balancing charge, discharge of battery bank, + multiple solar panels

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  • WMH Cheryl
    WMH Cheryl Registered Users Posts: 17 ✭
    #32
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    Re: balancing charge, discharge of battery bank, + multiple solar panels

    Since I have had so many nightmares and expenses with batteries over the years, I always try to avoid relying on batteries if I can. Water for the animals was vital. My 400 gallons per day is only needed in summer and since I have over 9000 gallons of storage in Various tanks around the ranch, then having no or little water pumping during some winter storms is not a problem for me.
    You will save money and headache if you put,money into another water storage tank that will last forever instead of adding batts to their pump.
    Then do your other household power separately and deal with the battery nightmare there without having to worry about water pumping power.
    They do sell a little portable DC generator to plug into well pump if no sun (watch the video) but I figured I could haul a battery out to my well without spending money on a convenience item I probably will never need. Maybe just buy a spare plug for a few bucks so you can easily make a wire harness to connect a battery in an emergency. Of course in an emergency you would want to use two 12volt batts connected to make 24v because that will make the pump pump Faster.
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  • edro
    edro Registered Users Posts: 15 ✭
    #33
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    Re: balancing charge, discharge of battery bank, + multiple solar panels

    Thanks, vtmaps, for the inverter links. I've contacted solar-electric.com and after some correspondence they recommended either the Samlex 2,000 Watt or Samlex 3,000 Watt 24 volt inverter. The 3,000 watt is 91% efficient as opposed to the 85% efficiency of the 2k watt. There are some other considerations. $.

    Thanks, BB, for all your thorough calculations. I have to take a break after you post so I can figure out what's going on.

    Thanks, WMH Cheryl, for the brushless DC motor well pump referral. I've contacted them and they have been a big help.

    Also I really do appreciate and take to heart your account of "nightmares and expenses" regarding batteries. Me, too. Lead acid batteries and I have never quite been friends. But I've learned a LOT in the past few months as I've been planning my solar well project. I didn't realize how (literally) high maintenance they were. Did you know that "Lead sulfate that exists when a battery is not fully charged crystallizes to become a hard lead sulfate when left in a battery for a period of time. (2~3 days is said to be enough.)" (source: http://boatelectric.com/sulfation.htm )

    I've had much better success with AGM batteries which I use with my electric wheelchairs. I've been in a wheelchair for about 14 years now so that experience has helped me a lot. I charge them at least once a week to keep them topped off.

    The thing is that I really need this to work consistently, reliably, and autonomously. I going to have to use batteries.

    So---anyone who is good at "translating" calculations into something easier to understand: I received the following from the pump manufacturer. I need the calculation broken down for me into equations that I can use. i don't want to discharge my batteries 50%. Rather I am shooting for somewhere between 15% to 25% at the very most.

    Here is what I received:
    The pump will require a maximum of 5 amps under full load. With 92 feet of head and working at 24 vdc, your power requirements should be far less than maximum, and will probably be about 3 amps. If your pump is pumping at 1.7 gpm, in one hour it should pump 102 gallons. You should never use a battery past the 50% rating of said battery, so two 100 amp/hour batteries in 24 vdc series should be more than adequate with a pump consuming 3 amp hours.

    How did he translate using two 100ah batteries down to 50% charge to operate a pump at 3 amps for one hour? Is there an equation that I can use to plug in my own numbers?

    Thank you,
    Ed
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #34
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    Re: balancing charge, discharge of battery bank, + multiple solar panels
    edro wrote: »
    How did he translate using two 100ah batteries down to 50% charge to operate a pump at 3 amps for one hour? Is there an equation that I can use to plug in my own numbers?

    According to my calculations, 3 amps for 1 hour is 3 amphours. If you draw 3 amphours from a 100 amphour battery bank, you should be at 97% SOC, not 50% SOC.

    This assumes that your draw (3 amps) is less than 5% of the battery's amphour rating (which it is). The reason is that the battery's rating is based on drawing it down to 0% over 20 hours. If you were drawing more than 5 amps, the battery would have a capacity of less than 100 amphours.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • WMH Cheryl
    WMH Cheryl Registered Users Posts: 17 ✭
    #35
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    Re: balancing charge, discharge of battery bank, + multiple solar panels

    Maybe he meant using two 12v batts to bring you up to 24v. Not that you would need two 24 v batts.
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  • edro
    edro Registered Users Posts: 15 ✭
    #36
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    Re: balancing charge, discharge of battery bank, + multiple solar panels

    vtmaps-- I need to double check my understanding.
    the battery's rating is based on drawing it down to 0% over 20 hours
    If you were drawing more than 5 amps, the battery would have a capacity of less than 100 amphours.

    So 100ah battery / 20 hours is 5 amps per hour. Is that correct?

    Yes, WMH Cheryl, that was for two 100ah 12v batteries in series.

    So that's 24v for 100ah.

    If I wired two 100ah 12 batteries in parallel then it would be 12v at 200ah.

    What I'm worried about is that this seems too good to be true.

    If I ran this configuration:
    Attachment not found.
    Then I would have that autonomous, robust well pump system that I'm looking for.

    What am I missing?
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #37
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    Re: balancing charge, discharge of battery bank, + multiple solar panels
    edro wrote: »
    I need to double check my understanding.
    So 100ah battery / 20 hours is 5 amps per hour. Is that correct?

    it's 5 amps, not 5 amps per hour. Amps is a rate.

    5 amps per hour is a rate of a rate.... if you were drawing 4 amps at noon and 9 amps at 1 PM and 14 amps at 2 PM then your current draw would be increasing at the rate of 5 amps per hour.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • edro
    edro Registered Users Posts: 15 ✭
    #38
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    Re: balancing charge, discharge of battery bank, + multiple solar panels
    vtmaps wrote: »
    it's 5 amps, not 5 amps per hour.
    --vtMaps

    Oops. I knew that--what I meant to say.

    Thanks.

    Ed
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  • jasoni
    jasoni Registered Users Posts: 1 ✭
    #39
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    hi I am abit new to battery bank systems or stand alones

    I have a quick question.   I want to purchase a  standalone to run a security system and 4 points of sale . the load comes up to 6228kw I wanted to use a 7kw inverter. the points of sale will be used in the day and just the security system at night. how many batteries and how much amp hours do you recommend and how big should the array be? any suggestions on equipment would be  greatly appreciated.

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