Wiring for 16 6 volt batteries

tkc100
tkc100 Solar Expert Posts: 67 ✭✭✭✭
in General Solar Power Topics #1
I have a 24 volts solar system with a bank of 16 - 6 volt batteries.
I kind of inherited the system with the house and have been doing a lot of upgrading and general maintenance.
Yesterday I was servicing the batteries and for the first time took careful notice of how they were wired.
The attached picture (Battery 01) is how they are currently wired. It seems to be to be wrong.
I think the wiring diagrammed in the second picture (Battery 02) to be a better way to do it.
What do you all think?
Is there still yet a better way?
Or is the original wiring correct and I'm just not seeing something?
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Wiring for 16 6 volt batteries

    I can't see your drawings properly on my netbook, but the proper way of wiring 16 6V batteries for a 24 Volt system is:

    Four in series for a 24V bank times four banks in parallel to increase the Amp/hr capacity.

    The devil is in the details; using properly sized wire at all points and bringing the (+) and (-) of each bank to a common terminal point, and then from there to the inverter & charge controller. Keeping wire lengths between batteries and between banks (different lengths for inter-battery than inter-bank connections) equal in size & length (short as practical is necessary to keep current flow in and out of all batteries as even as possible.

    Separate fuses on each bank is a darn good idea too.

    Edit to add: if you are concerned about inverter and controller connections being to different banks, don't be; this is often done to try and equalize current flow in/out. It only works well with dual banks, however. The inverter draws off the (+) of one bank and the (-) of the other, whereas the charge controller is hooked to the 'diagonally opposite' set of terminals. For four banks, you need a common access point.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Wiring for 16 6 volt batteries

    tkc100,
    i agree with you on the 2nd drawing as it will afford a better balance by tapping the + and - at opposite ends of the bank.

    for coot and anybody else having difficulty seeing the drawings the 1st drawing had the + tap at the blue string and the - tap at the yellow string. this means 3 jumpers to go from the green string to the taps for both polarities. the 2nd drawing had the + tap at the blue string and the - tap at the green string. this allows no more than 2 jumpers to reach a tap from the green string.:D
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #4
    Re: Wiring for 16 6 volt batteries

    The method shown in the second diagram is more balanced. But not best. See Smart Gauge for the best way.

    The series connections are fine. It's the parallel ones that can result in unbalanced charge/discharge.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #5
    Re: Wiring for 16 6 volt batteries

    Thanks for all the input.
    The article from Smart Gauge is very informative.
    I'm not an EE boy but I could see the way they are wired wasn't correct.
    It looks as if I followed the wiring in my second picture I would be better off and perhaps even acceptable.
    To achieve the balance suggested in the Smart Gauge article I'm going to have to do some head scratching and a little pen an pencil work.
    I will work on it some tonight but it's too nice a day out and I've got some outside chores to do.
    My foremost concern with trying to achieve the ultimate balance is that on the surface it appears that it will require more wire and wire connections. Also there is the issue of making it all work mechanically. Getting all those cable connection on a battery post could present a problem.
    Has anyone seen a diagram for 16 batteries wired for 24 volts in the manner Smart Gauge suggests?
    Has anyone go suggestions on tacking the hardware issues?
    Thanks again and I will post again either tonight or tomorrow.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #6
    Re: Wiring for 16 6 volt batteries

    You have 4 strings of 4 batteries. If we consider each string as one 24V battery, you have 4 batteries in parallel. Quote from Smart Gauge...

    "The difference in results between this and the 2nd example are much smaller than the differences between the 1st and 2nd (which are enormous) but with expensive batteries it might be worth the additional work. Most people (myself included) don't consider the expense and time to be worthwhile unless expensive batteries are being fitted or if the number of batteries exceeds 8."

    You have 4. Your rewiring plan should be adequate.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #7
    Re: Wiring for 16 6 volt batteries

    Well I played with this thing for a while and I agree the wiring diagram outlined in the attached scan should be adequate.
    Now I am wondering what size wire I should use.
    All 16 batteries are approximately 205 AH
    So I have 4 - 24 volt 205 AH batteries or one 24 volt 820 AH battery.
    Please correct me if I'm off base.
    The Inverter is a Xantrex DR3624
    DC current at rated power is 210 amps
    Short circuit current 720 amps
    It seems to me that I have 3 different requirements.
    The series interconnects, the parallel interconnects (each would have to carry 1/4th of the total load) and the power feed to the inverter.
    I know the length of the wire has a lot to do with the size and I haven't measured them yet. I am doing all that is possible to keep them as short as possible.
    I will error on the side of going perhaps a bit long.
    The series interconnects 16"
    The Parallel interconnects 4'
    The final feed to the inverter 12'
    What does experience tell you the proper wire gauge should be?
    I looked at several wire size calculators but they all dealt with 120,240 etc.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #8
    Re: Wiring for 16 6 volt batteries

    IMHO, to determine the gauge of cabling (I use the term "wire" for lower current circuits,) you need to know the magnitude of current that will be flowing through it. The AH rating of the battery has very little to do with it. You do give the DC current rating of your inverter. Do you plan to operate the inverter at its design limit? My guess is that you do not. But we still don't know. It is one thing to size your cabling to take advantage of all that your inverter can deliver, but heavy gauge cabling is very expensive. Again, IMHO, it is better to specify the total current that you expect the cabling to support and size from that.

    I would probably use the same gauge for all interconnects. Just seems easier to me.

    Others on this forum are better at this detail than I.

    Enjoy!

    K
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #9
    Re: Wiring for 16 6 volt batteries

    I stand corrected, your right it is cabling.
    Everything about it is big stiff and hard to work with.
    I've got a sizable investment in the rest of this set up it seems foolish to skimp on the cabling but at the same time don't want to waste money.
    In my way of thinking I would need
    2 cables approximately 12' long that can handle 24 volts at 210 amps without undue loss. The manual says typical current is 180 amps so I guess somewhere between 180 and 210.
    4 cables approximately 4' long that can handle 24 volts at 53/45 amps without undue loss. ( This is my calculation and it may be completely wrong but I'm figuring the parallel interconnects would only carry 1/4 the total load at any one time)
    12 cables approximately 16" long. Now here where I draw a blank. I don't how much amperage each of the 6 volt interconnects within the 4 battery set will carry.
    If I am reading the installation manual correctly it recommends #4/0 AWG for an inverter lead up to 15 feet in length. Now that really is a sizable piece of cable.
    What are your thoughts on this?
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #10
    Re: Wiring for 16 6 volt batteries

    that's allot of wire and allot of amps to go through it. go with the heaviest you can as even with 4/0 there will be losses. maybe an even heavier busbar could be obtained to parallel the strings. interconnecting this could be a bear with keeping losses down at full current.
    you could also play around with the voltage drop calculator to see what changes to the wires that will yield what in voltage drops and their respective percentages.
    http://forum.solar-electric.com/showthread.php?t=29
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #11
    Re: Wiring for 16 6 volt batteries

    I really wish others would chime in here because the is one of my weaker points of knowledge. But here goes regardless...

    Still don't know what it is you are trying to achieve. Please try to specify your loads, that is, with regard to cable sizing, the max current you expect. I can't see where you have given this info.

    Setting that aside, 24V at 210A is over 5,000 Watts! Again, what is it you expect this system to power???!!! Instantaneous!

    I remember reading here that wire/cable gauge nomenclature is such that # and /0 don't go together. The # part works down to #0, after that you drop the # and add zeros.

    I hope others come to your aid. And now Neil has.:D

    I'm probably just going to confuse you on this point.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #12
    Re: Wiring for 16 6 volt batteries

    In my system, I have a round trip run of six feet that must handle 100A and #4 AWG was recommended and has, so far, performed. A 300A fuse protects this run.

    Design run was 6. Actual closer to 4.5.
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  • vanman
    vanman Solar Expert Posts: 29 ✭
    #13
    Re: Wiring for 16 6 volt batteries

    Check this out it will explain all about batterys and connecting them in banks.



    http://www.smartgauge.co.uk/batt_con.html
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: Wiring for 16 6 volt batteries

    i think we have established the configuration part of this, but that the op wants specific info on what size wires. although the theory is sound on those diagrams, putting them into actual practice can be more difficult than one may think when dealing with very high currents in large battery banks. i hope the op will not need the very top end currents so that he can possibly downsize the cables or buses somewhat with the aid of the voltage drop calculator, but in any case it will still be very large wires or buses and no easy task to complete.
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  • vanman
    vanman Solar Expert Posts: 29 ✭
    #15
    Re: Wiring for 16 6 volt batteries

    I have 28 yuasa 6v cells wired 24v and its hard to make the connection leads but well worth it.
    I used 100amp multi strand as thick as my little finger. From a welding shop
    used a vice to crimp the eye hole ends,it took a few days but looks great and works great

    Never had a bad connection since

    takes a lot of effort.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #16
    Re: Wiring for 16 6 volt batteries

    First of all thanks to everyone for your input.
    However the configuration issue is not quite resolved.
    Forget about the cable sizing issue. I will sort through that after concluding this "cabling" problem.
    Sorry for addressing two things in one thread, promise not to do it again.
    Hope everyone is still on board because I would really like your advise on this one.
    I would have gotten back sooner but there was a considerable amount of head scratching that had to happen between then and now.
    At the start of this thread I address the "cabling" configuration for 16 - 6 volt batteries in a 24 volts system.
    The attached file "Original Battery Bank" show how the batteries in my system were configured. This was obviously wrong.
    The attached file "Battery Bank 01" shows my proposed changes. It is a workable solution and one used by many but another poster directed me to
    http://www.smartgauge.co.uk/batt_con.html
    and the possibility that there was perhaps still yet a better way of doing this. Now I got to tell you that this kept eating at me and I kept working on it.
    What I came up with is detailed in the attached file "Battery Bank 02"
    What do you all thing.....
    I followed two rules outlined in the article found at Smartguauge.
    1) "Notice that for each individual battery, the current always goes through a total of one long link and one short link before reaching the loads. This method also achieves perfect balance between all 4 batteries and may be easier to wire up in some installations."
    2) "Remember, count the number of links each battery needs to run through to reach the final loads and get these as equal as possible."
    After I was finished it's a simpler installation than I had originally proposed.
    All the cables are or at least can be exactly the same length and the current from each battery passes through 2 interconnecting lengths, one short and one long.
    My batteries are physically arranged 8 on a top shelf and 8 on the bottom. The blue batteries are above the white and the yellow are above the green.
    With the load being centered it will be easy to achieve equal length wiring to the controller and inverter. Finally this configuration uses a lot less "cable". Less expense and less voltage drop.
    So if you are still hanging on to this thread please let me know what you think.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #17
    Re: Wiring for 16 6 volt batteries

    what i see in bb 02 is the same as bb 01 as each polarity shows 1 lead going to one battery on one wire and then another lead with a seriesed secondary lead to the last battery string. rather than the short secondary lead (which is viable, but not perfect) it may be advantageous to run its own lead to and from the main connection point. this can be the additional wire or a bus. ideally the 3 wires on each polarity going to the other battery strings from the main battery connection point should be equal in length to avert resistive differences. that is why the last diagram in the smartgauge link shows individual wires. in fact, it should be 4 equal wires rather than from the main battery connection point with 3 wires as that would have no resistance to the first battery.
    i hope this isn't confusing you with this train of thought, but to visualize the end result of all of this, say the positive leadin you will have the main positive wire with a lug. from this lug the lugs of the 4 other positive string wires that are equal in length and wire size are bolted together. the other ends of those equal in length positive wires shall go to the positive post for each of the series battery strings. this would be duplicated for the negative wires and connections as well and would be the most balanced configuration. follow this on smart gauge while reading what i say and it may be clearer to you.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #18
    Re: Wiring for 16 6 volt batteries

    Niel
    You know I have looked at these and many other configuration so long perhaps I can't see the forest for the trees but I see a great deal of difference between the first (01) and second (02) configuration. Forget about the original it is obviously wrong.
    1) In my final setup for starters there is half as much parallel interconnecting cable.
    2) The final load to the inverter is of equal length.
    3) From what I can see any current from any of the 4 - 24 batteries will travel over one long and one short cable, each one the same length.
    4) What I though I have is one large balanced 24 volt battery
    The diagramming I followed on the Smart Gauge site is not the one with a bus but the next one down. The one sent in by some other contributor to the site.
    If you label the batteries at that website from top to bottom, 1-2-3-4 and the label the batteries in my final configuration as (blue 1) - (yellow 4) - (green 3) and (white as 2) you will hopefully see I maintained the same pattern.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #19
    Re: Wiring for 16 6 volt batteries

    you are going with #4 and #3 is better. i'm not citing using a bus, but a simple bolt through the lugs tying all 5 connections together. a bus would setup some inequities in relation to the main lead (5th) due to some batteries needing their current to travel further along the bus to get to the 5th wire (assumed to be in the center of the bus). this is why i often state that the bus should be able to carry at least 2x the current as the wire to overcome the extra resistance the small distances in the bus will set up. the bolt is setup similarly as the main 5th wire's lug would be central and the bolt acting like the bus, but it doesn't get any shorter for multiple connections than this arrangement. any resistance setup by a bus, or bolt for that matter, can be made up for by shortening the end wires or lengthening the middle wires so all resistances are identical.
    i'm probably confusing you some, but it is rather simple in actuality as you are looking at it from a resistance point of view.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #20
    Re: Wiring for 16 6 volt batteries

    Yep. You got it.

    Your 3rd diagram is equivalent to the final example at smartgauge. I have attached a drawing in which each of your series strings are represented by a single (24V) battery. The batteries are reoriented in a way similar to those on the smartgauge site.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #21
    Re: Wiring for 16 6 volt batteries

    Kamala
    Thanks for jumping back in. I was hoping you would as you are the one that started me down the path with the SmartGauge site.
    The reason I have a rather unorthodox configuration is to accommodate the actual physical arrangement of the batteries.
    They are arranged in a rack 8 on the top and 8 on the bottom. After a number of attempts that was the simplest way I could come up with. I also wanted to keep both of the load terminal as close together as possible.
    It seems to me that what I proposed in "Battery Bank 02" should work and achieve the goal of one large balanced 24 battery.
    What do you think?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #22
    Re: Wiring for 16 6 volt batteries

    Either your 2nd (simplest & cheapest but still adequate) or 3rd (best) config is fine. I looked more closely at smart gauge and see that in config2 there is still a >3A difference in (dis)charge between the inner and outer battery pairs. Your physical layout actually makes config3 look "elegant". The lack of which was lamented by smart gauge. If you're willing, go with config3. But config2 would be adequate.

    One other aspect of this problem is, what batteries do you have. Are they high end or just off the shelf? If they are expensive to replace, go with config3.

    Craig
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #23
    Re: Wiring for 16 6 volt batteries

    Kamala
    Now I'm a bit confused.
    I posted three diagrams:
    "Original Battery Bank" Obviously wrong!
    "Battery Bank 01" An interim design before you directed me to SmartGauge.
    Is this what you are calling 2nd configuration? If so I am interested in why you think this would be the simplest and cheapest. It would require more cable. I think this maybe the more intuitive but I don't think it's balanced.
    "Battery Bank 02" It is my best interpretation of the principles set forth by SmartGauge given my physical constraints. Is this what you are referring to as 3rd configuration?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #24
    Re: Wiring for 16 6 volt batteries

    I am SO sorry. I did not pay much attention to your BB01. BB02, which I called 3rd config, is the way to go.
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  • tkc100
    tkc100 Solar Expert Posts: 67 ✭✭✭✭
    #25
    Re: Wiring for 16 6 volt batteries

    You know that is what I thought but I just wanted to be sure.
    You may also be interested in the fact that I have struck up a conversation with David Small. I don't know if he is the author of this article we keep referring to or not but he is with SmartGauge (recently acquired by Merlin Equipment Ltd). He has offered to look over the configuration and give me his input.
    I will post his comments as soon as he get back to me.
    Thanks for all the comments.
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  • Kefalonianman
    Kefalonianman Solar Expert Posts: 60 ✭✭✭✭
    #26
    Re: Wiring for 16 6 volt batteries

    Tvk100

    I have studied your thread and you are miles ahead of me as I am knew to all this solar I too have the dilemma of 16 t105 batteries stacked on top of themselves in a 4 +4 array

    Can I take that the third diagram of yours is the best way forward in wiring the batteries and can you confirm all the curved cables in drawing are one size and the straight line cables are all a longer size but equal

    Sorry to sound stupid I have three charge controllers would I connect these to the same terminals as the inverter leads and I presume theses are all the same sizes as well

    Sorry to ask simple questions but I want to get the most efficient way of wiring the batteries

    Paul
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #27
    Re: Wiring for 16 6 volt batteries

    Paul;

    If you're going to use four strings you need to use method 3 from the SmartGauge site: http://www.smartgauge.co.uk/batt_con.html

    Instead of individual batteries as depicted they would be your strings of four in series.
    Connections for all charge controllers & inverters go to the common points for positive and negative. In this case that should be bus bars. The length of wires to and from each battery strings should be equal (and of the same gauge wire). Ideally there would be a separate fuse on each battery string (+) before the bus bar.

    In addition, each controller should have its own fuse on output before connecting to the bus bar (+) and the inverter(s) likewise should have circuit protection. Make sure all wires are sized to handle the maximum expected current for the particular circuit and the fuses (or breakers) are sized accordingly.
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  • Kefalonianman
    Kefalonianman Solar Expert Posts: 60 ✭✭✭✭
    #28
    Re: Wiring for 16 6 volt batteries

    i ahve constructed a diagram for my eletrician and i would like you to confirm i have it right for a 900 amp/h system if the batteries are 225 each


    also can confirm should i connect the charge controllers before the breaker or after the breaker and what kind of fuses on the breaker should i go for (60 amps) enough

    may thanks in advance
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #29
    Re: Wiring for 16 6 volt batteries

    The upper part of that illustration, since it is from Smart Gauges' diagram, illustrates a parallel connection. You have continued their example by keeping those 4 groups all wired in parallel, giving you 3600AH at 6V. To achieve 24 Volts, these 4 groups need to connected in series. If I remember the battery FAQ, the interconnecting cable between the 4 groups needs to be able to carry the total current of each parallel set.


    Kefalonianman wrote: »
    i ahve constructed a diagram for my eletrician and i would like you to confirm i have it right for a 900 amp/h system if the batteries are 225 each


    also can confirm should i connect the charge controllers before the breaker or after the breaker and what kind of fuses on the breaker should i go for (60 amps) enough

    may thanks in advance
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  • Kefalonianman
    Kefalonianman Solar Expert Posts: 60 ✭✭✭✭
    #30
    Re: Wiring for 16 6 volt batteries

    It is , this is the one that was recommended as the best configuration am I right that this gives me 900 amp/h

    Thanks paul
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  • Kefalonianman
    Kefalonianman Solar Expert Posts: 60 ✭✭✭✭
    #31
    Re: Wiring for 16 6 volt batteries

    Sorry to sound thick where is the best place to make the series connections

    Paul
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