New Inverter

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Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: New Inverter
    JESSICA wrote: »
    BB, two questions:

    First: What about the panels (Kyoceras 130)?
    Second: Isn't the MX60 supposed not to overcharge batteries?

    [I cheked the battery bank, with a craftman volt meter, just minutes ago
    (2:00 PM in Puerto Rico). Reading: 28.5 (Four 6 volt golf cart batteries, 24 volts nominal.)]

    How accurate is the craftsman meter ?

    Do you have a hydrometer & thermometer to measure charge with?

    What has the water usage been in the batteries ? Do they need lots of water, do you hear lots of bubbles ? Can it possibly be in the middle of an EQ cycle?

    Let battery bank charge for 2 days, no loads. 5 hours after sunset, and with 5 hours no loads, not using the battery for anything, the voltage read by your meter should be
    ** 25.4V ** at 77F If not, you battery is bad somewhere, or your meter needs to be calibrated. Meters do drift with age, and getting banged around.
    http://www.windsun.com/Batteries/Battery_FAQ.htm
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New Inverter

    28.5v seems high for a float charge. what voltage did you program into the mx60 for float and what is the manufacturer's recommended float voltage value? as was said, this could be around 27v or so and this will vary for float depending on the battery manufacturer and type. err on the side of caution and stop the charging process until you work out any possible bugs. if you don't change anything then reconnect the system to the batteries say about once a week for a few hours to give a maintenance charge to them.
  • JESSICA
    JESSICA Solar Expert Posts: 289 ✭✭
    Re: New Inverter
    mike90045 wrote: »
    How accurate is the craftsman meter ?

    Do you have a hydrometer & thermometer to measure charge with?

    What has the water usage been in the batteries ? Do they need lots of water, do you hear lots of bubbles ? Can it possibly be in the middle of an EQ cycle?

    Let battery bank charge for 2 days, no loads. 5 hours after sunset, and with 5 hours no loads, not using the battery for anything, the voltage read by your meter should be
    ** 25.4V ** at 77F If not, you battery is bad somewhere, or your meter needs to be calibrated. Meters do drift with age, and getting banged around.
    http://www.windsun.com/Batteries/Battery_FAQ.htm

    Mike:

    How accurate? I really don't know; but the reading of the craftman meter has always been the same as that in the mx60.
    No, I don't have any hydrometer.
    Water usage is normal. I have not have to add water in the past few weeks.
    I do hear bubbles, but never after dark, nor early in the morning; I only hear the bubbling when the mx60 is in "mppt mode", or "float", or "absorbing".
    And gladly (I think), the reading is 25.4 - 25.6 four or five hours after sunset, with no loads present.


    "28.5v seems high for a float charge. what voltage did you program into the mx60 for float and what is the manufacturer's recommended float voltage value? as was said, this could be around 27v or so and this will vary for float depending on the battery manufacturer and type. err on the side of caution and stop the charging process until you work out any possible bugs. if you don't change anything then reconnect the system to the batteries say about once a week for a few hours to give a maintenance charge to them."

    Niel:

    My mistake: The reading (28.5) was at 2:00 PM, just before the mx60 went into "float". During "float", the reading was 26.5.

    Mike and Niel:

    I am a LOT MORE WORRIED about my panels and my MX60 than about my batteries. (Batteries: $280 for all of them; Panels: $4,000; mx60: $600). If shutting off the system (turning off the DC breaker in between the panels and the mx60) doesn't hurt either panels or the mx60...That's what I need to know!

    Thanks again.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: New Inverter

    Having the panels "unloaded" in the sun will not hurt anything... And th MX 60 should not care either (just looks like "extended dark" to the controller).

    If I have a choice, I would prefer to turn off the panel breaker when the sun is down and/or when the MX 60 drawing little current (floating)... That will be the "easiest" on both the breaker and reduce any inductive kickback that may occur (turning off DC with high current can cause breakers/switches to arc, and voltage spikes from DC inductance in wiring/etc...--not that it will occur every time, and with properly rated switches/breakers it should not be a problem--just if you have a choice, turn off DC when there is no/not much current flowing).

    I will leave it to Jim/Crewzer about whether or not to turn off the MX 60 to battery breaker too (or instead)... The MX 60 will put a little load on the batteries--but if you let it recharge once a week or so--should not be a problem at all to leave the MX 60 connected to the battery bank with the panels "turned off" for most of the week/month until you have your loads reconnected. Again, my suggestion would be to turn off the MX 60 with little/no current flowing (dark/float).

    Hopefully, your battery box is well vented an there is no hydrogen buildup near the DC breakers/switches.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New Inverter

    your pvs and controller will be fine. no need to worry about them so you can recheck for the batteries as nobody wants you to have to throw them away either.
  • JESSICA
    JESSICA Solar Expert Posts: 289 ✭✭
    Re: New Inverter

    Great!

    Thanks a lot!

    I will leave the mx60 on, precisely to draw some "juice" from the batteries.
    And yes, my battery bank is VERY well vented. No problem with that.

    Good night.
  • JESSICA
    JESSICA Solar Expert Posts: 289 ✭✭
    Re: New Inverter (Please read)

    It is 9:20 PM in Puerto Rico.

    I turned off the DC breaker from the pvs. And this happened (or is happening):

    Usually, at night, the main screen in the mx60 reads “PV voltage 09 V” (That’s when the mx60 is in “sleep” mode.). However, when I turned the breaker off, and cut off communication from the panels, that reading began to go up: 12…13…14…and up, until it stopped at 20 volts.

    Is this normal? Is something wrong? Should I turn the breaker on again?

    [Note: I have not turned off the breaker between mx60 and batteries.]
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: New Inverter

    It is probably normal...

    Many electronic circuits have "high resistance" paths where electricity can flow (feed back circuits, FETs with leakage current, dust and humidity on circuit boards, and such)... The current flow is small (probably uAmps or 10's of uAmps--1/1,000,000th to 10/1,000,000th of an Ampere)... When you disconnected the solar panels--the little leakage current to ground they also have is now "gone"--and you have higher voltage reading on the internal MX 60 volt meter (also probably a very "high impedance meter").

    I would not worry about it at all... (I don't have an MX 60--so I cannot confirm your observations).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: New Inverter
    Since the system is still "running" (I mean: PV panels are still on the roof, MX60 is on, batteries are been charged.), but without an inverter; Will all this cause any damage to any of those parts? The batteries are always on "float", (obviously: there is no load connected!)...I really need to know if I should turn off the MX60, or cover the panels, or disconnect the batteries.
    Jessica,

    In general, it’s OK to leave the PV array, the MX60 controller, and the battery bank connected and operating, even if the inverter has been removed and there’s no significant load. The system will just keep the batteries near/at full charge, and the MX60 will indeed keep the batteries from being overcharged.

    The batteries will self-discharge a bit at night, and the array and controller will recharge them during the day. Once the absorb stage parameters have been met (temp compensated target voltage, and time), the MX60 will switch to float mode and maintain the battery bank at that voltage until the Sun sets.

    In general, use the float voltage setting recommended by the battery manufacturer. This is typically ~26.6 V ref 77 F (25 C) battery temperature for a 24 V nominal system.

    While waiting for the inverter to be repaired, returned, and installed, you might want to set the absorption target voltage at the lowest value recommended by the manufacturer, again ref. 77 F (25 C). :cool:
    It is 9:20 PM in Puerto Rico.... I turned off the DC breaker from the pvs. And this happened (or is happening):... Usually, at night, the main screen in the mx60 reads “PV voltage 09 V” (That’s when the mx60 is in “sleep” mode.). However, when I turned the breaker off, and cut off communication from the panels, that reading began to go up: 12…13…14…and up, until it stopped at 20 volts.

    Is this normal? Is something wrong? Should I turn the breaker on again? [Note: I have not turned off the breaker between mx60 and batteries.]
    This is normal. There’s a small resistor in the controller’s input circuitry that charges a capacitor, and this leads to the “strange” input voltage reading. Nothing to worry about! :cool::cool:


    Regards,
    Jim / crewzer