MPPT's working

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  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT's working

    That is the standard function with an off-grid inverter-charger: when AC is detected on AC IN all loads are passed to it and the inverter goes to charge mode to keep the batteries up. If AC IN loses power it switches seamlessly to inverter and powers the load from the batteries.

    Several times I've helped with design of such a system for use in areas of the world where the grid is less than reliable. ;)
  • drraptordrraptor Solar Expert Posts: 218 ✭✭
    Re: MPPT's working
    That is the standard function with an off-grid inverter-charger: when AC is detected on AC IN all loads are passed to it and the inverter goes to charge mode to keep the batteries up. If AC IN loses power it switches seamlessly to inverter and powers the load from the batteries.

    Several times I've helped with design of such a system for use in areas of the world where the grid is less than reliable. ;)
    Thanks

    Hurrah that solves everything,

    all load on AC grid/utility power, and if it fails it switches over to Batteries (charged by solar).8)

    any particular models ?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT's working
    drraptor wrote: »
    Thanks

    Hurrah that solves everything,

    all load on AC grid/utility power, and if it fails it switches over to Batteries (charged by solar).8)

    any particular models ?

    Most any inverter-charger will function this way. It has to be sufficient to handle the loads, that's about all. You can't expect a 2kW inverter to power 3kW of load obviously. Make sure the Voltage matches as well; you can't easily feed 240 VAC in and out of a 120 VAC inverter. :p
  • drraptordrraptor Solar Expert Posts: 218 ✭✭
    Re: MPPT's working
    Most any inverter-charger will function this way. It has to be sufficient to handle the loads, that's about all. You can't expect a 2kW inverter to power 3kW of load obviously. Make sure the Voltage matches as well; you can't easily feed 240 VAC in and out of a 120 VAC inverter. :p

    Yes. you can't run a 120VAC inverter on a 240VAC system. So I will need a 240VAC 6KW or 2X 240VAC 3KW inverter.

    Any reliable brands/models with atleast 5 years of warranty.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: MPPT's working

    I don't know about the warranty, but the only inverter I can think of that meets those power demands is the Xantrex (now Conext) XW 6048 http://www.solar-electric.com/xaxwhyin1.html

    The Outback Radian is larger, but also more money http://www.solar-electric.com/outback-power-radian-series-inverter-gs8048.html

    Magnum and SMA are both smaller than 6kW so you'd need more than one.

    When you consider any inverter, make sure you look in to the details for programming and connection requirements.
  • drraptordrraptor Solar Expert Posts: 218 ✭✭
    Re: MPPT's working

    is there a rule which states
    "Always Connect battery/bank first before connecting Panels to a charge controller ? " :blush:
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: MPPT's working

    Warranty on XW is 5 yr from purchase. In last part of User Manual
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: MPPT's working
    drraptor wrote: »
    is there a rule which states
    "Always Connect battery/bank first before connecting Panels to a charge controller ? "

    That is a rule for outback and midnite controllers. I'm not sure about other brands. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: MPPT's working

    It is true for most controllers... Although there were a couple we have typed about here that said to connect the panels first (rare).

    Many controllers set the battery bank size (12/24/48 voltage) when the battery is first connected. Which also means that the battery bank has to have a reasonable voltage first--And you cannot connect a "dead bank" and have the charge controller turn on/work correctly (let alone that most dead banks have been badly damaged).

    In the end--Read the manual first.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MPaulHolmesMPaulHolmes Solar Expert Posts: 35 ✭✭
    Re: MPPT's working

    So charge controllers don't have precharge resistors for the input capacitor and output capacitor? I could see that working OK on the solar side, since the current is limited by the panels. Almost like having a light bulb in series with a battery bank. But what about the battery side? Isn't there an LC filter on the output just before the battery bank? Or do they switch so fast that it can be a small C? I've got a large capacitance on the output just before the battery bank, since my switching speed is limited to 10KHz, due to a very large IGBT module. It would be bad to short right to a battery bank I think. Instead, each night, when it shuts down, when the solar voltage drops below a certain value, the pwm duty goes to zero (the current is zero anyway at this point), and the contactor connecting to the battery bank and contactor connecting to the solar panels both open. In the morning, when the voltage from the panels is high enough, the precharge relays fill up both capacitors slowly through their own resistors, and then the contactors close, putting the battery bank and solar back in the circuit.

    So, the battery bank is always always connected to the capacitor inside the charger in general? Does that ever cause issues with leakage from the capacitor running the battery bank dead if things aren't running for several months?
  • BB.BB. Super Moderators, Administrators Posts: 32,612 admin
    Re: MPPT's working

    There is not much in the way of filter caps for the output of solar charge controllers... They expect the battery bank to do that. Same thing with AC inverter's DC input--The battery bank is expected to carry most of the 120 Hz sine squared current wave form. Another reason to keep wiring short and heavy (better filtering for PWM/MPPT/Inverters on the DC side).

    Yes, you can get a healthy spark when first connecting a charge controller to the battery bank (not huge--just enough of a snap to give you a little surpise--generally).

    You are "disconnecting" the output of the MPPT charge controller from the battery bank? I guess that can help reduce phantom current draws at night. And most people would still have the daily sun (or poor sun in bad weather)--So there would not normally be a huge issue with phantom current draw (unless they were putting the panels away for the winter and left the charge controller still connected).

    For the "more fancy" (typically MPPT charge controllers), they can draw significant current from the battery bank "at night"--Powering the microprocessor, logging, networking, remote displays/controllers, etc.). 3-16 watts are a few numbers I have seen here (2.5 watts for Midnite Classic at night)...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • drraptordrraptor Solar Expert Posts: 218 ✭✭
    Re: MPPT's working

    how many watts of Solar Panel I need for running a single 10-15watt led outdoor light at night ? sunhours as low as 4 hours/day.
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: MPPT's working
    drraptor wrote: »
    how many watts of Solar Panel I need for running a single 10-15watt led outdoor light at night ? sunhours as low as 4 hours/day.

    If your night is 8 hours, then 15x8/4 = 30W/0.7(efficiency) = 40W. If your night is shorter because you're usually asleep after midnight, then less than this.
  • drraptordrraptor Solar Expert Posts: 218 ✭✭
    Re: MPPT's working

    thanks, Charge controller will act as a switch, so it night will 20 hours long ;) Which voltage I should use 12 V Leds bulb ? Battery is 12V 145AH.
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: MPPT's working
    drraptor wrote: »
    thanks, Charge controller will act as a switch, so it night will 20 hours long ;)

    If you only need it for 4 hours, it'll be cheaper to do a timer switch-off than build 5x system.
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