Hello all. New here.

King-01
King-01 Registered Users Posts: 28 ✭
in Solar Beginners Corner #1
Been doing a lot of research, but have a question I can't seem to find an answer to. Is it possible to wire two 12 volt batteries for 24 volts, but charge them as individual 12 volt batteries? Most of my equipment runs 12 volts, but due to a long run for the Nemo well pump, I need to kick up the voltage so I don't go broke buying copper wire. Thanks.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Hello all. New here.

    Welcome to the forum.

    The short answer is "no"; a system is either 12 Volt or 24 Volt.

    The long answer is there are ways around the short answer. :D

    Mostly it has to do with how exactly the system is laid out in terms of positioning loads, batteries, and panels. For example if you have a 12 Volt pump you want to run at one location but the panels need to be quite a ways away from there, you put the batteries and an MPPT type charge controller near the pump. Then the solar array can be run at a higher Voltage to overcome the V-drop over the distance; the MPPT controller will down-convert the Voltage.
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #3
    Re: Hello all. New here.

    Thanks for the reply. I have my batteries, panels and various equipment located central to the garage. The well pump is 275 feet from the garage. Putting the panels, batteries, etc. next to the well head is a no-go.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Hello all. New here.
    King-01 wrote: »
    Thanks for the reply. I have my batteries, panels and various equipment located central to the garage. The well pump is 275 feet from the garage. Putting the panels, batteries, etc. next to the well head is a no-go.

    In that case you have a fairly large problem: how to get nominal 12 Volts @ 'X' Amps across 275 feet of 'Y' gauge wire without losing so much power the pump doesn't run.

    Unfortunately it isn't AC so you can't step up/step down with transformers.

    All of the solutions, such as very large wire or 24V to 12V converter at the pump, are painful (i.e. expensive).
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
    Re: Hello all. New here.
    King-01 wrote: »
    Thanks for the reply. I have my batteries, panels and various equipment located central to the garage. The well pump is 275 feet from the garage. Putting the panels, batteries, etc. next to the well head is a no-go.

    What do those pumps cost? It might be cheaper to buy a 120 volt AC pump than to put in enough copper to make a 12 volt model work.

    If you run power from your house to the pump, consider lightning issues. The exterior of your pump sees ground at the well. The wires inside the pump are referenced to ground at you house 275 ft away. When lightning strikes in your neighborhood the ground at your house and the ground at the well may be 1000's of volts apart. That means sparks will fly between the wires in your pump and its case. Of course you will need lightning arresters at each end of the power cable.

    Is it possible to put a small 12 volt power system out by the well, and have no wires between the house and the well? If you do that you can avoid lightning issues.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #6
    Re: Hello all. New here.

    The Nemo pumps are $220. This is just a backup system. Still have the 240 volt main pump powered by the grid. Looks as if the only solution is to install a separate 24 volt system just for the pump.

    Putting anything by the well is not an option.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #7
    Re: Hello all. New here.
    King-01 wrote: »
    This is just a backup system. Still have the 240 volt main pump powered by the grid.

    Do you have vehicular access to the well? If its only for an occasional backup, you could drive up there with a battery for the pump, or even use jumper cables from your car.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
    Re: Hello all. New here.
    vtmaps wrote: »
    Do you have vehicular access to the well? If its only for an occasional backup, you could drive up there with a battery for the pump, or even use jumper cables from your car.--vtMaps

    My initial thought exactly, Sneaker Net for batteries!
    or use a inverter to boost your 12V to 120V, run an ext cord out there, and a power supply to the pump.
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #9
    Re: Hello all. New here.

    I'ts in my front yard. While I could do that, I'd prefer not to. Would rather have a permanent system.
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #10
    Re: Hello all. New here.

    It would cost more to convert the 12 to 240.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: Hello all. New here.

    Do you need back-up for pump failure or back-up for power failure?
    An alternate 240 VAC source may be much easier to come up with.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #12
    Re: Hello all. New here.

    Would one of these make you happy?
    http://www.solarconverters.com/index.php/products/85-dc-dc-step-up-controllers-cv/166-cv-12-24-6

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #13
    Re: Hello all. New here.
    Cariboocoot wrote: »
    Do you need back-up for pump failure or back-up for power failure?
    An alternate 240 VAC source may be much easier to come up with.

    Backup for power failure, short or long term.
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #14
    Re: Hello all. New here.
    vtmaps wrote: »
    Would one of these make you happy?
    http://www.solarconverters.com/index.php/products/85-dc-dc-step-up-controllers-cv/166-cv-12-24-6

    --vtMaps

    That would work out nicely. Thanks for finding that.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
    Re: Hello all. New here.
    King-01 wrote: »
    Backup for power failure, short or long term.

    The cheapest way to do that is to provide 240 VAC for the existing pump with a generator.
    Putting in solar for occasional back-up use is a poor investment.
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #16
    Re: Hello all. New here.
    Cariboocoot wrote: »
    The cheapest way to do that is to provide 240 VAC for the existing pump with a generator.
    Putting in solar for occasional back-up use is a poor investment.

    I have solar in place now for other things, so it's just an expansion.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: Hello all. New here.
    King-01 wrote: »
    I have solar in place now for other things, so it's just an expansion.

    If the inverter can handle the pump's power demand it would still be a better way to go even if you have to install a transformer to get the 240 Volts. Otherwise even swapping out the inverter might be better. Adding a low Voltage pump (and would it handle the pumping requirements?) and more wiring makes for a complicated install with, as you've seen, some significant problems.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #18
    Re: Hello all. New here.
    Cariboocoot wrote: »
    The cheapest way to do that is to provide 240 VAC for the existing pump with a generator.
    Putting in solar for occasional back-up use is a poor investment.
    King-01 wrote: »
    I have solar in place now for other things, so it's just an expansion.

    King, he is correct. Backup power systems need to do two things. One, run base loads 24/7 or at least enough hours in a day to keep things like fridges cold enough to last the rest of the un-powered time (a minimum of 8 hours a day broken up into 2 hours on, 4 hours off chunks). Your solar system meets this need.

    A well pump needs far less run time. If you are only getting water to drink you can store up all you need for a week by running it less than 10 minutes. If you are taking showers you only need to run it for an hour a day, even every-other day. A cheap contractor screamer will do this job for a few hundred bucks. Expanding your solar system to do this will take several times that amount. The cost-to-benefit analysis doesn't add up.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #19
    Re: Hello all. New here.
    techntrek wrote: »
    King, he is correct. Backup power systems need to do two things. One, run base loads 24/7 or at least enough hours in a day to keep things like fridges cold enough to last the rest of the un-powered time (a minimum of 8 hours a day broken up into 2 hours on, 4 hours off chunks). Your solar system meets this need.

    A well pump needs far less run time. If you are only getting water to drink you can store up all you need for a week by running it less than 10 minutes. If you are taking showers you only need to run it for an hour a day, even every-other day. A cheap contractor screamer will do this job for a few hundred bucks. Expanding your solar system to do this will take several times that amount. The cost-to-benefit analysis doesn't add up.

    Money isn't an issue. I enjoy the project time. I found something similar on Amazon to what vtmaps posted. It allows the voltage to go higher than 24V, so taking into account line loss, I could use a smaller gauge wire and still end up at 24V. Please take a look and correct me if I'm wrong. Max amp draw on the pump is 5 amps. Thanks.

    http://www.amazon.com/DROK-Constant-Current-Converter-Regulated/dp/B00E8D7XYG/ref=cm_cd_ql_qh_dp_t
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #20
    Re: Hello all. New here.

    Even at 24v 235 feet (each way) means you are going to need 1 awg to get the vdrop down to 2%.

    Have you pondered the idea of running a small gauge wire out to the pump to tricklecharge a pair of small AGMs at the pump site?

    BTW "all the gear is 12v" is no reason to run a 12v battery, as you can use 24-12 converters to run the 12v stuff.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #21
    Re: Hello all. New here.

    Why has no one mentioned a 12-24 voltage doubling transformer A little device that draws 12 vdc and converts it to 24 vdc. I use one n my shurflo submersible. The total current draw from the batteries remains the same (albeit with less line loss) but the loses will be significantly less in the pump feed.

    I think our site host sells them, but I couldn't find them on a quick search on thier web site. It got mine from NAWS for under z$100 iirc.

    Tony

    PS. Here it is:http://www.solar-electric.com/12to24or24to.html (also a bit more expensive)
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #22
    Re: Hello all. New here.
    icarus wrote: »
    Why has no one mentioned a 12-24 voltage doubling transformer

    From earlier in this thread:
    vtmaps wrote: »
    Would one of these make you happy?
    http://www.solarconverters.com/index.php/products/85-dc-dc-step-up-controllers-cv/166-cv-12-24-6

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #23
    Re: Hello all. New here.

    As referenced in my earlier post, I found a variable voltage output DC to DC convertor on Amazon. Running this convertor, I calculated 26V output using 8 gauge wire for the 350 foot run would give me 23.4V & 4amp max draw at the pump. After talking with the people at Nemo, the pump will run at any voltage between 12 and 24. Am I missing something here, as a previous poster mentioned 1 gauge wire?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #24
    Re: Hello all. New here.

    The wire gauge required is a function of Voltage, Amperage, and distance with "acceptable" loss.

    So a 350 foot run @ 12 Volts and 8 Amps would actually require 3/0 wire to keep the V-drop below 3% (the usual standard) but if you double the Voltage you halve the Amperage for the same amount of power and then the wire size can be smaller: 4 AWG gives you <3% V-drop. That is with copper; the 1 AWG reference was probably for aluminium.

    Personally I wouldn't want to foot the bill for 350 feet of 4 AWG wire either.

    If you want to output 24 Volts at the source and allow loss up to 50% at full power you can use much smaller wire. 10 AWG for example will drop 12% over that distance, leaving you with about 20 Volts to run the pump. You'd probably have trouble with anything smaller than 14 AWG.
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  • King-01
    King-01 Registered Users Posts: 28 ✭
    #25
    Re: Hello all. New here.
    Cariboocoot wrote: »
    The wire gauge required is a function of Voltage, Amperage, and distance with "acceptable" loss.

    So a 350 foot run @ 12 Volts and 8 Amps would actually require 3/0 wire to keep the V-drop below 3% (the usual standard) but if you double the Voltage you halve the Amperage for the same amount of power and then the wire size can be smaller: 4 AWG gives you <3% V-drop. That is with copper; the 1 AWG reference was probably for aluminium.

    Personally I wouldn't want to foot the bill for 350 feet of 4 AWG wire either.

    If you want to output 24 Volts at the source and allow loss up to 50% at full power you can use much smaller wire. 10 AWG for example will drop 12% over that distance, leaving you with about 20 Volts to run the pump. You'd probably have trouble with anything smaller than 14 AWG.

    Luckily I can buy the wire at contractor price, so it's pretty cheap, the 8 gauge THHN would run me .33 per foot.
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