Two Off Grid Shed solar systems review help

[voidstar]

I have a few acres of remote land, but with no power (nor water, but that's a separate topic). I put up two sheds, which I'll just call BLUE SHED and GREY SHED (they are both about 10'x10', small stuff).

It's an evolving work in progress. What I have works for me, though I would like an extra set of eyes for any "safety" concerns.

I have some simple not-to-scale connection diagrams attached below.

BLUE SHED: overview
- 2x300W panels that are remote from the shed (mounted on poles). (I actually have 5 of these, but one of them was severely cracked in shipping. Long story short, I got a partial refund for the damage since that was cheaper/simpler than a complicated return - I nursed that 5th panel back to health with basically some clear epoxy, and that 5th panel is what ended up on the other shed discussed later. The two other panels ended up for a different project, but here I just wanted to focus on these two shed projects.).
- The tail ends out of the panels are marked 12 AWG, but I used 10 AWG wiring throughout the rest of the connections
- I used Y-Connectors to connect these panels in parallel - I confess to being too cheap to put a fuse on each tail, and opted for a single 20A after the Y-connector (also since it's a small system and I think those fuses are overkill anyway -- as down the line, I have a 20A circuit breaker also as a quick disconnect, and the CC itself has an external 25A fuse).
- Between the CC BATT. connectors and the battery, yes I have a 50A breaker. I started with a 40A but I think it went bad, so I'm temporarily using a 50A and plan to reduce it down to a 30A breaker. Any issue there?
- Between the battery and inverter, I don't have a fuse yet. I have ANL fuses on the order. Do I take inverter 3000W peak / 12V = 250A, apply x1.25 just because, so then should I target a 300A fuse there? Or is there some other rule of thumb here?
- So why am I using 2/0 AWG between the battery and inverter? Well, the first cable I used was maybe 2AWG and there was a time when I physically felt it getting warm. That concerned me. After reading a bit, the maxAmps per cable size seems a little subjective (based on temperature and tolerances). I did 2000/12 and settled on "rounding" to 175A, which I think 2/0 AWG can handle. Any advise here? These thick copper cables get quite expensive. I do get a little confused here, because with 2x75AH batteries, does that mean the max "push" should be 150Amps? Or probably it doesn't work that way. In any case, the cables don't get warm any more, not that I've noticed.
- So speaking the batteries: this set is a couple cheap-o Duracell NG-24 deep cycle (despite "NG-24" or DC24 or SLI24MDC designators, they are actually 12V batteries). It was never completely clear, but I think I had determined that their rated usage was 75AH.
- The inverter could boil water, but struggled a bit with a microwave. So I just use it for basic things - drills, vacuuming, lights, etc. -- roughly limiting it to 5Amps draw. I think the portable induction oven I tried pushed 8 Amps in some modes.
- Thoughts? I estimate it all retail roughly $1200. As with both these sheds, I just use things lightly on the weekends, not daily survival.

GREY SHED: overview
- Similar general arrangement as above, except 1x 300W (the left over repaired one as described above). In this case, the panel is roof mounted, hence the shorter line distance to the CC. I didn't read about or see any obvious Fuse for the Renogy CC, so I'm not sure what it has internally for fuses. I kept a 10A fuse to the PV, but so far don't have any inline circuit breaker switches.
- Renogy CC MPPT instead of Victron. They both have pros and cons, but overall I'd say I prefer the Victron for being more compact.
- Battery here, 2x100AH AGM deep cycles in parallel for total 200AH. Roughly speaking, the little AC unit uses about 5Amps, so I expected it be able to run at least 1 day on these battery. I haven't yet been able to verify that, the longest I have run them is about 6 hours.
- There is a beefier inverter here, 2000W instead of 1500W. This inverter ran the AC and microwave at the same time. The JackHammer actually uses a little less than 2200W (maybe 1800W; whereas the Microwave uses a bit more than 700W)
- The cabling between battery and inverter is only 2 AWG. I've never felt them become warm so I leave them alone.
Thought here on this one?

 

[snoobler]

Blue:

2/0 is a good choice. I use it on a bank that sees currents as high as 300A. It gets a little warm there, but anything below about 250A is fine.
As depicted in the wiring diagram, the 10awg wires between the two batteries is grossly undersized. It should be the 2/0. The battery to which the cables are connected is going to get hammers. Best to parallel with 2/0 and connect to (+) of one batter and (-) of other.

I didn't see any other issues with your conclusions, temporary measures and plans to rectify known issues.

Loads aren't specified, so it's hard to tell if there are any issues there.

Gray:
Same issue with battery interconnects.
Microwave likely uses closer to 1100W as they are very inefficient.
10A fuse from panel is marginal.
The A/C unit uses 5A at 120V for 600W
Your 200Ah*12V batteries have 2400Wh
You can power your A/C unit for 4 hours via battery, and you will rapidly kill them discharging them all the way. Limit to 50% use to prolong life, so only 2 hours run time + a little extra when the panel is providing juice.
2200W jackhamer - don't understand why you would select an inverter with a power output lower than a device. Surge currents of electric motors always swing heavily into the overload area and plans for operating in the area above rated usually meet with substantially reduced inverter life.

After the issue I see with Gray, I'm curious how the 2awg are fine in Gray but weren't in Blue.

After seeing the disparity, I would encourage you to do an energy audit. Look at the usage of all devices you intend to power, i.e., either published Watts or amps AND volts. Then determine how long you want to run each item every day. That will determine how much solar you need and how much battery.

Beware the pumps. If they're 110VAC pumps measured in hp or fraction thereof (12V RV-type pumps are fine), then they have a MASSIVE surge current. My 2kW inverter couldn't handle the surge current of a 3/4hp pump.

 

[voidstar]

No edit button? Well, I noticed in my diagram I used "Gray" instead of "Grey"

For "BlueShed" I never did resolve why the BATT to INVERTER cables got warm one time. Maybe they were just exposed to direct sunlight for awhile (the way one door opens, it's possible -- but that door is normally latched closed now after the install).


But that is one of my general question: how does one size the cable between inverter and batteries? Normal Wattage of the Inverter divided by Voltage of the battery? Peak Wattage? Is there a negative if we use too large of a wire here, between the battery and the inverter? Or is the only negative is that it is harder to install any fuse? Regardless of what device you plan on using on the inverter, it has to ramp up to 110V AC.

As for fuses, should it be relative to hottest expected temperature (like with no fans, maybe it gets 140deg in there in the summer)? I just haven't been able to find clear guidance about it (the wire size and corresponding fuse amp).



Also, I like the Bluetooth monitor for the CC's - but it's like an RS232 to Bluetooth bridge device. I wonder if they make a "Bluetooth to Wifi" bridge (or better yet Bluetooth to 4G bridge) so I could monitor them remotely.

 

[voidstar]

Thanks for the notes snoobler. Have some errands to run but will respond more later.

but one quick note:
In the diagrams I was noting the Wattage reported in the booklet of those devices, but I know those need to be taken with a grain of salt - many reviews of that cheap-o JackHammer mentioned it doesn't really pull over 2KW, and indeed microwaves are known for using some factor more than their advertised W (so yeah, I figure it uses about 1000-1050). I do have one of those P3 Kill o Watt devices to monitor more actual draws, just I didn't have those notes in front of me (left in the shed that's couple hours away; next time).



Mostly I needed the jack hammer to bust thru rocks to put the poles for the external panels to sit on. While I verified the jackHammer will run off that inverter if I really had to, I mostly use a separate 3400W Flex fuel generator (only use Propane in it) for actual heavy work. I love that generator


And you're right about the AC runtime - I did run it for about 5 hours (I said 6 but meant closer to 5, since I forgot I had things disconnected for awhile while re-arrange some things) and I did notice the battery voltages got down to ~11.8V - and I was disappointed the inverter didn't throw an alarm or shut off, so I'll have to check on that setup.


More later when I get back home, I'll have to think about that wiring between the batteries.

EDIT: ah, the Edit option had a time expiration. Good to know. IMO Edit should be like 1-week instead of a few hours...

 

[voidstar]

Ok, good news is that the cable I am using to connect between the two batteries in parallel is not 10 AWG. Bad news is, the cables aren't labeled and I don't really know what they are. If I had to guess, they are 4 AWG. For those connectors, I used the "starter battery" cable that came with the inverters (they aren't marked anywhere, not in the manual or on the product site; I suppose I can e-mail them to ask, but they probably vary that cable throughout seasons) - another instance on my part of cheaping out and just using what was available.


Also, I think I have an answer why the cables aren't getting warm: I setup the BLUE shed in winter (February) and the GREY shed more recently in summer. Temperature effects the amp rating of the cables. Glad I'm double checking this now, to avoid some surprises next winter!


For reference:
Temperature effects on amps (roughly speaking, higher temperature allow for higher current -- probably why most house fires happen in winter, and not just because more people are using space heaters and such)

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com

SmartGauge, and way deep down in the notes he mentioned the cross connect when just using two batteries.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

Cool, thanks for noticing this, and I'll work on replacing those (maybe not with 2/0 - 1 or 1/0 might work, although I suppose 2/0 won't hurt).

 

[voidstar]

For LOADs, I found my notes:

Small LED lights all ~.2 amp (probably too low to actually be accurate; in any case, they sip very little)

Space Heater
- max setting: 9.9 - 10.2 amp
- low setting: 6 amp (will be a problem in the winter since this is more than the AC; but I have a propane bottle heater as well)

Induction heat plate (iron/magnetic pots only)
- HEAT lvl 8 12.3 amp (this was enough to get water boiling to 212degF)
- HEAT lvl 5 6.7 amp


Shop Vacuum 8.5 amp (bit more than I thought to suck up dirt)

Microwave PL10 9.9 amp
(seems all Power Levels use 9 amp, but it just "pulses" or cycles when it is actually on - so Power Level 5 still used 9 amps, but would cycle off more often -- recall this is with a "700W" rated microwave, lowest I could find)

1 HP air compressor 8.9 amp (inflate/deflate rafts and such)
Hammer Drill 2.7 amp (4.4 peak)
Reciprocating Saw 2.6 amp (don't think that was while actually cutting wood, so not peak)
JackHammer "2200W" 6.0 amp (probably not peak either - several other reviews put this at between 1500-1800W)


I haven't measured my water pump, but it is rated as "1200W" ( 1.6HP and it's pretty quiet ). It just enough pressure to draw from a water barrel and sprinkle some fruit trees at about 30-40ft.

Couldn't find the written notes notes on the air conditioner. I think the startup is roughly 10 amps, but normal use on max settled on around 5 amps.

 

[voidstar]

GRAY:
- agree 10A fuse is marginal. The open circuit amp on the single solar panel is 9.71A (per Renogy label on the back). If it matters, this is the "repaired" panel (I think I did a pretty good filling back in the cracks in the glass -- but it's not perfect like-new). And it is roof mounted - the pitch is 6:12 (uh, that's 45deg right?), I'd have to think about which season that favors at 32.5 latitude (the shed is mostly level, slight slant to south east corner). The shed could fit 3 of these panels, and originally I did plan to do that - just holding off for now, if it takes a week or two to recharge the batteries that's fine. But would you go 15A for this single panel, or just go ahead with 20A and be consistent with the other setup?


- follow up on the AC: the 5 hours "stress test" I mentioned was during a full sunlight daytime (good juice). But duly noted, won't make it a habbit to drain the batteries. BTW, the inverter buzzer alarm (per the PDF manual) doesn't go off until 10.6V. I thought I read that this was configurable - probably I got mixed up with a different brand. Anyway, dropping to 11.8V maybe wasn't too cruel during my usage test. As mentioned, I do have the 3400W generator also, and a "stress test" with that kept the AC going 14 hours on a 20lb bottle (not continuous, but spread across about 3 days).


I did want to mention some notes about the circuit breakers... Turns out I ordered two 30A breakers. They look quite similar, but I noticed a few difference between them when replacing the 50A breaker. Attached is a photo of the differences.
A = copper set screw terminal (or at least copper colored) versus silver colored [ and not just the set screw is copper colored, but inside the terminal is a copper colored sleeve as well ]
B = the bottom side of one is more "serviceable" (exposed screws where I could open or disassemble it, if I had to -- I like that, to confirm what's going on inside if I had to)
C = "rounded" versus straight sides, I don't like the rounded or buldged side since it makes it harder to mount (the rounded one does have 4 mount holes, but the buldge still makes it slightly hard to get a bit in there)
D = label in white instead of black - not a huge deal, just the white might be easier to read in low-light condition if we had to hunt for this in the dark with a flashlight

As mentioned, I had a "40A" version of this breaker "fail" on me -- I'm not quite sure how, all I can say is my charge controller wasn't charging my batteries, and after swapping the circuit breaker, now it is (and that failed 40A was the "buldged, silver color set screw, black label" variety, for what it's worth).

 

[voidstar]

*grumble* 2/0 cables ordered to go between the batteries. I'll post updated diagrams when I get them on.

 

[voidstar]

Ok, updated BLUE...

- 50A temporary circuit breaker reduced to 30A between CC and battery
- battery connect cables now 2/0 AWG
- 250A ANL fuse between battery and inverter [note: ignoring the manual, the sticker on the inverter says input 150A]
- CC and inverter connections extended across + and - terminals of both batteries


Waiting on orders to update GRAY.


Main remaining question:
- what gauge wire to use on the ground for the inverter? (14? 16?) and should I even bother about it? Should the inverter ground be connected to the ground used on the panels?

 

[snoobler]

Whoa. Sorry. Been out of town most of the weekend and just saw these updated.

Nothing was intended by grey/gray. I'm inconsistent.

You are correct about microwaves. 100% on always. 50% means it's on 100% for 50% of the time. Note that each time, you get a notable surge beyond the published amps as the magnetron energizes. It's best to run them at 100% for however long you need them rather than cycle on and off. They are also very inefficient. They tend to use 50-60% more power than they output, i.e., a 1000W microwave consumes about 1600W. Panasonic makes an INVERTER microwave that actually runs at the set power, i.e., if you program 50%, you get 50% power for 100% of the time. They are a little more expensive ($179 or so), and they are slightly more efficient than a regular microwave, but they can be ideal for an off-grid situation to be able to throttle the peak power required.

It really helps to multiply your amps # by 120V to get the actual WATTS needed.

The revised diagram looks pretty good. You're probably being a bit hard on that 1500W inverter with so many devices that use very nearly that. The compressor and vacuum cleaner likely bite deeply into the unit's surge capablility.

 

[voidstar]

Thanks, didn't realize about the inverter microwaves. I'd just stick with PL9 tho for now, to reheat certain foods.

Mostly I'm just listing devices I've tried, and had measured with the P3 "Kill A Watt" device. 1500 / 120 = 12.5A (on the inverter they list this 12.5A on the output spec). But you're right, I should swap it up for at least the 2K version like I have on the other shed.


Typically I just use lights, fan, and laptop - so about 2.5A (enough for an evening on charge). Everything else is typically on the generator with propane - but verified they could run on the inverter for a couple hours while getting a new tank. (not all of them at once, of course)

The GREY shed is nearer the larger water pump, which I haven't measured yet (for amps). The smaller pump is 0.6 - 1.0A. And I do know the laptop is under 1A also (about 0.3 to 0.7).


I've now attached the image instead of full insert, since then it might be easier to view.

 

[snoobler]

Since you're using a killawatt, those also report power in Watts. That's the better measure as it equates directly to the power of the inverter.

Pumps use about 1000W/hp (conservative), and they can have a massive surge current. My 2kW inverter couldn't handle the surge of my 3/4hp jet pump.

 

[voidstar]

For completeness, here are the updates to GREY. The original diagram was wrong, I actually had a 1/0 AWG between the batteries (whew!). But I've replaced both that, and the cable between the batteries and inverter, with a 2/0 AWG just to be extra safe all year round.


While it is sad to have a nice CC and batteries with just a single panel -- the plan is to eventually increase that to 3 panels (max the shed roof can physically support). For now I don't mind taking 2-3 days to recharge (with at least 6 good hours of sun exposure daily). 250AH batteries would also be a nice upgrade -- I think both could be done without too much re-wiring.


Only thing to add now is a mid-50% charge alarm buzzer. I think I've found one and will try it next weekend.

 

[snoobler]

Looks good.

AGMs don't do well being run to lower states of charge. The battery literally eats itself below about 70% SoC and worsens as you go lower. When you're cycling them daily, the movement through that range is less stressful than letting them sit overnight at 70%. The flow of current.

Daily recharging is optimal. The addition of a second panel would put you in the sweet spot of max charging current for those batteries.

If your panel has MC4 connectors, putting in a second panel could involve nothing more than a set of parallel MC4 connectors. The second panel would also "pay" for your A/C during full solar.

10A is still marginal, and it would need to be upgraded for the second panel.

 

[voidstar]

I found an external charge buzzer, which is adjustable; I'll probably set it to 12V for the AGMs, and maybe 12.2V for the flooded Duracells. Will see how it goes and how accurate it is. Certainly set above 11.6V, since the inverter itself only alarms at 10.6V (which unfortunately I did hear that go off once, before I realized the 40A circuit breaker wasn't really working and so the CC was "stuck" in Float during the daytime even though the batteries were quite depleted).


By the way - I used AGMs since I'll sometimes nap in that GRAY shed. I went out of my way to seal it up fairly nicely (the shed is insulated, sealed at all the corners and edges; but has gable vents at both front and back sides also -- so not totally sealed). I felt safe enough doing that with an AGM batteries. (BTW - that wall mount A/C works so well in there, just the right size - to me, A/C is humanities greatest invention!).


For BLUE with the deep cycle flooded batteries - the shed isn't very well sealed, and has a vent fan (wind, not powered) at the top. I thought about burying the batteries just outside the shed - maybe using an old safe with good doors (but still have to drill holes for the cables, and vents). Anyway, the batteries are inside the shed still. I'm not too concerned, since it is a large shed (plus its general lack of being well sealed). Any problems there? (like consider also running a heater in there during winter).

 

[snoobler]

For perspective I sit next to 4 giant 468Ah 6V Rolls S-605 FLA (~900Ah 12V) every single day. I shove 300A in to them on a regular basis. This is INDOORS in my office 6' from me. The only time they vent noticeably is when I'm doing an equalization. I have a whole house fan for that when the weather is cooler.

If AGMs vent, they're being damaged. They are designed to never vent, to operate laying on their side, etc. Just NEVER take them over the absorption voltage by more than a wandering charge controller might do. Always use temperature compensation according to the manufacturer's instructions, and make sure you have the absorption termination criteria set. Time limit is typically 2-4 hours with a current limit of 1-3% of 20h C rating.

In other words, nap with wild abandon in GRAY.

Concerning BLUE, again, I sit next to big FLA every day in my reasonably well insulated house in the Phoenix area, where I share your love of the A/C invention. I do not fear your choice of indoor battery storage.