upgrading the battery bank

Discussion in 'Alternative Energy' started by hoofinitnorth, Jan 12, 2007.

  1. hoofinitnorth

    hoofinitnorth Well-Known Member

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    We're in Southcentral Alaska.

    We need longer use time between charges in the winter when we don't get a lot of sunlight so we want/need to upgrade the battery bank but are having trouble finding $$ to do it.

    We currently have 4 Rolls/Surrette batteries (I think they are 1000AH but not sure) in a 24v configuration, a 7500w Outback stacked inverter, a 6KW gennie with authostart as back-up and charger, and all that jazz. Just running the gennie way too much for our likes in the winter.

    Ideas on what we can do? We hear to add more batteries (either 8 in 24v or 8 in 48v - which is better and why? I forget!) we have to replace all batteries at once if they are over a year old. If that's the case, then what am I realistically going to have to spend or is there some other way to do this cheaper? We have been quoted around $1,000/battery installed (consistent with the original installer's costs) so 8 could be as high as $8,000!!! GoodNESS!

    Ideas? Experience? Warnings?

    I don't think we have used but still good golf-cart batteries available to us... :p
     
  2. mightybooboo

    mightybooboo Well-Known Member

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    One thing you can do is add a new bank,then just switch between the 2.Dont have to worry about matching ages then.

    The higher your voltage,the smaller the wires you can use.

    Trojan L-16HC's were 225.00-275.00 each last I checked,6 volt,420 amp hours.

    BooBoo :gromit:
     

  3. Jim-mi

    Jim-mi Well-Known Member

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    Yes a second bat bank would be one way to go.

    BUT . . .Beware that if using such as a Trojan L16 that you will have two different charging rates.
    Those wonderfull Surettes are known to be hard to get the last 5-10% (charging) into the bat.
    So if you were charging them (the Surettes and the Trojans) together you would stand a good chance of over cooking the Trojans.
    Sollution; A good Bat switch--- 1 _ 2 _ both positions.
    Charge and use both bats seperately.
    Get good metering for both ( TriMetric ? )

    Manual switching yes . . . . .much cheaper that way.

    Sollution #2 . . . .reduce your load. (to lessen gen run time)
     
  4. Runners

    Runners A real Quack!

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    Solving one problem might lead to another...

    To me, the bottom line consideration would be the life of the battery(s). For instance...

    2 24v strings might sound good, but if they're hooked up to the same inverter, you'd probably keep them both connected in parallel. If you only use one string at a time, then the tendency of deeper cycling would wear out the string faster.

    On the other hand, I'd go ahead and hit the older string first, keeping the new string 100% charged/equalized, ready to go - just shallow cycle it. In a half-dozen years or so, save whatever units you can out of the old string - and add another new string, migrate the shallow cycled string to the heavy load position. Just a thought...

    I'm glad you covered the charge rate / equalization concerns! Mixing types or old/new units in a string eventually kills everything!

    Some of the back issues of HP magaqzine - Richard Perez addressed the woes of mixing types pretty good!
     
  5. WisJim

    WisJim Well-Known Member Supporter

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    If you switch to a different battery voltage you will need to switch inverters, too.
     
  6. hoofinitnorth

    hoofinitnorth Well-Known Member

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    Thanks for the ideas! Keep 'em comin'!
     
  7. hoofinitnorth

    hoofinitnorth Well-Known Member

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    Bump...

    Still looking for guidance on my original questions...
     
  8. idahodave

    idahodave Well-Known Member

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    Adding more battery storage may save on the number of charge periods, but make each one longer in order to fully recharge, so the net saving could be small. Is the battery bank large enough to cover a couple of days without charging?

    Reduce the load as much as possible, if you haven't done that already.

    Try to schedule generator runs to be coincident with larger demand periods. If it's been cloudy I run the genny to charge while we shower to keep the pump and bathroom lights from drawing out of the battery.

    Consider a small 24 vdc generator for recharge, it should be more efficient than running a 6.5kw genny lightly loaded.

    How much of your daily need does the array provide during sunny days? If you don't meet the daily demand when the sun is out, add more panels.
     
  9. hoofinitnorth

    hoofinitnorth Well-Known Member

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    idahodave - no the bank was advertised to give us 3-4 days between charges but it is not even CLOSE in winter when we get no sun. Obviously the seller/installer didn't know his stuff because he couldn't even give us basic equations for calculating loads & usage to figure out how much battery power we'd need to go 3-4 days. At best we make it 24 hours between charges in winter (at worst it can be as little as 12 hours)!!! Now that is only about 3 months of the year at most when we have a bunch of cloudy, cold days, but that is UNACCEPTABLE given what we paid for the system and were supposed to get. We told him up-front that while we would conserve energy, this house would have to run like any other "normal house" with "normal loads" for its size and intended use (which we described to him and let him see first) for future marketability.

    Yes, we're aware of the longer charging periods, which do not bother us but may push us to buying a bigger generator since I personally think it is undersized for our needs.

    My husband does what you suggest as well - use your big appliances while the gennie is already running. The only trouble with that is microwave, which are notoriously problematic for gennie use and you don't run for long periods of time anyway.

    We actually have more panels than our system can handle in the summer, as we've discovered - another issue the installer didn't anticipate. We have to add another MX-60 to use all the power we get on sunny summer days!

    We think we can make the basic upgrades without the battery & gennie stuff for under $1,000 including install but the batteries are the biggie. Are the figures I mentioned earlier really reliable? Are there other sources or other types of batteries I can get cheaper somewhere?
     
  10. hoofinitnorth

    hoofinitnorth Well-Known Member

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    WisJim - Our inverter can handle a different voltage, just needs to be reprogrammed/set-up for the new voltage. Or so we've been told...
     
  11. Jim-mi

    Jim-mi Well-Known Member

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    Hoofing, Your last post shure has me wondering.

    Your first post said you have 7k of Outback (two stacked).
    Outback does not make a multi input voltage inverter.
    Its one or the other.---24 or 48.

    I shure dislike my stupid microwave. It says 600 watts
    That might be cooking power, but the damn thing takes 1100 watts input. . . . . . .thats ugly.
    So it sits on the counter__only__ used when theres enough sun or wind.
    I really ought to throw it out.

    If you could change your habbits and NOT use the micro your batterys would love you.
     
  12. hoofinitnorth

    hoofinitnorth Well-Known Member

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    Jim-mi - The seller/installer told us we could just change the software on the inverter when/if we wanted to change the battery bank (which will also require different wiring). Another installer told us that is not so but that there are ways around replacing the entire inverter...

    We rarely use the MW, mostly use the propane oven/range. :)
     
  13. justmyluk

    justmyluk Well-Known Member

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    Where are your batteries located? Are they in an insulated building where they stay warm in the cold winter months or are they in an uninsulated building/ battery box? Cold weather will suck the life AND charge out of good batteries in just a very short time.
     
  14. Jim-mi

    Jim-mi Well-Known Member

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    Hate to tell ya but that guy is blowing smoke at ya.
    (I'm a seller\installer)
     
  15. tnhomestead

    tnhomestead Well-Known Member

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    Have you tested the batteries? I can go 2 plus days with 1/4 the battery power you have! A good 24 vdc gen setup will be easier to run, can build it yourself cheep too, or buy one for about a grand.(OUCH)
     
  16. idahodave

    idahodave Well-Known Member

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    It's too bad that you can't (or shouldn't) add a second string in parallel with the first, and not have to think about switching between banks.

    I'd drop a note to Rolls and ask their advice about paralleling another string to the one you have. If you have a TriMetric include the "Cumulative Battery Amp Hours" which might be useful information to Rolls.

    Maybe if you ran on the new string for a year it would better match the older one so they could be paralleled.
     
  17. TechGuy

    TechGuy Well-Known Member

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    Its the transformer that really determines the operating voltage of the inverter. A transformer is used to boost the voltage up to the AC output level. I can't imagine that a simple software upgrade would permit the inverter to operate at a different voltage (at least while maintaining the same level of efficiently). Its possible that the transform primary might be wired with multiple taps to handle different input voltages, but this would probably require some manual reconfiguration to use a different voltage.

    Your best bet would be to find the manual that came with the inverter. If you can't find it. Search on the internet for it. In the worst case you should be able to contact the manufacture and ask them if can be reconfigured for a different voltage. Your best bet is probably to keep using the existing operating voltage.
     
  18. idahodave

    idahodave Well-Known Member

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    Possibly confused the charge controller and inverter? A MX-60 will work for different system voltages.
     
  19. Gunga

    Gunga Well-Known Member

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    Have you looked into wind or micro hydro units? When it's dark or cloudy they could charge your batteries.
     
  20. hoofinitnorth

    hoofinitnorth Well-Known Member

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    justmyluk - yes, they are in a separate heated building in an insulated box with a built-in vent that comes on when the batteries are gassing.

    Jim-mi - we know a lot of what this guy told us was BS - went to court and proved it. Now there's a nice record of his dealings in detail for others in the area to read.

    tnhomestead - yes, batteries all test out fine and Surette/Rolls says that is about right for our loads. Remember, we have a fairly large house in Alaska with all modern appliances (although they are energy savers they still suck power). Summer is not a problem at all unless we have several days of clouds. The problem here is that we don't get enough direct sunlight for a few months of winter to get the batteries really healthy so when they get low the gennie comes on and batteries hate gennies vs. solar for charging so they get worse and worse until the sun comes back. When we can do a really good corrective equalization things do improve but it's tough until then. I'm confused by your suggestion though - we already have a 24vdc genset installed...

    idahodave - what's a TriMetric? Will contact Rolls/Surette. Good suggestion on running another string for a while to "age them" to match existing string. Would need some way to automatically switch between banks though... I do have the manual and have read it several times but it's not set up for our specific system - has a lot of "if you have this then that" and if you don't have all the technical knowledge to identify the "this" then you don't know the "that"! ;) I know we have some sort of transformer that the 2nd installer we consulted for maintenance & court case said we could make some changes here and there but it will cost us a lot more. *sigh* I know the difference between the MX60 and the inverter but good thought on that possibility.

    Gunga - hydro isn't an option here but we are looking at wind. The trouble is the ugly and costly tower we'd have to stare at and high expense of guy wires to secure it (in addition to the ugly solar tracker we already stare at). Still would need to upgrade batteries though!

    Keep the ideas coming - they're making us think!