Earth Grounding Battery Bank

ZakarumeZakarume Solar Expert Posts: 143 ✭✭
Is it really necessary to earth ground a battery bank?
1460 Watts Solar @24v. 675 AH Battery Bank using 12 6v Trojan T-105. 1 Midnite Classic 150. 1500 Watt 24v Samlex Pure Sine Inverter

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    There is no functional reason to earth ground a battery bank.

    However, grounding is a complex set of conditions and, many times, there are good reasons to ground (and bond battery ground to local metal grounds--pipes, plumbing, chassis, etc.).

    True earth grounding is to dissipate static electricity (solar arrays, wind turbines mounted above ground, radio antenna, etc. can pickup 100 volts per meter above earth or much more under a thunder storm cloud). And obviously lightning can be an issue too *want lightning energy to go to ground beside the house instead of being brought into the home)..

    Then there is bonding battery ground to plumbing/metal boxes/pipes/etc... This prevents something from becoming "hot" if there is a hot lead to metal box/sink/etc. and a person grabs a metal faucet and gets shocked. Also bonding the return side of a battery bank (or AC inverter) allows us to use single pole breakers/fuses to prevent short circuits from frying wiring. If you have a "floating" battery/AC power system, you really should use ganged pairs of circuit breakers (breaker in both + and - leads) to protect against random short circuits.

    Functionally, there are a few grounding issues to be aware of. For AC ground bonded systems, certain automatic gas flame spark igniters need the earth/green wire bonded neutral. And some florescent tube fixtures start better when grounds are setup correctly.

    And, there can be corrosion issues if you have a (for example) metal water pipe charged wire respect to earth ground.

    True earth (i.e., dirt) ground can be as high as 25 Ohms resistance. Plug 120 Volts between two ground rods and you will get:
    • 120 Volts / 25 Ohms = 4.8 amps... Obviously, not enough to pop a 15 amp breaker--So in and of itself, earth grounding is not a primary safety need.
    What is your application/need?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ZakarumeZakarume Solar Expert Posts: 143 ✭✭
    As you can see in my Signature what i have. When i have most of the stuff running off my inverter i am using about 500 watts. The main items i run is the Computer setup i have and/or TV. Just wondering if earth grounding is necessary for what i have
    1460 Watts Solar @24v. 675 AH Battery Bank using 12 6v Trojan T-105. 1 Midnite Classic 150. 1500 Watt 24v Samlex Pure Sine Inverter
  • BB.BB. Super Moderators, Administrators Posts: 29,724 admin
    It looks like Missouri has a fairly high number of lighting strikes per year. Maybe 15-18 strikes per square mile per year(?).

    So, I would be concerned. Things to do would include grounding the frame of the solar panels/mounting racks to earth (ground rod or buried ground plate).

    Assuming that the batteries are either outside of the home, or at an exterior wall, I would run a 6 AWG to outside the foundation and drive a 8-10 foot (what ever is "required/legal" per your code ground rod and attach 6 awg cable.

    Adding surge suppressors where the PV array cables come into the building and at the AC main panel would be good too.

    And lightning rod above/behind the solar array and on the peak(s) of the home would not be a bad idea either.

    If you don't use the system when there is lighting in the forecast, you could not do any of the protections--But you do run the risk of lightning damage (of course, none of the electrical would survive a direct strike--You just don't want people to be injured/killed).

    My initial guesses--I have not seen your property/installation and I am not any sort of lighting control expert.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • engy-restengy-rest Banned Posts: 2
    No there isn't any need for do it.
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