Running 12V and 24V together

mulia
mulia Solar Expert Posts: 62 ✭✭✭✭
Hi,

My system currently consists of 4 T105s formed to supply 12V for Morningstar (MS) inverter. Great for backup.

Unfortunately, blackout happen more often and I need to power well pump in blackout which my inverter can't run.

I'm planning to acquire new inverter to work together with my current one. Probably an Exceltech 1100.

If I can make my current system to work with 24V, I'd like to get the 24V version. If not, then I'll be going with 12V one.

I'm thinking about reconfigure battery bank to form 24V to work with 24V inverter and tap 12V for the MS. But, that'd be bad idea due to uneven power drawn by 2 inverters.

I wonder this can be solved without using another new battery bank to supply 24V system (one already hard to maintain).
Please help me regarding this matter.

I really appreciate any input about this.

Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    You can get a 24V to 12V converter/equalizer which connects to the 0, 12 and 24V taps of your battery bank and supplies 12V by drawing equally from the upper and lower 12V batteries.
    Check out the price and see whether it will make the two voltage system work for you.
    Sorry, no link but I will try to find them again later....
    SMA SB 3000, old BP panels.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    inetdog wrote: »
    You can get a 24V to 12V converter/equalizer which connects to the 0, 12 and 24V taps of your battery bank

    Is there an advantage to that over a 24 to 12 volt converter that taps only the 0 and 24 volt taps?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    What are the details about the well pump? Many are too large even for a 1,100 watt AC inverter.

    Can you use a smaller/more Off Grid Power Friendly pump in the well? Or, in many places, people use a water tank to hold enough water for use during power outages--And you can use a small 12 or 24 volt DC Water pump (common here for Recreational Vehicle use) to pressurize for in-house faucet/shower/tub use.

    This would let you use your present system pretty easily.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mulia
    mulia Solar Expert Posts: 62 ✭✭✭✭
    inetdog wrote: »
    You can get a 24V to 12V converter/equalizer which connects to the 0, 12 and 24V taps of your battery bank and supplies 12V by drawing equally from the upper and lower 12V batteries.
    Check out the price and see whether it will make the two voltage system work for you.
    Sorry, no link but I will try to find them again later....

    0, 12, 24V? I wonder what does it means? I saw some step down converter on eBay, but only for small current/watt, the output is about 600W-ish and cost about $40. With max 90% efficiency, I wonder if this is a good option because I'll loss more than 10%.power to inefficiency.
    Bill wrote:
    What are the details about the well pump? Many are too large even for a 1,100 watt AC inverter.

    Can you use a smaller/more Off Grid Power Friendly pump in the well? Or, in many places, people use a water tank to hold enough water for use during power outages--And you can use a small 12 or 24 volt DC Water pump (common here for Recreational Vehicle use) to pressurize for in-house faucet/shower/tub use.

    This would let you use your present system pretty easily.

    -Bill
    Attachment not found.
    The well pump is as above, I've 2 of them currently, but use the smaller one, GP-129JXK more often. But I also need to know if it's okay when running GP-200JXK.

    It draws 125W and 200W, the input power is 1,55A and 2,3A. We're on 220V. What do you think about it Bill? Will it works fine?

    Unfortunately, such pump aren't available here. These are the lowest wattage pump but with best quality I can found in market in my country.

    I've bough a water tank several months ago, but haven't have enough time to install it, since it require lot of time to do in day time and I need to do many changes in piping system.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Ok... Not too large of pumps. Note that we need to not only pay attention to the Wattage (which does translate to amps/watts of battery bank power), but to VA (volts*amps) regarding wiring and Inverter/Generator ratings (for most residential type inverter and generators, Maximum Watts = Maximum VA rating).

    For your pump:
    • 1.55 Amps * 220 VAC = 341 VA rated input
    and it is not unusual for induction motors to have upwards of 5x (or even more) starting surge:
    • 341 VA * 5x surge rating = 1,705 VA surge rating
    A typical good quality inverter would have a 2x surge rating:
    • 1,705 VA surge / 2x surge rating = 852.5 VA minimum VA or Watt rated AC inverter
    Looks like a nice Panasonic pump:

    http://www.panasonic.com/my/consumer...gp-129jxk.html

    It is an induction motor with a "motor run" capacitor (permanent split phase/capacitor motor)--They do not have high starting torque--So probably not too high of starting current either (from a quick read, roughly 2x running current). Not the most efficient motor, but common usage for smaller motor applications (200 watt or 1/4 hp or less).
    • 341 VA * 2x starting surge = 682 VA.
    • 682 VA starting / 2x surge rated inverter = 341 VA (or Watt) rated inverter minimum
    For the 200 Watt motor:
    • 2.3 Amp * 220 VAC = 506 VA (watt) rated inverter minimum
    • 506 VA * 2x starting surge * 1/2x rated inverter surge = 506 VA (Watt) minimum rated inverter (200% starting current for PSC type motor--best case)
    • 506 VA * 5x starting surge * 1/2x rated inverter surge = 1,256 VA (Watt) rate minimum inverter (500% starting current for capacitor start type motor--worst case)
    Since the motor is a small PSC type--It would appear that an 1,100 Watt (VA) rated inverter should be very nice to drive either pump.

    In theory, you should be able to draw 1,200 Watts from your 12 volt battery bank reliably (albeit with very heavy copper wire from battery bank to AC inverter):
    • 1,200 Watts * 1/0.85 inverter eff * 1/10.5 cutoff voltage = 134 Amps of DC current (12 volt battery bank).
    For such a system running 12 volts, I would suggest short/heavy wiring with a maximum of 0.5 volts drop (use an online voltage drop calculator or V=I*R -- resistance of wire run) to figure drops.

    A 24 volt battery bank would cut the current by 1/2 (and you can use much smaller wire). However, if you need 12 VDC power for other needs--You may be better off sticking with 12 VDC.

    Do you start against pressure? Obviously, pumps that start against pressure take more energy to get running.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    vtmaps wrote: »

    Is there an advantage to that over a 24 to 12 volt converter that taps only the 0 and 24 volt taps?

    --vtMaps

    In theory, it is delivering half the current directly from the 12V tap and the lower battery and the other half from a 1:1 DC to DC converter with isolation. That should allow it to be more efficient than a 24-12 converter with only two input terminals. But I cannot point to specifications that bear that out in practice.
    The converter active circuitry also only needs to be sized for half the current, making it less expensive.

    It is analogous to using an autotransformer to go from 240 to 120 instead of a 2:1 isolation transformer.
    SMA SB 3000, old BP panels.
  • mulia
    mulia Solar Expert Posts: 62 ✭✭✭✭
    BB. wrote: »
    Looks like a nice Panasonic pump:

    http://www.panasonic.com/my/consumer...gp-129jxk.html

    It is an induction motor with a "motor run" capacitor (permanent split phase/capacitor motor)--They do not have high starting torque--So probably not too high of starting current either (from a quick read, roughly 2x running current). Not the most efficient motor, but common usage for smaller motor applications (200 watt or 1/4 hp or less).
    • 341 VA * 2x starting surge = 682 VA.
    • 682 VA starting / 2x surge rated inverter = 341 VA (or Watt) rated inverter minimum

    For the 200 Watt motor:
    • 2.3 Amp * 220 VAC = 506 VA (watt) rated inverter minimum
    • 506 VA * 2x starting surge * 1/2x rated inverter surge = 506 VA (Watt) minimum rated inverter (200% starting current for PSC type motor--best case)
    • 506 VA * 5x starting surge * 1/2x rated inverter surge = 1,256 VA (Watt) rate minimum inverter (500% starting current for capacitor start type motor--worst case)

    Since the motor is a small PSC type--It would appear that an 1,100 Watt (VA) rated inverter should be very nice to drive either pump.

    In theory, you should be able to draw 1,200 Watts from your 12 volt battery bank reliably (albeit with very heavy copper wire from battery bank to AC inverter):
    • 1,200 Watts * 1/0.85 inverter eff * 1/10.5 cutoff voltage = 134 Amps of DC current (12 volt battery bank).

    For such a system running 12 volts, I would suggest short/heavy wiring with a maximum of 0.5 volts drop (use an online voltage drop calculator or V=I*R -- resistance of wire run) to figure drops.

    A 24 volt battery bank would cut the current by 1/2 (and you can use much smaller wire). However, if you need 12 VDC power for other needs--You may be better off sticking with 12 VDC.

    Do you start against pressure? Obviously, pumps that start against pressure take more energy to get running.

    Yes, it's one of the best on market, though one of the pump broken in less than a year, I'll need to have it fixed before.

    Excellent, seems like a 1000W good inverter will work well. Although I'm not too sure it's possible to get 220V version of this Exceltech (NAWS didn't specify the voltage, I'll need to ask).

    For my Morningstar, I use a 16mm cable from inverter to battery bank (about 1meter distance), it's already hard to insert it into inverter terminal. If possible, I'll fit 25mm cable to 1000W inverter, although I'm not sure it will fit.

    Against pressure? What it means? I think there are no pressure to against with when it work.


  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    inetdog wrote: »
    In theory, it is delivering half the current directly from the 12V tap and the lower battery and the other half from a 1:1 DC to DC converter with isolation. That should allow it to be more efficient than a 24-12 converter with only two input terminals.

    I must be missing something. If you use a 24V DC to 12V DC converter with a single 24 volt input, wouldn't it draw the same current from both of the 12 volt batteries which are in series?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    I tried to find a US source for this pump. I agree it is pretty nice Bill!
    http://www.panasonic.com/my/consumer...gp-129jxk.html

    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    When I mean starting against pressure--If you have a pressure tank (a water tank that has an air pocket in it--Pump water into the tank, and the the air bubble keeps something like 20-60 PSI of water pressure--Also known as an accumulator in hydraulics)---The water pump when it starts needs to pump against the original 20 PSI of the water system--This can take more Watts to get the motor up to speed.... Vs just dumping water into an open tank (no or little back pressure).

    By the way, why did the first pump fail? Was it the motor (to much pressure overheating the motor) or something in the pump section (i.e., sand in the water)?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    vtmaps wrote: »

    I must be missing something. If you use a 24V DC to 12V DC converter with a single 24 volt input, wouldn't it draw the same current from both of the 12 volt batteries which are in series?

    --vtMaps

    It would. Let's put in some numbers:

    Say you have a 12V 20A load and you have a 24V battery.

    A straight 24V to 12V converter will (ignoring efficiency for the moment) take in 10A at 24V and put out 20A at 12V. The active elements in the converter will be carrying that full 20A.

    With a converter/balancer that uses a tap for the 12V midpoint you will be drawing 10A from the lower battery and converting 10A from the upper battery to work in parallel with the lower battery.
    End result: The converter is taking in 10A at 12V and putting out 10A at 12V. The active elements only have to carry 10A so they can be smaller and waste less energy.
    The 10A from the lower battery is not being manipulated by the converter, although it will be going through a shunt or Hall Effect sensor so that the converter can measure the current being drawn directly and match that current with the converter output.
    SMA SB 3000, old BP panels.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    inetdog wrote: »
    Let's put in some numbers:

    Say you have a 12V 20A load and you have a 24V battery.

    A straight 24V to 12V converter will (ignoring efficiency for the moment) take in 10A at 24V and put out 20A at 12V. The active elements in the converter will be carrying that full 20A.

    With a converter/balancer that uses a tap for the 12V midpoint you will be drawing 10A from the lower battery and converting 10A from the upper battery to work in parallel with the lower battery.
    End result: The converter is taking in 10A at 12V and putting out 10A at 12V. The active elements only have to carry 10A so they can be smaller and waste less energy.
    The 10A from the lower battery is not being manipulated by the converter, although it will be going through a shunt or Hall Effect sensor so that the converter can measure the current being drawn directly and match that current with the converter output.

    Huh? ! ? I'm still missing something...

    If you are taking 10 amps from one 12 volt battery, and the load is 10 amps at 12 volts, I don't see how the other 12 volt battery has a matching current drawn from it.

    Or are you trying to say that the current from each 12V battery is 5 amps and the output of the device is 10 amps at 12 volts? If so, then its not fair to compare a "two tap" DC to DC converter that outputs 20 amps at 12 volts with a "three tap" converter that outputs 10 amps at 12 volts.

    You mentioned earlier that purpose of the device is to match the current in the two 12V batteries. I can't think of a simpler and more foolproof way to do that than to put the two batteries in series and draw a 24V load (through a "two tap" DC to DC converter).

    --vtMaps What am I missing here?
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • mulia
    mulia Solar Expert Posts: 62 ✭✭✭✭
    BB. wrote: »
    When I mean starting against pressure--If you have a pressure tank (a water tank that has an air pocket in it--Pump water into the tank, and the the air bubble keeps something like 20-60 PSI of water pressure--Also known as an accumulator in hydraulics)---The water pump when it starts needs to pump against the original 20 PSI of the water system--This can take more Watts to get the motor up to speed.... Vs just dumping water into an open tank (no or little back pressure).

    By the way, why did the first pump fail? Was it the motor (to much pressure overheating the motor) or something in the pump section (i.e., sand in the water)?

    -Bill

    I got it. My pump isn't working against any pressure, it just pumping the water up from well to bathroom and kitchen directly, so no pressure tank present here.

    I brought it to service centre since it's still under warranty. The reception (who receive my pump and deliver it to technician and also deliver it back to me) didn't explain any further, he just said, "The motor failed and we've got it repaired, here you go".

    I'm not a brand lover, but it seems (based on my experience) Panasonic brand already got their products' quality fall after they changed their name from National. Out of the topic, I once went to To**** factory in Japan, meet their representative, I asked him why their cars (in my country) are built so weak and with low safety resulting in there are always death victims when an accident occurs involving their car. He replied, "Our marketing demands lower price while our factories want to produce better safety car". I believe this is caused by people demanding cheaper price while there are no standard for safety assurance here.
  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    vtmaps wrote: »

    Huh? ! ? I'm still missing something...

    If you are taking 10 amps from one 12 volt battery, and the load is 10 amps at 12 volts, I don't see how the other 12 volt battery has a matching current drawn from it.

    Or are you trying to say that the current from each 12V battery is 5 amps and the output of the device is 10 amps at 12 volts? If so, then its not fair to compare a "two tap" DC to DC converter that outputs 20 amps at 12 volts with a "three tap" converter that outputs 10 amps at 12 volts.

    You mentioned earlier that purpose of the device is to match the current in the two 12V batteries. I can't think of a simpler and more foolproof way to do that than to put the two batteries in series and draw a 24V load (through a "two tap" DC to DC converter).

    --vtMaps What am I missing here?


    The load is 20A at 12V from a 24V bank of (2) 12V batteries. I agree with him that it would use lower value parts and could save some energy. I am not sure I would worry about the difference.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Yeah quite low wattage for an induction motor pump. From the shape of it it looks like a peripheral/regenerative design (modified centrifugal). They can do quite high pressures, dont mind the odd bit of air, but run hot if worked hard. Hence will need either a pressure switch plus tank, or a press controller. Without which, run them against a closed tap and theyll die real quick.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    zoneblue wrote: »
    Yeah quite low wattage for an induction motor pump. From the shape of it it looks like a peripheral/regenerative design (modified centrifugal). They can do quite high pressures, dont mind the odd bit of air, but run hot if worked hard. Hence will need either a pressure switch plus tank, or a press controller. Without which, run them against a closed tap and theyll die real quick.


    Can you get the in country?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    vtmaps wrote: »

    Huh? ! ? I'm still missing something...

    If you are taking 10 amps from one 12 volt battery, and the load is 10 amps at 12 volts, I don't see how the other 12 volt battery has a matching current drawn from it.

    Or are you trying to say that the current from each 12V battery is 5 amps and the output of the device is 10 amps at 12 volts? If so, then its not fair to compare a "two tap" DC to DC converter that outputs 20 amps at 12 volts with a "three tap" converter that outputs 10 amps at 12 volts.

    You mentioned earlier that purpose of the device is to match the current in the two 12V batteries. I can't think of a simpler and more foolproof way to do that than to put the two batteries in series and draw a 24V load (through a "two tap" DC to DC converter).

    --vtMaps What am I missing here?
    I think that you are not reading what I wrote carefully enough.

    The three input converter is taking 10A directly from the lower battery and transforming 10A at 12V from the upper battery to an additional 10A in parallel with that from the lower battery.

    The net result is 20A at 12V to the load.
    SMA SB 3000, old BP panels.
  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,039 ✭✭✭✭✭

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Can you get the in country?

    Ive used this one, it draws 450W lifting 5m, 400kpa / 20l/s.
    http://www.smallfish.co.nz/shops/pum...tps60-jet-pump
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,731 ✭✭✭✭✭✭
    zoneblue wrote: »

    Ive used this one, it draws 450W lifting 5m, 400kpa / 20l/s.
    http://www.smallfish.co.nz/shops/pum...tps60-jet-pump


    Thanks Zoneblue. It looks like another model that I can't easily get here. Most of our 1/2 HP or less pumps are never associated with the word Quality or long lasting. How was the surge with that pump with your lighting? Is that blue box in the link picture a pressure switch?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    I wouldnt say either of those pumps are particularly quality pumps, not name brand at least. (doubt panasonic actually builds them). The start surge is pretty tame because of the impeller design, but regen pumps are known for sucking the amps just before they shut off. Peak (closed tap) amps are at least twice running amps. That controller is a automatic pressure controller, not a pressure switch. Actually not that well suited to regen pumps for the above mentioned reason. The pump tends to whine a bit near shut off, or low flow conditions.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • mulia
    mulia Solar Expert Posts: 62 ✭✭✭✭

    It's indeed not cheap. :-s

    Seems like what I'm looking for. For the cost it needs to use 12V and 24V together, perhaps stick to 12V is much more cost effective. Thank you so much.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    mulia wrote: »

    It's indeed not cheap. :-s

    Seems like what I'm looking for. For the cost it needs to use 12V and 24V together, perhaps stick to 12V is much more cost effective.

    The alternative to a battery balancer is a simple 24V to 12V DC to DC converter. It may cost less than the battery balancer and it guarantees to draw the same current through each of batteries in series. I've read the specs on Solar Converters battery balancer. It does NOT draw the same current through each battery, rather it tries to hold equal the VOLTAGE (not current) of each battery.

    I don't know that one method of discharge is better for the batteries than the other.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    DC converters are cheap, readily available, in a range of quality and power ranges, and just an all round nice easy solution. Even the no name ones just seem to go and go. These for the price are great:

    http://www.ebay.com/itm/WaterProof-24V-to-12V-20A-240W-DC-DC-Step-DOWN-Power-Converter-Regulator-/301160477491

    20A for 20 bucks
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar