HELP! me with this junk system

I have been asked to sort out a solar system for a friend andI need help.

It goes like this,

Most of the equipment has been salvaged so not much details.

we have 5 solar panels,

1 x 100w
2 x 110w
2 x 110w (very old, probably producing 50%)

6 x Tudor Tipo 5-DRP-100 heavy duty batteries producing 2.5VDC per cell total output 15.6VDC

1 x 1000w Inverter 12V/24V to 220V

Cables run from panels to cells, hot cable has a 100a fuse (i dont know why), from the fuse the cable goes into some kind of device the size of a bolt connected to a heat sink ( i do not know what this is or what it is for) from there conects directly to the batteries.

The last inverter conected to the system blew up. It was repoted to be a factory fault.

We do not want to conect a new one until we are sure that the system is faultless.

Maximum demand of the system is about 750W @ 220V at full load.

220v side is protected by 16a fuse (to big I suspect)

can any one see any obvious problems with this? Is something missing?

Thanks for any useful advice.

Comments

  • halfcrazyhalfcrazy Posts: 717Solar Expert ✭✭✭
    Re: HELP! me with this junk system

    The bolt you describe is a diode you have no charge controller. This needs to be the first thing you fix the inverter may have not liked the high voltage?
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: HELP! me with this junk system

    i wonder if there's any electrolyte left in the batteries?
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    The batteries have recentley been topped up. I dont know what the condition of them were before although they seem to be healthy enough.

    Yes, of course its a diode. Why?!?!

    A charge controller? Can you direct me to a link or something for more details.

    You could be right as my tester didnt seem to like the high voltage either!
    The inverter reportedly blew up at night and was rated 12V to24V.

    Is there a wiring schematic any where on the forum that I could copy???

    Thanks Niel and Half Crazy (its a good job that its the other half that is crazy):D
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: HELP! me with this junk system

    "Thanks Niel and Half Crazy (its a good job that its the other half that is crazy):D"

    yw and he's not my other half.

    "Yes, of course its a diode. Why?!?!"

    so that during the nights it does not discharge the battery(s) through the pv.

    "A charge controller? Can you direct me to a link or something for more details."

    at this time i can't as the new links are deadending with page cannot be found.

    "Is there a wiring schematic any where on the forum that I could copy???"

    1stly you aren't being very specific as to what all you need a diagram of, but you could try searching the forum.
  • BB.BB. Posts: 28,044Super Moderators, Administrators admin
    Re: HELP! me with this junk system

    Our host NAWS has a website for solar RE equipment--and here is a link to Solar Charge Controllers.

    Basically a Charge Controller is a regulator for the batteries... Pump in more energy when they are discharged--cut back on the voltage once they are charged so that you don't "boil" the electrolyte away.

    An MPPT Charge Controller has a (typically) Buck Mode Power Supply (Digital Power Supply) that can efficiently take "high voltage" (typically 2 volts over battery voltage to ~140 VDC) and drop it down to battery voltage very efficiently.

    PWM controllers are "Pulse Width Modulation [not mode]" Switching power supplies that can also charge batteries--but the solar panel voltage should be ~2-4 volts over the battery voltage for efficient use.

    In any case, try to get a charge controller with a remote battery temperature sensor--for some controllers, their internal temperature compensation can leave the battery significantly undercharged.

    There are two FAQ's about charge controllers in the above link... For the size of system you have, an MPPT type charge controller would probably make the most sense.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: HELP! me with this junk system
    BB. wrote: »
    PWM controllers are "Pulse Width Mode" Switching power supplies that can also charge batteries--but the solar panel voltage should be ~2-4 volts over the battery voltage for efficient use.

    -Bill

    I thought that PWM stood for Pulse Width Modulation? o_O
  • BB.BB. Posts: 28,044Super Moderators, Administrators admin
    Re: HELP! me with this junk system

    You are correct... Pulse Width Modulation. :blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: HELP! me with this junk system
    Sun Fun wrote: »
    Is there a wiring schematic any where on the forum that I could copy???

    Pretty simple.

    solar panels (PVs)
    to
    diode(s) (to prevent backflow - some PVs have their own diodes builtin)
    to
    fuses (one per string if in series, one per panel if in parallel)
    to
    charge controller (to prevent overcharging the batteries)
    to
    batteries

    batteries
    to
    fuse
    to
    inverter


    No doubt I left something out, but that's the basic idea.
  • BB.BB. Posts: 28,044Super Moderators, Administrators admin
    Re: HELP! me with this junk system

    Forgot to add--Outback has some sample schematics of systems (some pretty large ones too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    I now realise I should be in the beginners corner!

    I am getting there just need to clarify something.

    Should the fuse go before or after the diode? And why is there a fuse?
    Like wise with the inverter, can the current from the batteries really damage the inverter?

    I am sure I will be back with more dumb questions later. I will do in the dunces corner.

    Thanks yall.......
  • BB.BB. Posts: 28,044Super Moderators, Administrators admin
    Re: HELP! me with this junk system

    Fuses/Circuit Breakers are to protect the wiring from shorts/faults. Not to protect the equipment.

    So, the battery bank is the first thing to look at--as lead acid batteries can products 1,000's -10,000's of amps of current.

    Think of a "star" of wiring, with the battery at the center and wires going to your solar panels, your inverter, etc.

    Each wire that leaves the battery should be protected by a fuse that will prevent the wire from melting/catching fire if the wire is shorted anywhere.

    In your case, you have ~540 watts of solar panels. Roughly the maximum current from the solar panels should be:

    540 watts / 15 volts = 36 amps (probably a bit less)

    So the fuse (installed close to the battery + common connection) should be (note: 1.25x maximum current is a standard US safety factor in our code):

    ~1.25*36 amps =>45 amps
    ~2x36 amps =<70 amps

    So--a fuse somewhere between 45-70 amps should be fine... Below 45 amps, the fuse may blow in normal operation. Above 70 amps--not really protecting much.

    Of course, your wiring should be able to safely carry 45 amps without overheating. Most people use heavier wire (thicker copper) to reduce voltage drop (and be more efficient). Do you need help finding the right size wire (square mm?):

    Since the battery is the "high current" source, the fuse should be installed a close to the battery + connection as practical--the diode (or charge controller) and wire to the solar panels should be after the fuse.

    Also, ideally, you should have a fuse on each solar panel (or each series connected solar panel string). Your panels are ~110 watts, each should have a fuse:

    (110 watts / 15 volts) x 2 = 7.3 amps

    Each should have a ~7-10 amp fuse. This protects the panels and their wiring from internal shorts being fed by the other 4 panels.

    Regarding the Diode--if you get a solar charge controller, you should be able to remove the diode (the solar charge controller should turn off at night and prevent current back flowing to the solar panels).

    The Battery to Inverter connection would be evaluated as:

    1,000 watt inverter
    80% efficiency assumed
    10.5 minimum operational voltage for inverter (battery dead)

    1,000 watts * 1/0.80 * 1/10.5 volts = 119 amps maximum current to inverter

    The size of the wire and fuse should be ~1.25x (round up to next standard wire/fuse size):

    119 amps * 1.25 = 149 amps

    So the wiring/fuse should be sized to handle 150-200 amps. Larger diameter wire will sometimes be used to reduce voltage drop (particularly if the wire is more than a meter long (longer wire, more resistance, more voltage drop).

    The output fuse for the inverter is not really needed--but to calculate the appropriate size:

    1,000 watt inverter * 1.25 * 1/220 volts = 5.7 amps maximum

    So, round up 6 amps to the next standard wire/fuse size. Again, thicker wiring will help reduce voltage drop (don't need to increase fuse size).

    A fuse on the output of the inverter is not needed if you size the wire large enough to carry the load--the inverter cannot output more than its rating without shutting down. The output fuse is not really there to protect the inverter or the load. But it is your choice as to use a fuse or not.

    Again--the current will not damage the inverter. The fuses are to protect the wiring from catching fire if there is a short inside of the inverter or the wire is cut or a connection breaks.

    Fusing and proper sizing of wire is important in larger systems and if they are in areas with lots of wood (building/roof) and/or brush (easy to catch fire / fuel).

    In general, keep your low voltage wiring short (to reduce voltage drops) and only put fuses in the "+" lead--do not put fuses in the ground "-" lead. And the ground/return lead should be the same size wire (or larger) as it "mate" "+" positive lead.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    WOW!

    Now that was one very detailed post. Thank you.

    Having come from an AC electrical background I follow you perfectly well. It has been an education since my knowledge of DC is..........

    However I am slightly confused because my knowledge of solar systems is.... hu hum......

    Since asking my questions I was under the impression that the diode was needed. You say that with the regulator/charge controller it is not needed. Is this true. Its fine by me since the diode only has a small lug and is awkward to connect.

    You talk about the panels being in series. They are currently wired in parallel and I am led to believe that this is the better configuration of the two. Is this correct?

    OK. so we shouldnt nee a fuse between the regulator and panels since the regulator is rated at 45a but you say the panels should have protection, does that include wired in paralell too.

    Finally I will put a residual current device and a 6a breaker on the out put side of the inverter to protect cables, equipment and the elderly people living in the house.

    Thanks for such a detailed and interesting post BB. It is slowly sinking in, sorry its a bit of a learning curve for me.
  • dwhdwh Posts: 1,341Solar Expert ✭✭✭
    Re: HELP! me with this junk system
    Sun Fun wrote: »
    Since asking my questions I was under the impression that the diode was needed. You say that with the regulator/charge controller it is not needed. Is this true. Its fine by me since the diode only has a small lug and is awkward to connect.

    Ok, my bad. When I gave that quickie layout I included the diode *and* the charge controller - sorry to have made it confusing.

    I did that because your OP mentioned that the system you were working on already had the diode.

    As Windsun and BB said, if you have a charge controller between the panels and the battery, you can omit the diode. If it's already there it won't hurt to leave it (and being a belt and suspenders type, I'd probably leave it myself).
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    RCD and breaker is because its 220V system.
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    I am all over the place with these posts.

    Im a bit finicky with details so its good to add a bit of confusion. Keeps me on my toes and helps with the learning process.

    :D
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    https://download.yousendit.com/WnBRN3RhU1BxRTBLSkE9PQ

    my attempt to demonstrate what I have learnt

    corrections please.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: HELP! me with this junk system

    you may benefit from fusing each pv and adding an optional pv disconnect.
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: HELP! me with this junk system

    Why are you fusing the Pv leg with an 80amp fuse with only a 45 amp controller? Will the wire size carry 80 amps? (#3 or 4??)

    Icarus
  • Sun FunSun Fun Posts: 16Registered Users
    Re: HELP! me with this junk system

    mistake copy and pasting its a bit late as well. cable would definatley take it as they have put in what looks like a 30mm cable which is crazy considering there is only 4mm coming out of the pv!! i will alter the drawing to a 45 or 50A
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