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Re: 7KW PV with 10KW Inverter

You are 1/2 a world away from most of us... So I do not have much I can add regarding specific manufactures... But with the low prices for solar panels and hardware, expecting that you will be responsible for warranty costs is a good assumption (solar mfg and distributors come and go--Even some of the "good/well financed companies" seem to have failed or exited the market).

GT solar is pretty straight forwards these days.. Well made panels should last 10-20 years pretty easily... If you need replacement/more panels 5+ years down the road--Do not count on being able to match size/wattage/Vmp/Imp with your existing panels. As manufacturing cost reductions and market demands change, available panel models charge too. My 15 year old array of 175 Watt panels--It would probably be more cost effective to buy a whole new set of panels rather than try to replace a few damaged by hail or early life failures (my original panels were probably USD$10 per Watt, now there are panels in the $0.50 per Watt range).

Inverter wise, I would budget for a replacement every ~10+ years... Power electronics (and electronics in general) tend to go out of production in 5+ years (5 year warranty, although 10 year inverter warranty is required for some markets in the USA)--And repairing 5+ year old inverters can be difficult (finding parts/boards, and a facility that can repair them--Let alone if the computer/memory goes bad and no replacement software/memory).

Circuit breakers require a specific chosen GT inverter and array configuration. Also code requirements for your country. In North America, our breakers and wiring following the National Electric Code are for "typical" installations with intermittent/relatively low average current usage. However, solar power (and battery banks) can pull 5+ hours of rated current. Breakers and Fuses for our market generally are specified to not trip at 80% or less of rated current, and will trip at 100%+ rated current (can take hours to trip)... So, for solar/battery/inverter wiring, suggest that if you have a rated current for wiring and breakers of (for example, 10 amp continuous current) of 10a*1/0.80derate=12.5a or ~15 amp minimum breaker/wiring.

You seem to have chosen the array Wattage to meet your average monthly energy requirements and amount of sun for your city--So sizing looks OK.

For solar--Make sure you have no shading at all on your array (at least around 9am to 3pm at least)... Solar electric panels do not work well if there is any shading on the panel(s). Overhead electrical wiring, a vent pipe/chimney, etc. anywhere on the array can pretty easily kill 50% of the array harvest (details do matter--But in general--NO SHADE during harvest time). There is equipment that, in theory, is supposed to help reduce losses from shading--But they add complexity (and costs).

You can also look at "micro inverters" (a single inverter every one or two panels) which can help reduce shading losses--Although there are complexities with micro inverters too (needing a inverter monitoring system, if one fails, having to pull up panels to get to the failed micro inverter to replace, etc.). A single central inverter is generally easier to maintain/service.

If you have lightning in your area--Then using surge suppressor(s) is a good thing. Having suppressors on both the solar input to the GT inverter and on the AC output of the GT inverter is the better solution. These are good suppressors--They help with nearby strikes, but few inverters will survive a direct hit to the array. Using lightning rods to redirect strikes away from the array can help (added expenses and complexity of design).

http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=23&productCatName=Surge Protection Devices

Look very closely at the Net Metering Billing rate plan... In the USA, they started out with very good terms for the solar customer (subsidizing GT Solar systems)--Basically, they would pay us back the retail power rate for every kWH we generated... Very easy to "break even" (we could not "make money" selling power to utility).

HOWEVER, as GT solar became more popular, and the politics changed, the rate plans have become much less "GT Solar friendly". We now have time of use (high cost power all they way to 9pm at night--Obviously no sun to generate power), some places have high "GT Solar connection fees" ($48 to $96 per month), and low payments for power ($0.06 per kWH paid by utility vs $0.10 to $0.40 per kWH paid by customer for power). And in some regions, new GT solar installations have been made illegal--Or at the very least, not cost effective (I understand why--Lots of GT Solar, utilities do not make money, and subsidies from state/utilities raise prices and taxes for the non-solar customers and tax payers).

From "your" point of view--A well functioning GT Solar system is "transparent" to you. Your appliances/lights/electronics all work exactly as they have before. And you (hopefully) see a greatly reduced power bill. My electric bill is $10 per month (minimum connection fee) vs $60-$100 per month without GT Solar.

Another thing to be aware of... Standard GT Solar systems have no energy storage--So if you have a power outage, the GT Solar system provides ZERO POWER to your home... Utility power fails, it also fails to your home.

There are various "solutions" for solar and emergency backup power (one is SMA's "secure power" system--It can give you ~1,500 Watts of AC power when the sun is shining--And you can plug a few appliances into the the GT SMA--Another is to go with a battery bank and hybrid GT/Off Grid inverter--Batteries supply energy when the AC mains fail and there is no sun). But that add expense--And batteries are a cost/maintenance issue all of their own.

And my first suggestion... It is almost always cheaper to conserve energy than to generate it. Look at your present power usage. LED lighting, efficient appliances/TVs/Computers. Is your Heating and Air Conditioning system "efficient'. Is your home well insulated (walls, ceilings, windows, etc.)?

It sounds like you have done the research and are probably aware of most of the issues/suggestions I have made... When buying the hardware--Getting good quality is first choice. Second is look at costs... For the most part, a good quality XXX Watt solar panel (crystalline, glass cover, mono or poly crystalline). I would not "pay extra" for PERC or Mono Crystalline panels. In day to day usage, you probably could not measure the extra $$ spent. There are some advantages to Mono and other "high efficiency" panels--That you can harvest more energy from the same square meter space can be worth it to you--If you are limited for space.

Your thoughts?

-Bill

BB.

2 ·

Re: What's in a name? With Industrial/Forklift batteries everything you need to know.

I'm looking for a good new/used forklift battery supplier in Northern Arizona. I have a 2004 Raymond 36v r30‑c30tt. It is also going to be my SHTF backup battery but they are super expensive from what I see.

SafariParkEarth

5 ·

Re: Should I upgrade from a PWM to an MPPT with only 170 watts of Panels?

Thanks. Makes sense. OK, I'm bored... you tubing... re-searching... I was seeing that the new hotness are battery temp sensors. I wouldn't know if I had a problem. I mean my batteries seem to charge... but.... they are on the tongue in a box... I am in south Texas... should I upgrade my PWM Sunforce 30w to one with a temp sensor on it?

Being an amateur ... I still can't imagine 170 watts of panels overheating 2 6volt golf cart batteries. I mean I also have a progressive dynamics 91xx charge wizard on there that runs all year mostly. It doesn't have temp sensor... I do top off the water in the batts monthy... just a little.

yawn...

Maybe I should take up knitting.

Bass-O-Matic

5 ·

Charge Controllers and Max Array Watts

I am looking to add a 3rd array to my system. I have 10 Trina 250 watt panels available. I currently use 2 FM60s on my other arrays and have a Mate3 for monitoring/programming. The specs for the FM80 I am looking at, say max array is 2000 watts and max amps are 80.The panels are rated at 8.85amps short circuit current which would exceed the 80amps. I planned to have 5 strings of 2 panels each to come in at 44.25amps. But the array wattage would still exceed the 2000 specified. Would I be safe in going foward?

RickR

0 ·

Re: Under performing LiPo

Thanks for responding. The batteries are Renogy lithium iron phosphate LiFePo4. The main question I have is, why on the occasions when The bank does get above 12.8v it seems to lose voltage very quickly. Example, last night Before I parked for the night at around 9:30 I went for a ride and charge the batteries up to 13.1V, (12.9 when I turned the charger off) I turned off my fridge and had only my Maxxair fan and one LED light on. I had to run the engine/charger at 1:30ish because the voltage had dropped to 11.8 and experience has been that won’t make it through the rest of the night without shutting down. So from 9:30 to 1:30 my vent fan and one 15 watt LED took my bank from 12.9v to 11.8v. I may be wrong but that seems excessive.
As for adding panels to my array I sized the charge controller so that I can add two more 100 watt panels but as I said in my post I’m laid off now so that’s not an option. Thanks again for responding.

onebad

5 ·

Re: Battery damage in one night of low voltage?

12 volts for one night is not that bad. Everyone is acting like it went stone cold dead. Guessing Prius has a feature that shuts off drain when flashers run battery down to ~ 12 volts.

I'd have thought led flashers would be a smaller drain. Then again, Prius employs a small battery. I suspect that capacitors spend a second or two driving up the power level when starting. It always waits a second or two then boom - instant start. Doesn't crank at all. Just hesitates then starts. Prius are a bit odd. Recommend for city driving though - that is where Prius really shines.

softdown

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Re: Undercharged Battery Bank? Low Specific Gravity

jonr: Yes, the Conext 4024 is an inverter/charger.

Estragon: The panels are 2-3 feet from the CC with 6AWG cable. I measured the voltage coming into the CC at the combiners: 40.3 volts. It has been overcast/snowing the past two days however. Probably won't be full sun until 2 days from now.

BB: I will eventually get the panels and CC upgraded, but given the costs, I'm looking for short-term solution. Using your figures, if I remove one string from the bank, I can get a 10%+ rate of charge with one additional panel giving me a 1,920 watt array. I can run my house on the two strings. The bank I had before was 625AH and that was adequate. 24 volts would also be ok for that size bank, agreed?

Someone suggested that I charge the batteries one string at a time to get them to full charge. That seems like a good suggestion. After that I could remove one of the strings. If I do that, I would move the 4 batteries to my storage shed for a stable ambient temp. I could keep fully charged batteries in storage for a few months, I believe. What do you think?