Discharge Protection Confusion

Discussion in 'Off Grid Living' started by wpmasterdesign, Apr 21, 2017.


  1. I am a little confused about something and I hope one of you pros can help.

    So my charge controller is supposed to keep my battery from over discharging and from over charging. I understand how overcharge protection works because the cc will stop charging the battery when it is full. What I am confused about is the discharge protection.

    If I have it setup correctly, then there is nothing between the inverter and the cc to stop the discharge. You can't/shouldn't plug your inverter or load into the load ports on the cc (other than a small light maybe) from what I have been told. But that seems the only way over discharge protection can work

    So I have the chain like this: Solar panel to CC>> CC to battery>>battery to inverter>>Inverter to load.

    It seems to me that in order to stop the battery from discharging at a certain point, there would have to be something to cut off the electricity between the battery and the inverter.

    So how can a CC prevent over-discharge? Do I have my system wired completely wrong?

    This instructable says connect the inverter to the charge controller, but that is a heavier load than a light, especially if I have my devices running on the inverter. So that doesn't seem right.
    Solar Power System - All
     
    Last edited: Apr 21, 2017
  2. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Any descent Inverter will have a Low Battery Bank Voltage Cutoff Setting... This is NOT a function of a Charge Controller, except if the Charge Controller has a Feedback Mechanism that can be programmed to shut down the Inverter when the Bank Voltage falls below the CuttOff Voltage.... Check the Docs.. The only other possibility is on some cheaper non-MPPT Charge Controllers that do monitor the Battery Voltage and can Cutoff the Small Loads connected to the Load Terminals... Most Good MPPT Charge Controllers do NOT have Load Terminals....
     
    techsar and sec_monkey like this.
  3. Great to know! Thanks for clarifying that. So as long as I get an inverter that has a low voltage cutoff, I should be fine, other wise just keep using my current method of disconnecting the battery when not in use, does that sound right?
     
  4. techsar

    techsar Monkey+++

    It's also possible that the CC is saying that it prevents discharge into the solar panels at night or when there isn't enough sun to bring the voltage high enough to charge.

    But to echo Bruce, higher end controllers typically don't have load terminals ;)
     
  5. oil pan 4

    oil pan 4 Monkey+++

    A standard 10.5v cut off is way too low it will damage most batteries.

    My $225 Morningstar MPPT controller has load terminals. I think thy are only good for 10 or 15 amps.
     
  6. Agreed, that is why I cut off at 11.9
     
  7. Cruisin Sloth

    Cruisin Sloth Special & Slow

    The KID , & the Brat do have a load control with a LVD setting , So know the controller & many "good" inverters do have a LVD setting also. If you reach that to often , Your buying batterys all the time .
     
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