Amy Beaudet's posts

Right, 60W is the instantaneous draw. Over 1 hour, it is (60 Watts x 1 hour = 60 Watt hours). Over 24 hours it is (60W x 24h = 1440Wh).

Sorry, my PC was messed up, I was looking at the wrong prices. You are right. I updated my reply with the right prices, and swapped to a different charger to get you back on budget.

You are fairly limited in that price range for the features you want. Samlex just came out with an incredible new pure sinewave inverter/charger, EVO. The 2200W 24V model is $1300. https://www.altestore.com/store/Inverters/Off-Grid-Inverters/2000-to-2999-Watts/Samlex-EVO-2200W-24V-Pure-Sine-Wave-InverterCharger/p11913/

To stay within your budget, and because you don't have high wattage needs, the idea of having a separate inverter and AC charger may be the way to go. The Samlex SA-1500-24 would give you plenty of room for the surge of your tools, and is over $500. https://www.altestore.com/store/Inverters/Off-Grid-Inverters/1000-to-1999-Watts/Samlex-1500-Watt-24V-Heavy-Duty-Inverter/p9791/.It has a low power mode to save energy at under 1.5W.

Then an Iota AC Charger at around $200 would keep you in budget, https://www.altestore.com/store/Charge-Controllers/AC-Battery-Chargers/Samlex-SEC-2415UL-24-Volt-15-Amp-Battery-Charger-UL/p10217/

Sorry for the delay in answering.
1. Depending on where you are, and how hot the roof gets, the standard space of the L-foot plus the width of the rail is generally enough air space between the roof and the panels. If you are in extreme heat, additional standoffs or a longer L-foot may be helpful to increase air flow and keep the panels cooler. For metal roofs, I like the EcoFasten L-foot with the EPDM bushing to help seal the hole. They are available in 3" or 6" lengths, for a higher mount, https://www.altestore.com/store/Solar-Panel-Mounts-Trackers/Roof-Mounts-for-Solar-Panels/Flashing-for-Roof-Mounts/EcoFasten-Solar-SIM-L-102-6-Tall-L-Foot-with-Simple-Seal-Bushing/p11108/ .
2. It depends. There are calculations to determine the length of the lag bolt needed that include wind loading for your area and type of wood for the rafters. Let's assume 10.6 sqft per panel and 4' spacing between L-feet (3 rows of 11), that would require 60 roof connections. Assuming the array needs to withstand 50psf wind uplift force the equation is 50 psi x 10.6 sqft = 530 lbs per panel x 33 panels = 17,490 lbs for the array / 60 L-feet = 291.5 lbs per L-foot. There is a chart in the Wood Engineering and Construction Handbook for what length Lag bolt is needed based on if the rafters are Southern Yellow Pine, White Spruce, or Douglas Fir. For example, a 5/16" bolt in White Spruce can handle 227 lbs per inch. 291.5 lbs / 227 lbs = 1.3" of the lag bolt must be in the rafter. Add an inch for going through the L-foot, roof, underlayment, etc, and you need at least a 2.5" stainless steel lag bolt. I'd use 3" for good luck ; )
3. Yes, use stainless steel lag bolts.

Amy Beaudet
Solar Queen
altE Store

What an interesting question. While there is not one "right" answer, my instinct is to have 2 parallel strings of 24V, with a breaker for each string. When you have to fold up one string, open the breaker to take it completely out of the system, preventing any potential unwanted interaction between the 2 strings.

However, I know space is always at a premium, so I'm thinking the idea of wiring them all in series may actually work. Even with 2 blocked out, you'd still be at nominal 24V and enough to charge the battery.

I'm interested to see if anyone else has thoughts on this.
Amy
altE Store

The cool thing about MPPT charge controllers is that the input is low current, high voltage, but the output is high current, low voltage.
Watts = volts x amps.

So, if you have two nominal 24V 100W panels in series, that's 36Vmp x 2 = 72Vmp. One string is 2.78A Imp. 72V x 2.78A = 200 watts.

The MPPT charge controller takes that and reduces the voltage to about 14V to charge the 12V battery bank.  200W / 14V = 14.2A output into the battery bank.

You have two 12V 130Ah batteries in parallel (is that true, or are they 6V batteries?).  That's 260Ah at 12V. 260Ah / 14.2A = C/18 charge rate. That's a little slow, those batteries would be happier with under a C/10 charge rate, so if possible, 400W would be better.  However, you are currently charging the batteries with 130W, and you say it's working great. So while it is not ideal, it seems you have low enough loads that you are not using that much power. So jumping up to 200W is better than what you are currently doing.

Jeff,

Yes, running a higher voltage panel (or panels) and running it through an MPPT charge controller is the way to go. Ideally, if you can do two 24V panels in series, that's even better. We've got a 100W 24V panel that can ship by UPS to control the shipping costs. https://www.altestore.com/store/Solar-Panels/altE-Poly-100-Watt-24V-Solar-Panel/p10355/.With two of them in series, 10AWG wire gives you 3.3% voltage drop for 69V at the charge controller! Then with a Midnite Kid charge controller, https://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Midnite-Solar-Charge-Controllers/Midnite-Solar-The-KID-30A-MPPT-Charge-Controller-150V-Black/p11138/ , that'll drop it right down to where you need it. Also note that the current you should be using for your calculations is the Imp of the panel, not the draw of the load. So it'll be down around 3A. High volts, low amps is the way to travel the distance.

Amy
Solar Queen
altE Store

Dan, it may help if you say where they are located. It's easier to pick them up in person than to ship them by truck.
Amy
altE Store

Gosh, you're making me blush.

I'm sure the batteries are fine, you are not the first person to get a bad start to their system. If you kept repeating what you were doing and had them deeply discharged often, you would certainly damage the batteries. But once, you're probably fine.

Looks like you are getting more rain in TN today, so I'm not sure if your trip out there today will be very telling. Maybe stay home and rescue another beer, and head out another day after you have a good day of sun.

Amy
Solar Queen
altE Store

OK, jumping in here a bit late, sorry, was away for the weekend. Let's step back and summarize the situation. Note that we don't sell Renogy products, so my knowledge of the details is from reading the manual.

Six Renogy 100W panels. 22.5Voc, 18.9Vmp, 5.75A Isc, 5.29A Imp
Renogy MPPT 40A charge controller
battery bank: 6=12v, 155 ah wired in 3 strings of 2 in series to make 24v and 465 ah.

The charge controller is MPPT, so you can input more than the nominal 24V and it will adjust the output voltage down and current up. 100V max is the temperature adjusted Voc output. You are in TN, so it doesn't get insanely cold (compared to up here in New England), so let's say 1.15% increase in voltage when it gets cold. 100V max \1.15 = 87V max Voc input. 87V / 22.5Voc of your panels = 3 panels max in series. So you can do 2 parallel strings of 3 in series. The MPPT charge controller will drop the voltage to the 24V battery bank, and increase your output current to about 12A per string x 2 strings = 24A out. (This is all theoretical without system losses calculated).

The manual is confusing on page 22. What it is saying is that for a 24V battery bank system, the most power you can put in is 800W. It's not saying the most voltage you can put in is 24V. You can do strings of 3 panels in series.

So, let's figure out what is going on. It's good that you got a display, that will help with troubleshooting. Did you set the amphour on the display? The default is 200Ah, you have to change it to 465Ah.

Now that you took care of the beer (good thinking), and have the fridge unplugged, it will be very good to see if the solar is able to recharge the battery bank without a load on it.

I think the meter shows the amps going from the charge controller to the battery bank. Next time you are there when it is sunny, see what it is saying. On a perfect day, you should be seeing in the 20A range. Also, it should be keeping track of amp hours added to the bank, that will be important to see. Are you making about 80Ah a day?I'd also like to confirm the power used by the fridge, I'd recommend getting a Kill-a-watt meter to keep track of the actual power usage of the fridge plugged into the inverter (https://www.altestore.com/store/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Power-Meters/Kill-A-Watt-Electricity-Usage-Meter-P4400/p932/) It may not work perfectly with a modified sine wave inverter, but you should get a good feeling for it. Being a "cheapo modified sine wave", the inverter itself may be using a lot of your power as well, not just the fridge.

Now let's look at the system as a whole, to see if it is correctly sized. 600W of panels, although you started with 400W. Let's guess 4 sun hours. 400W x 4 sun hours x .6 system losses = 960Wh generated a day. Fridge draws 80W. Continuously? Or is it on half the time? The Kill-a-watt meter will tell you that. Let's be nice and say it's on 12 hours a day. 80W x 12 hours = 960Wh a day (which is what you estimated). So you started out theoretically making exactly what you needed for the fridge, but not figuring any losses by the inverter. It's maybe 85% efficient, so you are losing 15% through that. So you started out at a deficit. You then added 200W of solar, giving you 1440Wh. If you always have perfect sun, that's probably fine. but you had a rainy day, so you lost 1140Wh for that day. Plus starting a bit low from when you had 400W of PV. I think it just started to snowball down from there.

Sooooo, long way of saying, let's see what you get this week without the fridge plugged in, and go from there next weekend.

Amy
Solar Queen
altE Store

You really need to do a loads list before you go any further to figure out how much power you need. Some of the items you listed don't use much power, but anything that makes heat or cold uses more power than you would expect, and you listed a fridge and a toaster. Check out the loads list calculator here, https://www.altestore.com/store/calculators/load_calculator/ , and then go to the off grid calculator to see how many solar panels and batteries you need. https://www.altestore.com/store/calculators/off_grid_calculator/?dwhrs=0  Don't make the mistake of buying equipment before you know if it will work for your needs, that's  sure way to loose money.

Amy
Solar Queen
altE Store

Also, if you are interested, I did�  quick video doing an overview of grid tie solar string inverters, DC Optimizers, and micro-inverters you may be interested in watching. https://youtu.be/H2aeV8d7SJY I used a Fronius instead of Sunny Boy, but the message is the same.

Amy
Solar Queen
altE Store

Ah, the eternal debate, string vs panel level inverting. In your situation, there really is no right or wrong choice. Since you don't have shading issues, there really is no need for managing each module. And quite frankly, monitoring per panel is fun, but really not needed. Do you need to know if you have bird poo on one panel that will wash off with the next rain?

With a switchable combiner or pass-thru box, like Midnite Solar's solutions, http://www.altestore.com/store/Enclosures-Electrical-Safety/Electrical-Enclosures/Rapid-System-Shutdown-Components/c1255/, you can meet NEC 2015's requirement to shut off within 10' of the panels.

SMA's SunnyBoy TL grid tie inverter also has a great feature that no one else has right now, their Secure Power Supply, which gives you up to 1500W of 120VAC power during the day in a power outage. It's nice to be able to charge up your phone and laptop and other small devices when the grid is out. http://www.altestore.com/store/Inverters/Grid-Tie-Inverters/5000W-TO-7600-Watt-Grid-Tie-Inverters/Sunny-Boy-5000TL-US-transformerless-5kw-Inverter/p10863/

Amy
Solar Queen
altE Store

You need to determine the dynamic head, which is the total height including the friction loss for the 70' across, in addition to the static head, which is the 20' up you are going. Assuming 1/2" pipe at 2GPM, that's 3.5' for every 100'. So let's say 3' + the 20' static = 23' head.

The ShurFlo is rated in PSI, not head, so searching online for a foot of head to PSI calculator, I see you have to achieve 10PSI.The amps for that pump at 10PSI is 5.3A. Now granted, you will likely need more than that to get it started, but since you need so little water, you don't need to get it running first thing in the morning, so you can wait until midday for the pump to start. I'd probably go with a 100W panel, to ensure that it does have enough current to get the panel started. It has a Max Power Amperage (Imp) of 5.56A.http://www.altestore.com/store/Solar-Panels/altE-Poly-100-Watt-12V-Solar-Panel/p10353/

If you are not using a float switch, what is your plan to control water flow?Will you just have it overflow? Is there something you can think of to do with the extra water? I hate to waste.

Amy
Solar Queen
altE Store

I've seen that quote before, which is why I have one foot in that camp. My other foot is in the other camp of being a boater, and making due with what you have available. I think you've come up with a good solution.

BTW, I just wired up the outside horn on our schooner yesterday with heat shrink butt connectors, then wrapped the whole outside wire harness onto the rigging in high quality electrical tape to prevent UV exposure and accidental catching on something while under way. To Tom M's point, we used a dab of dielectric grease in the connector just for good luck.

Amy
Schooner Queen
altE Store

Lion, excellent questions, which unfortunately don't have a black and white answer, nor a short answer.

None of the wires altE offers are tinned. Likewise, the cables coming off your solar panels also are not tinned. This is an age old dilemma for boaters, tinned wire is definitely best for boats, but no one I know of makes tinned wire with the solar connectors, and to correctly make them yourself requires a very expensive tool.

Most boaters we deal with in your situation buy the SMK pre-crimped wire like this, http://www.altestore.com/store/Cables-Wiring/Wiring-For-Solar-Panels/100-SMK-Connector-Cable-10-AWG/p10449/ twice as long as you need to go for your first connection and cut it in 2, one piece for plus and one for minus. For example, if you are using a combiner box, you would use this wire to the combiner box, and then provide your own tinned wire for the rest of the system.The advantage of using professionally crimped connectors vs tinned wire you crimp yourself is worth using a length of non-tinned wire for the outside connection that will be most exposed to the elements.

Unless you have other components that I don't know about that are MC4, I don't see any reason to convert over to MC4, just keep with SMK. Or are you wiring them in parallel with an MC4 coupler like this, http://www.altestore.com/store/Cables-Wiring/Wiring-For-Solar-Panels/MC2MC4-Branch-Coupler-1-Male-to-2-Female-Ends/p7163/? If so, the answer to whether MC4 and SMK are compatible is also a little controversial. Yes they will work together, but some are concerned about long term connectivity, will they eventually not make a solid connection. I've got a foot in both camps for that one. Again, most people just connect them together with no problem. If you are concerned about it, you can use an adapter set like this, http://www.altestore.com/store/Cables-Wiring/Wiring-For-Solar-Panels/SMK-to-MC4-Array-Adapter-Set-MF-Pair/p10616/ .

Sorry, as I said, no short clear answer available. You can give us a call and we can discuss pros and cons with you to help you decide.

Amy
Solar Queen (and boater)
altE Store

Brad, I'm curious how low the voltage on the battery bank was without the charge controller on it.  Since it is a PWM charge controller, it basically opens the connection from the panel to the battery.  If the battery voltage was very low, it will pull the output down as it is charging it up.  Have you seen any difference today, as it gets another day of charging?

It's hard to completely eliminate an electric bill. Remember you still need them for cloudy days, so they still have to be prepared and able to provide 100% of your power at any time, day or night. That's worth something there.  $6 a month plus whatever else is still a better deal than having to buy a big enough battery bank to go off-grid.

If you can get around the Big Brother aspect of the Nest, I just saw this article today about the Nest potentially tying in with your solar system and making the time of use smarter.  It's giving Google a bit more information than I'm personally comfortable with.

http://www.forbes.com/sites/aarontilley/2015/04/20/how-googles-nest-will-make-residential-solar-smarter/

You are right, due to the basic design of a grid-tied inverter, they are specifically designed for net metering, spinning the meter backwards. Many folks who have turned on their inverter without a net metering agreement from the grid have ended up paying double, as they count the power generated by your inverter as power they provide and charge for it, since they don't know any differently. 

Since the inverter is designed to connect directly to the main breaker box, which is connected to the grid, you can't keep it from going out if your house is not using the power. And it is designed, per UL1741, to turn off if the grid isn't present, to prevent killing the linemen working on the lines during a power outage. So you can't disconnect it from the grid.

There's really not a huge demand to not send power to the grid, as that is the benefit of grid-tied systems, you use the grid as a battery to to send your extra power to, then buy it back when needed at night. I understand some grids are not "solar friendly", but they are currently the minority, and as such probably don't provide enough of a market for inverter manufacturers to completely change how the power is distributed.

And what is the question?

Amy
altE Store

The FlexMax 60 can handle 6 of the Canadian Solars, the FlexMax 80 can handle 8 of them. The 6 you could wire in 2 parallel strings of 3 in series, or 3 parallel strings of 2 in series, either way, you are right, with 1/0 cable, voltage drop shouldn't be a problem. If you switch to the FM80, the 8 can be 4 parallel strings of 2 in series.

Specs for the panels: 255 Watts

Max Power Voltage (Vmpp): 30.5 Volts
Max Power Current (Impp): 8.35 Amps
Open Circuit Voltage (Voc): 37.7 Volts
Short Circuit Current (Isc): 8.74 Amps

I usually recommend higher voltage to reduce voltage drop. The MPPT charge controller will drop the voltage to match the battery bank and increase the current, so the volts and amps on the output will be the same regardless of how you wire it. The advantage is you can use smaller wire with the higher voltage.

If you are doing 3 nominal 20V panels in series, you will have 20V x 3 = 60V nominal in / 24V nominal out = 2.5 ration of voltage dropping and current increasing.  So if you have 4 parallel strings with 8.74Isc x 4 strings x 2.5 ratio = 87A out. NEC says you have to add another 25% when selecting a charge controller, so you would need a charge controller that can handle 87.4A x 1.25 = 109A. I don't know of any that can handle that, so you will need to break it into 2 circuits, with 2 strings of 3 going into each charge controller.
8.74Isc x 2 strings x 2.5 ratio=43.7A x 1.25 NEC requirement = 54.6A minimum charge controllers, so probably two 60A charge controllers needed.

Note that if you were doing a 48V battery bank, you could use just 1 charge controller. 60V in / 48V out = 1.25 ratio.  8.74Isc x 4 strings x 1.25 ratio x 1.25 NEC = 54.6A charge controller for the whole system.

What a great project.

The Outback GSLS-Ac includes the following:
Ground bus bar, 500 Amp DC shunt assembly, neutral bus bar, AC bus bars, two 175A panel mount breakers, remote-operated circuit breaker
(ROCB), control relays, four 50A 120/240VAC double pole panel mount breakers, sliding bypass interlock, AC wiring, and enclosure mounting hardware

So it has some 50A AC breakers in there that can be used for the grid and a generator until the DC breakers are needed for the PV system. Just use the breakers you need for now, and then use the rest later.

Ah, the eternal question, which is better, micro or string. It looks like you did quite a bit of research, so I probably won't be telling you anything new.  Without shading as an issue, and if you are not planning on expanding in the future, the string inverter is the more affordable choice.  You won't get per module monitoring, but that can be way more info than you need anyways.

 I think labor is about the same for both types of inverters, just a little different.  With the micros, you mount each of the inverters on the rail first, then put the modules on top of them, and bring the AC wire back to the house to the Mains breaker box.  With the string, you just wire the modules to a combiner box, and bring the wires back into the house to the inverter, which then goes to the breaker box.  Bringing the DC wires for the string and the AC wires for the micro are the same amount of work.   

If, for some reason, an inverter does fail in the future, it is easier to replace the string inverter, many of them are modular and allow field replacements.  The micros require you get up on the roof and remove the panels to get to the inverter.  However, if something happened to a module years from now, after that module is discontinued, finding a matching panel to replace it is required for a string, but not required for a micro, as they are managed independently of each other. 

As you can see, pros and cons to each option.  Both are a good choice, you can't go wrong with either.

If you have a 200A Mains breaker box, I suggest not going above 7.5kW for your system.  A 7.5kW inverter will require adding a 40A breaker into the box for the inverter (regardless of which kind), and that is the max that NEC code will allow for a 200A bus bar box.  Anything bigger would require you to have to pay to have the electrician upgrade you to a bigger box, or do a line side tap, which can add to the install cost.  Just something to keep in mind.

We'd be happy to put a design together for you, give us a call.

Thanks for the backup Jason.

You say you want to use the battery the way it was intended, but you are not.It was not designed to power an inverter with a huge surge. Don't throw good money after bad trying to do what they are not able to do, get a bigger battery bank, and it will work.

60ah is waaaaaay too small. If you figure the surge of a fridge when the compressor turns on can be around 600W or more, that's trying to pull about 50 amps from the battery (600W/12V=50A). It just can't handle that kind of draw. I understand trying to save money with a small battery, but it just can't handle the kind of power you are tying to pull out of it. 

You are also trying to put too much in at once with the 270Wx3=810W of solar. If you figure 810W x 6 sun hours x.67 losses = 3256 watt hours generated in a day.  You can't use more than half the capacity of your battery, so you have 30ah x 12V=360 watt hours capacity in that battery.   

The problem remains that the battery is too small for the load. CCA has nothing to do with it. When there is a surge, the inverter pulls the power from the battery, and if the battery amp hours is too small, there's not enough power in the battery to support the surge, and the inverter pulls the voltage down. Can you check the battery and see if it lists the amp hours on it?

My only other guess is that the cheap inverter can't handle the surge of the fridge, do you know what the power spec of the inverter are?

Ah, that explains the 220V in the battery calculation. Then yes, you were right, 220V / 24V batteries = 9.1, round up to 10 batteries in series.

But if you are using 220V as the battery bank voltage, you would do
37,500 wh / 220V = 170ah / 250ah battery = .68, round up to 1 string of 10 24V 250ah batteries.

Genasun now has a charge controller that can be used with up to a 325W panel on a 36V golf cart.  You can see details here: http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/Electric-Vehicle-Golf-Cart-Chargers/Genasun-8A-36V-MPPT-Boost-Charge-Controller-for-Golf-Carts/p10634/.

Amy
altE Store
Solar Queen