system and components voltages

karamyhosbanykaramyhosbany Registered Users Posts: 9
Hello friends

Is it important to choose the overall voltage of the system to be equal voltage of batteries , voltage of inverter and voltage of charge controller ???????

Can i choose different voltage levels for PV parts ????

Thanks alot

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,027 admin
    Re: system and components voltages

    For an off grid/battery based power system... Selecting battery voltage can be critical for long term sanity and keep short term copper wiring costs/complexity reasonable.

    Basically for small/lower power systems (call it less than 1,200 watt, 100 amp @ 12 vdc loads, DC charging less than ~80 amps), a 12 volt system can work fine.

    For 1,200-2,400 watt load system, and those with larger battery banks, 24 volts is not a bad place to go.

    For >>2,400 Watt systems and large battery banks, then 48 volts is usually the better choice.

    For the PV Array--You need to "match" Solar array Vmp voltage (Vmp-array) to the batter bank voltage... A 12 volt bank needs around Vmp~17.5 to 18.6 volts for optimum operation with a PWM charge controller (2x that for 24 volt, 4x that for 48 volt systems).

    If you get the more expensive MPPT type charge controller--The minimum voltage is as above--But, depending on charge controller, you can typically go upwards of Vmp-array~100 VDC just fine (typical rule of thumb is Vmp-array should be around 2x battery bank charging voltage for "optimum" MPPT controller operation).

    In the end--Start at the beginning. What are your loads (Watts peak, Watt*Hours per day usage, any "native DC voltage" devices?)....

    As a start--lets talk specifics for your system/needs. It makes it less confusing/frustrating talking about all the possibilities/variations under the sun.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: system and components voltages
    Hello friends
    Is it important to choose the overall voltage of the system to be equal voltage of batteries , voltage of inverter and voltage of charge controller ???????

    Can i choose different voltage levels for PV parts ????

    Voltage of batteries, charge controller and inverter must all be the same. The voltage of the panels depends on the type of charge controller. For the cheap PWM charge controller the panels must have a Vmp rating of around 17V for a 12V battery, 36V for a 24V battery and so on. But if you choose an MPPT charge controller then you can use higher voltage panels with a lower voltage battery, for example you could use a 29V panel with a 12V battery.
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