SW4024 gridtie

mikeomikeo Solar Expert Posts: 386 ✭✭✭
Got a PM from eMonitor but his profile allows no private PM's back.
so I will post it here so other may comment.
Mike


How come two mx60's for such a small set of arrays?
I would wire them into a combiner for just one mx60 if I were you in a 5 series 4 parallel or 4 series X 5 parallel array. Then you could add another 1600 watts to the second MX60 when you need it. Also you need to set the mx60 float voltage one full volt above the SW4024 float voltage. This depends on your particular battery banks needs of course, but I have mine set at 27.4 float on the SW4024 and 28.4 on the MX60. The float and sell voltage is set to the same 27.4 on the SW4024. I have 940 amp hour fork lift batteries. You might need to up the MX60 float a little more, you will just have to experiment with your particular equipment needs.
Regards
Mike

eMonitor wrote:
Hi Mike,

My setup from (2004) is:

1600W via 2 x (10x80Watt) AstroPower Panels.
2 x Outback MX60 charges controller
Trace SW4024 GTI
12 x 2Volt lead acid batteries

My setup has been offline for awhile - so all settings are now default - My Panels seams to charge the batteries fine - but I reach the Batt Full status fast =no SELL/net metering takes place.

I guess it's because the float difference between the MX60 & the SW4024 is not correct. Even though I had the system for a long time I just getting interested in fully understanding the settings.

I have a cool House circuits/PV monitoring system that should help me optimize the system - but I need to get started with the basics.

I will also post this public as well

Thank you in advance for any advice you might be able to give me.

Carsten

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: SW4024 gridtie

    We hiccup with Emonitor's profile--PM's and posting should be working for him now.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: SW4024 gridtie

    Thanks for the help!
    I will try those settings tomorrow (supposed to be sunny and VERY cold).
    I agree that's an overkill with 2 x MX60 - but that's what the installer recommended - I do consider adding additional panels soon.

    Thanks
    Again
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: SW4024 gridtie

    sorry about that as we do get it wrong occasionally.:blush:
  • System2System2 Posts: 6,290 admin
    Re: SW4024 gridtie

    Thank BB,

    I followed your recommendations and I am now "selling" - is there rule of thumb how high the Bulk value have to be compared to the float value (MX and SW)

    Thanks

    Carsten
  • BB.BB. Super Moderators, Administrators Posts: 31,171 admin
    Re: SW4024 gridtie

    Actually, that was Mike who help you...

    Niel and I where just working on your account in the back ground (part of the great spam control--Niel and I are like ducks--it looks like we are cruising around above the surface, but below the surface, we are paddling like crazy:roll:).

    Look at the SW like a "shunt controller"--It takes anything above XX.X volts and ships that out your AC power like (backfeeding the grid and providing local AC energy to your home). The "sell voltage" will effectively be the Float Voltage for your battery bank (as controlled by the SW settings).

    The Solar Charge Controllers should be setup to provide 100% of the available energy to the battery bank--and should only cut back if the SW fails to shunt the "excess" energy production to the grid.

    So, you should have the Solar Charge Controller's Bulk charging set to the maximum voltage recommended for your type of battery bank. And you should set the Float Voltage to Bulk Voltage too (or disable Float--depending on the controller's programming).

    If you set the bulk or float too low, the Solar Charge Controller will attempt to bring the voltage back down (float charging ~13.7 volts or so for 12 volt bank) and the SW will never turn on to produce power for the grid.

    I don't know how the SW works--But I believe it should monitor the battery bank itself, and if the voltage falls below ~12.7 volts (or equivalent) for a short period of time (such as during a power failure), the SW should go into "charge mode" and let battery bank voltage drift up to the SW's "bulk charge" setting until the battery bank reaches its 100% definition.

    Of course, when setting the Solar Charge Controller Bulk/Float to maximum (safe) rated charging voltage for the battery bank, if the SW fails to do Grid Tie operations for some reason--you will need to crank the SCC settings back down to "normal" until the SW issues are addressed to prevent overcharging the battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: SW4024 gridtie
    I followed your recommendations and I am now "selling" - is there rule of thumb how high the Bulk value have to be compared to the float value (MX and SW)
    Since you are grid tied, you can program the SW to bulk the battery's at a given time, usually at night, or early morning. I would use the battery manufactures recommended setting for float and bulk, as well as equalize and use the SW to maintain your batteries. Use your MX to keep the batteries between the float setting of the SW and the MX. This way all the solar power you produce during the day goes to feed your local grid load, any excess goes on out the utility line and the MX never goes to Float. So the answer is just set the bulk on the MX to the MX float which is at least 1 volt higher then the SW's float. In my case, I have designed an micro controller that actually shuts the SW down after the arrays are producing no useful power and turns on the SW when the arrays are producing more then 6 amps in the early morning. The SW's behavior is to start a BULK cycle when turned on and then drop to float. IHTH's
    Mike
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