Mppt for rv is it worth it

I've been using a rv for full time off grid in summer in Virginia, I spend winter 30 minutes from myrtle beach. Currently I have 2 6v us battery gc 208 amp hrs @12 volt. With 4 100 watt panels 18.9 vmp 5.29 imp. a 30 amp non adjustable pwm controller puts out 22 amps and 308 watts. About a c/10 charge rate. A hybrid system a 2000 watt generator for microwave a toaster and an occasionally couple hrs for a 8000 btu ac. For cloudy days a 35 amp charger. A small 300 watt psw inverter for tv. On to my situation I'd like to double my battery bank to 416 ahrs. My thoughts are that I need 800 watts. 44 amps for roughly c/10. Twice the bbank double the panels and cc amps from 30 to 60. 4 100 watt panels $400. A 60 tristar pwm $200 for a 25 or 30 ft array the wire and the mc4 fusing $100. =$700 for 100% increase in power for About $50 more than a 60 amp tristar mppt $650 Most mppt claim 35% increase in winter and 15% for summer or 25% annual average increase. (25% for $650 or 100% for $750??) I understand if the array is 120 foot away the cost of wire alone would tip the scale. But not for a 12 volt rv. I no that I still havery racking to deal with but am I missing something? Any input would be appreciated.
Blue ridge mts. Renogy pwm 4 100 watt and 2 190 evergreen on Epever mppt 30. 4 Gc 208 ah @12 volts 300 watt psw inverter. 2 kw genny. Iota 45.
Comments
Roanoke
Measured in kWh/m2/day onto a solar panel set at a 53° angle from vertical:Average Solar Insolation figures
(For best year-round performance)
With loads taking some of the solar, hazy third day etc, you may need to run the generator occasionally to give the solar a head start in the morning. In good weather, the solar would likely catch up in a day or two anyway though.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
https://www.esrl.noaa.gov/gmd/grad/solcalc/azel.html
Moving east to west in summer at higher latitudes would definitely increase production in summer.
In summer, I generally get to float even after a couple of rainy days anyway though, and in winter, it wouldn't make much difference. In your situation though, I imagine it helps a lot on catch-up days.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
> A 1000 watt array and 700 ah? with 800 watts I could have a 600 amp hr bank??? Whats your nightly usage; I never get to float after a couple dark days unless I pull the cord. But I'm working mine way too hard. The reason I need more battery capacity.
I assume you're referring to the 12v system in my sig? That part is meant to run light loads for a long time. A 12v fridge/freezer that draws little, and a few lights. In summer, 3 days no sun might get it down to 90%SOC. It's meant to keep the 12v fridge running for a week or more unattended if need be. In winter, there's less fridge load, more lighting load, so about the same overall. That bank has a pretty easy life, and will likely die of old age.
I also run a 48v bank that runs pumps, tools, an AC fridge in summer etc. That bank will run down ~15-25%/day in normal use in cloudy weather. After a couple of cloudy days, I'll fire up the genny to charge if need be. It's rarely needed in summer, but likely in fall/winter. The 48v bank gets cycled deeper daily, so I expect it to die of work.
I don't think you need to get to float after a couple of dark days. If you get to absorb voltage, or close, that's good enough. If you finish absorb and get to float weekly or so, that 's ok.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
30% x 400 AH battery = 120 AH
120 AH / 35 Amps = 3.4 hours
120 AH / 65 Amps = 2.2 hours
Assuming the charger is in bulk charge mode (battery voltage below 14.5 volts or so. Absorb set point voltage).
Many chargers and alternators can drop their output current if running near or at rated current for longer periods of time.
Iota is known for operating at rated output without derating after 10 to 20 minutes.
Bill
I'm going to add on in steps first getting batteries. then upgrade from my 35 amp for a lota 55 charger for bulk.Naws has the best price I've found on them. And use my 400 watts for finish charging. Cc next and then panels 1at a time. Easier on the pocket that way.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Im aware of the new x model with a 3 year warranty. All i can find on Iota specs is ac amp requirements and .80 eff nothing on pf.
I would expect that they will add to the product line over time... They are really decades behind the times here.
https://www.iotaengineering.com/news_item2015_0309.htm
Short of looking at the new Inverter-chargers (many have some very nice charging options), the Xantrex TC-2 series seem to be very nice (but not cheap).
http://xantrex.com/power-products/battery-chargers/overview.aspx
https://www.solar-electric.com/residential/batteries-battery-storage/battery-chargers.html?manufacturer=Xantrex
-Bill
Just watch the temperature of the genset "head and windings" as it runs. Remember your high altitude deratings also apply to poorer cooling at higher altitudes too.
You do have to check the ratings... A Honda eu2000i is rated for 2,000 watts maximum but only 1,600 watts continuous... What is the continuous rating of your genset?
-Bill
And most of the time... Good enough is good enough.
In engineering... A factor of 2 (or 1/2) difference is almost negligible. A factor of 10x (or 1/10) is a night vs day difference (and you can usually "ignore" the smaller factor).
-Bill
5% rate of charge is fine for Equalization.
5% rate of charge tends to be more of an issue if you are running loads in the daytime (too, or predominantly)... Those daytime loads reduce available current for charging the battery bank (to less than 5%).
If you are montly weekend usage, then the weekday 5% rate of charge and no/low loads is an OK way to go.
Generator charging is fine, but tends to be expensive. For many people, they charge (for example) from 50% to ~80% state of charge in the early monring, and let the solar continue finish charging. Gensets tend to be more fuel efficient at 50% or higher loading. Some folks even have used a smaller genset (like a Honda eu2000i or equivalent) for afternoon charging (during bad weather) as the batteries go above 80% state of charge (and the Lead Acid battery naturally limits charging current).
As long as you are actively cycling the battery bank, you really do not need to get over 90% state of charge once per week (one battery mfg. even suggested to a poster here that you only need to fully charge a cycling battery once every ~28 days maximum).
You do not need to get to 100% state of charge very often... That is mostly done when you "equalize" your battery bank (over charging "full cells" to bring up weak/less than full cells to 100% state of charge--Measure and long specific gravity)--Typically once per month (Trojan has suggested equalization when high to low SG variation is 0.015 to 0.030 or higher difference).
Note that sealed batteries (AGM, GEL) do not need high voltage equalization. Doing an extended "absorb" charging cycle (4+ hours? Don't remember), has been suggested as the AGM "eq" cycle (once over 6 months).
-Bill
Fully charged (excluding equalization) would be >~90-95% state of charge. Going to 100% SoC often (daily, even weekly) is hard on Lead Acid Batteries (basically near-equalization, gassing, loss of electrolyte, erosion of plates, positive grid corrosion--Oxygen forms on positive plates and causes grid oxidation). Also, keep batteries relatively cool (watch charging at >90% state of charge, Lead Acid batteries tend to get hot at this level, even with 2.5 to 5% rate of charge--Let batteries cool and start charging again the next day if equalizing stubborn low SG cells).
This is the "theory" I have gathered from years of reading here... Anyone with differing or more detailed suggestions, please feel free to post.
-Bill "not a battery engineer/expert" B.
You just put the O in the wrong spot.
https://en.wikipedia.org/wiki/Coulomb's_law
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Coulomb--Yep, got it to work (only when wifi connected to spell check with Google--Still could not get the off line spell check to work).
-Bill