Current Wiring Doubt

quique
quique Solar Expert Posts: 259 ✭✭
I currently have 2-210W solar panels (12V-17.5A) in parallel (for 12V-35A) which drive thru a 12V-30A CC charging an 8-6V battery bank in 4 series-pairs for 12V battery bank. The wires from the CC lead into the 1st and 3rd pairs of batteries and from that same terminal, the 3kW/15A inverter pulls its charge to an IOTA ITS30 AutoSwitch which switches between the grid power cables coming off the main breaker panel, the inverter cables and the cables that feed an auxiliary breaker panel where ive connected only lights and 120V power outlets for things like lamps, fans, computer and such.

Im concerned about shunt and the IOTA switch wiring.

1) The shunt, i dont have one, and i think i should have one. Im not clear on the concept, i understand its a breaker- or fuse- cable that installs between the live power cable coming from the CC to the battery bank?

2) Im concerned about the wiring of the switch. The iota told me not to use the neutrals coming from the grid, but rather ground cables. I tried using ground cables and the switch didnt work, it never powered the aux panel. I had to use the grid neutrals for it to work. But a few months back, there was a brown out and of course, the relay cboard stopped working and i had to order a new one. Any suggestions?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Current Wiring Doubt
    quique wrote: »
    I currently have 2-210W solar panels (12V-17.5A) in parallel (for 12V-35A) which drive thru a 12V-30A CC charging an 8-6V battery bank in 4 series-pairs for 12V battery bank. The wires from the CC lead into the 1st and 3rd pairs of batteries and from that same terminal, the 3kW/15A inverter pulls its charge to an IOTA ITS30 AutoSwitch which switches between the grid power cables coming off the main breaker panel, the inverter cables and the cables that feed an auxiliary breaker panel where ive connected only lights and 120V power outlets for things like lamps, fans, computer and such.
    Can we backup a moment... 210 watt Vmp=12 volts; Imp=17.5 amps... If those numbers are correct, then you cannot connect these "12 volt" panels in parallel directly to a "12 volt" battery bank. You will not properly charge your batteries.

    Basically, the batteries require around 14.4 volts or so to properly (and quickly) recharge. And you generally use 15.0 volts or a bit more to "equalize" the battery bank (if flooded cell batteries).

    Next, the charge controllers and wiring have a couple volts of drop, plus panel Vmp falls as the panels get hot (summer sun, no wind, high air temperatures)... All told, the proper voltage panels to connect with a 12 volt battery bank is Vmp~17-18 volts or so through PWM charge controller.

    Large panels (over 100 watts), are typically designed to work with Grid Tied Solar systems which need a panel string voltage of ~200-600 VDC worth of Vmp... Generally they put 10-20 panels in series to achieve those voltages.

    Many MPPT type charge controllers can operate with Panel Vmp as high as 100 VDC (up to 150 VDC maximum Voc rating)--and that is one of the MPPT charge controller's major advanatages. To use higher voltage panels/strings with low voltage battery banks and charge very efficiently.

    Next, watch the amount of charging vs the amount of loads you place on your battery bank... It is very easy with solar to undercharge your battery bank (or over discharge because of lots of loads) and damage your batteries in weeks or months with "deficit charging".

    You typed in another thread about the inverter giving you a warning when the battery is low... The typical inverter, when it gives the warning, is frequently very close to damaging the battery bank (nearly full discharged) when the warning/cutoff point is reached.

    You really should read these Battery FAQ's to ensure that you treat your batteries properly and get long battery life:

    Deep Cycle Battery FAQ
    www.batteryfaq.org
    Im concerned about shunt and the IOTA switch wiring.

    1) The shunt, i dont have one, and i think i should have one. Im not clear on the concept, i understand its a breaker- or fuse- cable that installs between the live power cable coming from the CC to the battery bank?

    A shunt is either a large power resistor, or a heavy piece of wire (short/shunt a circuit), or a type of charge controller (uses external loads to divert charging current).

    If you want a shunt to measure battery charging / discharging current... Typically the shunt in installed between the "-" battery bank common terminal and the "-" bus bar/frame ground connection (if a metal vehicle). You then put the amp meter (really a sensitive volt meter) on the sense terminals.
    2) Im concerned about the wiring of the switch. The iota told me not to use the neutrals coming from the grid, but rather ground cables. I tried using ground cables and the switch didnt work, it never powered the aux panel. I had to use the grid neutrals for it to work. But a few months back, there was a brown out and of course, the relay cboard stopped working and i had to order a new one. Any suggestions?

    Again, I am not sure what you are typing about...

    Isolating neutrals is frequently done with AC Transfer switches and AC Inverters... Many Inverters (typically MSW type inverters) cannot have their neutral connection grounded (and the battery "-" grounded at the same time). If this is done, the Inverter will fry (let out the magic smoke).

    And if the AC power coming in (typically utility power) has its Neutral bonded to "earth/safety ground" (a North American Code requirements) and the battery bank is also DC grounded to earth/safety ground--Then you would use two pole transfer switch to Break both the "hot" and "Neutral" connections to your loads when the inverter is "on".

    Now, there are a few loads that don't work correctly with "floating neutrals" (my natural gas stove with spark ignition system won't reliably spark if neutral is floating or hot/neutral are reversed) won't work. Also, some florescent tube lighting fixtures may not start reliably without a grounded neutral/grounded metal frame.

    I don't think that the above is really your question--As it sounds more like an issue of how the AC Transfer Switch control circuitry is wired up.

    Do you have the user/installation manual for the product (I have found the manual on the web before)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Current Wiring Doubt

    i too am confused, to my knowledge there aren't any 12v 210w pvs in existence as they all tend to be 24v pvs. if i'm wrong then tell me what pv it is and by whom is it made. the battery arrangement is also unclear to me for did you put 2 in series and then put another 2 in series and then parallel the 2?
    we should inquire as to what controller you are using and how is it configured? ie 24v in 24v out or 24v in and 12v out. if you believe it is 12v in and 12v out this cannot be with 24v pvs without huge power losses.
  • lorelec
    lorelec Solar Expert Posts: 200 ✭✭
    Re: Current Wiring Doubt

    I think he might have the numbers swapped -- maybe should be 12A Imp at 17.5v Vmp? Evergreen makes 210w 12v panels, with specs that are close to those.

    Marc
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Current Wiring Doubt

    ah, i think you're right marc, but he still should elaborate further so we know exactly what the story is.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Current Wiring Doubt

    Yes, sorry, it's 11.7a & 17v!

    Ok so I've got too little panels for too much battery! So I'm doing good in adding 2 more panels, right!?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Current Wiring Doubt
    quique wrote: »
    Yes, sorry, it's 11.7a & 17v!

    Ok so I've got too little panels for too much battery! So I'm doing good in adding 2 more panels, right!?

    well that would depend upon the battery bank ah capacity so you know where it is you stand percentage wise. 5%-13% is the recommended general charge range. for 11.7a pvs x2 this is 23.4a and at 5% is 468ah total battery capacity. 4 of them would represent 936ah capacity at a 5% rate of charge. we still don't know what controller you are using, but it doesn't matter as this gives you enough to know where you stand.

    if the pvs are 11.7a each and if you need 4 of them then this will be far above the 30a controller rating. either another controller in parallel or replace with a higher rated controller.

    now in adding the iota to charge the battery bank, if you plan on measuring it's current as well as the pv current then connect it on the same side of a shunt as the pv input or the opposite side of the shunt as that which is connected to the battery. shunts are for current measuring purposes. anything you don't want included in a current measurement would go to the battery side of the shunt or straight to the battery bypassing the shunt and thus not being within its measurements. i'm not wording things well today so i'm not describing as best as i guess i should. hope this helped.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Current Wiring Doubt

    I'm not sure how my post got moved over here; but what do you mean by 117ah and 234ah!? Where didthose numbers come from?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Current Wiring Doubt

    i explained that you have a set current output capacity from the pvs totaling 11.7ax2=23.4a. if 5% is the minimum rate then 23.4/.05=468ah and i see my math error that i will fix. is my math error what confused you?

    as far as this thread being here goes, you had to have put it here. if you would like we can combine them or we can eliminate one of the threads.
  • quique
    quique Solar Expert Posts: 259 ✭✭
    Re: Current Wiring Doubt

    Ok my pv charging current should be at least 5% of my total ah battery bank.

    If my bbank is 4 pairs of 225ah 6v-pairs, then i have 4x225=900ah. So since i currently have 23ah, 23/900 which is only 2.5% so if i add 2 new panels in a new CC, i would have 46/900= 5%! Which i know is still on the edge but its better!

    So i will add these 2 new panels with a separate Cc to the same terminals as the current one.

    In the meantime i will add fuses to each since they are missing from my setup. From what i understand, the shunts are only for measuring purposes so i wont do that now, im more intetested in adding the fuses for safety.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Current Wiring Doubt

    Add to your tools a Hydrometer to monitor state of charge/specify gravity.

    For monitoring, when funds permit--I really do like Battery Monitors (meter + shunt). Can also save your battery bank from an early death (deficit charging).

    If you will be powering AC loads, and even just to monitor power usage around the home -- A Kill-a-Watt meter. If you want to measure your DC loads and you don't have a battery monitor, Amp*Hour meters like these can be good for a fill-in.

    Wiring in fuses and breakers is always a pain.

    This is about the cleanest fuse mount I have ever seen:
    Steve961 wrote: »
    Here is the simplest thing that I have found. It is a terminal fuse block from Blue Sea Systems that attaches directly to the battery post. Fuses are available from 30 to 300 amps.

    http://www.blueheronmarine.com/Detail.bok?no=5552

    5191_182x182.jpg

    Otherwise, you can check out our host's website for fuse/breaker options.

    High current fuse blocks
    Midnite Solar Protection Devices
    Outback Protection Devices

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset