Battery Brands?

stmarstmar Solar Expert Posts: 369 ✭✭✭
I am going to replace my battery bank and am leaning toward changing out my 12 volt to 6 volt. I think I have it narrowed down to U.S. Battery, Concorde and Trojan. I have had good service from my 12 volt Concorde AGMs so I am going to stay with AGM but I don't know much about the other brands. Does anyone have any input so that I can make an informed decision? I am going to take my time and do as much research as it takes to make the right call since everything is working as of now, I just want to be prepared when I have to do it. Another thing I notice was that 6 volt banks seem to come in 8 or 16 units for a 24 volt system, is there a reason not to use 12 batteries in a 24 volt bank?

Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Battery Brands?
    stmar wrote: »
    ....is there a reason not to use 12 batteries in a 24 volt bank?

    No reason at all, as long as they are 2V cells.
    Try to configure a system that has parallel banks, they become unbalanced easily and can suffer early death.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • Sun DogSun Dog Solar Expert Posts: 115 ✭✭
    Re: Battery Brands?
    mike95490 wrote: »
    No reason at all, as long as they are 2V cells.
    Try to configure a system that doesn't have parallel banks, they become unbalanced easily and can suffer early death.

    I'm pretty sure that is what you meant :p
  • stmarstmar Solar Expert Posts: 369 ✭✭✭
    Re: Battery Brands?

    You can be assured that if I spend thousands of dollars for a battery bank I will make sure they are configured in the most efficient correct manner. I was looking at the Smart Gauge site and it had several ways to wire with explanations and that is helpful. When you say "not" to have parallel banks what do you mean? That you should not have "separate" banks but have them tied together with a common conductor going to the inverter, say per the Method 3 and 4 at Smart Gauge? http://www.smartgauge.co.uk/batt_con.html
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery Brands?

    Even when you use the Smart Gauge diagrams the multiple parallel strings of batteries increase the possibility of problems just due to the sheer number of connections. Hence the basic battery bank advice: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
  • wirenutwirenut Registered Users Posts: 22 ✭✭
    Re: Battery Brands?

    If you want to stay with AGM batteries I would look at Deka. I've installed hundreds with good results. I've heard that a Trojan AGM is really a Deka anyway.
    However, if you want a really large battery bank I would use 2v batteries. I would recommend Lifeline SunXtender PVX-9015T.
    Parallel battery strings are to be avoided if at all possible no matter how you wire them up.
  • stmarstmar Solar Expert Posts: 369 ✭✭✭
    Re: Battery Brands?

    I had not even looked at 2 volt. Let me pose this question: What would be the pros and cons for using the following for a 24 volt system?
    1. 4 - 12 volt AGMs
    2. 8 - 6 volt AGMs
    3. 12 - 2 volt AGMs
    I have had good luck with my Concorde bank of 4 - 12 volt but I am open to other opinions and want the best bang for my buck. Space is not a issue, I have a fairly substantial mechanical room for my system. This system is used for grid back up so it is not taxed to any degree and the grid is reliable, the only 24 volt direct from battery bank appliance is a Sun Frost RF-16.
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: Battery Brands?

    I probably would tend towards #2, with #3 a reasonable second.

    #1--I don't like to parallel batteries--But some folks look at parallel strings as giving them a redundant battery string--A little extra safety that allows them to run a 1/2 bank for a few days-weeks until a spare can be obtained.

    I like #2 because it allows you to measure the voltage of each smaller battery block. This is the only way you have of checking the health of smaller battery units (you cannot get to individual cell connections in most multi-cell batteries these days--Better corrosion resistance and such). Also, if you have a "problem" cell/battery, smaller units to move/replace.

    #3 is fine too--Just larger "bank" of cells to check/replace. Less external wiring connections (less maintenance/copper costs).

    #1--That is a lot of personal opinion here. From an engineering point of view, more cells means a greater chance of failure (always the down side of redundancy--More parts/more complexity/higher costs usually mean that you will be using "redundancy" more often that a "more reliable" single string system).

    And if you get a short in a cell, it can discharge the the parallel connections too. More connection hardware costs (perhaps a fuse/breaker per string, possibly an A+B battery switch). More difficult to monitor string currents--But with DC Current Clamp meter these days--It makes checking per string battery currents (sharing during discharging/charging/etc.) much easier these days. If you are willing to do the "work"--People do seem to get good/similar life out of parallel strings.

    Redundancy of parallel battery strings--If you have a reasonably fuel efficient genset and smaller loads (i.e., something that can run from an Honda eu2000i / Yamaha inverter/generator), you can limp for a period of time on the genset while working on the battery bank. For off grid systems, you usually will have a generator (or two) for backup anyway.

    On neat thing about 48 volt battery bank and individual 2 volt cells--It is usually perfectly fine to run the system on 23 cells (46 volt battery bank) until the bad cell can be replaced. Just adjust the charging voltages down by 2.x volts).

    Price out the various options and see if there is a significant cost difference between the options.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery Brands?
    stmar wrote: »
    I had not even looked at 2 volt. Let me pose this question: What would be the pros and cons for using the following for a 24 volt system?
    1. 4 - 12 volt AGMs
    2. 8 - 6 volt AGMs
    3. 12 - 2 volt AGMs
    I have had good luck with my Concorde bank of 4 - 12 volt but I am open to other opinions and want the best bang for my buck. Space is not a issue, I have a fairly substantial mechanical room for my system. This system is used for grid back up so it is not taxed to any degree and the grid is reliable, the only 24 volt direct from battery bank appliance is a Sun Frost RF-16.

    It's not quite that simple. Because you have different Amp hour values the various combinations that can make up the Voltage may not make up the desired capacity. As a rule when you go down in Voltage you go up in Amp hours.

    Looking at Crown to stay within one manufacturer:
    Smallest/largest 12 Volt; 95 Amp hour/130 Amp hour
    Smallest/largest 6 Volt; 225 Amp hour/395 Amp hour
    Smallest/largest 2 Volt; 500 Amp hour/2550 Amp hour

    So you see trying to make up the same size battery bank from the three different Voltages is problematic. In your first configuration you'd have at most 260 Amp hours @ 24 Volts, which is about half what you'd have with all 2 Volt cells.

    You need to determine the capacity of the battery bank first, then work out the best configuration from the batteries available (not just Crown).
  • stmarstmar Solar Expert Posts: 369 ✭✭✭
    Re: Battery Brands?

    I should have stated that I had PVX-2580 AGMs, if I understand the chart 4 of these gives me just over 500ah @ 24 volts @ 24 hour rate. So to stay with a similar range of capacity, if I understand the calculations, I could go with 8 of the 6 volts @ 250ah or 12 of the 2 volt @ 500ah for my 24 volt system.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery Brands?
    stmar wrote: »
    I should have stated that I had PVX-2580 AGMs, if I understand the chart 4 of these gives me just over 500ah @ 24 volts @ 24 hour rate. So to stay with a similar range of capacity, if I understand the calculations, I could go with 8 of the 6 volts @ 250ah or 12 of the 2 volt @ 500ah for my 24 volt system.

    Once again you have a difference: AGM's vs. flooded cells. Whereas it is possible to have 6 Volt and 2 Volt AGM's one of the things that has been missed is the price: 2 Volt cells of any type tend to cost much more per Watt hour capacity than other battery types (due to low sales volume probably).

    But in terms of Amp hours @ Voltage and which is best the things you look at (in order of importance) are the number of parallel connections (fewer is better), the number of series connections (fewer is better), and the number of cells to check (fewer is better). The last one may sound silly, but for flooded cells it is important.

    So the four 12 Volt batteries gives you two parallel connections (not bad) and two series connections (not bad). If they were flooded it would be 24 cells to check.

    The eight 6 Volt batteries gives you two parallel connections (not bad) and six series connections (worse than the 12 Volts). If flooded it would be the same 24 cells to check.

    The twelve 2 Volt batteries gives you no parallel connections (excellent) and eleven series connections (worse than the other two options but remember series connections are not as troublesome as parallel). If flooded it would be 12 cells to check (except for certain batteries like Trojan that parallel the cells in a 6 Volt battery to increase the Amp hours).

    If not flooded the cell checking becomes irrelevant. Paralleling two strings is not a big problem and in this case I'd probably stick with the 12 Volts because that has the fewest connections overall.

    This may sound contrary to the usual advice on here, but it isn't. You will most often read that you should use two 6 Volts in series rather than two 12 Volts in parallel, and that is correct. The reason for this is exactly the same as the reason for choosing the 12 Volt units here; fewer connections (starting with reducing the parallel ones). Most often the selection is two 12 Volt 100 Amp hour batteries in parallel or two 6 Volt 200 Amp hour batteries in series, in which case you pick the series connection over the parallel one.

    Complex, isn't it?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Battery Brands?

    And for the nit-pickers out there, weight is also sometimes a consideration. As a battery goes up in Volts and/or Amp hours it gets heavier because it simply is the same technology 'glued together' inside the case rather than outside. Sometimes it's much easier to handle lots of smaller batteries rather than great big monoliths (like ones for forklifts).

    Edit to add: Crown 530 Amp hour 24 Volt industrial battery weighs 930 lbs.
  • BB.BB. Super Moderators, Administrators Posts: 32,800 admin
    Re: Battery Brands?

    My mistake--8x6 volt--My reasoning was for 4x6 volt (single string) batteries.

    Sorry,
    -Bill :blush:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stmarstmar Solar Expert Posts: 369 ✭✭✭
    Re: Battery Brands?
    BB. wrote: »
    My mistake--8x6 volt--My reasoning was for 4x6 volt (single string) batteries.

    Sorry,
    -Bill :blush:
    That raises another question: Would it be "better" to go with 4 high AH 6 volt bank (24 volt) so that you would have no parallel string instead of going with 4 12 volt with the same AH total? I am still going with AGM and will check what is available/price for options.
    I can't believe how long the bank I have has lasted (knock on wood) but I like to be prepared before hand. It takes me 2 years to buy a new vehicle, I do my homework, decide what I want and look for the "deal" that works for me.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Battery Brands?
    stmar wrote: »
    Would it be "better" to go with 4 high AH 6 volt bank (24 volt) so that you would have no parallel string instead of going with 4 12 volt with the same AH total?

    Single string is much better, especially with AGM (because of their lower internal resistance.)
    short explanation: http://www.wind-sun.com/ForumVB/showthread.php?14674

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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