Battery Price Solution

Is there any kind of 'best' battery solution... that is a battery where price, reliability and amp hours really does lead the competition?

I have heard 6 volt batteries often last longer than 12 volt batteries. Is this correct or just folk lore? My own answer is yes, 6 volt batteries can, when properly maintained, offer the same amperage over more time but I have never seen 6 volt batteries applied in solar applications. The real problem I see using 6 volt over 12 volt batteries is cost.

Also, are AGM batteries that much better than plain acid cell batteries when used in solar installations? My answer is yes again but since I have no direct experience with AGM batteries I can not be sure the literature I have read is correct.

Any comments would be appreciated.

Thanks.


sundownr

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Battery Price Solution

    Oh boy... A can'o worms set of questions.

    Yes, AGM batteries are about the as close to "perfect" that you can get with Lead Acid Batteries (clean, freeze resistant, more efficient, no water to add, usually do not outgas during normal operation, can be mounted on side, etc.).

    And Gel Batteries should not usually be considered for solar pv/deep cycle applications (too easy to damage with high charging currents/voltages).

    The downside for AGM is they are, roughly, 2x the cost of flooded cell batteries, may only last 1/2 as long as high end flooded cell batteries.

    True deep cycle batteries (with thick plates) tend to last/cycle longer.

    Forklift type batteries, can last 15-20 years, but are (typically) less efficient and use more distilled water.

    I believe in keeping parallel battery strings to a minimum (ideally 1 series string of cells; 2-3 maximum parallel strings--difficult to share current, a bad cell can take out the other strings, plus you need extra wiring/fuses/breakers per string for safety). So, it is not the 2/4/6/12 volt per battery that is really the question, it is the AH rating of the cells and your ability to move them (a 2 volt 300 lb cell vs a 12 volt 300lb cell, the 2 volt cell will have 6x the AH rating, so fewer parallel strings needed).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sundownrsundownr Solar Expert Posts: 25
    Re: Battery Price Solution

    Thanks Bill... good answers.

    A friend of mine suggested I would be money ahead to stay away from Walmart deep cycle batteries (1 year warranty) and buy typical 12 volt auto batteries (acid cell) with a 4 or 5 year warranty. He then said if you do not allow the batteries to discharge below 70% of full charge these less expensive batteries can last for years with proper maintenance.

    Can you venture a opinion on this approach?

    Thanks and have a great day.

    sundownr
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Battery Price Solution
    sundownr wrote: »
    Thanks Bill... good answers.

    A friend of mine suggested I would be money ahead to stay away from Walmart deep cycle batteries (1 year warranty) and buy typical 12 volt auto batteries (acid cell) with a 4 or 5 year warranty. He then said if you do not allow the batteries to discharge below 70% of full charge these less expensive batteries can last for years with proper maintenance.

    Can you venture a opinion on this approach?

    Thanks and have a great day.

    sundownr
    No. Do NOT use automotive batteries for solar applications.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Price Solution

    Some folk here have had good luck with "warehouse" brand golf cart-type batteries. Especially if you consider the cost per Amp hour - and the value of not risking expensive batteries on your first system just in case something doesn't get done right or goes wrong. It happens.

    The only reason people think 6 Volt batteries last longer is that inevitably with the same physical size the 6 Volt will have more Amp hour capacity than the 12.

    To add to what ggunn said, don't use the RV/Marine type "deep cycle" batteries either; they will disappoint in the long-term.
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Battery Price Solution

    A little light bedtime reading:

    Deep Cycle Battery FAQ
    www.batteryfaq.org

    And the Walmart, as others have said, may be great for a short term (3-5 year) battery bank setup. Let you get some real world experience without a 10-20+ year commitment (and not even knowing your loads yet for new construction).

    The issue seems to be, buy 2x larger battery bank and the battery bank may last 2.1x longer. Buy 2x more expensive high end batteries, and they may last 2x longer.

    So far, from what I have seen, the big issue is the number of years between change out... Having to replace batteries every 5 years vs every 10-15+ years may be really nice. As is only limping along on a degraded bank every 10-15 years vs every 5 with small/cheap bank.

    But, in the end, if this is your first trip into solar/at this home/facility... Buying smaller/less expensive battery bank and beating it up a bit to see how much power/fuel/etc. you use--then with your new found/hard won knowledge--Go out and buy the "ultimate" battery bank/array upgraded/etc. as needed).

    We are, in general, a pretty cheap group of guys here and try to answer questions on the best use of money. But--everyone has their own needs and situations--And why we just don't point to one "Off Grid Configuration Post" for all the newbie questions.

    There is rarely one "optimum answer" in this field.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Re: Battery Price Solution

    I think there is definitly a cost advantage to buying batteries that are produced in greater quantities, Hence if your looking for 'solar' batteries they tend to be expensive as there aren't as many HUP1 or sunsaver(?) batteries made as generic Golf cart or forklift batteries. (YET!)

    I think Golf cart batteries are a great entry into a solar flooded lead acid battery, they have some minor maintanace that needs to be done, but it will help you understand the battery life cycle. They do have some limitations, read the battery FAQ's, a link was provided for you. I too, like minimal strings of batteries and have just made the jump from a set of Golf cart batteries to a forklift battery.

    My Golf cart batteries made it almost 6 year running an AC during the summer months, 4 of those years, the fellow I gave them to says one of them has a near dead cell, so perhaps I just made it!

    You might search for threads on Sams club and/or costco batteries for others opinions/results.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • sundownrsundownr Solar Expert Posts: 25
    Re: Battery Price Solution

    Great information here... thanks for the information.

    I have found a Prosine 1800 [link removed] for $1049.00. Is this good price?

    Thanks.

    sundownr
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Re: Battery Price Solution

    I wouldn't jump on anything until you think through your system.

    1800 watts is a fence sitting size, and you may well want a 24 volt battery system rather than a 12 volt which would waste money on reselling the wrong model.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • green_fieldgreen_field Registered Users Posts: 7
    Re: Battery Price Solution

    An issue I've seen no one address is that of new developments. I'll be buying a shorter lifetime, less expensive set soon, largely because I read a lot, and have seen several new battery technologies that, if they make it to market, could well run circles around lead-acid, at a fraction of the cost.

    Nothing wrong with a long lifetime system, but with the huge focus currently being given battery technology development, I'd hate to spend a pretty penny on a 15 year battery bank, just to see, in a couple years, something hit the market that's substantially superior at a fraction of the price per amp-hour.

    For example, check out this new material discovered recently: http://www.gizmag.com/energy-storage-membrane-created/19996/
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Re: Battery Price Solution

    I would not hold my breath. There have been lots of "break throughs" and nothing yet comes close to replacing lead acid for low cost, low tech, fixed power applications.

    However, buying a 7.5 year battery bank vs paying 2x for a 15 year battery bank--it is all your choice.

    If your application and loads are known, and you will be there for 10+ years--The more expensive batteries may be very nice.

    If your application is still evolving and/or this is early on in your off grid life, buy a smaller bank and you can up grade in 5 years without feeling too bad (or if you make a mistake and kill your bank--you are out much less money).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Battery Price Solution
    I'd hate to spend a pretty penny on a 15 year battery bank, just to see, in a couple years, something hit the market that's substantially superior at a fraction of the price per amp-hour.

    On the other hand, if the new technology ends up being just another cold-fusion story, and in the meantime the cost of replacing your existing batteries doubles, or worse in 7 years - - - - - -
    If only we could see the future :cry:
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