help utilizing two different arrays

hello i have two separate arrays of panels one is for my house, (four 85w kyocera panels running to a charge controller)and the other(four 130 watt sharp panels running to a pump controller) runs a submersible pump. I want to utilize the pump panels when the pump is not running. What are my options here i have limited resources as i am in west africa.

Can i run a transfer switch that will stop power to the pump and transfer the power to another charge controller that will charge the same battery bank? Are there any implications of charging the same battery bank with two separate charge controllers?

or is there any other options

thankyou very much for any advice


tom

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: help utilizing two different arrays

    You can have several charge controller charging the same battery bank (assuming the charge controllers are all set to the correct battery type and voltage)...

    You did not say what the voltage of the two arrays are... Ideally, if this is a 12 volt battery bank, both arrays should be around Vmp=16-17 volts or so.

    If the arrays are two different voltages, one 17 volts (12 volt battery bank) and the other 34 volts (24 volt pump)--then the issue becomes a bit more complex (Using a more expensive MPPT type Solar Charge controller can efficiently drop the 34 volts down to the 14-15 volts required to charge the battery bank).

    If you need a bit more information, you can read about charge controllers in this two FAQ's.

    All About Charge Controllers
    Read this page about power tracking controllers

    Also, you will need to worry about common grounding between the two systems (you don't want to cause accidental current flow between your two power systems, or charge the metal water/well pipes and cause them to rust out--not likely, but you are there, and I am not).

    If the two systems are "far apart" more than a few meters, the voltage drop to run the low voltage DC from one system to the other may become an issue (voltage drop. Low voltage DC has lots of current and requires lots of copper to move the current any distance).

    There should be nothing "special" with your solar pump / charging wiring. Mostly, just follow the normal rules for any low voltage DC system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2
    System2 Posts: 6,290 admin
    Re: help utilizing two different arrays
    BB. wrote: »
    You can have several charge controller charging the same battery bank (assuming the charge controllers are all set to the correct battery type and voltage)...

    You did not say what the voltage of the two arrays are... Ideally, if this is a 12 volt battery bank, both arrays should be around Vmp=16-17 volts or so.

    If the arrays are two different voltages, one 17 volts (12 volt battery bank) and the other 34 volts (24 volt pump)--then the issue becomes a bit more complex (Using a more expensive MPPT type Solar Charge controller can efficiently drop the 34 volts down to the 14-15 volts required to charge the battery bank).

    If you need a bit more information, you can read about charge controllers in this two FAQ's.

    All About Charge Controllers
    Read this page about power tracking controllers

    Also, you will need to worry about common grounding between the two systems (you don't want to cause accidental current flow between your two power systems, or charge the metal water/well pipes and cause them to rust out--not likely, but you are there, and I am not).

    If the two systems are "far apart" more than a few meters, the voltage drop to run the low voltage DC from one system to the other may become an issue (voltage drop. Low voltage DC has lots of current and requires lots of copper to move the current any distance).

    There should be nothing "special" with your solar pump / charging wiring. Mostly, just follow the normal rules for any low voltage DC system.

    -Bill

    thanks bill that helps the house array is 24v but i use a mppt charge controller that brings it down to 12v to charge the 12v battery bank. what is common grounding? the arrays will be right next to each other, i was going to but them on the same metal structure.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: help utilizing two different arrays

    Tom,

    Grounding has been an issue for decades...

    There is the Negative Grounding (traditional US grounding for cars). And positive (traditional grounding for British cars from times gone by). And positive grounding for telecommunications systems and pipe line anti-corrosion systems (helps prevent electrolysis from destroying buried metal pipes).

    Most (US anyway) Charge Controllers assume negative grounding.

    I don't know how your system is wired--so I am just giving generic warnings so you keep safe.

    You may want to have the transfer switch break both + and - wires (double pole, double throw or DPDT switch) from the Pump Array over to the Pump Array Charge controller.

    Some of the newer MPPT Charge Controllers (like the Xantrex XW system) will not work if the the Array connections are positive or negative grounded (the array has to "float" when connected to the Xantex XW MPPT Charge Controller or it will not work correctly).

    Other brands of charge controllers may not care if the Solar Arrays share a common negative ground (+/- power wiring) or not.

    Generally, leave the array wires floating (to the charge controller). And ground the battery bank terminal (in one place). Even then, that is a "safety practice"; not an operational practice (if you are in wood/'concrete construction with little metal around--grounding becomes kind of a non-issue).

    That is different than grounding the metal frame around the solar panel--that is a "safety ground" for lightning protection (and that is a large discussion in its own right too).

    It is hard to give a generic answer without knowing your setup and controllers involved -- and even then may not be able to give a "correct" answer.

    Beware that switches are rated for AC and/or DC operation. DC switching under load (current flow) is much harder on switches than AC switching is. DC tends to sustain arcing better than AC does (burn out contacts sooner with DC loads).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset