battery bank switch wiring

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Groser
Groser Registered Users Posts: 10
I have a question on wiring a blue sea marine battery switch selector. This is what I would like to do if it is safe and can be done. charge one battery bank and/or two banks at the same time.
bank one equals eight trojan L16H-AC bats. bank two is the same as one. total sixteen trojan L16H-AC bats

12 volts out of a xantrex C-60 to a fuse. from fuse to a blue sea 9001e battery switch. out of switch to pos terminal of number one battery, Bank one. At the same time, out of switch to pos terminal of number one battery, Bank two.

bank one has all pos terminals up against a wall.
bat1 bat2 bat3 bat4 bat5 bat6 bat7 bat8. bank two will look the same.

Two neg wires out of the C-60. one wire going to neg terminal number eight bat, Bank one. one wire going to neg terminal number eight bat, Bank two.

Am I somewhat correct in the wiring? Will the C-60 put out enough power to charge both banks at the same time?
solar panels. two 40watt kyc, one 85watt kyc, one 130watt kyc. I have a 135watt kyc on order.
I will appreciate all advise. thanks
groser

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: battery bank switch wiring

    One bank is eight L16's: two in series for 12V times 4 parallel banks? That's 1280 Amp/hrs @ 12V.

    One C60 won't handle enough current to charge one of these banks, let alone two.
    5% of 1280 Amp/hrs is 64 Amps, and an L16 type battery really needs more than the 5% minimum current.

    Unless I got the numbers wrong. It happens!
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: battery bank switch wiring

    The BIG problem is not the controler but the 430 w of panels(incl the one he has not bought yet) thats total 36amps:confused::grr
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: battery bank switch wiring
    john p wrote: »
    The BIG problem is not the controler but the 430 w of panels(incl the one he has not bought yet) thats total 36amps:confused::grr

    For some reason I kind of assumed he was going to come up with the necessary 2272 Watts of panel per 1280 Amp/hr bank that would be needed to do a good charging job. In Watertown, NY it might need more. :p
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: battery bank switch wiring

    Cariboocoot ya gettin old. ya gota read all Grossers post which included the slightly undersized solar panel aray..
    solar panels. two 40watt kyc, one 85watt kyc, one 130watt kyc. I have a 135watt kyc on order.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: battery bank switch wiring
    john p wrote: »
    Cariboocoot ya gettin old. ya gota read all Grossers post which included the slightly undersized solar panel aray..
    solar panels. two 40watt kyc, one 85watt kyc, one 130watt kyc. I have a 135watt kyc on order.

    Getting old? I'm already there! :p
    My wife actually had me take an Alzheimer's screening test today. It came out negative.

    Sorry to the OP for getting a bit silly here.

    But if your battery bank really is that big, you need a lot more panel and two charge controllers to handle the current.

    Or you could cut the 1280 Amp/hr bank into two 640 banks with the switch.
  • Groser
    Groser Registered Users Posts: 10
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    Re: battery bank switch wiring

    Thanks for the replies. I'm still learning.
    right now, I have the solar panels feeding one bank of eight batteries. I would like to keep the bank the way it is. I'm tight on space in the room.
    My peak input is 16 amps to the xantrex C-60. average input I would say is 10.
    on an average day I come home from work plug in the computer. it draws 9 amps
    run that for about one and one half hours. unplug the computer and plug in a hot plate. it draws about 65 amps. run that for about 5 to 8 minutes. unplug the hot plate, plug in the television and one dc light bulb. together that draws 7 amps.
    watch tv for about three hours. At 10 pm I turn off the inverter. At that time it will show me the batteries read, on a good day 12.5 volts. on a bad day 12.2.
    My starting voltage is 14.3 / 14.5. I getting sun till 7 pm now so the panels are charging during most of the useage. the inverter is a xantrex prosine 1800 pure sine, two GFI outlets.
    I'm thinking if i add a second bank of eight batteries I could use one bank for the normal day. the second bank for the small frezzer. Not frost free.
    I agree I need more solar panels, that is a must. Is the switch a do-able thing?
    can I charge one bank and use another at the same time? Can I charge both banks at the same time? Is the wiring complacated?
    thanks
    groser
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: battery bank switch wiring

    YES Groser the switch is simple and daable. but at the moment the simple fact is you need about 4 times the solar panels you have to be able to charge up that amount of batteries.. If you charge them at to low a rate they are going to sulphate up badly.. About 10% charge rate of battery size is good ie 1200 ahr =120a charge rate.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: battery bank switch wiring

    I'll second (third) the notion about undercharging. Instead of buying more batteries, consider way more PV.

    That said, please explain what it is you are trying to achieve? Is this a hobby system, or an emergency system, are you doing to to try to save grid power costs?

    My first suggestion is to get both a kill-a-watt meter and a battery monitor. With a kill a watt you can get an reasonably idea of your average (daily/weekly) loads. With a battery monitor (like the bogart Tr-metric) you can accurately determine how much power you have taken out (or put back in!) a battery bank.

    My next observation is, in general, (as you may well know) grid power is in almost all cases the cheapest power you can get. Battery based solar is almost the most expensive. (depending on some variables!) So if your goal is to save money you probably should consider grid tie solar.

    In addition, using a battery based system to power resistance heating loads is very inefficient. The "rule of thumb" with any solar installation is look for every way to conserve before you invest in PV and batteries. For example the amount of money required to build a solar system to power the hot plate dwarfs what a simple camp stove would cost. (Same idea between a lap top and a desk top Pc).

    It is a pretty simple equation, no matter how you cut it. For every AH you take out of a battery, you have to put ~1.25 back in just to stay even. My rule of thumb (to do a quick calc) is take the name plate rating of your system divide that number in 1/2 to account for all system loses, then multiply that number by 4 which is the number of hours of average good sun you can expect. (most people over estimate the amount of sun they actually get!)

    So in you case 430/2*4=860 wh/day or 70 ah (@ 12 volts)

    By my calcs of your loads, it seems like you are drawing ~45 ah, so you might be fine on the loads.

    So if on an average day you are drawing more than ~860 wh, you are going backward, not even including the issue of not enough current to PROPERLY charge your bank.

    It is a common misconception that a bigger battery bank is better, since it allows you to draw more/bigger loads. The problem is that the battery needs to be properly sized for the charging current and the draw current.

    Just for the record, we live with 400 watts of panel, charging 450 ah of battery. We draw ~600 wh/day. We have an average charge current of ~ 25 amp,, or ~5% of battery capacity. We tend to draw down ~10-15% per day.

    Tony
  • Groser
    Groser Registered Users Posts: 10
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    Re: battery bank switch wiring

    I agree I need more panels.
    The solar started out as a hobby. then turned serious. I'm saving approx $40.00 a month on electric bills. My average monthly bill now is approx $55 give or take.
    I really screem when I see a $60 bill. Some time in the (far) future I would like to eliminate all 120 ac volts and only keep the 220 ac voltage items that I need.
    Ok, what am I missing. I'm not understanding something. maybe I'm making this to hard for myself.
    I can (at times) watch the charge controller reduce the amperage coming in from 16 amps to say 7 amps and the battery voltage is 14.1.
    I have seen a few times one amp input in full sun. the batteries are fully charged and (what I call ) boiling.
    That tells me I have an abundant amount of power coming in. I would like to have approx 30 amps coming in from the solar panels, but still with only eight batteries I can overcharge the batts. the batteries are rated at 435 a/h each.
    Confused
    groser
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: battery bank switch wiring

    Groser;

    The part that hasn't been clearly explained to you is that there's 'two parts' to recharging batteries. The first part is replacing the 'used' Amp/hrs, which you appear to be doing. The second part is putting enough current to the batteries to re-mix the electrolyte. Short form: when the power is used the sulphur in the sulphuric acid mix sticks to the plates, covering them up and rendering them useless over time. Enough current during recharging helps keep this inevitable process to a minimum. Otherwise, you don't notice the effect until one day you have batteries that don't stay charged overnight.

    This is a very, very common problem: too many batteries and not enough panel. A lot of 'commercial' installers who don't actually know what they're doing make this mistake, thinking the batteries can be recharged over time.

    If your bank is eight L16's in a 12 Volt configuration, it can only be the massive 1260 Amp/hrs I mentioned before: four parallel banks of two in series. This sort of battery bank has other problems too; like being able to keep the current flow in to and out of the batteries even, so that one set doesn't do more of the 'work' while the others just leach. To do it properly, you'd need a negative and a positive buss bar with equal length cables from each series battery set to the buss bars, and a separate fuse on each set. The inverter and charge controller then attach to the buss bars.

    You have 430 Watts of panel. In a best case scenario, that could supply probably 1300 Watt hours on a given day. Your loads may not be that much, so you stay ahead on replacing Amp/hrs. But this same panel arrangement could at best supply perhaps 25 Amps of current, which is far below the minimum recommended 5% of Amp/hr rate for charging (1260 * 5% = 63 Amps). Worse yet, the L16's are 'tall case' batteries and need their charge current to be towards the top recommendation of 13% to keep them properly 'stirred and mixed'.

    Is this explanation helping you any?
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: battery bank switch wiring

    I probably shouldn't go here, as it strays from your original question,, but I think it should be noted.

    You suggest that you are 'saving' ~ $40 per month on your electric bill. Unless you have the worlds highest grid power rate,, something doesn't compute. Your savings work our to ~$1.33 per day.

    By your own calculations you are using ~540 wh of power with your solar system per day. That would therefore translate to grid power cost of +$2.00 KWH,, about ten times the national average.

    So the cost of 8 L-16, might be ~$300@=$2400, with an life span of 10 years (in your case I would guess you would be lucky to get 3-5 at current course and speed!) costs you ~ $240 per year, or about $0.65/day.

    My point here, is that to do this for learning, for fun, for hobby is fine, and indeed I encourage it, but to do this to save money is probably not going to net/net save you any money.

    If it were me, I would take the ~$2400 in batteries, and instead buy a grid tie inverter, or say 3 enphase invertersa ~ $200 @ ($600) then spend the remaining $1800 on ~800 watts of PV, and grid tie it. You production capacity would be way further ahead.

    It is also important to note, that basic battery based systems under ideal conditions only yield ~ 50-55% of nameplate rating out of the inverter. Grid tie does better than ~90% (Not to mention that once the batteries are charged, the potential that doesn't have "anywhere to go" is also wasted.

    So grid tie comes with twice the system efficiency, at ~1/2 the price, leading to (rough numbers) net/net 4 times the price per useable KWH out of a battery based system.

    Sorry to stray, Good luck with your endeavor,


    Tony

    PS, I would look seriously at your KWH usage on your bill to figure out what your real KWH cost is. The $40 reduction is due surely in part due to your PV, but much of it may have come from other conservation measures that you have done, knowing now the benefits thereof.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: battery bank switch wiring

    Tony;

    I've become more philosophical about the money issue. If people want to spend their $ making a statement about the environment or whatever, so be it. Arguably, this is somewhat irresponsible of me. :blush:

    So if they ask "Will this save me money on my electric bill?" the correct answer is "Yes". But you're absolutely right to give the provisor. The question they should ask is: "Will this save me money?" The answer to which is almost always "no" if utility power is available.* Some people don't realize the whole capital expenditure at once, so they don't notice how much it's really costing them.

    *I say "almost always" because there are some places in the world where electricity is more expensive than just the monthly bill. If power is undependable, it becomes costly in other ways than per kW/hr.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: battery bank switch wiring

    Marc,

    I agree,, which is why I mentioned it with some trepidation. Far be it for me to question the motives of everyone. That said, I think it important to mention it once,,

    T
  • Groser
    Groser Registered Users Posts: 10
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    Re: battery bank switch wiring

    Cariboocoot

    I do understand that the batteries have to boil to help prevent buildup.
    that is a requirement for good bat maintainance
    Yes, my bat bank is made up of eight L16H-AC. $331.00 each, new.
    I agree with your thinking on the buss bars, getting equal usage out of the batteries. I really like that idea. that will be my next project.

    What I have learned is, to put the switch and second battery bank off till next year when I have the proper amount of solar panels to feed things.

    Thank You all for furthering my education on solar.
    Groser
  • BB.
    BB. Super Moderators, Administrators Posts: 33,472 admin
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    Re: battery bank switch wiring

    Tony has a fair observation--I would not be surprised that most people after they have installed solar now look at wasted power in a whole new light... Going around turning of lights (following your kids and spouse ;) ), turning off computers/entertainment stations/dvrs/digital TV receivers/replacing the old fridge/freezers with modern Energy Star Appliances/etc. can easily save people almost 50% of their "pre-enlightenment" power bills.

    For us, just replacing lights with (ugly :roll:) CFLs, using task lighting, laptop computers, new fridge, etc. has not only saved us money with our electrical bill--it also has kept the home much cooler in the summer--leaving us the option to never install an A/C system (or starting up a couple window A/C units).

    And don't forget insulation / double pane windows / skylights (free light and extra ventilation).

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