Battery ground

JESSICAJESSICA Solar Expert Posts: 289 ✭✭
If my inverter is properly grounded, do I need to, additionally, ground my battery bank to the same ground?

P.S.: My mx60 controller is also grounded to the same point

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Battery ground

    What kind of inverter? True Sine Wave inverters can have one AC output grounded for "Neutral" and have a the DC negative grounded too (TSW inverters are typically isolated from DC to AC). You may earth ground / DC ground one lead on the AC TSW inverter or not--your choice.

    MSW inverters, typically, if you ground reference the "Neutral" and DC ground one of DC power inputs can toast the inverter (MSW inverters are typically not isolated from DC to AC). Normally, you cannot DC ground reference the AC "Neutral" on MSW inverter because it will not work/cause damage.

    There can also be an issue with Earth / Neutral Bonding--with larger generators, they typically also connect earth ground to neutral. If this is done both at the genset and the inverter AC neutral output--It can cause overheating in the wiring too...

    As always, refer to the inverter manual for details.

    There is also the Frame/Green Wire grounding for the Inverter. Typically all metal enclosures of electrical equipment should be earth grounded.

    Lastly, Earth Grounding (green wire) of your DC battery bank. I would do it, at one location (as I remember, you have lightning in the area and it has hit your home before).

    Typically, the DC Ground to Earth Ground is made on the battery negative bus connection.

    You could make it at the charge controller or the inverter DC negative connection--although, the battery is usually the better choice because it is the heaviest wiring connection and more central to the entire system.

    What you do not want to do is have two or more DC ground to Earth ground connections. If you grounded both at the DC negative of the Charge Controller and the DC negative terminal of the inverter, you could get "shared" current flow both in the DC power wiring and the DC earth ground. In many cases, the DC earth ground wire is smaller than the DC power cables--and you could overheat the earth ground wiring.

    Also, in some cases, depending on how the multiple earth grounding to DC negative grounding were done, you may end up being more susceptible to lightning damage--another reason for only one earth ground to dc ground connection.

    Probably way more than you asked about--but proper grounding is one of the more tricky wiring issues with DC/AC power systems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JESSICAJESSICA Solar Expert Posts: 289 ✭✭
    Re: Battery ground
    BB. wrote: »
    What kind of inverter? True Sine Wave inverters can have one AC output grounded for "Neutral" and have a the DC negative grounded too (TSW inverters are typically isolated from DC to AC). You may earth ground / DC ground one lead on the AC TSW inverter or not--your choice.

    MSW inverters, typically, if you ground reference the "Neutral" and DC ground one of DC power inputs can toast the inverter (MSW inverters are typically not isolated from DC to AC). Normally, you cannot DC ground reference the AC "Neutral" on MSW inverter because it will not work/cause damage.

    There can also be an issue with Earth / Neutral Bonding--with larger generators, they typically also connect earth ground to neutral. If this is done both at the genset and the inverter AC neutral output--It can cause overheating in the wiring too...

    As always, refer to the inverter manual for details.

    There is also the Frame/Green Wire grounding for the Inverter. Typically all metal enclosures of electrical equipment should be earth grounded.

    Lastly, Earth Grounding (green wire) of your DC battery bank. I would do it, at one location (as I remember, you have lightning in the area and it has hit your home before).

    Typically, the DC Ground to Earth Ground is made on the battery negative bus connection.

    You could make it at the charge controller or the inverter DC negative connection--although, the battery is usually the better choice because it is the heaviest wiring connection and more central to the entire system.

    What you do not want to do is have two or more DC ground to Earth ground connections. If you grounded both at the DC negative of the Charge Controller and the DC negative terminal of the inverter, you could get "shared" current flow both in the DC power wiring and the DC earth ground. In many cases, the DC earth ground wire is smaller than the DC power cables--and you could overheat the earth ground wiring.

    Also, in some cases, depending on how the multiple earth grounding to DC negative grounding were done, you may end up being more susceptible to lightning damage--another reason for only one earth ground to dc ground connection.

    Probably way more than you asked about--but proper grounding is one of the more tricky wiring issues with DC/AC power systems.

    -Bill

    Bill:

    Now I am COMPLETELY lost.

    I have 2 ground rods: One only for my lightning rod, and another one (about 50 feet away) for the ground terminals (what you just called the "Frame/Green Wire grounding...") of controller and inverter.

    Are you telling me that I need to ground the negative/white terminals of charger and inverter?

    I appreciate your help.

    P.S.: My present inverter is a MSW
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Battery ground

    In general, one 6awg or heavier wire from the battery bank negative bus connection to your earth ground rod for your home.

    Generally, your green wire ground (frame grounds, etc.) should all make their common connection to one point too, at this common ground rod.

    And, your metal water pipes, propane gas line ground, etc. should all make their one ground connection to this common ground rod.

    The idea is, no matter what ac or dc circuit accidently makes a short to a piece of metal or pipe, it will flow safely to the common earth ground rod and back to a battery, inverter, or generator and trip a fuse or breaker.

    The other reason for tying all the grounds together this way is if lightning strikes a piece of metal pipe, electrical wiring, etc., all metal will be at the same voltage and keep the people safe (for example, reduce the chance of lightning hitting your electrical wiring and jumping over to you gas stove or sink).

    The lightning ground rod should be near your lightning rod with very soft bends going straight down the outside wall of your home to the ground rod near your foundation. As I understand, I am not a lightning expert by any stretch of the imagination.

    There are a whole bunch of details like size and braid of lightning cable, clamps/bonding, rod or ground plate requirements and such that can help protect your home better.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • JESSICAJESSICA Solar Expert Posts: 289 ✭✭
    Re: Battery ground

    Will do. Thanks a lot for your help.
Sign In or Register to comment.