Oops, Am I moving the wrong direction?

miketmiket Registered Users Posts: 12
Oye!!

I'm off grid for the last several years with pretty good success, I have the following setup:

One DR 2412 inverter
Four Trojan L-16 HCs connected for 12 volts
One Outback MX60.
Eight KC 130 panels connected in two 48 volt arrays.
One TriMetric display.

I have no 240 volt equipment my water pumping is all solar.

this is a brief look at my performance.

My average power consumption is about 400 watts per day this time of year and I get about 600 to 700 watts of charge by the readout on the MX60 before it goes into float. in the summer my consumptin is higher but my collection and track each other pretty well.

I required a run of my Diesel Battery charger just twice last year due to extended stormy weather. In both cases I was down to 80% charge after 4 days. I got some solar each day but not enough to keep up.

I've decided to upgrade my system with a Magnum MS4024 pure sine wave inverter. and Midnite Solar enclosure.

Since I'm going to a 24 volt system, my charging will start later as I wait a bit longer to get to 24 volt output off the MX60 to begin charging.

What is the concensus? Am I making a step backwards in efficiency or is it a wash? I've gotten pretty used to not having to add much power to my system with the generator?

The long term goal here for growth is to further increase my system capacity and the next phase is to add more PV to about 1500 watts from the current 1000 and increase my battery bank to about 20000 watts from the current 10000 watts.

What say ye?

Mike

Comments

  • hillbillyhillbilly Solar Expert Posts: 334 ✭✭✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    I'm not sure about the waiting longer for the charger to have (higher than) 24v output to begin charging. I don't think that would be the case at all, and not a factor... I'm no expert here, maybe I am missing something. From our own system, the PV voltage is fairly high right away, it's the current that takes a bit to come up to full output.
    I would think that it wouldn't change your overall power output much at all, other possibly being very slightly more efficient at down converting from a 48v array to a 24v battery bank (vs 48v>12V).
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    Please clarify,,

    Are you using 400 watt HOURS/ day?

    Are you charging to 600-700 Watt HOURS/day?

    It seems if you are only using 400 wh/day yet you have 1kw of charging you have way more panel capacity than you need. A great place to be, IMHO. I wish that I had 1kw of panel with only 400 wh of use! I have 200 watts of panel, with 4-600 wh/day of use.

    Tony
  • miketmiket Registered Users Posts: 12
    Re: Oops, Am I moving the wrong direction?

    Icarus
    Yeah, I'm probably a little overpowered :-)! In the summer I use more to run the evaporative cooler. In the summer I get to float fairly early in the afternoon but this time pf year It is the last sun of the day before I have a full charge. I also have a lot of panel shading so insolation suffers, ESPECIALLY this time of year. I just hate to cut my beautiful trees.

    Hillbilly (Mountain William?)

    Yes, you are exactly right on the current. WATTs is WATTs regardless of voltage, I recall. Thanks for joggin my memory.

    I've been growing things in phases the last couple years as money comes available. I'm growing the thing to be FULLY self sufficient when I retire and work each day in my little guitar building shop downstairs. Soon, I hope!

    Mike
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    So is it 400 watt/hours/day?

    If so, that is incredible! I thought I was doing well with 400-600wh/day, with Propane fridge, and the genny for shop tools!

    Tony
  • miketmiket Registered Users Posts: 12
    Re: Oops, Am I moving the wrong direction?

    400 to 600 is a good range. I have all LED lights... and never more than two on at time. I use my computer maybe 20 minutes a day. I get up very early and go to sleep early as well.

    My son refers to me as the "Electricity Nazi"!!!

    My water tank is on the hill, so no boost pump needed. I may add one cuz I don't have enough water pressure for my washer to work. Buy more clothes?

    Propane Fridge for me too. Thinkin about a Sunfrost DC Freezer (chest type) with an add on electronic controller to make it run about 90 seconds an hour and maintain 34 to 38 degrees on 130 watts a day!!

    Yeah. The shop doesn't count since I have a Onan DKD 8 KW diesel there. Shops are fun let's splurge!

    Mike
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    Can you figure out a way to move the panels seasonally to take maximum advantage? Since you are running a mppt controller, you can get fairly far away from the batteries and run higher voltage with smaller wire.

    I have one pair of panels permanently fixed on the roof, and one pair wired with Anderson connectors, that I pull out on to the ice in winter to get past afternoon shading.

    (My wife calls me the electrical Nazi too). We live with a nice selection of 3-15 watt cfls, which put out a much warmer light. The radio is a big draw in our system, 1-1.5 amps for 18 hours/day. (12 vdc car radio with i-pod adapter and satellite receiver, playing through home speakers).

    Tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Oops, Am I moving the wrong direction?

    Sounds to me like you've got an excellent system to start with!
    I've got somewhat fewer panels, but have made the same switch from 12 to 24 and from MSW to TSW in order to accommodate motors. There is technically some charge time loss that comes from needing high PV voltage to meet the higher V batteries, but it wasn't very noticeable in my case. And I switched from 72 volt array (which was going over-volt in some conditions) to 48. There was also an increase in power consumption of the inverter itself.

    How many kW/hrs per day does your system produce? I would estimate in the neighborhood of 3? Do you really use less than half a kilowatt/hr per day? I'm envious! Sounds like you could add more battery capacity now, as is.
  • miketmiket Registered Users Posts: 12
    Re: Oops, Am I moving the wrong direction?

    Insolation at my location this time of year is probably 50% (or less) of optimum due to obstructions (less than 3 hours... but this is during peak hours). In the summer maybe 75 to 80% of peak insolation.

    I honestly don't think I have ever seen the actual peak system output because the batteries reach float early in the day and the MX60 tapers way back! I've seen daily output from the MX60 of 1.5 or 1.6 KW a couple times in the hot summer when I run the evaporative cooler to keep the house cools during the heat of the day. With 15 amps load, the MX 60 will keep up and end the day in float.

    I'm pretty thrifty 400 to 600 is pretty typical. I track things with my Trimetric which is just an amazing piece of technology that every RE system owner should have. When my son is home from college, 1800 watts is not at all unusual till I have to slap him down.

    I' ve look at at alternate panel locations and surveyed every possible location and the current is the best fixed location. I sweated so mny bullet getting them in place, that is the final location. I have Uniracs so I can adjust the tilt pretty easily, but generally leave them in the winter position -5 degrees as a compromise.

    mike
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    Even though it is not in most of our natures,,,,if it aint broke,,why fix it?

    Tony
  • miketmiket Registered Users Posts: 12
    Re: Oops, Am I moving the wrong direction?

    Very true!

    In nearly all respects, the system runs well and meets my needs. Just some fine tuning to accomodate future needs and tidy up the installation.

    Solar water heating is on tap for this year.

    Mike
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    Solar water heating is a snap,,,depending on where you live. I built a simple flat plate collector with a loop of ~200' of 1/2" copper sitting on a piece of 3/16 scrap steel, over 3"of thermax, all covered by 2 salvaged patio door (28"x76") tempered glass panels. A grunfos watt pump with a differential controller, all circulating into a salvaged 40 gallon electric water heater tank,, preheating a demand water heater. This is in a Pacific NW installation, and it provides about 20% of the hot water in mid winter,,but come March it nears 100%. Summer brings 150%. Total cost,,,~$400 maybe.

    Commercial flat plates would be more efficient, but way more costly. If you are in a freeze prone climate life gets more complicated. The controller I used ( http://www.azeltec.com/ )has a anti-freeze cycle that cycles the water through the collector if the temperature nears freezing. It kept this system from freezing at temperature ~10f with 40 mph wind! After two days, I had to run some fresh water into the tank from the well (55f) to warm it up, as the tank was getting near 40f. If you are consistently real cold a glycol/evacuated tube system would make sense. I also wired the elements of the water heater to a piece of #10 wire routed out of the house so that when the stand by generator is run, it heats the water.

    (This is not the house we live in shown in my picture, but a house we frequent now and again).

    Tony

    PS a 12vdc version of the pump controller can be had here: http://www.arttecsolar.com/ I can't remember if this one has a freeze protection system built in.
  • BB.BB. Super Moderators Posts: 26,837 admin
    Re: Oops, Am I moving the wrong direction?

    Solar panels do not generate significant levels of power until the get enough sun to make Vmp--In other words, I doubt that you will see any difference in when the 48v panel strings start/stop generating power for a 12 volt or 24 volt battery bank.

    You could use the wiring calculator to check your voltage drop from the solar panels to the charge controller. It is possible that wiring both strings in parallel will reduce the current, and lessen the power losses in your wiring.

    On the other hand, I understand that as you increase the input voltage to any MPPT type controller, you may lose a percent or so of power due to the higher input voltages...

    In the end, you probably could not measure the difference in power output without a lab setup.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • miketmiket Registered Users Posts: 12
    Re: Oops, Am I moving the wrong direction?

    Thanks Bill

    Ohm's law in practical application, eh? That wiring caulator has been my constant guide!!! A priceless piece of work!!

    As you suggest, I did wire both strings in parallel to minimize voltage drop when When I installed the the second array, my goal was for voltage drop to be well under 1% and it worked out that way (the original installation, as I bought the house, with was in excess of 20 percent!!!!).

    As the last year has shown, I have plenty of power, and require hardly any backfill from the generator.

    In fact, each of the two times I've run it in the last year, my charge was at 85% and the very next day I got a full sun day... total... 1/2 gallon of diesel for the year!!!

    I'm actually considering doing a discharge to 75% periodically and a full finishing charge to keep the batteries "limbered up". I've been told by reliable sources that I'm almost "floating" the batteries, which has it's own drawbacks over the long term.

    Thanks again!

    Mike
  • MoeMoe Solar Expert Posts: 60 ✭✭✭✭
    Re: Oops, Am I moving the wrong direction?

    Thanks to you all who are off-grid for posting your experiences. It would help me a lot putting them in perspective if you filled in your location in your profile (click User CP in the blue bar above, then click Edit Your Details, and scroll to the location (where you live) entry). Thanks to those of you who already do.
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