Suggestions for system expansion

jcheil
jcheil Solar Expert Posts: 722 ✭✭✭
I was hoping to get advice/opinions from the experts here.

I am needing to expand my system. My full system is in my sig but currently I have a 48v system with 430ah of batteries (16 gc2’s, 2 strings of 8). I have a lot of standing 24/7/365 loads. About 200w all the time. My array is 2460w. All my other loads "seem" to be balanced well with the system I currently have. I generally stay at 80% SOC overnight and even with the AC (window unit) running in the daytime I rarely do not hit 100% by 2pm.

However, now I want to run my AC (window unit) overnight. I know a mini-split may save me a bit on energy usage but the way my place is set up, and the way I live, I have 3 rooms, each with a window AC and I am always in only one room at a time so I never have more than one unit running at a time. For example, Office 8am-5pm, living room 5pm-9pm, bedroom 9pm-8am. Sure I could get a 3 zone mini-split but that would be for another day/topic.

In any event, I know the window unit draws about 500w when the compressor is on. I will assume for the sake of this expedition that the compressor will be running 50% of the time. The other 50% of the time the fan (100w) will be running.

So, what is the recommended expansions (battery and panels) that you would recommend.

And I am essentially Orlando, FL so we have great sun/hours.

Thanks for your help/suggestions/guidance in advance!
Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Suggestions for system expansion

    Well you're a tad under-paneled as it is. 430 Amp hours @ 48 Volts ought to be 2680 Watts of array.

    200 Watts for 24 hours is 4800 Watt hours. That's 100 Amp hours on 48 Volts so about 25% of your battery capacity. That's good.

    Now you want to add 500 Watts for 9:00 PM to 8:00 AM @ 50% duty cycle? That's another 2.75 kW hours, plus 550 Watt hours more for the fan. 3200 Watt hours total. Sounds like you just doubled your system capacity needs.

    So do you want to increase your DOD on those batteries? Add the 200 Watts for the same 11 hours and you get 5400 Watt hours overnight. That's 113 Amp hours @ 48 Volts or about 25% of the battery capacity right there. You could take some of the daytime load off them by increasing your array significantly. Maxing out the FM 80 at 4900-ish Watts for example. The FNDC should be capable of preventing the batteries from getting hit with 80 Amps while still providing maximum PV power for daytime loads.

    It may also be advantageous to add PV facing in different direct in addition to your tracking array to supplement power early and late hours specifically.
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    So do you want to increase your DOD on those batteries?
    Not sure...I guess I wouldn't be too concerned bringing them down to 70% but I wouldn't wanna go much further than that. I like the 80% just in case I get a couple of really crappy days in a row (rare) and I don't happen to be there to get the generator started (yes, auto-start generator someday).
    But if I wanted to keep it at 80%-ish, with adding another 215ah of batteries (which you are saying is the proper amount for my additional load request), what total more wattage of panels are you suggesting?
    It may also be advantageous to add PV facing in different direct in addition to your tracking array to supplement power early and late hours specifically.

    I get GREAT unobstructed coverage now (or any time of the year). Being so far south in the US here in FL, my winter panel position is 45deg, spring/fall is 22deg and summer is perfectly flat. Not sure that I would be able to face them any other way to get much more of a benefit? I guess perhaps a tad to the SW maybe for afternoon for this new set? Just not sure it would make that much of a difference??? Thoughts???
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Suggestions for system expansion
    jcheil wrote: »
    Not sure...I guess I wouldn't be too concerned bringing them down to 70% but I wouldn't wanna go much further than that. I like the 80% just in case I get a couple of really crappy days in a row (rare) and I don't happen to be there to get the generator started (yes, auto-start generator someday).
    But if I wanted to keep it at 80%-ish, with adding another 215ah of batteries (which you are saying is the proper amount for my additional load request), what total more wattage of panels are you suggesting?

    If you add 215 Amp hours more to the 430 you'd have 645. Following the 10% rule-of-thumb that's 64.5 Amps * 48 Volts / 0.77 or 4020 Watts of array minimum.
    I get GREAT unobstructed coverage now (or any time of the year). Being so far south in the US here in FL, my winter panel position is 45deg, spring/fall is 22deg and summer is perfectly flat. Not sure that I would be able to face them any other way to get much more of a benefit? I guess perhaps a tad to the SW maybe for afternoon for this new set? Just not sure it would make that much of a difference??? Thoughts???

    I wasn't suggesting you change the angle of your existing array but rather supplement it with East-facing and West-facing arrays to extend daylight hour production. Even with a tracking array this can be advantageous as early and late solar production is lower than midday (more atmosphere to get through).

    So you might have an additional 500 Watts pointing East, 500 pointing South, and 500 pointing West to increase the over-all daily production. This would keep loads running off the PV for longer, rather than eating into battery capacity.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Suggestions for system expansion

    the main question I see is just how much of your loads can you run via 'opportunity load'' configuration and as you point out, what happens on a poor solar gathering day?
     
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  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    westbranch wrote: »
    the main question I see is just how much of your loads can you run via 'opportunity load'' configuration and as you point out, what happens on a poor solar gathering day?

    Well, in the daytime, I'm at 100% usually by noon-2pm even running full loads (fridge, freezer, pool pump, etc). After 100% it stays in the 97-100% for the rest of the day with all the "extra" loads running (like ac). If I run the ac early in the morning, it almost always still hits 100% by the end of the day with everything else running also. So I "think" I am good in the daytime, it's nighttime that concerns me with the extra ac usage I want to add.

    And ironically, on poor solar days, the fridge and freezer run (a lot) less, nor do I have to run the ac, so it's kinda a perfect "balance" - in the daytime. I still always seem to be at 100% by the end of the day. In the past 30 days I only got as low as 98% once.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    If you add 215 Amp hours more to the 430 you'd have 645. Following the 10% rule-of-thumb that's 64.5 Amps * 48 Volts / 0.77 or 4020 Watts of array minimum.

    Ok, since I have my panels in series of 3 (205's), I would have to add 9 more (205's) giving me +1845 for a total of 4305w. So I am guessing I would be good there with 645ah of batteries.

    I wasn't suggesting you change the angle of your existing array but rather supplement it with East-facing and West-facing arrays to extend daylight hour production. Even with a tracking array this can be advantageous as early and late solar production is lower than midday (more atmosphere to get through).

    So you might have an additional 500 Watts pointing East, 500 pointing South, and 500 pointing West to increase the over-all daily production. This would keep loads running off the PV for longer, rather than eating into battery capacity.

    hmmm...well based on my data logging/graphing, I am always "positive" (making more or at least what I am consuming) right up until the sun pretty much sets (behind the trees about 600 feet to the west) around 7:30ish. And considering the panels are flat most of the time (summer) they can't really "face" any different way anyways. The rest of the seasons, yes I could see facing a bit se/sw but I wonder what difference it would make or how I could "test" that without having to build the mount and then move it.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Suggestions for system expansion

    Try modeling it on PV Watts and see what results you get. Even though that's for grid-tie it will give you some relative numbers for over-all power output vs. positioning of panels.

    What you'd be trying to do is increase that positive production number to where the amount used during daylight is negated entirely by the additional PV. It gets a bit tricky balancing this off because of the intermittent nature of loads. The idea is to save all battery capacity for that nighttime use.

    You people that live close to the Equator have no idea how lucky you are! :p:D
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Suggestions for system expansion
    jcheil wrote: »
    Not sure...I guess I wouldn't be too concerned bringing them down to 70% but I wouldn't wanna go much further than that. I like the 80% just in case I get a couple of really crappy days in a row (rare) and I don't happen to be there to get the generator started (yes, auto-start generator someday).

    If you're not there and it's cloudy, do you still need to run the air conditioner? If not, then you probably won't get down below 70%.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    vtmaps wrote: »
    If you're not there and it's cloudy, do you still need to run the air conditioner? If not, then you probably won't get down below 70%.
    --vtMaps

    Correct, if I am not there, the AC is not running. I only turn it on when I am there.
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion

    Also, Currently I have 12 of the 205 panels, 4 sets of 3 in series going into an FM80 at 48v battery bank voltage.
    The specs on these are: VOC: 33.2, IMP 7.37, VMP 28.1

    Since I won't be able to get the exact panels any more (what are the chances of that huh?), what exact specs should I be looking for in ourder to add to this existing array in the configuration I have it now. From what I am reading, panels in series you want the IMP to be as close as possible and panels in parallel you want the VMP to be as close as possible correct?

    So in my case, would I look for 3 panels that are rated around 7.37 for the IMP (only)? And what of the VMP/VOC? Will that matter (although somehow I think they are related yes?)
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Suggestions for system expansion
    jcheil wrote: »
    Also, Currently I have 12 of the 205 panels, 4 sets of 3 in series going into an FM80 at 48v battery bank voltage.
    The specs on these are: VOC: 33.2, IMP 7.37, VMP 28.1
    <snip>
    So in my case, would I look for 3 panels that are rated around 7.37 for the IMP (only)? And what of the VMP/VOC? Will that matter (although somehow I think they are related yes?)

    If you want to make a fifth string of panels to put in parallel with your other 4 strings, the Imp is irrelevant... but the Vmp should be the same as your other 4 strings.

    If you can't find a good match, perhaps you should take some of Cariboocoot's advice:
    You could take some of the daytime load off them by increasing your array significantly. Maxing out the FM 80 at 4900-ish Watts for example.

    I don't like the thought of maxing out the controller (assuming you can find matching panels). Does your tracker have enough capacity to double your array? If it does, you could use another controller for the new panels.
    It may also be advantageous to add PV facing in different direct in addition to your tracking array to supplement power early and late hours specifically.

    Your expanded array could be facing east, west, or both (virtual tracker).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    vtmaps wrote: »
    If you can't find a good match, perhaps you should take some of Cariboocoot's advice:

    I don't like the thought of maxing out the controller (assuming you can find matching panels). Does your tracker have enough capacity to double your array? If it does, you could use another controller for the new panels.

    --vtMaps

    Well, based on what coot said, I don't think I can do that any more than I already do; because I already reach full charge nearly every day in the early afternoon and usually stay at 100% SOC until the sun sets around 7:30pm. So I likely have power to spare in the daytime (and nowhere to put it).

    I don't want to bring my minimum SOC down any lower than 75% so that means with the new additional AC load at night, I have to increase by battery bank capacity by adding another string. And by increasing that, I have to add more panel to keep at the 10% charge rate. I have plenty of room to add the panels and did comment on the "virtual tracker" a few posts ago and I don't think it is really going to give me much (and I might actually end up losing some). Now, if I was not at 100% SOC at the end of the day, then I think I would explore that "virtual tracker" a bit more -- or is my logic flawed?

    And regarding new panels and VMP. If I could not find exact ones, and they were off by say 1v, would it be better to have the new ones (it would be 9 more panels) be slightly higher or slightly lower than the original 12 panels VMP?
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Suggestions for system expansion
    jcheil wrote: »
    And regarding new panels and VMP. If I could not find exact ones, and they were off by say 1v, would it be better to have the new ones (it would be 9 more panels) be slightly higher or slightly lower than the original 12 panels VMP?
    Now that is a serious question!

    First, the general rule is that is you can get within 5% of the Vmp of your original panels you will get pretty close to the nominal additional power out of your new string in parallel with the old ones.
    Second, as to higher or lower, I do not think it will really matter much. The old strings will dominate in the CC's search for the MPP, and in particular for the Vmp value, so it really comes down to whether your new panels output curve gives more power when operating at 1V above Vmp or at 1V below Vmp. And since the true Vmp point is a maximum, the two values on either side should be close to equal.
    SMA SB 3000, old BP panels.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Suggestions for system expansion
    jcheil wrote: »
    I don't want to bring my minimum SOC down any lower than 75% so that means with the new additional AC load at night, I have to increase by battery bank capacity by adding another string. And by increasing that, I have to add more panel to keep at the 10% charge rate.

    How much lower than 75% would you go if you don't add another battery string? You already have 48 cells... do you really want to buy into the problems of three parallel battery strings with 72 cells?

    For most deep cycle batteries it is actually more cost effective to have deeper discharges... as long as you recharge them right away. I have some trojan battery L16RE data sheets in front of me now, so to use them as an example: 4000 cycles at 20% DOD, and 2000 cycles at 40% DOD. Therefore, if you were running at 40% DOD with one string of batteries, you could double your investment in batteries (two strings), run at 20% DOD, and get twice the life. Except that you would be buying into all the problems of parallel battery banks and you would probably get a bit less than twice the life because of that.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Suggestions for system expansion
    vtmaps wrote: »
    How much lower than 75% would you go if you don't add another battery string? You already have 48 cells... do you really want to buy into the problems of three parallel battery strings with 72 cells?

    For most deep cycle batteries it is actually more cost effective to have deeper discharges... as long as you recharge them right away. I have some trojan battery L16RE data sheets in front of me now, so to use them as an example: 4000 cycles at 20% DOD, and 2000 cycles at 40% DOD. Therefore, if you were running at 40% DOD with one string of batteries, you could double your investment in batteries (two strings), run at 20% DOD, and get twice the life. Except that you would be buying into all the problems of parallel battery banks and you would probably get a bit less than twice the life because of that.

    --vtMaps
    The only problem is that they will be long dead before you ever get to 4000 cycles. There is a big difference between theoretical cycles and capacity in the real world.
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Suggestions for system expansion
    The only problem is that they will be long dead before you ever get to 4000 cycles. There is a big difference between theoretical cycles and capacity in the real world.

    I think that depends on which real world you are in.

    In a controlled environment (like a forklift truck) where there is a specified daily discharge and an immediate full recharge from the grid, I think the manufacturer's numbers are realistic :D

    In my real world with PSOC cycles, you are absolutely correct :cry:

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Suggestions for system expansion
    vtmaps wrote: »
    I think that depends on which real world you are in.

    In a controlled environment (like a forklift truck) where there is a specified daily discharge and an immediate full recharge from the grid, I think the manufacturer's numbers are realistic :D

    In my real world with PSOC cycles, you are absolutely correct :cry:

    --vtMaps
    You think ?? why do you think a forklift battery is is warranted for 1,500 cycles ? It becomes a capacvity issue. I can stretch a set of GC-2 7 years, but after 5 years they have less than 40 % capacity. You'll be dumping the ones you have as soon as you cannot to get them to take you through the night.
  • AuricTech
    AuricTech Solar Expert Posts: 140 ✭✭
    Re: Suggestions for system expansion

    Just throwing this question out there for discussion:

    Given the OP's requirement to run at least some A/C overnight, would this be a situation in which the OP would benefit by overpaneling the PV system to "make hay while the Sun shines," by using PV power to run A/C (with the thermostat set somewhat higher than the OP's comfort would require) in rooms he's not currently occupying?

    That way, the OP wouldn't have to rely solely on battery power to cool the space in which the OP wants to run A/C at night. That space would already be somewhat close to comfort levels, having been precooled using PV power while the Sun was still able to provide power to the system, thus reducing the need to draw power from the battery bank to provide fully-comfortable A/C for the needed time. :cool:
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    vtmaps wrote: »
    How much lower than 75% would you go if you don't add another battery string? You already have 48 cells... do you really want to buy into the problems of three parallel battery strings with 72 cells?
    --vtMaps

    Interesting thought....hmmm....I suppose I could just get the panels first, and then see where I end up (on the low side of SOC each night). Then if I had to, add the 3rd string. Yeah, I know it adds more maintenance and is right at the edge of "max strings recommended". I guess I just figured that
    So if I ended up with keeping them in the 75%-80% range would extend the life of them a bit more (as per what everyone states on here).

    So I found some 220W panels that are [my numbers in (below)]:

    Current at Pmax -- Imp 7.46A (7.37)
    Voltage at Pmax -- Vmp 29.5V (28.1)
    Open-Circuit Voltage -- Voc 35.4V (33.2)

    So those seem like a good match yes?

    The next question being, if I try the "keeping 2 strings at first" route, I will now have 4440w going into a 430ah bank (48v). I am thinking that is pushing the edge of too much?
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion
    AuricTech wrote: »
    Given the OP's requirement to run at least some A/C overnight, would this be a situation in which the OP would benefit by overpaneling the PV system to "make hay while the Sun shines," by using PV power to run A/C (with the thermostat set somewhat higher than the OP's comfort would require) in rooms he's not currently occupying?

    That way, the OP wouldn't have to rely solely on battery power to cool the space in which the OP wants to run A/C at night. That space would already be somewhat close to comfort levels, having been precooled using PV power while the Sun was still able to provide power to the system, thus reducing the need to draw power from the battery bank to provide fully-comfortable A/C for the needed time. :cool:

    Yes, I kinda do this now. I tend to start running the ac in the "bedroom" towards the end of the afternoon while I am still at 100% SOC. I can run it for a few hours after the sun goes down and I will usually shut it off when I get to 95% SOC. Sometimes that is an hour or two other times it can be a lot longer (depending on the temperature out).
    Off-Grid in Central Florida since 2005, Full-Time since June 2014 | 12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total) | Custom built single-axis ground mounts | Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnet-DC, Mate-3, Hub-10, FW500 AC/DC | 24 x Trojan L16RE-B Batteries 1110ah @ 48v | Honda EU7000is Generator and a pile of "other" Generators | Home-Made PVC solar hot water collector | Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Suggestions for system expansion

    AuricTech's advice is good advice: keeping a space cool takes less energy than cooling it down to begin with. So long as the nighttime is not oven-hot this should work.
  • jcheil
    jcheil Solar Expert Posts: 722 ✭✭✭
    Re: Suggestions for system expansion

    Ok, In addition to the many suggestions here of pre-cooling, load shifting, etc, I also decided that I am going to expand the battery bank to 645ah and add more panels. At this point, they are so cheap and I have the "room" for expansion already built-in. Plus I was lucky enough to sell my on-grid house (closing tomorrow) and my job is allowing me to work-from-home everyday from now on that means I can finally be/live at the off-grid 24/7/365!

    These are the panels I found that are very close to my existing panel specs:
    Attachment not found.

    By luck, they are in stock at a local dealer 1mi from my on-grid house. So my total price is only $0.72/watt out the door.
    So now the big question, do I go with 9 more or 12 more? 9 more puts me at 4440w total for the array, 12 puts me at 5100w total for the array.
    I know the max for the FM80 is 5000w but as I have learned, we rarely get full potential out of the panels unless it is cold, and that rarely happens here in FL.

    But if it did, in those cases, I believe the FM80 just clips the extra, it won't hurt it correct?
    And does the 9 or 12 keep me at a nice "balance" of charge rate, etc? Or should I set a max charge rate in the FNDC to something?

    Thanks again for all the great advice and comments/suggestions.
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