My New system comments.....

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adas
adas Solar Expert Posts: 136 ✭✭✭✭✭
in General Solar Power Topics #1
Aloha, as you probably read from my recent posts, I am putting together my warehouse/fabrication system with the specs below.

Should I have any special considerations in putting together my system with regards to the following uses:
The mig welder may be drawing 2.5k on and off on and off as the arc is struck. Another worker may be using a sawsall, another 2 using 4 1/2 grinders going on and off all the time. There may be moments when 0 watts are drawn and another when 4000 watts are being used variously over a period of 8 hours.

So since I will be working during the day, most of the wattage will be taken from the 48 x 70w panels with the batteries being used as a "buffer or reserve tank". I figure the high demand of electricity should keep the MX-60's in constant "absorbing", but will the varying loads cause the sweeping mmpt of the MX-60 screw things up, ie: if the sweep is done at high loads and then the loads go down to "0" will the mx compensate to "no need to charge now". Or if a sweep happens when "0" watts are used and then a 4k load comes on will the mx-60 kick in?

thanks
Frank

Warehouse System (in Progress) 3360w-4200w * BP 48x70w (expand to 60) * 3xMX60's * 3 or more 850AH 24v Batteries.(Used Forklift Type)
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #2
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    Re: My New system comments.....
    I figure the high demand of electricity should keep the MX-60's in constant "absorbing", but will the varying loads cause the sweeping mmpt of the MX-60 screw things up, ie: if the sweep is done at high loads and then the loads go down to "0" will the mx compensate to "no need to charge now". Or if a sweep happens when "0" watts are used and then a 4k load comes on will the mx-60 kick in?
    Frank,

    Any charge controller will start the day in its bulk (MPPT) mode. Depending on the battery bank’s state of charge, the array size, the weather, and loads, it may reach its absorb target voltage during the day and then switch to absorb mode. Once the absorb mode is complete, it’ll switch to float mode. The charge current (and therefore charge power) won’t drop to zero until the Sun sets.

    If the battery load is switched from essentially zero to, say, 4 kW, the battery voltage will drop and the controller will respond accordingly by selecting the correct charging mode for that voltage. Similarly, if the battery load is dropped from 4 k to zero, the battery voltage will rise, and, again the controller will respond accordingly by selecting the correct charging mode for that voltage.

    In short, the controller will “do the right thing” in dynamic conditions, be they environmental or loads.

    HTH,
    Jim / crewzer
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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #3
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    Re: My New system comments.....

    Quote from Jim:

    The legacy MX60 does not include dynamic / active MPPT. It's still uses the periodic "sweep and sleep" MPPT algorithm. The new FLEXmax 80 and the XW include dynamic / active MPPT.

    Jim, How often does the MX60 sweep? How long does it sleep, and does it wake up as a result of a changing load or after a set period of time? If the load size varies often, it seems to me that the MX60 would seldom compensate properly for the size of the load. If that's true, then I wouldn't want to settle for anything less than dynamic/active MPPT.

    John
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #4
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    Re: My New system comments.....

    John,

    The “sweep and sleep” description is something of a misnomer, as the controller doesn’t really “go to sleep” during normal daytime operating conditions.

    Rather than “sweep and sleep”, a more accurate description of the MX60’s MPPT function might be “periodic sweep”. The “sleep” term was somewhat derisively chosen because the MX60 is not operating in active MPPT mode between the end of a sweep and the start of the next period. The only time the controller truly “goes to sleep” is when its output current falls below a user selectable value of between 0.2 and 1.0 A.

    In short, while operating in Bulk / MPPT mode, the MX periodically sweeps the array looking for the combination of array voltage and current that produces the highest output charge current to the batteries. It basically holds the array voltage setting for the duration of the period. The sweep interval can be user set from between 0 and 15 minutes. Dynamic environmental conditions may result in less than optimal performance until the next sweep occurs.

    While operating in absorb or in float modes, the MX60 does not operate in MPPT mode at all. Instead, it operates in PWM mode to maintain target battery voltage by limiting charge current. This is not an operational limitation of the MX60. The TS-45, TS-60, Xantrex XW, OutBack FLEXmax80, and Apollo T-80 all operate in essentially the same way.

    The MX60 also does not operate in an active MPPT mode when the controller output current is < 5 A. Instead, it sets the array voltage at the “U-Pick %”of array Voc. Although not really at all active, it’s still a useful form of MPPT, and the result is usually higher output current than what would be available from a PWM controller.

    Finally, since the controller isn’t ever “asleep” from the perspective of this discussion, it doesn’t really ever have to “wakeup” when conditions change. If the battery load increases dramatically, the battery voltage will drop and the controller will respond accordingly by selecting the correct charging mode for that voltage. For example, if might switch from absorb mode back to bulk/MPPT mode.

    I hope this additional information is useful to. See the following old posts for additional reading:

    http://forum.solar-electric.com/showthread.php?t=1470
    http://www.outbackpower.com/forum/viewtopic.php?f=9&t=2333

    HTH,
    Jim / crewzer
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: My New system comments.....
    adas wrote: »
    The mig welder may be drawing 2.5k on and off on and off as the arc is struck. Another worker may be using a sawsall, another 2 using 4 1/2 grinders going on and off all the time. There may be moments when 0 watts are drawn and another when 4000 watts are being used variously over a period of 8 hours.


    What about the possibility of using air tools, and a compressor running off your solar? That will make motors MUCH happier, and inverters don't like seeing huge surges & spikes. I'd hide the welder behind a 1:1 transformer with some power conditioning, and that may help save the inverter from it's noise spikes. You are trading a huge battery bank for a huge air tank, tool oilers, and hoses instead of power cords.

    Also, with a compressor, you can easily plumb in another power source - like a gas powered pump, in case solar is wimpy that day. If you have gird power, switch to time-of-use plan, and use an electric compressor to pump the tank up at nighttime rates
    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 ,

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  • Telco
    Telco Solar Expert Posts: 201 ✭✭✭✭✭
    #6
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    Re: My New system comments.....

    I agree with Mike on the air compressor, an air compressor with a very large tank will be much friendlier to the electrical system. The compressor can be a soft start, and will just run when the air tank gets to a certain PSI of pressure. Air hose can be routed anywhere, and an air powered grinder works better than an electrical one. The air grinder will run quieter, cooler, and can safely be used in a wet environment. This will also mean that you will occasionally have a single load on the electrical center drawing wattage rather than several high draw motors cycling constantly. The air compressor might draw more power than a couple grinders will, but will also draw its power constantly whether the grinders are running or not. This means the peak draw at any one time will be lower. And, provided you shut down at 5PM every night, there might be enough power from the panels at the end of the day for the air tank to charge to its max set PSI for a full air charge the next morning.
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  • adas
    adas Solar Expert Posts: 136 ✭✭✭✭✭
    #7
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    Re: My New system comments.....

    Aloha, good one on the air.. I was going to go air in the future anyway as It is much better I think. we burn out a 4 1/2 grinder at least every 2 weeks, no matter what brand. Probably use a very large tank or 2 and a SMALL compressor that will be on most all the time and a larger one to help out when the loads are heavy.

    frank
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