Xantrex C60 Controller? AC amp vs DC amp fundamentals?

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System
System Posts: 2,511 admin
in General Solar Power Topics #1
I have several odd solar panels, all are 12v nominal but have different specs and wattage. If I wire these together and use a Midnite combiner with breakers, can I run that combined 12v into the C60 as source. Or do they all need to be consistant to each other.

Would this create a problem to combine these odd and variable power sources together. Will the C60 work OK with that to charge the battery 12v bank.

Same question, a bit different, 2 C60 controllers charging one battery bank, different wattage and stuff at each C60 coming in at their own amps/watts, Xantrex says they will work fine like that, but the foreign lady's resp[onse as if from a que card, not much authority from the foreign accent support desk. Just wanting confirmation to that.

Also, they say it's a 60amp controller... When I asked is that 60 amps at 12v, so would only be 30 amps at 24v, the lady says that these are DC amps? She says that DC amps are not same as AC amps when you are figuring voltage/amps etc.... WHAT??

I just don't understand that. And I don't see clarification anywhere that says the C60 can handle 60 amps at every voltage? Wouldn't this make it a 30 amp controller at 24v? A 15 amp controller at 48v.

I got same issue to determine proper breaker sizes. I don't want my breakers over sized where they will take too high an amp to trip. I have gotten info that has me second guessing how to size my breakers. Is volts/amps same relative relation with DC as it is in AC? In AC, 60 amps at 240v would be same as 120 amps at 120v. So, in DC isn't 30 amps at 24v same as 60 amps at 12v when you size wiring, breakers and the like?
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #2
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?
    new2it wrote: »
    I have several odd solar panels, all are 12v nominal but have different specs and wattage. If I wire these together and use a Midnite combiner with breakers, can I run that combined 12v into the C60 as source. Or do they all need to be consistant to each other.

    Would this create a problem to combine these odd and variable power sources together. Will the C60 work OK with that to charge the battery 12v bank.

    If you are just trying out solar, I would use what you have. It is best to have all of the same. But is cheaper to use what you have. Then if you grow, remove these and add new ones of the same type.
    new2it wrote: »
    Same question, a bit different, 2 C60 controllers charging one battery bank, different wattage and stuff at each C60 coming in at their own amps/watts, Xantrex says they will work fine like that, but the foreign lady's resp[onse as if from a que card, not much authority from the foreign accent support desk. Just wanting confirmation to that.

    Yes they will work just fine.
    new2it wrote: »
    Also, they say it's a 60amp controller... When I asked is that 60 amps at 12v, so would only be 30 amps at 24v, the lady says that these are DC amps? She says that DC amps are not same as AC amps when you are figuring voltage/amps etc.... WHAT??

    I just don't understand that. And I don't see clarification anywhere that says the C60 can handle 60 amps at every voltage? Wouldn't this make it a 30 amp controller at 24v? A 15 amp controller at 48v.

    Yes, it will work up to 60 amps for 12 or 24 volts.

    new2it wrote: »
    I got same issue to determine proper breaker sizes. I don't want my breakers over sized where they will take too high an amp to trip. I have gotten info that has me second guessing how to size my breakers. Is volts/amps same relative relation with DC as it is in AC? In AC, 60 amps at 240v would be same as 120 amps at 120v. So, in DC isn't 30 amps at 24v same as 60 amps at 12v when you size wiring, breakers and the like?

    For fuses or breakers, the rating is that, no matter what the voltage is. So a 10 amp breaker will trip at 10 amps weather the voltage is 12, 24, 48, 120,240, etc.

    The voltage is what the maximum rating that device can handle. Some fuses are good for only 32 volts. Some are rated for AC only.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?

    not having the same specs will not be as critical when using a pwm controller. most of the excess voltage from all of the pvs is somewhat wasted anyway. now with an mppt you may wish to have the specs line up better as the mppt controller will attempt to recover some of the power in that waste area.
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  • System2
    System2 Posts: 6,290 admin
    #4
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?

    Hi Guys, thanks for the help, Happy New Year to You.

    So, somehow the amps with DC does not calculate same as with AC? So, what does that do with watts calculations? I guess maybe in the weeds there, sorry, I feel like I am in the weeds with some of that.

    Watts = Amps x Volts

    So, a 63 amp din rail breaker that goes in a midnite combiner is 63 amps trip at 24 or 12 v, either voltage will trip at 63 amps?

    The same breaker says is rated up to 150v or something, also will trip at 120v.. 63 amps. That's what I think I am hearing and understanding.

    With regard to sizing wire and resistance, AC/DC the math works same way correct? Both less volts AND OR more amps means heavier wiring to keep resistance down.

    BACK to C60, so 60 amps whether 12v or 24v is what I am hearing. It's interesting because 60 amps at 24v is 2x the watts that it s handling. Also, with the huge difference in price between a C60 and a MPPT, I am looking carefully at that. I think it's going to take a really large system to justify that.

    With am MPPT would it only require 1 controller and take more various feeds at more odd watts and amps and charge more smoothly than having a couple of C60s would do. The normal voltages at panels is actually about 19v to 22v.

    So, if that is normal input, charging to 14.6v to my 12v battery bank most of the time. You are saying that the MPPT will waste less in that area between 22v in and 14.6v out. Doesn't the PWM, C60 just pulse that in without actually converteing that voltage, so it shouldn't be losing much? It doesn't actually step it down to 14.6v

    The MPPT does what? It actually does like a line conditioner or transformer? So, it's smoother and loses less, is that the idea? The MPPT is actually converting voltages and stepping it down.. right? I wonder what the percentage is between C60 vs say, outback MPPT. I need to figure out where the ROI would be.

    Will either a C60 and a MPPT take 24v nominal from one source, 12v nominal from another source coming into a combiner and charge a 12v battery bank. Both could do that right, but would need to put blocking diodes before the combiner.

    like 24v nominal, to blocking diode, to midnite combiner, to C60

    like 12v nominal, to blocking diode, to same midnite combiner, to same C60

    Would that work or would I have to get 2 seperate C60's to do that. Would a MPPT do that? Or would it be wired differently. Because I have an odd number of panels I was looking at staying with 12v in parallel, instead of wiring it all to 24v.

    I have 9 panels, 12v panels but also have 2 nice ones that are 24v nominal that I'd like to use in this little sytem.
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  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    #5
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?
    new2it wrote: »
    Hi Guys, thanks for the help, Happy New Year to You.


    So, a 63 amp din rail breaker that goes in a midnite combiner is 63 amps trip at 24 or 12 v, either voltage will trip at 63 amps?

    The same breaker says is rated up to 150v or something, also will trip at 120v.. 63 amps. That's what I think I am hearing and understanding.


    Those breakers ~should~ be good up to and including 63 Amps. At higher currents, the breaker will trip. The higher the current, the faster the trip will occur, normally. Also, those breakers are what they call "magnetic-hydraulic" breakers, which makes them much less sensitive to temperature variations, however, higher temperatures can make the breakers trip a bit ~faster~ above that current rating than at lower temperatures. This is because the hydraulic fluid becomes less viscous, just like motor oil.

    I like to keep the current through it slightly lower just to avoid nuisance tripping though, like, 60 Amps maximum when using a 63 amp breaker, but 63 Amps should be OK. Even temporary higher Amps through the breaker will not usually make it trip if it is fast enough of a transient and not too much higher than the current trip rating.

    The Voltage specification (150V, 120V, 12V etc), has nothing to do with where it actually trips at. That voltage spec has to do with the highest voltage the breaker will see when it is open. Opening a DC current is much harder than breaking an AC current, especially in high voltage systems. They have special ways to extinguish the arc when opening.

    When the breaker is "ON", there is no voltage across it. (very little anyway).

    Happy new year ! :D
    boB
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #6
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?

    in general, the 24v pvs will be too far out for 12v operation without an mppt controller being able to downconvert the voltage. there would be way too much wasted power and blocking diodes on the smaller 12v panels if paralleled to them should be used in such a case. if 12v pvs are far enough out of whack with each other blocking diodes may then also be warranted to prevent the larger pvs from dumping some of their power into the smaller ones voltage wise. an example would be a pv with 16.9vmp output mixed with one at 18.2vmp
    if you desire 12v operation you can use 2 separate controllers with the 12v pvs on a cheaper pwm cc if you would like and the 24v pvs on an mppt controller to handle the downconversion to 12v. to go with a 24v output on all pvs may work also by putting the 12v pvs with 2 in series, but that would leave 1 pv unused as it would be the odd one out.

    "The normal voltages at panels is actually about 19v to 22v"

    i assume that to be voc and not vmp correct?

    "You are saying that the MPPT will waste less in that area between 22v in and 14.6v out."

    correct.

    "Doesn't the PWM, C60 just pulse that in without actually converteing that voltage, so it shouldn't be losing much?"

    it limits the power delivered by pulsing on and off and that holds the voltage down by such action. when the transistors are switched off no power is delivered to the load. there isn't any converting being done by a pwm cc as it is just limiting the voltage and leaves the current unchanged as well up to the limit of the cc. an mppt can almost be viewed as a dc transformer and technically there is no such thing. it does achieve this because the vdc is changed to vac and then worked with and made to go back to dc. this may not be 100% accurate as to what goes on, but that isn't important as the effect is of having a dc transformer of sorts and as such it is transforming power and not just voltage. for example, a pwm controller with a 100w 24v pv used on a 12v battery will not increase the current to the battery beyond that which the pv is rated. if an mppt cc is in its place the current can nearly double what one would normally see from the pv. i would handle the 24v pvs with an mppt to go to 12vdc and if you desire you could use an mppt on the 12v pvs as well, but would not be necessary as a standard pwm could be used there if desired.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #7
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?
    new2it wrote: »
    So, somehow the amps with DC does not calculate same as with AC? So, what does that do with watts calculations? I guess maybe in the weeds there, sorry, I feel like I am in the weeds with some of that.

    Watts = Amps x Volts

    That mostly true for both AC and true for DC. For AC watts you need to know the power factor.
    new2it wrote: »
    With regard to sizing wire and resistance, AC/DC the math works same way correct? Both less volts AND OR more amps means heavier wiring to keep resistance down.

    That is true.
    new2it wrote: »
    BACK to C60, so 60 amps whether 12v or 24v is what I am hearing. It's interesting because 60 amps at 24v is 2x the watts that it s handling. Also, with the huge difference in price between a C60 and a MPPT, I am looking carefully at that. I think it's going to take a really large system to justify that.

    Yep, I have a 920 watt system using a C60 at 12 volts. Look at a MTTP, but not needed right now.
    new2it wrote: »
    With am MPPT would it only require 1 controller and take more various feeds at more odd watts and amps and charge more smoothly than having a couple of C60s would do. The normal voltages at panels is actually about 19v to 22v.

    So, if that is normal input, charging to 14.6v to my 12v battery bank most of the time. You are saying that the MPPT will waste less in that area between 22v in and 14.6v out. Doesn't the PWM, C60 just pulse that in without actually converteing that voltage, so it shouldn't be losing much? It doesn't actually step it down to 14.6v

    The MPPT does what? It actually does like a line conditioner or transformer? So, it's smoother and loses less, is that the idea? The MPPT is actually converting voltages and stepping it down.. right? I wonder what the percentage is between C60 vs say, outback MPPT. I need to figure out where the ROI would be.

    Will either a C60 and a MPPT take 24v nominal from one source, 12v nominal from another source coming into a combiner and charge a 12v battery bank. Both could do that right, but would need to put blocking diodes before the combiner.

    like 24v nominal, to blocking diode, to midnite combiner, to C60

    like 12v nominal, to blocking diode, to same midnite combiner, to same C60

    Would that work or would I have to get 2 seperate C60's to do that. Would a MPPT do that? Or would it be wired differently. Because I have an odd number of panels I was looking at staying with 12v in parallel, instead of wiring it all to 24v.

    I have 9 panels, 12v panels but also have 2 nice ones that are 24v nominal that I'd like to use in this little sytem.

    Here is what the difference between an PMW and a MPPT system:

    PMW- the panel voltage is the same as the battery voltage- If the battery is at 14 volts, the the panel could be delivering 14 volts X 10 amps = 140 watts.

    MPPT- the panel voltage is for the most part higher than the battery voltage- If the battery is 14 volts, the the panel could be delivering 17 volts X 10 amps = 170 watts.

    Also, when using a PMW controller, the panels must be the same voltage as the battery bank. You have both 12V and 24V, it would be best to go the MPPT route.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,445 admin
    #8
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?

    Regarding AC vs DC current...

    For a first approximation, the math is the same:

    Power = Voltage * Current

    However, with AC, there is a very important component that is the relationship between Voltage and Current and DC. They are the Sine Wave and Phase Angle.

    The "power" of a DC circuit is simply the Voltage * Current (assuming steady state conditions). For AC, it is a sine wave that is going between a positive peak voltage and zero volts and a negative peak voltage. Mathmatically, it turns out that to figure out the power under the voltage/current curve you need to do a Root Mean Square of the area. For DC the RMS value or conversion factor is 1.0 -- For Sine Wave based AC, the RMS conversion factor is 1/sqrt(2)...

    So, for example, a 120 VAC is really:
    • 120 VAC * sqrt(2) = 120 * 1.414 = 170 volts peak (plus and minus centered around zero volts)
    Where as 120 VDC is simply 120 Volts Peak.

    Also, there is the relationship between the voltage and current sine waves. When powering a resistor (or filament light bulb)--DC voltage and current are unchanging so Power=V*I works just fine.

    For AC with a resistive load, when the voltage is zero Volts, the current is zero amps. When the voltage is maximum, the current is maximum. The phase angle difference is 0 (zero) degrees--So we end up with the following formula:
    • Power= Volts * Current * Cos (phase angle)
    If the load was an inductor (electric motors are a form of inductor), the Voltage changes first, and the Current follows the voltage change. The difference is no longer zero degrees, but some where between 0 and 90 degrees. You will hear about the Power Factor of devices--PF is simply the Cos(phase angle) between the voltage and current wave form.
    • Power= Volts * Current * PF (Power Factor)
    If you remember the math--Voltage and Current are "Vector" quantities... They have both a magnitude and a direction.

    This is very much like pulling a car with a rope. If you stand right in front of the car and pull, 100% of your effort goes into pulling the car forward.

    If you stand 90 degrees to the side, zero percent of your effort goes into pulling the car forward.

    It, of course, does get more complex. PF is a nice mathematical concept for stable sine waves. However, for non-linear wave forms, the current may no longer be a clean sine wave, but may be zero for much of the cycle with a very high current peak at the voltage peak. The math is more complex--but people can still relate that back to Power Factor and just give it a number. The "peaky" current wave form is common to older computer/TV/etc. power supplies and CFL lamps.

    The reason that this also matters with current (and voltage) is that the equations for power are not linear:
    • Power=Volts*Current=V^2 / R=I^2 * R
    Notice that when current (I) doubles, the amount of heat loss actually goes up by 2^2=4x .... So, having an unwanted increase in current (low voltage, poor phase angle, "peaky non-linear current wave forms", etc.) causes the wiring, transformers, etc. to heat up much worse than if there was just steady DC current flowing.

    And there are other effects too... For, as boB said, DC arcs are much harder to extinguish vs AC arcs (the current stops flowing 120x per second). So DC ratings tend to be much smaller for an AC rated switch--and switches designed for DC use have much heavier contacts and open wider/faster/special arc suppression components/etc. than a similar rated AC switch would have.

    Here is a nice read about AC circuit theory.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • a0128958
    a0128958 Solar Expert Posts: 316 ✭✭✭
    #9
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    Re: Xantrex C60 Controller? AC amp vs DC amp fundamentals?
    BB. wrote: »
    Regarding AC vs DC current...

    For a first approximation, the math is the same:

    Power = Voltage * Current

    However, with AC, there is a very important component that is the relationship between Voltage and Current and DC. They are the Sine Wave and Phase Angle.
    ...

    Bill, this summary on AC and DC current / power is very much appreciated. Nice job, and thanks!

    Best regards,

    Bill
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