected to the "LOAD" terminal.

    If you are not using the LVD, then LVR does not matter.

    Basically, if you run the battery "dead"--the C12 turns off the LOAD terminals. You can set the LVR level (or set to manual) and when the battery is partially recharged, it will turn the loads back on automatically.

    -Bill
    It is dark now, and ALL battery load has been disconected. The PV terminals show 0.5v--is this discharge??
    The battery terminals show 13.1 now, and I think droping--no load
    any ideas??
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Charge controller help!

    Typically, a resting battery (no charging/discharging currents for several hours) should have around 12.7-12.8 volts if fully charged (around 70-80F battery temperature). So, we would expect the voltage to fall over few hour period from the 13-14 volts when under charge to the 12.7 volts or so resting voltage.

    To be honest, I have not measured the leakage current / resistance of a solar cell for decades (of course, there were no 200 watt solar panels back then)--So, I don't know if 0.5 volts would result in much leakage current (don't think it is problem--but I am not sure).

    Our host, NAWS, in one of their FAQs says that blocking diodes are not really even needed for 12 volt solar arrays because the leakage current is so low.

    So, if your battery voltage is not dropping below 12.6-12.8 volts over night -- then it is still fully charged and you are just measuring the "resting voltage". If the battery drops below ~12.7 volts--it could because the battery is either not yet fully charged, or their is a parasitic load somewhere on the battery.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Charge controller help!

    C-12 has a nifty bi-color blinky indicator light. Does it show that the battery IS charging in the daytime?
    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
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  • rockyinnm
    rockyinnm Registered Users Posts: 6
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    Re: Charge controller help!
    mike90045 wrote: »
    C-12 has a nifty bi-color blinky indicator light. Does it show that the battery IS charging in the daytime?

    I went to town today---30 mile one-way--bought a hydrometer!
    It showed all (6) cells as very low, or bad.
    It appears the controller is working fine, as stated in first post.
    The battery just didn't have any reserve to it!!
    It was at 12.7v this AM, but no draw was on it--as I had everything disconnected!
    It charged right up to float level of 13.5v--and is there now, but after testing with the hydrometer--I know why it went down SO QUICK with a load on it1
    I again want to thank every-one--who chimmed in!!
    Now I need to do the (2) 6v battery conversion--this is in a 1161 Lance overhead camper.
    I have heard the (cut & paste)

    US 2200 XC 6V Deep Cycle Battery The workhorse of standard flooded 6 Volt batteries, the US 2200 Xtreme Capacity delivers an astounding 750 cycles at 50% Depth of Discharge and 232 Amp Hours of capacity with it's patented Diamond Plate Technology! That's 232 Amp Hours! More than Trojan T105 -- More than Exide 3600... and certainly more than the 208 Ahr rating of your club store battery. No other standard flooded 6 volt battery out performs the US 2200 XC

    $159.97----free shipping
    what do you think, these will be a TOUGH fit, with modifcation--but a lot of bang for the buck!!

    Rocky in NM
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Charge controller help!

    Shipping costs can be a killer--That sounds like a good deal for you.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Charge controller help!

    it's a good deal if you can keep a proper charge on it without any deep discharges that will ruin the lifespan of the batteries. remember batteries need between 5% and 13% as a charge rate without any loads connected.
  • rockyinnm
    rockyinnm Registered Users Posts: 6
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    Re: Charge controller help!
    niel wrote: »
    it's a good deal if you can keep a proper charge on it without any deep discharges that will ruin the lifespan of the batteries. remember batteries need between 5% and 13% as a charge rate without any loads connected.

    That is a VERY good point--I was just thinking bigger is better!!
    I just have a 50 watt panel now--and may add a 75 to 100 watt in the future.
    What would be a good 12v battery size for me, as we just use the camper 5 or 6 times a yr.
    I know the formula is around--please point me to it---thanks
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Charge controller help!

    i wouldn't call it a formula, but to preserve the life of a battery it is unwise to drain it below 50% or 50% dod (depth of discharge) as you may have read on the forum. that means for example, if you have a 100ah (amp hour) 12v battery and you drain 50ah that it would be 50ah x 12v = 600wh (watt hours) you drained. that would be the max one would want to drain from the battery, but if you can't replace what it drained then another condition will rear its ugly head called sulfation and that too can take away capacity, battery life, or even kill the battery. that would dictate for that 50ah drained that you would want to put it back in in a day, or 2 if cloudy, but shoot for the same day. there are other losses due to resistance, battery charging efficiency, and controller efficiency even if one would have sunshine so you may be in the 70% to 80% area there upping the pv current capacity of the pv needed to 120-130%. this translates to, for instance, with the same example battery that over say 5 full sun hours (intensity rating based on 1000w/m^2) that the 50ah/5hrs is 10a. 10a x 120% and 130% respectively is 12a and 13a from pv. edited my math error.:roll::cry:
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Charge controller help!

    So for a 232ah battery drained 50%, you would need to replace 116ah.

    (Warning, rough math ahead.)


    Your 50w panel + another 100w panel would generate (assuming that the panels put out at 18 volts) 8.3a per hour in full sunlight. So if you drained one of those 232ah batteries to 50%, it would take about 14 hours of full direct sunlight on those panels to recharge the battery.

    Except that there are some watts lost from the charge controller, and the wiring and whatnot, plus, as batteries get full they charge up that last bit more slowly - so really, you might even have to as much as double that time to recharge.

    Let's round it off and say it'll take 24 hours of full sunlight to fully recharge that battery if it is 50% discharged and you have 150w of 18v PV panels.

    If you get say 4 hours per day of full sunlight on the panels (no shade, clouds, etc.) then you can recharge it in about 6 days.

    Or, to recharge it fully in one day, you'd need 6x the solar, or 900w.


    If 116ah is enough for the few times a year you use the camper, and if you can park it in the sun for a week or more after the trip (or shore power at home), then you could probably get by with a 232ah battery and 150w of solar.

    Looking at it the other way, with 150w of PV in full sunlight 4 hours/day, you can generate about 33ah per day. With losses and whatnot, figure you'll really get maybe 24ah per day.

    If you can get by with only using 24ah per day, then you are in the sweet spot for your PV, and since you'll only be draining that big battery 10%, you would have a good 5 days of "no sun" reserve before you got it down to 50%.