Earth Ground Attachment

dagr51
dagr51 Solar Expert Posts: 72 ✭✭✭✭
In an off grid system, is the earth ground attachment made before or after the meter (Tri-Metric 2020) shunt?

Comments

  • dagr51
    dagr51 Solar Expert Posts: 72 ✭✭✭✭
    Re: Earth Ground Attachment

    Well, either no interest or the question seems frivolous. Let me try again. I just ordered (from NAWS) a BSP-2012 20 watt panel and a Sunguard 4.5 amp CC so that I could maintain a trickle or maintenance charge on my 6 Interstate U2200 batteries (660ah @ 12v) while I am away for months at a time from my remote cabin. The CC manual says to attach the negative to the battery and to further provide a negative earth ground AT the battery for effective lightning protection. However, the instructions for my existing TM2020 meter says to make all negative connections AFTER the meter shunt. Therefore, I am confused, which is why I asked my previous question. Any takers?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Earth Ground Attachment

    Normally, for the shunt to read correctly (i.e., reading all current going through the "battery" from all of the attached equipment), all connections are made after the shunt.

    Lighting/safety protection is to protect equipment (not just the battery)--I would attach the safety/lightning ground to the same point after the shunt where all of the other electrical connections are made. That is the common ground point of your system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Earth Ground Attachment

    Sounds like your meter will use most of the energy your single 20 watt panel could make.

    With such a small panel, all you need is a single blocking diode ... its would be impossible for the 20 watt panel to overcharge 660ah of batteries.

    As configured, between the Sunsaver and Meter, you are likely going to have dead batteries when you return
  • dagr51
    dagr51 Solar Expert Posts: 72 ✭✭✭✭
    Re: Earth Ground Attachment

    Thanks for your replies, but now I'm really confused. In NAWS 1-100 watt panel section, they explicitly state that any panel 15 watts and larger must have a charge controller, and they recommend the one I bought. It wouldn't be the first time I threw money away, but now who am I to believe? And would it make a difference if I turned off the meter?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Earth Ground Attachment

    Start with the basics, you need to size your solar to support your battery bank, at 660ah, that's a BIG bank ... batteries can lose 1-3% a day due to self-discharge for the battery type you have ( AGM's are about 1/10th this )

    http://www.vonwentzel.net/Battery/00.Glossary/

    So for a 660ah bank, figure it will take 20ah just to hold off self discharge with no loads ... your 20 watt panel might make 6-8 ah day ... on top of that monitors and chargers are 24 hour loads ... they may only use 100ma, but over 24 hours it adds up

    There is no one size fits all and no general rule for anything in RE.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Earth Ground Attachment

    in this " In NAWS 1-100 watt panel section, they explicitly state that any panel 15 watts and larger must have a charge controller," it would seem naws is thinking in different terms of usage and/or application. if one were to have say a 10w pv charging a 10ah battery you will most certainly need regulation on it, but more than likely not if it's going to a 200ah battery as the current is small. loads connected to a battery do affect the overall charge parameters even if it's only the loads are from the controller or battery monitor involved. this in turn changes the parameters you'd like to maintain a battery.
    generally between .5 and 1% of battery capacity is good for maintaining (and i have heard as low as .1% being used) plus any loads all of which need normalized for time factors. solar is limited daily charging while meter draws are 24/7. i am one who believes regulation to be good irregardless for slow damage can occur in some instances.
  • dagr51
    dagr51 Solar Expert Posts: 72 ✭✭✭✭
    Re: Earth Ground Attachment

    Thanks. I'll rethink this.