Charge Controller Question

Hello I had some questions about how charge controllers operate. I have installed grid tied systems before but this will be my first system with a battery backup. I am installing a system for someone who will be grid tied and only wants to use the batteries when the grid goes down (I tried to talk her into just using a generator but this is what she wants). Her system is small compared to her load - 2kW that will supply maybe 10% of her daily needs. I would size the battery bank to run critical loads for about 3 days(15kWhrs or so). My question is, is there a charge controller that would charge the batteries when applicable and then not draw from the batteries unless the grid was down. This way she could have adequate battery back up on a relatively small system. From what I understand they are not usually designed to operate this way. I would most likely be using sealed batteries that are designed for long life with a low number of discharge cycles. Thanks in advance.
Jake

Comments

  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Charge Controller Question

    Xantrex XW system does exactly this, Gridtie and Backup ... Outback FX does as well, but more parts for 240Vac and lower efficiency's when compared to the XW series

    This post has exactly what your looking for

    http://forum.solar-electric.com/showthread.php?t=4627
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Charge Controller Question

    This is Xantrex's website describing the XW system.

    It is a very nice looking system... If I had lots of power outages (long or often)--it would be a hard system to beat.

    I have a Xantrex GT 3kW inverter for the last three years--has been running perfectly (cool, no fans, just works).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Charge Controller Question

    I had read that post and didn't get from it that the charge controller would not discharge the batteries at all during the night with the grid up. Upon reading the Xantrex website and the info about the XW Hybrid Inverter/Charger it seems as though this thing has enough brains to do exactly that. Thanks for the help guys.
    Jake
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Charge Controller Question

    That is the normal operating state for the XW system (full GT, use batteries for outage only).

    Still may need a backup generator (for power during poor weather--unless the owner is OK without).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Charge Controller Question
    My question is, is there a charge controller that would charge the batteries when applicable and then not draw from the batteries unless the grid was down. This way she could have adequate battery back up on a relatively small system.
    Jake,

    OutBack systems can operate just as you describe.

    One thing to consider is the size (Watts) of the backed-up loads and whether they wil be 120 or 240. The XW is not available as a single phase unit. An OutBack single inverter solution is very cost competitive for single phase applications (up to 3.6 kVA), and adding a transformer on the output results in a cost effective 120/240 solution.

    The attached drawing may give you an idea for a possible solution. The generator could be left out.

    HTH,
    Jim / crewzer
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Charge Controller Question
    crewzer wrote: »
    The XW is not available as a single phase unit. An OutBack single inverter solution is very cost competitive for single phase applications (up to 3.6 kVA), and adding a transformer on the output results in a cost effective 120/240 solution.
    Jim / crewzer

    Jim, thats flat out misleading .. the XW is split phase with netural, you can run either 120 or 240 vac loads right from the Box. Another advantage to the XW, it can have both grid and generator inputs unlike the FX series.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Charge Controller Question

    it seems to me he is a bit confused about what a charge controller's job actually is. it is a specialized regulator designed for solar pv systems. they draw little power from a battery and i think he may be worrying more about losses from the inverter during the night being in standby. charge controllers do not connect to inverters, but are between the pvs and the batteries. both the xw and outback inverters can keep a battery from discharging too far as they have built-in chargers that operate from utility power. the pvs of course will not be configured like the high voltage gt systems you are used to as it is limited by the lower input voltage ratings of the charge controllers and this in turn dropped to the appropriate battery voltage the batteries and the inverter will operate at. the input voltage limits out there currently on charge controllers may change upwardly in the future with the release of the classic and when it would be released we cannot say as we don't know, but beta testing is going on.
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Charge Controller Question

    Henry,

    Can the XW run 120 only on a single phase? I don't intend to be misleading... I may have to change my wording.

    The real point is that the XW products are intended for 120/240 applications. For straight 120 V single phase applications, the "small" XW's (4024 and 4545) are pretty large, heavy, and costly IMHO compared to a single Outback inverter, with or without a transformer.

    As I recall, the OP was looking for a "small" solution: ~ 5kWh/day. A 4kW 120/240 inverter -- the smallest XW -- may be overkill.

    Sorry for any confusion...
    Jim / crewzer
  • halfcrazyhalfcrazy Solar Expert Posts: 717 ✭✭✭
    Re: Charge Controller Question

    I would say think about the idea of a generator backup with the XW you will get a nice inverter 4kw and up "as the op asked for".

    you get 120 or 240 so it is very versatile right out of the box. This is a nice feature as most modern houses have a 240 volt load or 2 they would like to back up.

    And the real biggy for me it will accept the generator input as well as the grid. It actually has 2 separate inputs one for the grid and one for the generator.

    Either way you cant go wrong but XANTREX really did there homework here this inverter will fill a void for us.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Charge Controller Question
    crewzer wrote: »
    Henry,

    Can the XW run 120 only on a single phase? I don't intend to be misleading... I may have to change my wording.

    Jim / crewzer

    Yes, and I confirmed this, the XW can be run using only half the output ( 120V to Neutral ), maximum wattage is 75% of the 240Vac rating. The XW is a more expensive unit, it also has more features, better efficiency and is legal for residential installations which the Outback products are not as the Outback products lack the FCC Class B certification.
  • halfcrazyhalfcrazy Solar Expert Posts: 717 ✭✭✭
    Re: Charge Controller Question

    Solar guppy if the xw was feeding a sub panel the 120 volt loads would be fairly distributed so i would expect the xw to be able to run close to 100% I would think it would be a rare occasion that there would be a 3-4kw single 120 volt load.

    what do you think? seems like the derating for only using 1 leg wouldnt really be a factor for any normal install?

    Also can you elaborate on the fcc thing is this for just grid tied or does it apply to any on grid home?
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: Charge Controller Question

    Equipment designed and used in residential applications (non-commercial) is supposed to be FCC Class B listed (B has tougher requirements to reduce EMI around the home).

    Nobody that I have ever heard of has gotten in trouble for having a Class A FCC device in the home...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: Charge Controller Question
    halfcrazy wrote: »
    Solar guppy if the xw was feeding a sub panel the 120 volt loads would be fairly distributed so i would expect the xw to be able to run close to 100% I would think it would be a rare occasion that there would be a 3-4kw single 120 volt load.

    what do you think? seems like the derating for only using 1 leg wouldn't really be a factor for any normal install?

    Also can you elaborate on the fcc thing is this for just grid tied or does it apply to any on grid home?
    BB. wrote: »
    Equipment designed and used in residential applications (non-commercial) is supposed to be FCC Class B listed (B has tougher requirements to reduce EMI around the home).

    Nobody that I have ever heard of has gotten in trouble for having a Class A FCC device in the home...

    -Bill

    The 75% of maximum per leg is pretty hypothetical, running loads off the XW should have no issues with mix of 120/240 as even the 120 loads can be on either leg. It seems more of a marketing talking point to compare 120 only VAC inverters to the XW as other manufactures try to influence a potential sale.

    Outback isn't even Class A FCC listed

    The law is just that , residential must be class B compliant, most inverter/charger manufacture skirt this by saying there products are for offgrid application, The Outback GT unit would have a hard time making this claim as is GRIDTIE, but as BB says so far it would appear enforcement is non-existent. From an end-user stand point, the non-class B units pollute RF around the installation and can interfere with anything from radio/wireless ect.

    The XW line is in a class by itself, its the newest RE inverter/charger, the highest efficiency, the most versatile and the only manufacture to be 100% compliant with all UL/FCC regulations, and watt for watt its lower cost than the competition. I like the integration it has with the Xanbus network, everything at on control panel, it really is one slick system

    And full disclosure, I don't work for Xantrex
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Charge Controller Question

    i do agree that the fcc has been shirking their duties and have even changed what their duties are so as to encompass the selling of frequencies for profit, banned us from monitoring some frequencies that cross our properties, and were even attempting to enlist an internet vehicle called broadband over power lines that would've spewed rfi over large areas and spectrum. btw, the bpl was stopped by hams in the courts and this is about as far as i can talk of this without involving politics.
    this ends my side rant on the subject of the fcc.
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