External Relay for LVD

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Tulumtam
Tulumtam Solar Expert Posts: 37 ✭✭
in Off Grid Solar & Battery Systems #1
Hi all,

The low voltage disconnect function on a 4-year-old (out of warranty) Outback FX2524T inverter isn't working. A few months ago, Outback sent out a firmware revision, but that has not resolved the issue. Someone mentioned that I should be able to wire a 12v relay into the Aux jumper in the inverter to take over this function. What type of relay would I need and how would I wire it in to do this?

Many thanks,
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: External Relay for LVD

    You would need a relay whose coil demands don't exceed the AUX function's output (12 Volts @ 200 mA if I recall correctly) and whose contacts are capable of handling the full current of the inverter (about 150 Amps). Good luck finding one. You probably would have to use two relays; the first to control the second and go up in current handling.

    Here's a better idea; there's a set of terminals in the FX for switching the inverter on and off. This does not handle the full inverter current. It's like setting the MATE control to INV OFF. It does not completely eliminate inverter draw, but it does kill AC OUT so nothing else can pull from the batteries. I can't find any actual specs for switching that, but I suspect it's less than 1 Amp. A simple relay like this one for gen start should do it: http://www.solar-electric.com/regest12vosi.html
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: External Relay for LVD

    Sorry; forgot to mention the wiring.

    You have an FM80. It's AUX output has a function for Low Battery Disconnect which is ideally suited to this purpose (page 34/35 in the manual). The AUX output can control the relay directly, the relay performs the switching operation on the terminals of the inverter (first two in the DC wiring connections marked 'inverter' if I recall).

    What else did I forget?
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  • Tulumtam
    Tulumtam Solar Expert Posts: 37 ✭✭
    #4
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    Re: External Relay for LVD

    Thanks for the quick and informative reply!

    I will look for a relay like that. I am in a small town in Mexico, so not sure what I can find.

    This actually isn't for my system, but the system has an FM-60, so have been looking at the manual and see what you are referring to. The battery voltage is usually dropping below the set point late at night. With the charge controller in sleep mode at night, will this work? Or will the charge controller wake up when the battery voltage gets to the set point and activate the relay?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
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    Re: External Relay for LVD
    Tulumtam wrote: »
    Thanks for the quick and informative reply!

    I will look for a relay like that. I am in a small town in Mexico, so not sure what I can find.

    This actually isn't for my system, but the system has an FM-60, so have been looking at the manual and see what you are referring to. The battery voltage is usually dropping below the set point late at night. With the charge controller in sleep mode at night, will this work? Or will the charge controller wake up when the battery voltage gets to the set point and activate the relay?

    Charge controller monitors Voltage all the time, so the AUX function should still activate/deactivate the relay at night. The 'SLEEP' mode refers to MPPT functioning; it shuts down to avoid using more power from the batteries.

    I would be interested to know if the system has a MATE attached and if running the LVD setting up/down makes any difference (whether this is a programming error or a hardware malfunction).
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  • Tulumtam
    Tulumtam Solar Expert Posts: 37 ✭✭
    #6
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    Re: External Relay for LVD

    There is not a Mate attached to the system. I take my Mate with me when I work on the system. The highest programmable voltage for lvd is 24v, which is what it is currently set at. If I could set it for something higher than 24v, I could check it without running the batteries down. According to the FM-60, the battery bank has been occasionally getting down to 23v before the lvd on the inverter shuts things down. There is a temperature sensor and the battery voltage at the charge controller is calibrated to the actual voltage of the battery bank.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: External Relay for LVD

    Okay, possible problem there. When you take the MATE away you take its programming with you. The default value of 21 Volts can return in the inverter.
    Have you tried leaving your MATE hooked up for awhile and seeing how the inverter performs?

    In general, system nominal Voltage is a good LVD set point. The inverter will allow Voltage to go under this for about 5 minutes before shutting down, which allows for heavy load starts. At 24, the batteries will be somewhat above 50% SOC after the inverter turns off and the batteries "rebound" to resting Voltage.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #8
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    Re: External Relay for LVD
    Cariboocoot wrote: »
    Okay, possible problem there. When you take the MATE away you take its programming with you. The default value of 21 Volts can return in the inverter.

    Wow - is that really true? I was under the impression that programming of the inverter and FNDC with the Mate stays until it is changed again (or maybe if inverter is disconnected from battery).:confused:

    I've had to replace my Mate once under warranty when the screen stopped working but Outback was good enough to send me a new one before I had to send the malfunctioning one back. I don't like the idea that any future out of warranty replacement would mean all programming is lost until A new Mate
    arrives.. My system would not function very well with the default inverter values... Maybe I need a spare??:confused:
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
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    Re: External Relay for LVD
    mtdoc wrote: »
    Wow - is that really true? I was under the impression that programming of the inverter and FNDC with the Mate stays until it is changed again (or maybe if inverter is disconnected from battery).:confused:

    I've had to replace my Mate once under warranty when the screen stopped working but Outback was good enough to send me a new one before I had to send the malfunctioning one back. I don't like the idea that any future out of warranty replacement would mean all programming is lost until A new Mate
    arrives.. My system would not function very well with the default inverter values... Maybe I need a spare??:confused:

    It has been my experience that the MATE programming is non-volatile and quite dependable. But the inverter programming sometimes isn't. Haven't yet figured out why this should be, since it is also supposed to be non-volatile. All I can guess is that sometimes weird electrical impulses occur on an inverter which alters its programming. The Catch-22 is that you don't see it without a MATE and if you have a MATE plugged in it doesn't happen. :confused:

    I just like to collect data about Outback system/component performance to see if there are any trends to things like this or if they're just anomalies.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #10
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    Re: External Relay for LVD
    Cariboocoot wrote: »
    The Catch-22 is that you don't see it without a MATE and if you have a MATE plugged in it doesn't happen. :confused:

    I just like to collect data about Outback system/component performance to see if there are any trends to things like this or if they're just anomalies.

    The question I would love the answer to is what happens when you have disconnected the MATE, the inverter has reset to defaults, and you connect the MATE again?
    Does the MATE just quietly reset the inverter without bothering to tell you that it had to do that? Is there any way to use the MATE to view the current inverter settings without resetting them? Or would that require an unprogrammed MATE?
    SMA SB 3000, old BP panels.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #11
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    Re: External Relay for LVD

    Thanks 'coot for the clarification

    Inetdog - that is a good question. I don't think the Mate will tell you if is resets the settings. I wish I could remember what happened when I swapped out my faulty screen Mate with the new one- that would answer the question. I honestly cannot remember if I had to reprogram the settings. My brain seems to have volatile memory....:roll:
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
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    Re: External Relay for LVD
    mtdoc wrote: »
    Thanks 'coot for the clarification

    Inetdog - that is a good question. I don't think the Mate will tell you if is resets the settings. I wish I could remember what happened when I swapped out my faulty screen Mate with the new one- that would answer the question. I honestly cannot remember if I had to reprogram the settings. My brain seems to have volatile memory....:roll:

    The other possibility which I did not think of and you reminded me of is that the MATE keeps the settings in its non-volatile memory but when it connects to a "new" inverter (checking the serial number???) for what it thinks is the first time, the MATE displays the current non-volatile settings of that inverter and loads them into its memory. :-)
    The easiest way to get the answer, I think, is to ask somebody (the right somebody) at Outback.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
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    Re: External Relay for LVD
    inetdog wrote: »
    The question I would love the answer to is what happens when you have disconnected the MATE, the inverter has reset to defaults, and you connect the MATE again?
    Does the MATE just quietly reset the inverter without bothering to tell you that it had to do that? Is there any way to use the MATE to view the current inverter settings without resetting them? Or would that require an unprogrammed MATE?

    The MATE polls new equipment and reads what settings are stored in it. Sometimes that doesn't work and you have to manually re-poll the equipment. This tells the MATE what it is and how it's set. You can then use the MATE to change it.

    So yes you can use the MATE on more than one system by moving it, but it's best to re-poll. I don't think it reads serial numbers, just equipment type. So if it had in its memory settings for a FX2524 and you connect it to a different FX2524 it would not recognize the change without re-polling.

    boB would know this for sure.
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