ready, fire, aim...ooops!

bobdog
bobdog Solar Expert Posts: 192 ✭✭
Well, I thought I had this stuff down and had made all the right decisions 2 years ago and now I'm thinking I didn't think far enough in advance. I would simply like your thoughts on my situation and I will appreciate all of them.

I have 2 Kyocera 130 watt panels, running in parallel at 17.6 Mpvolts, 7.39 Mpamps; in to a Mornigstar prostar 30 12/24 volt CC (running at 12 volts) all into a (4) 6 volt GC batteries para/series at 12 volts. I run a MSW 750 cheapy and just purchsed last summer a 300 watt Morningstar Suresine wave inverter[never used] (both 12 volt).

Here's my quandry(ies):

1) I'm under charging my batteries first off. Esp. early/late in the season (spring/fall). I say this after reading some recent posts on charge rate, battery to panel sizing, etc. I also "think" I'm running my genset + AC charger too long and too often during these times. SO my thought is I need another panel. Maybe a KD135sx which is the replacement for the ones I have. Is this true?

2) After said reading, am I right in thinking that if I was to go 24 volts instead of 12, I would be better off at the batteries? My reasoning may be off so please tell me if I will "have more energy" from my batteries and my panels at 24v verses 12v. I have plenty of big wire for the run right now so that is not an issue. But, in addition to another panel, I feel I need another battery pair. If I up the system voltage to 24 wouldn't I eleminate the need for either?

3) The down side to just switching over are 2 fold. A) I already own 12 volt equipment (inverters, charger, a few lights, etc.) and would have to buy at minimum a 24 volt inverter. B) How would I run 12 volt lights, etc.???

I'm really sorry for bothering you with this as I thought I had figured it out 2 summers ago. But, the more I have read recently, the more I realize I don't understand and didn't then either.

Thanks for your help.

Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: ready, fire, aim...ooops!

    "ready, fire, aim...ooops! "

    Looks like your doing it again...

    Any conversation needs to start with the loads on the system.

    Without that information the discussion is 2 Kyocera 130s are perfectly capable of keeping 2 6v golf cart batteries charged! ( if there are no loads)

    Even here I assume you have good sun exposure and they aren't mounted to the trunk of a live oak...lol.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: ready, fire, aim...ooops!

    bobdog,
    you are a bit over the 3% mark for charging and that is ok if allowed to charge over time. if you find your batteries are low then you are drawing out more than what is going in. pretty simple cause and the solution is to get enough in pv to handle your loads and achieve a better charge %.
    there won't be much advantage for the 24v system if you have to buy all new stuff and i assume you have run the calculations for voltage drop.
    http://forum.solar-electric.com/showthread.php?t=29
    if the v drop is over 3% there may be an advantage to lowering the %, but it may be best suited with heftier wire going shorter distances. keep in mind that the pvs would also need to be setup for 24v operation too so 2 pvs in series would be needed for a 24v battery system. that means you couldn't add just 1 kd135, but you'd need 2 in series to make the 24v needed.
    you may parallel that kd135 pv and if using the same wires back to the controller keep in mind that this added current could cause the v drop % to be worse so pay more attention to the wiring while adding another pv.
    there is also a limit for the current on the controller and if you add more current than the controller can handle that you may need to add another controller that can either handle more current or parallel more than 1 controller making sure that all pvs are not shared as each controller should have its own pv system running to it.
    i hope this isn't confusing to you.
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!

    My current, absolute maximum loads in the spring and fall per day are:

    AC:
    Heating blanket = 200 watts x 8 hours

    Lights:
    3 x 24 watt x 6 hours
    3 x 13 watt x 5 hours

    Crockpot = 200 watts x 4 hours
    Computer = 80 watts x 5 hours
    Answering machine = 8 watts x 16 hours


    DC
    Lights: (9) 12 volt lights x 25 watts x 4 hours


    Batteries: (4) 6 volt (210ah) in 2 parallel strings; so, running @ 12 volt (420ah)
    (1) 12 volt (105ah) marine "deep cycle" (mainly for a boat)

    Panels: (2) Kyocera KC130 (17.6 Vmp, 7.38Imp)

    Tim
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: ready, fire, aim...ooops!

    yes, you are undercharging the batteries and more pv will help, otherwise you need to keep running a generator to handle the extra loads.
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!
    niel wrote: »
    bobdog,
    you are a bit over the 3% mark for charging and that is ok if allowed to charge over time. if you find your batteries are low then you are drawing out more than what is going in. pretty simple cause and the solution is to get enough in pv to handle your loads and achieve a better charge %.
    there won't be much advantage for the 24v system if you have to buy all new stuff and i assume you have run the calculations for voltage drop.
    http://forum.solar-electric.com/showthread.php?t=29
    if the v drop is over 3% there may be an advantage to lowering the %, but it may be best suited with heftier wire going shorter distances. keep in mind that the pvs would also need to be setup for 24v operation too so 2 pvs in series would be needed for a 24v battery system. that means you couldn't add just 1 kd135, but you'd need 2 in series to make the 24v needed.
    you may parallel that kd135 pv and if using the same wires back to the controller keep in mind that this added current could cause the v drop % to be worse so pay more attention to the wiring while adding another pv.
    there is also a limit for the current on the controller and if you add more current than the controller can handle that you may need to add another controller that can either handle more current or parallel more than 1 controller making sure that all pvs are not shared as each controller should have its own pv system running to it.
    i hope this isn't confusing to you.

    The 3% charge is about what I figured as well. It bothered me hence my OP. With prices likely to drop on panels, I will likely purchase a KD135 down the road to bring up the charge rate. I would like to be in the 10% range.

    Thanks for clearing my head on the 24 volt issue. I was under the assumption I would get more power if I had a 24 volt system, and yet that didn't make sense.

    I did do the calculation on V drop last summer and then just now. I am around 1.2% so below the 3%. With adding another panel it still stays under 2% so adding a panel should be fine in parallel of course. Hadn't thought about the even numbers for series strings.

    Thanks for the help.
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!
    bobdog wrote: »
    My current, absolute maximum loads in the spring and fall per day are:

    AC:
    Heating blanket = 200 watts x 8 hours

    Lights:
    3 x 24 watt x 6 hours
    3 x 13 watt x 5 hours

    Crockpot = 200 watts x 4 hours
    Computer = 80 watts x 5 hours
    Answering machine = 8 watts x 16 hours


    DC
    Lights: (9) 12 volt lights x 25 watts x 4 hours


    Batteries: (4) 6 volt (210ah) in 2 parallel strings; so, running @ 12 volt (420ah)
    (1) 12 volt (105ah) marine "deep cycle" (mainly for a boat)

    Panels: (2) Kyocera KC130 (17.6 Vmp, 7.38Imp)

    Tim


    If I did the math correctly, I end up with a maximum of 4419 watt*hours of use. If I have 6300 watt*hours of battery juice, then DOD is 70%? Is that right? I've never seen that on the CC monitor. Where am I going wrong here?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: ready, fire, aim...ooops!
    bobdog wrote: »
    My current, absolute maximum loads in the spring and fall per day are:
    In general, maximum load calculations way over estimate your true daily power loading... Highly recommend the Kill-a-Watt meter to measure the WH/kWH per day load for each major usage (or you can group ones than run in consistent sets). For DC loads--look at a cumulative Amp*Hour / Watt*Hour meter like one of these.
    AC:
    Heating blanket = 200 watts x 8 hours=1,600 WH

    Lights:
    3 x 24 watt x 6 hours = 432 WH
    3 x 13 watt x 5 hours = 195 WH

    Crockpot = 200 watts x 4 hours = 800 WH
    Computer = 80 watts x 5 hours = 400 WH
    Answering machine = 8 watts x 16 hours = 124 WH

    DC
    Lights: (9) 12 volt lights x 25 watts x 4 hours = oops-wrong, but unsure which is correct:
    • 9 * 12 * 25 * 4 = 10,800 WH
    • 12 * 25 * 4 = 1,200 WH --- I think that this is the value you intended
    Total daily load = 4,751 Watt*Hours per day

    That is a lot of power--If I really try to conserve power on my suburban home I can get down to near that usage (2 adults, 2 kids, fridge, washer/drier/computers/TV/etc., natural gas for heating, hot water, cooking...)

    So--estimated panels for spring/fall. Using PV Watts website; 1kW of solar panels (even number), 0.52 derating (off grid, AC power), rest defaults for Albuquerque NM (nothing really close to you):
    "Station Identification"
    "City:","Albuquerque"
    "State:","New_Mexico"
    "Lat (deg N):", 35.05
    "Long (deg W):", 106.62
    "Elev (m): ", 1619
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 35.0"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 8.7 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 5.33, 84, 7.31
    2, 6.06, 84, 7.31
    3, 6.44, 99, 8.61
    4, 7.16, 102, 8.87
    5, 7.40, 105, 9.13
    6, 7.10, 95, 8.27
    7, 7.13, 98, 8.53
    8, 7.02, 98, 8.53
    9, 6.71, 91, 7.92
    10, 6.55, 97, 8.44
    11, 5.73, 85, 7.40
    12, 5.14, 81, 7.05
    "Year", 6.48, 1119, 97.35
    Let's call it 91 kWhrs per month per 1 kW of solar panels running an off grid system during September...
    • 4.751 KWH per day * 30 days * 1/91kWH per 1kW of panels = 1.56 kW of solar panels for 9 months of year
    Working the other way, your 2x130W=0.26kW of solar panels based on the above data:
    • 91 kWhrs per mnth per 1kW panels * 1/30 days * 0.26 kW panels = 0.79 kW = 790 Watt*Hours per day for September
    So--There is a big disconnect there... My guess is that you are not using near as much power as you think.

    Also (in my ever so humble opinion), you need to conserve your power usage (change DC power to LEDs or CFLs on AC inverter; change slow cooker to propane, solar oven, and/or Thermos based--very popular in Asia; look for 20 watt computer; get voice mail on phone line; use more blankets and turn off E-blanket after you warm up bed; etc.).

    Or, you need a lot more solar panels.
    Batteries: (4) 6 volt (210ah) in 2 parallel strings; so, running @ 12 volt (420ah)
    (1) 12 volt (105ah) marine "deep cycle" (mainly for a boat)

    Panels: (2) Kyocera KC130 (17.6 Vmp, 7.38Imp)
    Battery sizing... Basic rule of thumb is enough capacity for 3 days of no-sun and 50% maximum discharge (normal use--for long life):
    • 420 AH * 12 volts * 1/3 days * 0.50 max discharge = 840 Watt*Hours per day
    Which is a bit undersized for the existing solar panel power output for September of 790 WH per day.

    The other way to look at battery bank sizing is to set the charge rate to 5% to 13% of the C/20 AH capacity of the bank:
    • 420 AH * 0.05 = 21 Amps
    • 420 AH * 0.13 = 54.6 amps
    • 2x 7.38 A of solar panels / 420 AH = 0.035
    As long as your "average maximum loads" are less than C/10:
    • 420 AH * 1/10 * 12 volts = 504 watts or so
    Then, your current 12 volt bank/inverter strategy is OK.

    If, however, your loads are over ~1,200 watts or so (vacuum cleaner, hot pot, computer, lighting, etc. all on at the same time)--then you should look at a 24-48 volt bank, and a bigger battery bank too...

    -Bill

    PS: Fixed daily load addition and solar panel to 1.56 kW for September.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!
    BB. wrote: »
    deleted quote of my post--embarrassing math error.

    Also, no need to quote entire posts...

    -Bill
    :blush:

    Thanks BB. I will study this sheet very carefully. This is just what I needed to show me where I am, need to be and why. I hear alot on this site that people way UNDER estimate their power usage and so I tried to way OVER estimate it. Never would all those items be running at the same time or even running at all (DC lights are back up for inverter failure). However, good suggestions on the Crockpot and E-Blanket and other areas at which to look.

    Tim
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: ready, fire, aim...ooops!

    Tim,

    By the way, I fixed a calculation error... I will delete your quoting of my post to avoid the math error propagation/confusion. :blush:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RandomJoe
    RandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: ready, fire, aim...ooops!

    Your heaviest loads listed aren't usually going to be constant loads either, probably a large portion of the difference. The electric blanket will have a thermostat in it to cycle on/off to maintain your temp setting. I would assume a crockpot does as well, although I've never used one so am not sure. So they won't be drawing power for part - perhaps even most - of the time once they are up to temp.

    The Kill-A-Watt is an excellent way to accurately gauge loads. I found the nameplates for almost everything I measured were well over what the devices actually pulled in operation.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: ready, fire, aim...ooops!

    I have nothing to add to this thread,, except to say,,, I love the title! Some one finally is man enough to admit to what nearly all of us do! (I just like the phrase,,,, as you all well know!)

    Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Which Battery types?

    I forgot to add some information about Thermos Cooking...

    Here is one site that uses a standard wide mouth thermos to cook grains:

    www.thermoscooking.com

    My wife (and many other Asians) really like to cook stews, meats, and such in these ~4.7 QT thermos cookers. There is a stainless "pot" inside that you throw all your food in and fry the meats, boil the liquids--then put the whole thing in a thermos container and let sit for a few hours (sometimes, for cooking stew meats, I will reheat and let sit again).

    I don't know why they appear to be so difficult to find (Target, Amazon don't appear to have any)... If you have a local Asian market nearby--you might find them there too.

    They are not cheap ($100 or so?)... But very nice for what they do.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: ready, fire, aim...ooops!

    Moved above post about Thermos cooking to the intended thread (this one) about reducing crockpot cooking load on PV system.

    -Bill :blush:

    maybe I should just delete all this off-topic post here and the comments pointing out how dumb I was and pretend that this never happened... :roll:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!
    BB. wrote: »
    Moved Thermos cooking post to the intended thread about reducing crockpot cooking load on PV system.

    -Bill :blush:

    Where is that thread Bill? and what was the math error? You can PM if you like. Thanks.

    Tim
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: ready, fire, aim...ooops!

    Tim,

    Are you playing mind games with me? Or have I gone nuts...??? :confused:

    I moved the thermos post here and intended to offer it as a partial alternative to crockpot cooking... I had two tabs open into the forum and posted my thermos cooking suggestion to the wrong thread (as 12 people kindly pointed out in the other thread :roll: ).

    And this is the thread were I corrected my math/multiplication error... i think... I make so many of them... In the DC load section, I had typed 1,800 WH instead of 1,200 WH--but there was also the question of what the "(9)" meant... was it just saying there were 9 lights at 25 watts total or should it be 9 times 25 watts worth of lights (that second one did not seem right):
    DC
    Lights: (9) 12 volt lights x 25 watts x 4 hours = oops-wrong, but unsure which is correct:
    • 9 * 12 * 25 * 4 = 10,800 WH
    • 12 * 25 * 4 = 1,200 WH --- I think that this is the value you intended

    I think I have shoveled and covered my mistakes... There is always tomorrow. ;)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: ready, fire, aim...ooops!

    "I think I have shoveled and covered my mistakes... There is always tomorrow. ;)"

    is that nuts or just getting older like the rest of us old coots? welcome to cooterville.:p hey cariboocoot, do you want to be mayor?:cry::p i can be treasurer and forget where i put the $.:roll:

    good one for my 4000th post, eh?
  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Which Battery types?
    BB. wrote: »
    I forgot to add some information about Thermos Cooking...

    Here is one site that uses a standard wide mouth thermos to cook grains:

    www.thermoscooking.com

    My wife (and many other Asians) really like to cook stews, meats, and such in these ~4.7 QT thermos cookers. There is a stainless "pot" inside that you throw all your food in and fry the meats, boil the liquids--then put the hole thing in a thermos container and let sit for a few hours (sometimes, for cooking stew meats, I will reheat and let sit again).

    I don't know why they appear to be so difficult to find (Target, Amazon don't appear to have any)... If you have a local Asian market nearby--you might find them there too.

    They are not cheap ($100 or so?)... But very nice for what they do.

    -Bill
    Bill Your post about the thermos cooking gave me an idea to save some electric. I got to run the kilowatt meter on the coffee pot that is on about 3 or 4 hours in the morning. I bought an insulated thermos carafe. Just make the coffee and dump in the carafe and turn off the coffee pot. S:Dlarvic
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: ready, fire, aim...ooops!

    SolarVic,

    Yep--Thermos is a good deal for conserving power... One minor suggestion--I know many folks like their coffee really hot (I don't drink coffee--So I cannot attest to anything coffee related :roll: )--Put a little boiling water into the thermos first, slosh around, and dump... Then put in your hot coffee--will be much hotter for much longer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bobdog
    bobdog Solar Expert Posts: 192 ✭✭
    Re: ready, fire, aim...ooops!
    BB. wrote: »
    SolarVic,

    Yep--Thermos is a good deal for conserving power... One minor suggestion--I know many folks like their coffee really hot (I don't drink coffee--So I cannot attest to anything coffee related :roll: )--Put a little boiling water into the thermos first, slosh around, and dump... Then put in your hot coffee--will be much hotter for much longer.

    -Bill

    I drink lots of coffee and I agree with you Bill. A little hot water for a minute or 2 and then the coffee makes it stay hot for longer.

    As far as the Thermos link, I apologize. I was corn-fused.

    Tim