Wiring and Fuse/Breaker

Hello,

I am working on installing a one panel system on a parade float in order to power some led lights and a speaker. I have purchased the following:

Panel
REC250pe
250w

Charter Controller
MorningStar MPPT 45a

The maxim current from the panel is 8.2 amp, so I was advised to use a 12 gauge wire from the panel to the CC (about 6 feet away), then a 10 gauge from the CC to the battery as the current from CC to battery (another 6 feet) is about 20 amp. Is the correct?

The step I really seem to be needing help with is the fuse/breaker part. Where do I install it? What type and rating?

I have not purchased the batteries yet, but I intent to use two 6v golf battery of about 225 ah.

Anyway, any help here would be much appreciated.
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Wiring and Fuse/Breaker

    Welcome to the forum Fernandonh.

    Ideally, you want to install the charge controller with short/heavy wiring close to the battery bank to minimize voltage drop. However, the TS controller has a "remote battery voltage sense" lead connections that can accurately measure the voltage of the batteries directly.

    Normally, we recommend around 1-3% voltage drop, so using a generic voltage drop calculator.

    12 AWG @ 6 feet and 8.2 amps = 0.2 volt drop
    0.2 volts / 30.2 volts Vmp = 0.007 = 0.7% drop

    And for the other wiring:

    10 AWG @ 20 amps and 6 feet = 0.3 volt drop
    0.3 volt drop / 14.5 amp = 0.02 = 2% drop

    Fusing/breakers... The battery bank is the source of high current in your system. So, all wiring that leaves the battery bank should have a fuse/breaker sized for the wiring.

    For example, the charge controller. The typical maximum continuous current would be around:

    250 watts / 12 volts = 20.8 amps (typical worst case).

    The NEC has a 80% of fuse/breaker/wiring derating. So, 1/0.80 = 1.25 and:

    20.8 amps * 1.25 = 26 amp rated branch circuit/breaker

    If your in a cold area, you should use another 1.25x the solar panel output, so the wiring/breaker should be rated:

    26 amps * 1.25 = 32.5 amps -- Rounded up to the next highest standard value

    Wire Current
    Ampacities NEC Table 310-16


    So, using the NEC (which is conservative), they would be requiring an 8 AWG cable from the battery to the charge controller and a 40 amp fuse/breaker (depending on wire insulation rating, etc).

    This is a conservative setup... There are other standards (such as those used for boating) and 10 AWG would be OK.

    Each positive wire (assuming negative ground system) that leaves the battery bank should have its own fuse/circuit breaker that is rated 1.25x (minimum) the maximum continuous current you expect the circuit to supply.

    Also, 12 volt wiring has very little head room for voltage drop (roughly 0.5 to 1.0 volts maximum)--So wiring needs to be short/heavy to ensure sufficient voltage at your loads (note, you can oversize wiring and still leave the breaker sized for maximum current).

    I would also suggest using a remote battery temperature sensor with the controller if the quick/efficient charging of the battery bank is important and the batteries are subjected to a wide range of temperatures.

    Lastly, solar panels only work well under full sun/no shading. If the float spends a lot of time in a building, has superstructure above the panel, and/or in an open lot subjected to shading, the solar system will generate a very limited amount of power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Who picked that equipment? A 250 Watt 30 Vmp panel and a $400 charge controller to get 16 Amps of current on a 12 Volt system? Could have used the MS MPPT 15 and been in about the same state for about half the money.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Wiring and Fuse/Breaker

    As Marc/Cariboocoot says, our normal recommendation would have been:

    250 watts * 0.77 panel+controller deratings * 1/14.5 volts charging = 13.3 amps "typical" maximum current

    Which a Morningstar 15 amp MPPT controller would have been a good choice. The system would exceed ~15 amps only for a hand full of hours per year (very cold sub freezing/clear days, and with MPPT type controllers, they simply limit the output current to their maximum rated value--safely and reliably).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Bill, Thank you so much for the detailed answer. A lot of good information for me to digest and apply. I appreciate it!!!!!!!!

    Cariboocoot, the problem with the panel that I bought is that it has an Open Circuit Voltage of 37.5, which excluded most of the smaller CC that I looked at. I did consider the 15a MorningStar, which was where my initial budget was aiming, but the panel could potentially provide about 20 amps of current, which the 15a morning start would not work. At least, that's the understanding I got form my research.
  • Rybren
    Rybren Solar Expert Posts: 351 ✭✭
    Re: Wiring and Fuse/Breaker
    fernandonh wrote: »
    I have not purchased the batteries yet, but I intent to use two 6v golf battery of about 225 ah.

    You may want to rethink this, as 250W of panel is likely not enough to keep a 225AH bank healthy.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker
    fernandonh wrote: »
    Cariboocoot, the problem with the panel that I bought is that it has an Open Circuit Voltage of 37.5, which excluded most of the smaller CC that I looked at. I did consider the 15a MorningStar, which was where my initial budget was aiming, but the panel could potentially provide about 20 amps of current, which the 15a morning start would not work. At least, that's the understanding I got form my research.

    The panel under typical conditions will supply about 80% of its Wattage rating. The output maximum on an MPPT controller isn't likely to exceed 16 Amps (as the battery charges its current demand drops, then the only variable is additional current demand by the loads). The MPPT 15 would simply hold current to 15 Amps maximum regardless of conditions. The panel's Voc of 37 won't make any difference as it can take 60 Volts maximum.

    Doesn't matter now because you've already bought the 45 Amp Tristar MPPT, right? Maybe you can use that for some bigger project afterwards. :D

    As for what Rybren said, that panel's output is likely going to be about 16 Amps maximum or 7% on a 220 Amp hour 12 Volt battery. Without any loads it would work fine, but the loads take current and reduce the net charge rate.

    Just how much are these LED lights going to take? It's possible their draw would be so little that the panel can manage it no problem, but it's more than likely it wouldn't even be needed as the battery has about 1.2 kW hours stored capacity anyway. You could always just plug it in and charge it up after the parade for a lot less money than the solar equipment cost.

    Yet I suspect the float is about solar energy, no? :D
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Hey guys,

    tks for the input. Yeah, I misunderstood the output of the CC. I was under the impression that the CC output had to be at least the maximum amp the PV would provide otherwise it would cause damage to the CC. oh well, like you said, now with this CC I can always expend :-)

    This will be installed in an "art car" and taken to Burning Man, which is a 7 day festival in the Nevada desert, plenty of sun. Here is a picture.Attachment not found.

    The 1 speaker we wil be using: I used a kill-a-watt, and determined that the volume level I will be using for the most part consumes about 50 watts. At certain times I will crank it up to somewhere around 100 watts, which is really loud!

    The leds, up until now, were powered by the 50 ah golf cart battery, which is the same that was used to start the engine.

    What size batter, Ah hour, would you recommend for this PV and CC combo in order to keep battery healty?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Well I can tell you that your amplifier using 100 Watts off 12 VDC will draw about 8 Amps, but beyond that?

    Without info on the lights' power needs and the actual duration of the consumption it's impossible to judge how many Amp hours would be required. The motor driving this thing has no alternator? It would probably be easier (and cheaper) to make use of that mechanical power to keep things charged than to put in solar.
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    I am still tryin to figure out the led, but I used a 50ah batter and it would last about 16 hours before it began to look dim.

    Would you guys mind taking a look at this set up diagram that I put together. Am i getting close?Attachment not found.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Okay, a couple of things.

    There should be a fuse on the output of the charge controller. Nothing fancy, just enough to protect in case something goes 'kerblooey' (or other cartoon noise of your choice). Since the one panel is capable of <10 Amps it would not even have to be 'full size' (able to handle the 45 Amps of the controller).

    Second, you're powering the Amp with a 400 Watt inverter. This is likely an MSW type, so I hope you don't mind the noise that can put into your audio system (may/may not: everything is a crap shoot with MSW inverters). At 400 Watts it is going to draw about 40 Amps maximum. Check the inverter manual - it should recommend fuse and wiring size. If it doesn't, you will probably be all right with 4 AWG battery wires, providing the Voltage doesn't go too low and the output too high with the wires too long. And a 50 Amp fuse. Yes, I'm making rough estimates (that's engineering talk for "guessing").
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Wiring and Fuse/Breaker

    with the fuse or breaker placement best going near the battery as would be the case for the inverter breaker/switch.

    coot's estimate of the draw for the pa system is not accurate as audio amps are not very efficient in their conversion from dc watts to the audio ac watts put out by the amp. this does vary depending on the amps design as higher audio quality with lower distortion can cause the dc draw to be several times that of the output ac watts of the amplifier.

    i'm not sure why the solar is needed to charge up the battery as i doubt the parade should last so long that just plugging the battery bank into an ac charger to last during the parade would suffice for it. this may necessitate more battery capacity for longer parades and remember you don't want to drain a battery until dead as it should not go below 50% in order to preserve some battery life. of course solar could still be utilized to ease the drain on the batteries without the large burden of it being the one and only source of power.

    trial runs are highly recommended while monitoring both the drain on the batteries and the amount of charge the pv can deliver under the routes it must go through. this isn't always feasible as the roads need blocked off to allow parades and parade floats.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Actually I was just going by powering the 400 Watt inverter. What the amplifier will actually use is as Niel said a variable.
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker
    Okay, a couple of things.

    There should be a fuse on the output of the charge controller. Nothing fancy, just enough to protect in case something goes 'kerblooey' (or other cartoon noise of your choice). Since the one panel is capable of <10 Amps it would not even have to be 'full size' (able to handle the 45 Amps of the controller).

    Second, you're powering the Amp with a 400 Watt inverter. This is likely an MSW type, so I hope you don't mind the noise that can put into your audio system (may/may not: everything is a crap shoot with MSW inverters). At 400 Watts it is going to draw about 40 Amps maximum. Check the inverter manual - it should recommend fuse and wiring size. If it doesn't, you will probably be all right with 4 AWG battery wires, providing the Voltage doesn't go too low and the output too high with the wires too long. And a 50 Amp fuse. Yes, I'm making rough estimates (that's engineering talk for "guessing").

    Tks!!!

    a) so between the CC and battery, besides the battery termina fuse protecting in the even current flow back from the battery to CC, you I should also put a fuse (30amp?) on the wire as close to the CC as possible, correct?

    b) I am not really sure the type of inverter. I bought it at walmart for like $35 bucks. I tested the speaker using a 12v batter and inverter and I don't remember the inverter making much noise, besides the fan. The inverter came with a cable to plug into the battery, I will check the box to see if it tells me the gauge size then figure out the fuse based on that.
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Tks, Niel.

    So I tested the speaker using a kill-a-watt, and at a pretty loud volume it would vary from 25 to 50 watts, which converts to about 4.16 amps from the battery. Considering loss of power due to inverter inefficienty, would 6 amps be a realistic assumption of power consumption?

    Well, this is sort of a float. It's actually a mutant vehicle which we take to Burning Man every year. It's a 7 day festival in the Nevada desert without access to power.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    The battery can push far more current than the charge controller can handle. Thus the connection between the two has to be sized for the current from the controller to the battery, because if it's flowing the other way (so to speak) something is wrong. The wire gauge is the ultimate factor, as the fuse must give up first.

    If you were to plan on full controller capacity (45 Amps, which is impossible with the one panel) you;d be using 8 AWG minimum and a 60 or 80 Amp fuse.

    Definitely check the manual on the inverter for wiring specs. Oh and it isn't the inverter noise, it's the noise it can induce in the amplifier. This will vary with the quality of both units. If it isn't noticeable, you're good to go. You sure wouldn't want some 60 Hz hum playing out over the speaker!
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    In regards to the battery choice. I was planning on using two Trojan 6v, 225 ah.

    I was told that the panel may not provide enough current to keep the battery healthy. Do you think that is correct?

    I would be ok with a smaller battery, but for some reason the cost goes up for batteries of around 180ah.

    I did find a 12v of about 180ah, but I was also told that I should not use 12v batteries and to opt for 2 x 6v ones.

    Any suggestion on that?
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    We will only be using this one panel, which at max could provide about 20 amps from CC to battery. With a 10 gauge wire, which I understand can handle up to 30 amps, would I be ok without a fuse placed next to the CC and only have the battery terminal fuse to protect in the event current flows backwards?

    Tks for the tip on the possible sound problem due to inverter quality. That was if it happens I will know what the problem is.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    One 250 Watt panel isn't going to be perfect on 225 Amp hours of battery but it's not an "absolutely won't work". About 16 Amps, or a peak rate of 7%. Depending on how much the battery gets depleted, this will/won't work. If you can control the power consumption to about 600 Watt hours AC you should be good. The batteries could supply about double that. Worst case: you turn everything off during the day and let it charge.

    The T105/GC2 type batteries just tend to be a real good value in $ per Watt hour. Larger/smaller batteries tend to cost more for the equivalent power.
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    That's exactly what I wanted to hear. thank you :-)

    I figure I will be able to keep the batteries fully charged while using the speaker during the day, then use about 40 amps at night, which can be easilly replanished the next day.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Wiring and Fuse/Breaker
    fernandonh wrote: »
    That's exactly what I wanted to hear. thank you :-)

    I figure I will be able to keep the batteries fully charged while using the speaker during the day, then use about 40 amps at night, which can be easilly replanished the next day.

    not so fast here. we don't know how long the day drain of about 5-6a shall be taking place. the pv will push 250w/12v=20.83a and assuming about 77% or so efficiency = 16.04a. you may even have other losses because of voltage drops in the wiring. you just can't go by what the typical ac current rating for a wire is because at 12v the voltage is a tenth as much. the length of the wire, the gauge of the wire, the current going through the wire, and the voltage on the wire determine what is acceptable and should be under 3% total with under 2% preferred. voltage drop calculators are available including the one in my sigline. add to that if the pv is not aimed straight at the sun if the weather permits and you could find your system outputting far less than you figured.

    that output minus the draw on it is what is going to recharging the batteries. this is without a doubt under 10a and 10a/225ah=4.44%. this is too low for a proper charge as we recommend in the range of 5% to 13%. now you say you intend 40a at night, but is that 40ah or is that an actual load of 40a? if 40a then for how long?

    you may want a battery monitor also just to get a better handle on what might be available from your batteries and a hydrometer to periodically verify what you see on the battery monitor. solar isn't quite as easy and plug and play as many may think it is as it is a very hands on type thing due to the limitations set forth on solar setups. your utility is plug and play and you should never feel so lax about a solar setup to assume it to always be available.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    See what Niel said? That's why I said:
    Worst case: you turn everything off during the day and let it charge.

    If the panel has nothing to do but charge the battery for a full day, it should recover (providing it hasn't been dragged down too much).
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Here is a breakdown of what I will be using during Burning Man which takes place in the Nevada desert for 7 days. After Burning Man, we will be using the “float” on different occasions for different events. For the majority of the year, this system will not be used and it will be stored.

    During the day
    Speaker:
    Time of usage: between 11:00 and sundown
    Hours of Usage: 4 hours
    Load: 40 watts, average

    40 w / 12 v = 3.34 amps. Rounding up to 5 amps due to inefficient inverter.

    At nightSpeaker:
    Time of usage: between 11:00 and sundown
    Amount of Usage: 4 hours
    Load: 40 watts, average

    40 w / 12 v = 3.34 amps. Rounding up to 5 amps due to inefficient inverter.

    TOTAL: 20 amps

    LED
    Time of usage: night
    Hours of usage: 8 hours
    Load: 40 watts

    40 w / 12v = 3.34 amps.

    TOTAL: 26 amps


    That adds up to 46 amps of depletion by morning, which should be easily recharged even with the speaker being used in the afternoon.

    As you guys have mentioned, in the even I overuse the equipment, I can simply not use the speaker in an afternoon and allow for battery to fully charge.

    Am I being realistic here? If so, what batter size would you recommend?
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Would this battery be adequate?

    Trojan T-1275 Deep Cycle Golf Cart Battery

    150ah (20 hr rate)
    12v
    $239
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Your data is somewhat confusing. It looks to me like the amplifier will be using 40 Watts for eight hours a day: 320 Watt hours. Then the LED's a further 40 Watts for eight hours for another 320 Watt hours. That adds up to 640 Watt hours. Depending on what inverter is used (small one I assume) and adding in the efficiency conversion you get about 760 Watt hours DC. From 12 Volts that's roughly 64 Amp hours. That means a minimum 128 Amp hours, so the GC2's ought to handle it at 220 Amp hours.
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker
    Your data is somewhat confusing. It looks to me like the amplifier will be using 40 Watts for eight hours a day: 320 Watt hours. Then the LED's a further 40 Watts for eight hours for another 320 Watt hours. That adds up to 640 Watt hours. Depending on what inverter is used (small one I assume) and adding in the efficiency conversion you get about 760 Watt hours DC. From 12 Volts that's roughly 64 Amp hours. That means a minimum 128 Amp hours, so the GC2's ought to handle it at 220 Amp hours.

    That makes sense... thank you everyone!
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Wiring and Fuse/Breaker

    being it is your intent to operate during the day which is the time a charge is to be given you may want to get more in pv to cover this so as to keep the charge percent well into the good area. it may be better to over kill on the pv watts than try to be marginally acceptable during ideal charging conditions. as coot said at least 128ah battery too, but if you get bad weather you may want a bigger battery capacity so that it can go slightly longer than a day. of course there are too many variables and i would recommend a battery monitor and a hydrometer
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Small portable generator would probably solve any power shortage issues for less money and could be loaned to anyone who needed a boost. :D
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Tks Niel, an extra panel would be ideal, but I am afraid we only have space for one. Once I have everything set up and tested, we may need to change our expectations of speaker usage and either reduce the day time usage or completely not use it during an entire afternoon.

    Yeah, we have a honda generator, but didn't want to have to deal with noise and viabration. Plus, we really wanted to go with a solar systems just because it's way cool :-).
  • fernandonh
    fernandonh Solar Expert Posts: 35
    Re: Wiring and Fuse/Breaker

    Would this be the correct circuit breaker to install between the CC and battery?

    Midnite Solar MNepv30 30A 150VDC

    https://www.google.com/shopping/product/8843527999776442889?q=circuit%20breaker%20for%20solar%20system&hl=en&bav=on.2,or.r_qf.&biw=1079&bih=649&wrapid=tlif136459276388210&sa=X&ei=gwhWUbXtLcjAyAG-0gE&ved=0CGsQ8wIwBDgK

    If this is correct and I use it, would I still need a fuse on the battery terminal?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Wiring and Fuse/Breaker

    Well it would work but ... you need the whole DIN rail set-up to mount it. That will add to cost.
    You might consider two post mount fuses (they make double holders http://www.bluesea.com/products/2151/Dual_MRBF_Terminal_Fuse_Block_-_30_to_300A): one 30 Amp for the charge controller and one higher (100 was it?) Amp for the inverter. Fuses: http://www.bluesea.com/products/category/Marine%20Rated%20Battery%20Fuses

    You might be able to get these locally from a marine supply store.