Need help please, in selecting new charge controllers for an upgrade.

bethbeth Solar Expert Posts: 32
I have a 24v inverter (trace sw) and 12 Unisolar 12v 64w panels, (battery bank & generator)
I am going to add 10 Solarworld 24v 235w panels.
I want to install two new MPPT charge controllers, and would like some suggestions as to which controllers to buy, and what voltages to wire my strings to. (I will be rewiring my old panels) (the panels will be close to the inverter about 30')

Other thoughts, questions I am having are:

Will the controllers work separately or do some brands work together (so will I be setting up and monitoring the two controllers individually)

How and what's the best way to wire them.

I want to get a battery monitor and are there any issues with two charge controllers.

I was thinking about two Outback flex 80 amp units, if I use two of these do I need their Hub.

Thank so much for all the help!

Comments

  • bethbeth Solar Expert Posts: 32
    Re: Need help please, in selecting new charge controllers for an upgrade.

    Well Beth I guess no one want to help you with this.
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Re: Need help please, in selecting new charge controllers for an upgrade.
    beth wrote: »
    I have a 24v inverter (trace sw) and 12 Unisolar 12v 64w panels, (battery bank & generator)
    Regarding the Trace SW inverter--Is this unit being repaired by anyone these days? Almost any electronics over 10 years old is impossible to get parts for (IC's, Microprocessors, memory, etc.).

    If you are going to put a lot of work into the system--you may wish to review your options (new inverter now, or plan for a new one in the indefinite future).
    I am going to add 10 Solarworld 24v 235w panels.
    I want to install two new MPPT charge controllers, and would like some suggestions as to which controllers to buy, and what voltages to wire my strings to. (I will be rewiring my old panels) (the panels will be close to the inverter about 30')

    If you are looking at a new inverter--you may want to look at a 48 volt system... One of the advantages is that you will only need 1 new MPPT 60 amp charge controller to manage this array, instead of 2x at 24 volts.
    Will the controllers work separately or do some brands work together (so will I be setting up and monitoring the two controllers individually)
    The different MPPT (and PWM) can all connect to the same battery bank and effectively charge the bank without issue (assuming all of the controllers have the correct charging voltages/times programmed).

    Many of them offer networking to allow one controller manage/display various settings and readings (many require a computer or "added box" to set details like slightly different charging voltages and such).

    I am certainly not the expert here, but perhaps somebody else can say what brands/models/options they liked for monitoring their charge controllers.

    The new MorningStar 60 amp MPPT charge controller has an internal webserver and is really a nice sounding unit too (functional, efficiency, etc.). I personally would probably look at that model first (read the installation manual) and see if it does what you would like.

    As always, recommend the remote battery temperature sensor, and for the MorningStar models that have it--install the remote battery voltage sense leads.
    How and what's the best way to wire them.

    If this is the correct Solar World 235 watt panel rating:
    Pmax @ STC 235 W
    Pmax @ PTC 212 W
    Vmp at Pmax 29.3 V
    Imp at Pmax 8.02 A
    Voc @ STC 37 V
    Voltage change -136 mV/C

    If you stay with the 24 volt battery bank, you can have either two or three panels in series (with the MorningStar, Xantrex, and Outback 60+ Amp MPPT charge controllers).

    If you go with a 48 volt bank, only three Solar World panels in Series will work per string (and they will work fine).
    I want to get a battery monitor and are there any issues with two charge controllers.

    You are only charging one battery bank. Normally, you put the Shut Resistor (to read current) to the negative battery terminal (or common bus), and the other end of the shunt is the ground return.

    This is done so that all charging and discharging current goes through the shunt resistor so that you are monitoring the entire energy flow through the battery bank.

    That you have one, two, or more, charge controllers will not change how a battery monitor works for you.
    I was thinking about two Outback flex 80 amp units, if I use two of these do I need their Hub.

    I am not sure you need a hub--but it is probably pretty handy for detailed programming and sharing of charge controller states (both controllers will change between Bulk, Absorb, and Float at the same time; Also, only need 1 remote battery temperature sensor as you can share it among all charge controllers sharing a hub/network).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • VicVic Solar Expert Posts: 2,975 ✭✭✭✭
    Re: Need help please, in selecting new charge controllers for an upgrade.

    Bill, Think that the data for the SW 235 that you posted is close to the data from the Data Sheet, BUT the data that is listed on that DS is :

    STC
    Vmp 30.3 V
    Imp 7.77 A
    Voc 37.5 V

    NOCT
    171 W
    Vmp 27.5 V
    Imp 6.22 A

    An as you were questioning, it is not really a 24 V panel, but that is just a nit.

    Beth, Bill has very good advice, as usual ... I am strongly considering waiting (a few more months from the looks of things) for the Midnite Classic Charge Controller. Which appears to have a number of useful functions. You may have no use for this functionality, and waiting a few more months may not work for you.

    The recent additions to the MPPT CCs seem to lack some of the extended functions of the OB models -- both the Xantrex XW SCC, and the Morningstar TS MPPTs seem to lack an Auxilary output. This might be of no use to you, at least initially, but would be missed by folks like me.

    ENUF for now, Good Luck Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • bethbeth Solar Expert Posts: 32
    Re: Need help please, in selecting new charge controllers for an upgrade.

    Thanks so much guys for that !!!!!
  • bethbeth Solar Expert Posts: 32
    Re: Need help please, in selecting new charge controllers for an upgrade.

    Bill I was just mulling over your advice about upgrading to a 48V inverter, and then I would need only one charge controller. I understand that , but would the MPPT optimization work OK with the two types of panels. How would I set up my strings in that case. Like may be, six strings each containing 2 new 235 w panels and 2 old 64w panels?
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Re: Need help please, in selecting new charge controllers for an upgrade.

    What is the exact Vmp/Imp of the two differing panels (plus name and model number would be handy)?

    Your "ideal" String with the Solar World on a 48 volt system would be three panels in series to get the correct Vmp-array voltage...

    Two panels is not high enough voltage to charge the battery bank in all conditions (hot water, cool batteries). And four panels will over voltage the controller on cold winter days.

    The 64 watt panels--Ideally, they would add up their Vmp (2/3/4/etc. in series to reach ~Vmp of 90 volts) voltages such that the Vmp-64watt panel voltage is withing ~10% of the Vmp-235watt panel array voltage (three in series for 48 volt bank).

    In many cases, it is very difficult to mix and match different solar panels correctly... Sometimes the only way is to use a second PWM or MPPT type charge controller for the second set of panels... And that extra cost may not be worth it (sell the panels to somebody else and get a couple more Solar World Panels and install them instead).

    Sorry about not answering before--Have been pretty busy the last few days and I am not the expert in off-grid systems here--There are others that have more experience than I and I don't want say too many dumb things in one day. ;):p

    -Bill "been there, done that" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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