I welcome devil's advocates (shoot holes in this idea)

unyalli
unyalli Solar Expert Posts: 121 ✭✭
The discussion is moving to a 24 volt system.

Bottom line, for 300 bucks I can add another set of 6 volt golf carts from sams-club and a Samlex SDC-30 24 to 12 volt 30 amp converter and keep my Sunsaver and run my Samlex PST-300 at a full 300 watts.

The long version. I've realized for my needs a 200 watt 15 amp system ain't gonna do it. I will be installing 3 Solartech SPM130P-S-N panels on my roof for a hopefully realistic 350 watt's of power. Wired in series I should see close to 7 amps at over 50 volts. This is to much for my poor honorable little Sunsaver MPPT 15L at 12 volts so I started comparing upgrade options. Caveat, this whole thins is a fun hobby/science experiment for me. I'm having fun with the details so among all the other things I want to measure my loads. Ok onward, I've narrowed down my options to a Bluesky 3024iL with IPNPro-s, Tristar MPPT 45 with full Pentametric 3 shunt system, or the Outback 60 with Flexnet and Mate2.

Bluesky option is around $650 - $700 with parallel wiring of panels so increased wiring cost.
Morningstar/Pentametric is around $850
Outback is a whopping $1000+

Then I had a thought, my Sunsaver could handle the panels in series if I went 24 volt. Hmmmm??? Can I trust everything to the Samlex? I can't find any verifiable problems with Samlex equipment. The whole thing would rely on the DC to DC converter. For less than half the price of my lowest option I would have 30 amps of 12 volt DC power at my disposal and the monitoring I want.

What am I missing?

Jeff

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    24 Volt system is a good idea. 15 Amps on 24 Volts: 300 Amp hours max, 150 is better, 220 right about middle (6.8% peak charge rate). Needs about 450 Watts of panel.

    Run Samlex PST-300 off a 24-to-12 converter? Not good; power use and loss of efficiency. One more thing to go wrong. At peak inverter power the converter would be running pretty close to max (25 Amps). Surge over and the converter could pop.

    Samlex has almost no surge capacity. Not good for anything with a motor in it. Better off changing out for 24 Volt inverter (equivalent: http://www.solar-electric.com/sa300wa24vos.html).

    BTW, Bluesky controllers aren't very good in my opinion. They have some odd In/Out conditions so check carefully before you buy one.
  • Eric L
    Eric L Solar Expert Posts: 262 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    I agree; assuming that 15 amps into a 24 volt battery (with 400-450 watts of panel) is the most you would ever expect from this set-up. IMO, the Sunsaver MPPT 15 is such a versatile little controller once you get it working with MSview and the programming functions that it's worth squeezing every amp out of it by going to a 24 volt system (which also significantly increases your battery capacity, as you've no doubt figured out).

    Remember that at the top of the charge cycle on a 24 volt bank, you'd likely be looking at over 28 volts which means that after losses, the Sunsaver's 15 amp capacity could theoretically make use of a 450 watt array, as 'Coot said.

    Investing in a good quality 24 volt inverter and more panels/batteries seems to me preferable to investing in a more much more expensive controller for such a small system.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    you have to be sure that under any and all circumstances that the pvs will never deliver 75v or more. this is the voc of each pv added together and refigured at the coldest temp for your location.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    Coot, I had alarms going off in my head with the converter/inverter idea as well. Theoretically should work but how much of a rube goldberg do I want here? Agree add to the cost another $160 for a 24v inverter. Now were up to $450 - $475.

    Coot and Eric L, the whole charge rate thing is one reason I started thinking my system was too small. If I'm guesstimating correctly I should see around 300 watts from this array on a 90 degree (F) calm day with the sun close to straight up roasting these panels. In absorb the sunsaver holds voltage at 15 on my 12 volt system so I'm assuming 30 on a 24 volt system. 300 / 30 is only 10 amps. Could take a long time to reach float.

    Coot, Bluesky is intriguing. I don't believe they've ever heard of the concept of series wiring. They reticently unleashed an all new high voltage version of there 2512i series that will handle a whopping 40 volts!!! :blush:

    Niel, recently with two of these panels in series I saw 44.8 volts at 4 degrees F. Is it safe to assume I would never see more than 45 volts from this pair? If so that is 22.5 per panel and three would max out at 67.5 (maybe 68?). Is this sound thinking?
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    What about the WFCO 8955 charger? What would I replace that with for the switch back to shore power times? With what I'm looking at in solar I will probably need something when on shore I would run at least once a month to do a full top off and equalize.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    Panel Voc goes up as temperature goes down. If the Voc on one panel is 22.5 then three in series would be 67.5. Visit Banff in Winter and it could be 86.5 and there goes the controller. As long as you stay away from cold climates (or switch one panel out at low temps) it would work. But it's a pretty close thing.

    You'd be better off to use four 130 Watt panels as two parallel strings of two. Yes, that's well above the MPPT 15's rating, until you account for performance loss: 520 Watts * 0.77 typical efficiency = 400 Watts (also, RV applications usually don't have ideal insolation). Maybe 16 Amps max, which the controller would clip to 15. Check with Morningstar on this, but I think it would work. No cold temp trouble, and some advantage in hot temps and less-than-sunny days.

    Of course you may not be able to fit four panels on the roof.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    go to the midnite solar site, http://www.midnightsolar.com/ and scroll down to the classic string sizing tool. this will show good pv configurations for other mppt controllers and not just the classic. for cheyenne it looks like a max low of about -34 f. other areas in the state are as low as -41 f. input all of the pertinent info and the temp point the classic enters hypervoc is the indicator if you are pushing things too far. a classic won't get damaged if it enters hypervoc, but morningstar just states this voltage is a max and i would imagine that it could be below that voltage on some of them as i doubt the point of damage is that exacting in every case.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    The little guy will rate limit but not sure how much.

    Attachment not found.

    As you can see the sweep was clipped to just under 200 watts and the charge output was clipped to 15 amps even though the array was producing over 200 watts. Subtract load from charge amps and I had just over 14 amps going to the batteries. I ran a 4.5 amp load over night to run the batteries down.

    This data is not from msview. It's from Tom's C code compiled and running on a Raspberry PI lunux box.

    Temps are Fahrenheit
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    Midnight's string calculator says in the unlikely event we hit -40 the little guy would activate over volt protection and disconnect the array until the voltage dropped.
    Attachment not found.

    The Midnight 150 lite ($500), Morningstar TS45 ($409), and Outback 60 ($515) would be happy but best I can tell none of them monitor load's so each would need a full 3 shunt Pentametric Ethernet system (another $420) to provide what I consider the necessary scientific data.

    Note: In most of Midnight's drawings they show a battery shunt but they don't connect kelvin leads to monitor it. I really like the Midnight and it's PC app but don't see how it can provide me battery status, in other words total system status. In my opinion they could make a version that was devoid all the "useless stuff" and add this and we'd be partying. As it is they would be nothing more than a TS45 to me.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    Note: In most of Midnight's drawings they show a battery shunt but they don't connect kelvin leads to monitor it. I really like the Midnight and it's PC app but don't see how it can provide me battery status, in other words total system status. In my opinion they could make a version that was devoid all the "useless stuff" and add this and we'd be partying. As it is they would be nothing more than a TS45 to me.

    Charge controllers are not battery monitors. Some of the wiring diagrams supplied with them nevertheless show where a shunt for a monitor would be placed. In the case of MidNite it's also in anticipation of an upcoming addition which will allow it to monitor actual battery SOC and control charging accordingly. I'm not sure how much data read-out will be available to the user from this (it is not necessary for it to separate Amps In and Amps Out to control charging; it only needs the balance of the end result).

    I have seen many controllers devoid of "useless stuff". Usually it is when the owner wants a replacement because the very simple version doesn't work worth beans for them.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    Useless dribble to satisfy forum rules
    Charge controllers are not battery monitors.
    They should be and the SSMPPT is. If I don't see the daily AHC go at least 5-10% over the daily AHL, and (with charge vs load near equal) battery voltage in the 13's I know I'm loosing ground. I should also see float.
    In the case of MidNite it's also in anticipation of an upcoming addition which will allow it to monitor actual battery SOC.
    This is interesting, I wonder how patient I need to be.
    I have seen many controllers devoid of "useless stuff".
    Did I strike a nerve here? I did say in my opinion and we all know what there worth. :DNow the monitoring via their web server is great. This means I can watch my system from anywhere via my Android phone! (Useless I suppose to some).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    It's just that a lot of people look at all the 'extras' on the high-end controllers and say "I won't need that, why should I pay for it?" and then later find out it would be nice to have. A prime example of this is the lack of display on Morningstar base units.

    Outback, btw, has a battery monitor that can be integral to their systems; the Flexnet DC: http://www.solar-electric.com/oupoflsymo.html
    It can monitor 3 shunts so you could watch IN/OUT of the battery, power to DC loads, power to Inverter, et cetera. Similar to the Pentametric but with 'extras' tailored to OB systems.

    Options. Always options.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    Outback, btw, has a battery monitor that can be integral to their systems; the Flexnet DC: http://www.solar-electric.com/oupoflsymo.html
    It can monitor 3 shunts so you could watch IN/OUT of the battery, power to DC loads, power to Inverter, et cetera. Similar to the Pentametric but with 'extras' tailored to OB systems.
    Oh yes, I'm aware of this. I would consider this the Lincoln Continental of what I would like. I don't know if the flexnet comes with this

    Attachment not found.

    or if its extra so the below cart may be short.

    Attachment not found.
  • Eric L
    Eric L Solar Expert Posts: 262 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    As you can see the sweep was clipped to just under 200 watts and the charge output was clipped to 15 amps even though the array was producing over 200 watts. Subtract load from charge amps and I had just over 14 amps going to the batteries. I ran a 4.5 amp load over night to run the batteries down.

    That's different from what I observed in MSView with an MPPT15L and a 270 watt array (12 volt bank), which definately did not clip output at 200 watts, but did clip it at 15 amps. I routinely got over 200 watts at higher charge voltages. Maybe that sweep value is showing that something else was going on that MSView didn't track, but it seems strange to me that the controller would try to limit both watts out and amps, since all it needs to limit is amps.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    I have an observation and this is not pointed at anyone specific. In fact its not pointed at anyone at all. When I started down this fun little solar road every and I mean every serious discussion on "going solar" started with first and for most determining power requirements. Why is it prior to buying anything the "A" number one priority is measuring loads but after your installed it's forgotten and possibly even forbidden?
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    When I started down this fun little solar road every and I mean every serious discussion on "going solar" started with first and for most determining power requirements. Why is it prior to buying anything the "A" number one priority is measuring loads but after your installed it's forgotten and possibly even forbidden?

    I really do not have any sense of this happening. There is a lot of discussion about the best ways to minimize and schedule your loads to get the most advantage from your system once installed.
    But unless your loads must change or you are interested in reducing them, the details are not as important once the design process is complete.

    I do agree that having designed and built the system, the process of tuning and operating it long term must also involve taking a fresh look at your loads from time to time. But I do not see any reluctance here to doing that.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    If the system has been designed on a basis of known loads to begin with there usually isn't any problem after that. If a problem does arise, one of the questions asked inevitably is "have your loads changed?" On the whole if the batteries get charged and the power needs are met there's not much point in watching the loads all the time: the system works.

    When it stops working it's time to go back over the details. ;)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I welcome devil's advocates (shoot holes in this idea)

    I will attempt an answer--because I am probably a big time "abuser" here. :p

    We want the system to meet the users expectations. And power usage is a highly personal set of choices and behaviors.

    For example, I am "Cheap". I don't want to waste money so I attempted some serious conservation (not crazy, just serious :roll:) with my home.

    I got it down to ~175 kWH per month summer (we use natural gas for cooking/heating/etc.). For a family of four--I though I was doing pretty good. But--over time, I probably have gotten back to around 200-300 kWH per month. I have GT solar, and with a 3.5kW array, I pay $5.00 a month if I use 175 kWH or 300 kWH per month (I can probably go up to 400+ kWH per month with my existent system pretty easily and still have a minimum payment bill).

    Considering the average household power usage is 1,000 kWH per month--I am pretty happy with myself. However, I do have the (pretty cheap) natural gas crutch. I don't need A/C (especially after insulating the home, double pane windows, and using LED/CFL lighting to keep heat out of the home) and we get snow on the ground for 1/2 a day maybe once every 20 years.

    Others here live just fine on 0.5 kWH per day and would think I am a huge waster of energy (for sake of argument--everyone is very nice here).

    And I cannot rag on people that have all electric homes and no natural gas/propane, and need A/C to survive and use 2,000+ kWH per day (plus run a business from home, etc.).

    So--Asking the loads/expectations helps us not "project" our assumptions and biases on somebody that we don't even know.

    But--we are flexible too--Probably 1/3rd or more of the systems here I have helped design by asking what is there starting (i.e., YYY AH battery bank, $3,000 to spend, etc.), and then did a paper design and then gave them the specifications of how such a system will perform (AH per day, kWH per day, maximum surge current, etc.).

    Its really is the equivalent of "I need a vehicle--What should I get?".

    Bike, car, pickup, semi, boat, snow machine, plane, etc.--They are all perfectly reasonable vehicles--But six of those choices are probably not going t work for the poster.

    If you ever see me attempt to push a bias on somebody--Please jump in and help. Everyone here has their blind spots. And doing all of this on a text based forum leaves a lot to the imagination (good and bad).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    I may have run across the final stone in dropping this idea. The slide out. I don't know how many amps those motors take but it has to be a lot.

    - Jeff
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    I have an observation and this is not pointed at anyone specific. In fact its not pointed at anyone at all. When I started down this fun little solar road every and I mean every serious discussion on "going solar" started with first and for most determining power requirements. Why is it prior to buying anything the "A" number one priority is measuring loads but after your installed it's forgotten and possibly even forbidden?

    I find it amazing that people who have just "flipped a switch" don't setup systems that "work". While I am aware of my loads and load shift and watch where my system is at during heavy use and long cloudy periods. To me I have built systems that "Work" and unless I have a difficult situation, I can count on it to Work.

    To me I think people that have to have data on every minute of every day, need something else in their life. Off grid systems will have waste and need to have waste. It amazes me how many people are obsessive compulsive in the regulating of their system. Set up correctly you shouldn't have to hover over it, just routine maintenance. You take care of it, it takes care of you...

    I live with out a generator, solar only. Maybe I'm a bit peculiar, because I can't even find my battery monitor and looks like I'll have to buy a new one to watch my new system a tad more closely the first 6 months, then I'll likely look at it a couple times a year. I do think an integrated, shunt based, battery monitor is the greatest advance in solar in a while and am looking forward to it, but mainly so it will do the job of properly charging the battery while under load.
    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.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    I may have run across the final stone in dropping this idea. The slide out. I don't know how many amps those motors take but it has to be a lot.

    - Jeff

    Get a DC clamp-on Ammeter, put it on the battery cable, then push the button and find out. :D
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    Get a DC clamp-on Ammeter, put it on the battery cable, then push the button and find out. :D
    Exactly, don't know why I missed this. I did just that with all the other loads which is why I switch to LED's. I'll have to check this but will have to wait till after the blizzard.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    Photowhit wrote: »
    I find it amazing that people who have just "flipped a switch" don't setup systems that "work". While I am aware of my loads and load shift and watch where my system is at during heavy use and long cloudy periods. To me I have built systems that "Work" and unless I have a difficult situation, I can count on it to Work.

    To me I think people that have to have data on every minute of every day, need something else in their life. Off grid systems will have waste and need to have waste. It amazes me how many people are obsessive compulsive in the regulating of their system. Set up correctly you shouldn't have to hover over it, just routine maintenance. You take care of it, it takes care of you...

    I live with out a generator, solar only. Maybe I'm a bit peculiar, because I can't even find my battery monitor and looks like I'll have to buy a new one to watch my new system a tad more closely the first 6 months, then I'll likely look at it a couple times a year. I do think an integrated, shunt based, battery monitor is the greatest advance in solar in a while and am looking forward to it, but mainly so it will do the job of properly charging the battery while under load.
    Need I say more?
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    Need I say more?

    Maybe... :p

    Anyway, the slide out probably does not use more than 5-10 amps of 12 volts--And in the big scheme of things (Amps*Hours of use) were use is probably 1 minute or 1/60th of an hour, used twice in a weekend or twice in a week--That would probably one of those "don't care" loads.

    However, as Marc said, get a Clamp on DC meter and do the measurements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    BB. wrote: »
    The slide out probably does not use more than 5-10 amps
    -Bill
    You think that low? I was taking a WAG at 25 or so. Will be interesting to find out.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I welcome devil's advocates (shoot holes in this idea)

    Big motors cost a lot of money (plus the big gear box). You might check the wire size/fusing and see what the mfg. used.

    The starting motor on a car uses around 100 amps (+/-)... Would be surprised (and a bit scared) if they used a really large motor to fling out the slide. :roll:

    Anyway--when you measure yours, we will all know. :D

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    It isn't "waste" it's "margin for error". :D

    I'd suspect the slide-outs use low current, high speed motors with a lot of gear reduction to provide plenty of torque for shifting all that weight.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    unyalli wrote: »
    Need I say more?

    "...Maybe I'm a bit peculiar, because...."

    "PECULIAR" is NOT the word I used, It appears 'Coot changed the wording as an insult to me, the word I used started with P and might have been better changed upset, angry or annoyed, which I am now. The word I used is HERE and is NOT foul language. perhaps it means something else in Canada? Then again if we're editing for the world "fanny pack" an clothing accessory here can be a sex act between 2 males in England...

    Perhaps sometimes you can over edit?
    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.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)
    Photowhit wrote: »
    "...Maybe I'm a bit peculiar, because...."

    "PECULIAR" is NOT the word I used, It appears 'Coot changed the wording as an insult to me, the word I used started with P and might have been better changed upset, angry or annoyed, which I am now. The word I used is HERE and is NOT foul language. perhaps it means something else in Canada? Then again if we're editing for the world "fanny pack" an clothing accessory here can be a sex act between 2 males in England...

    Perhaps sometimes you can over edit?

    No, 'Coot changed the word because we have language rules on this forum which preclude the use of certain ones which may be deemed "not family friendly". Just because it is in the dictionary doesn't mean it's allowed on the forum. Sometimes we just can't find an exact replacement word. (The phrase used above is on the border, btw.) how about cranky with much anger? niel

    Thee and me both may be deemed peculiar for our lack of obsession with constant monitoring, which seems to be prevalent amongst the solar crowd for some reason.

    If you think that's upsetting imagine how much I cringe whenever someone misspells the short form of refrigerator.

    Before anyone gets their nose out of joint, remember the rules. Particularly the part about who has final say on such things.
  • unyalli
    unyalli Solar Expert Posts: 121 ✭✭
    Re: I welcome devil's advocates (shoot holes in this idea)

    Ok I'm a convert. Midnite Solar assures me...
    Jeff
    Monitoring a shunt and logging it on the Classic is very close. We have the MNCSM or Current Sense module well under way.

    I'm stoked.

    - Jeff