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sonbeau's avatar
sonbeau
Explorer
Apr 29, 2018

Magnum stand alone AGS question

Hi. I asked this in another section but nobody seemed to know anything about it. We have a factory installed Magnum AGS stand alone system in our 2017 Jayco Precept. with a 5500 gas Onan generator. I think I understand how the AGS is supposed to work and have set the limit at 10.5 volts, but when we enable it, even though we know the batteries are at full charge, the generator comes right on and doesn't shut off. Shouldn't it just stay enabled and only come on when the 2 house batteries drop to the 10.5 level?
  • MNRon's avatar
    MNRon
    Explorer
    Apr 29, 2018
    What jarrel said, I’d try 11.5v and see how that works and adjust from there. For *unloaded* battery 12.0 will be about 50% SOC so you might find it cycles too much if 12v is trip point for loaded batt; but you could try for a while and see.
  • jharrell's avatar
    jharrell
    Explorer
    Apr 29, 2018
    10.5 is low however from the Magnum manual on start volts:

    Where should I set Start Gen Volts? The VDC start voltage must be high enough to not overdischarge
    the battery, but low enough to keep from nuisance starting the generator. Typically,
    the start volts is set at approximately 50% of the battery capacity. Since this is an inverter/battery
    system, and the battery is normally loaded, the VDC used to determine 50% battery capacity
    should be set lower than what is shown on typical battery voltage SOC charts (approximately
    11.0-11.5 in a 12-volt system), which show the battery at rest (unloaded). A typical start voltage
    setting would be between 11.0 VDC - 11.5 VDC for a 12-volt system.
  • larry_cad's avatar
    larry_cad
    Explorer II
    Apr 29, 2018
    Battery voltage state of charge table
    State of Charge Sealed or Flooded Lead Acid battery voltage
    100% 12.70+
    75% 12.40
    50% 12.20
    25% 12.00
  • sonbeau's avatar
    sonbeau
    Explorer
    Apr 29, 2018
    BINGO! TIME2ROLL, we had the start temp set to 75 but the air off. I just turned the start temp to off and enabled the AGS and this time the green light stayed on but the generator didn't turn on. The setting for low voltage goes from 10 to 12 vdc so thought we could go on the low side but I guess we better increase that to 12? So much to learn and we appreciate all the help from you seasoned rvers.
  • MDKMDK's avatar
    MDKMDK
    Explorer
    Apr 29, 2018
    Don't know anything about your Magnum AGS system, but 10.5 V as a low end threshold seems a little low to me. I'm not sure if that's enough juice left to start anything, let alone a 5500W generator. Does the manual suggest using that number?
    Is the object of the game to simply replenish the batteries with the generator, or to start the generator and then start your AC or some other system requiring more power than the batteries themselves can provide?

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