I think I need to add a second CC, but unsure

Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
edited July 26 in Solar Beginners Corner #1
Hello! Currently struggling with my off-grid setup. I apologize for the long post, but tried to include all pertinent info.
I bought the system lightly used a few years ago and paid the seller (also a master electrician) to help with the installation.
I am still building the house, hope to finish in another year. But I can see that I'm not getting enough from the panels to charge the batteries in a day if I use more than 10% even though I get about 6hrs/day of sun.
Specs -
-System: 12v
-Batteries: 4 6v 300ah Lifeline AGM GPL-6CT, series/parallel
-CC: Morningstar tsmppt60
-Inverter: Magnum 2812 2800 pure sine
-Panels:
Hanwha Q Cell 385w Mono Duo Cell
Watts (STC)                                  385 W     
Max Power Voltage (VMPP)     40.05 V      Max Power Current (IMPP)         9.61 A      Open Circuit Voltage (VOC)      48.21 V      Short Circuit Current (ISC)           10.10 A   Max System Voltage (UL)        DC 1500 V
**Here's my issue:
I have 3 of these panels, but it seems (I may be wrong) the tsmppt60 can only handle 2, so I'm using 2 in parallel.
According to the manual:
Charge Rating                  60a
Max. PV Open Circuit Voltage (Voc) 150v
Solar Overload
The TriStar MPPT 150V will limit battery current to the Maximum Battery Current rating. An over-sized solar array will not operate at peak power. The solar array should be less than the TriStar MPPT 150V Nominal Maximum Input Power rating for optimal performance. For more  information see the Nominal Maximum Input Power asterisk on p. 63.
Nominal max. Operating Power*    800w
*Input power can exceed Nominal Operating Power. Controller will limit and provide its rated continuous maximum output current into batteries.
So do I need another CC/more panels? Different panels? Other?
Thanks for any help!

Comments

  • wellbuiltwellbuilt Solar Expert Posts: 683 ✭✭✭✭
    Honestly , for a house you should be running a 24 volt system . 
     12v is for a rv or very small cabin . 
      If you get a 24volt inverter 
      You could run double the solar panels on your controller so 1540 watts .
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    While I do agree, I have looked at that option, but it would cost more than any other upgrade possibilities. Like $1500, last time I looked.
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Hope2Learn,

    I like to have a "balanced" system... loads->batteries->solar panels... So, starting with what you have.

    For me, the Battery Bank is the "Heart" of your system. They define the loads you can support, and the size of the solar array... And, of course, a second calculation that takes loads+Hours of sun per day. We use some generic rules of thumbs to get "close" to a working+reliable system. None of the below is written in stone. Please as questions/make corrections in my guesses/assumptions.
    • 4 6v 300ah Lifeline AGM GPL-6CT, series/parallel as a 12 volt bank
    • gives you a 12 volt @ 600 AH battery bank
    First, solar panels based on rate of charge... 5% is minimum and can work OK for a weekend/summer usage. 10%-13% is good for full time off grid. And >13% in some conditions (heavy loads, reduce genset runtime/fuel usage):
    • 600 AH * 29.0 Volt charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 1,130 Watt minimum array
    • 600 AH * 29.0 Volt charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 2,260 Watt array nominal
    • 600 AH * 29.0 Volt charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 2,380 Watt array "typical cost effective" maximum
    Next, need to guess at your loads (over night, daytime in bad weather, etc.). Typical off grid cabin/home we assume 2 days of stored energy and 50% max planned discharge (for longer life)--This basically assuming 1/4 discharge of battery (to 75% State of charge on day 1, and 50% SoC on day 2 of no sun--Next day start charging with solar or backup genset):
    • 600 AH * 12 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 1,530 WH per day--Design usage
    • 10% battery usage * 600 AH * 12 volts * 0.85 AC inverter eff = 612 WH per day (of 120 VAC power)--Your usage?
    The several factors that could give you less idea battery usage:
    • Not enough solar panels/sun/backup genset charging
    • Batteries are sulfating. Lead acid batteries that sit below ~75% state of charge will begin to sulfate quickly (sitting under charged for day/weeks/months.
    • Vampire loads--Loads that you did not expect or small loads (few lights, computer, etc.) left on for hours/days at a time:
    https://www.solar-electric.com/magnum-ms2812-g-2800-watt-12-volt-pure-sine-wave-inverter.html

    This inverter if left on (not search mode) will use 30 Watts (8 Watts if in "search mode")... If left on 24 hours per day:
    • 30 Watts * 24 hours per day = 720 Watt*Hours just to "run" the inverter without loads
    • 612 WH "your daily usage" + 720 WH inverter tare losses = 1,332 WH per day system usage (inverter takes more power than your daily loads? If left on 24x7). 
    That would be my "guess" at your daily loads... Could be 2x that for a Weekend system in sunny weather--Or if you have lots of loads during the (construction equipment) and just overnight loads (LED Lighting, laptop, cell phone charging, RV water pumping, etc.).

    Next, sizing the solar array based on your location and daily loads (why I needed a load estimate to do the math for panels). Fixed array, facing south:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Memphis
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 55° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.26
     
    3.71
     
    4.49
     
    5.17
     
    5.08
     
    5.29
     
    JulAugSepOctNovDec
    5.47
     
    5.36
     
    5.28
     
    4.75
     
    3.58
     
    3.13
     
    Notice that 6 hours of "full noontime sun" on a solar panel per day--Not many places have that, and usually only during summer. In this case, assuming you use less power in winter and/or a backup genset to charge the battery bank and run your loads... Toss the bottom 3 months and have February 3.71 hours of sun per day (something like 20 year average):
    • 1,530 Watt*Hours per day * 1/0.61 off grid AGM battery AC system eff * 1/3.71 hours of sun (Feb) = 676 Watt array "Feb" break even
    And highly recommend that you do expect to use 100% of your daily "predicted" harvest... Suggest that you only use 65% to 50% of predicted harvest (for base loads--Those loads that you want to use every day):
    • 676 Watt array * 1/0.65 base load "fudge factor" = 1,040 Watt array with 65% base load fudge factor.
    So--An array from 1,130 Watts to 2,260 Watts to 2,380 Watts (all based on 5% to 13% rate of charge) would be really nice/justifiable.

    Batteries are expensive, and under charging / over discharging is usually the #1 "killer of lead acid batteries". AGM Batteries are very nice lead acid batteries--But you are looking at probably 5-7 years cycle life (hot batteries have shorter life, under charged batteries have shorter life).

    Other rules of thumbs... For a 12 volt system, suggest 1,800 Watts (continuous) is a good maximum. A 2,800 Watt inverter under full load can draw:
    • 2,800 Watts * 1/0.85 AC inverter eff * 1/10.5 low voltage cutoff = 314 Amps
    You need very heavy/short wiring to keep the voltage drop below ~0.5 volts (suggested) for 12 volt wiring...

    And for a 600 AH @ 12 volt Lead Acid battery bank (flooded cell/deep cycle type):
    • 600 AH * 1/250 Watts * 1/100 AH (12 volts = 1,500 Watt suggested max inverter wattage for FLA battery bank
    AGM batteries have higher surge/operating current... And larger AC inverters have higher "tare" losses. But drawing ~300 Amps (~2,800 Watts) from AC inverter would draw your 600AH battery bank dead in 2 hours...

    Suggest smaller AC inverter (or larger battery bank)--Again balanced system design. And if you want higher wattage AC inverter, suggest higher voltage battery bank and larger storage battery bank...

    An MPPT type charge charge controller (works on 12/24/48 volt batteries, at least) on a 12 volt bus and 60 Amp output rating, the maximum typical array would be:
    • 60 amps * 14.5 volts charging * 1/0.77 panel+controller deratings = 1,130 Watt "typical useful max" array
    Assuming a 150 VDC max input voltage--Then (very roughly) around 110 Volts Vmp-array (cold climate, Vmp/Voc rises, hot array/climate, Vmp/Voc fall)... So need to do a bit more calculations--But you can put 3 panels in parallel--Or 2 in parallel and 1 or 2 parallel strings (reality is that 2 parallel strings * 2 series panel--Is more wattage than is "useful" for your 12 volt battery bank and 60 Amp controller).

    Just to give you an idea of what you should expect from 3x 385 Watt panels (in parallel = 1,155 Watt Pmp in standard conditions) during July:
    • 1,155 Watt array * 0.61 AC AGM system eff * 5.47 Hours of sun (average July day) = 3,854 Watt*Hours per day harvest
    So--If you use most of the power during the day, and limit your battery overnight usage to 1,530 WH to (2x1,530= ) 3,090 WH (overnight typical/max). And with 3x of your panels (in July) will do a good job of recharging--Or supplying daytime loads (saw, charging tool batteries, etc.)...

    Make sure your battery bank is getting charged--If you are drawing the bank to "near dead" and only 1/2 charging--The batteries will not have a long life.

    I will stop here--I have made lots of guesses and suggestions...

    Your thoughts/comments/corrections?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭
    While I do agree, I have looked at that option, but it would cost more than any other upgrade possibilities. Like $1500, last time I looked.
    While it might cost more, it would be better to do it now than wait and do it later.

    The "Master Electrician" doesn't/didn't understand DC electronics. I do NOT know your expected loads. I would certainly stop now and look at your projected loads.

    The inverter you currently have is NOT UL1741 (designation for home safety) if you have to be inspected for building codes or insurance, you may need to switch. Sometimes if the power center (where the batteries, charge controllers and inverter live) is outside the AHJ (Authority Having Jurisdiction) may not care. I'm NOT saying the Magnum 2812 is a bad unit, but it would take very large wires to allow it to work well off a 12 volt battery bank.

    I'm NOT saying you need a larger inverter. I used an 1800 watt inverter for most f my 20 years of living off grid. Including running air conditioning units,  table top kitchen appliances, washing machine. But it's a 24 volt inverter, and truly would have liked to switch to a 48 volt system when I had to move from my cabin too my 16x60 mobile home.

    Charge controllers work on the amperage output. Quality MPPT charge controllers can be 'over paneled' to some degree to help get as much from your array as possible. Your 60 amps controller will handle 60 amps when charging a 12, 24 or 48 volt system. So with a 12 volt system it can handle about 13.8 (volts charging for 12 volt) x 60 amps or an array of about 828 watts without losses. Most panels are rated at STC (Standard Test Conditions) but produce closer to NOCT values (Normal Operating Cell Temperature) which are about 75% off STC.

    Without getting too much more involved, You single charge controller can handle about 1000 watts of array at 12 volts, 2000 at 24 volts and 4000 at 48 volts. If you switch system voltages now it may save you money in the long run. You may be able to get by with just 1 charge controller.

    From what Bill has said, it appears you are near Memphis in the sunniest part of the year. So you have been using 2 - 385 watt panels so you have found that 770 watts of array during 6 hours of available charging (assuming sunny days) is not recharging the battery bank with your current use. So any cloudy or overcast day will make the problem even worse. Roughly you should be producing 770 x .75 (NOCT) x 6 = 3460 watt hours per day. Will your loads change when you have half the available sun in Dec and Jan?

    According to the manual:
    Charge Rating                  60a
    Max. PV Open Circuit Voltage (Voc) 150v
    Solar Overload
    The TriStar MPPT 150V will limit battery current to the Maximum Battery Current rating. An over-sized solar array will not operate at peak power. The solar array should be less than the TriStar MPPT 150V Nominal Maximum Input Power rating for optimal performance. For more  information see the Nominal Maximum Input Power asterisk on p. 63.
    Nominal max. Operating Power*    800w
    *Input power can exceed Nominal Operating Power. Controller will limit and provide its rated continuous maximum output current into batteries.
    It sounds like you can put all 3 in parallel and it would help production during low light times in the morning and evening and limit output to 60 amps when more power is available.

    I would suggest looking at your perceived total loads in the future. I wanted at very least a window air conditioner running 24/7 in the summer. I built a cabin, in the shade, with 6" thick walls, I never got to try out the system when I had a battery capacity to run 24/7, but I'd bet I was close. I only had 4 golf cart batteries, about a 430 amp comparable 12 volt battery bank to what you have now. I started with a 1000 watt array and could run about 4-5 hours along with the rest of life, lights, computer, TV, fans. No fridge the first year. I added bringing the array to 1600 watts and added a fridge for a couple years. The last year of 4 (batteries 5yrs old, from my earlier 12 volt system), I turned off the fridge as my batteries were showing signs of reduced capacity. 

    I suspect you'll want air conditioning in Memphis?

    A 5200 btu (small window unit) will run about 450 watts with the compressor running, that's 450/12= 37.5 amps each hour of 100 % duty cycle, and on top of that you will need energy to charge the battery bank. There will be additional losses in converting DC to AC.

    For my 16x60 mobile home I bought, had to move. I have a 5000 watt array, 'stuck' at 24 volts since I bought a 660 ah, 24 volt forklift battery, that I moved to the new home.

    There are some on line calculators to figure out your intended usage, here's one;

    Off Grid Solar Load Calculator | Northern Arizona Wind & Sun (solar-electric.com)

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭
    While I do agree, I have looked at that option, but it would cost more than any other upgrade possibilities. Like $1500, last time I looked.
    So, I normally wouldn't recommend one of these all-in-one units, But I trust boB of Midnite Solar to have checked them out and and it has a 1 year warranty from Midnite.

    The owners of Midnite Solar boB and Robin Gudgel started at Trace/Xantrex (Now Schneider), Started Outback Solar (producing one of the first effective MPPT charge controllers) then moved on to start Midnite Solar.

    MidNite Solar DIY Series MN3024DIY Inverter & charger | Northern Arizona Wind & Sun (solar-electric.com)

    This has an internal MPPT charge controller, and says it will handle up to 1700 watt array. You can use your existing batteries in a single string of 4 batteries. This won't give you a huge storage bank, but I'd hate to see you have to start with a new set of batteries.

    This is NOT UL1741!!! so please check with your AHJ if you need to have your system checked. Here's a link to a current discussion where boB says they will have the next versions inspected to UL 1741;

    MidNite Solar DIY Series — northernarizona-windandsun (solar-electric.com)

    With something like this you can move up to a 24volt system voltage and use your current batteries (usually a bad idea to add new batteries to old unless, less than 6 months old) and just add solar capacity using the internal charge controller and you current charge controller in addition if needed. That should get you up to a 3500 watt array support.

    Look locally for used or cheap solar panels. I recently bought 6 - 310-330watt panels for $450 left overs from a new install. Only 2 actually used. 1 have the backing nicked and I used some liquid electrical tape too seal and one had the frame bent when installing so they replaced it.



    If you can't find anything locally, you might check with Santan Solar, they buy used panels from commercial installs that are upgrading out in Arizona. Cheap, but ask about labeling.

    Hope this helps! FWIW- my forklift battery is now 10 years old, and will need to be replaced in the next year or 2. I'm considering one of Midnite's 48 volt DIY systems. I would keep at least 1 of my 24 volt inverters in case of emergencies and need to use at least 1 of my Midnite classics charge controllers, I have 3 now with my 24 volt system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    edited July 26 #7
    I really appreciate everyone's replies. You've obviously given me a lot to consider. I'm going to try to be just as thorough in my replies, but first I'll need to parse this info to be sure I fully comprehend as solar isn't my first or second language as it is for you guys. Thank you for your help and patience.
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    edited July 27 #8

    @BB. Thanks for the suggestion of using the 3rd panel in parallel, I've ordered a pair of 3to1 connectors. My only question so far, can you tell me what you mean by (or direct me to read) "rate of charge". eg 5%,10%, 13%?
    About my loads and usage: I currently have no overnight loads. I turn the inverter on when I come to the house to work in the morning.  Most of the year I balance my daytime loads (tool battery chargers, shopvac, tools, fans, dehumidifier, fridge {keezer}, lights, etc,) with the incoming sun as shown on the Trimetric battery monitor. So usually the batteries stay at 100% except during periods of low sun when I may let them come down 10-15% then use the generator tomorrow or the next day if there is no sun. In the summer, i have to use a window AC unit (1500w), mainly for dehumidification, as there is a lot of wet mud and concrete in my build, so the generator runs most of the day. I recently had generator issues and tried experimenting with the AC.  It could only run for 36 minutes before I was down to 90%. I have also tested the keezer, letting it (and the inverter) run all night, got me down to about 86%.
    While I am aware of load calculations and have done them and have the numbers, they are a pure guess, as this "house" I'm building and the life I will live in it, are wildly atypical. The point of the house was to build something as efficient as I could imagine/afford. It's built into a slope, so half underground using earthbags and whole log timbers from the site. Most walls are 18" thick, so a lot of thermal mass. It's facing south, the roof is covered in several inches of soil with a 3' overhang to keep the sun out in the summer, but let it in for heat in the winter. The front is not yet sealed, insulated or sided, but so far it doesn't get too hot or too cold, the rest is underground, should finish around $20k. There are a lot of unknowns at this point as to what my electric needs will be. I might be able to get by with a 5000btu window unit, running for 2hrs a day. I really dont know yet how easy it will be to cool and how long it will hold the temp. It would be amazing to do everything on solar, but if I have to seasonally run the generator for AC, I will. Once the house is done and I have a better idea of loads, I will be interested in trying to match my system to those loads, but currently I just don't know and all my money is going to building materials. I'm just trying to do the best I can with what I have, but keeping an open mind towards upgrades. Thank you.
    @Photowhit Thanks for the all-in-one suggestion from Midnite, that looks like a nice upgrade when my finances can be directed to anything besides this build. Yes, I'm finding that master electrician was not a solar pro. My "house" is uninsured. No permits, no inspections. Batteries and inverter are connected with 4/0 wire. I looked locally for panels a few days ago, could only find one on c-list, they want $500 for a single 400w panel (ha). I will check out Santan when the time comes. Thank you.
  • wellbuiltwellbuilt Solar Expert Posts: 683 ✭✭✭✭
    Your battery is 600AHs @12 volt most battery manufactures recommend 10% rate of charge so600AH = 60 amps
      
    Out back  flex power one  with out back 3648 inverter fm80 charge controler  flex net  mate 16 gc215 battery’s 4425 Watts solar .
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    The battery capacity is typically based on ~20 Hour discharge rate (i.e., a 100 AH battery / 20 hours = 5 amps continous from 100% full to 0% full (dead). There are other discharge rates--But 20 hour rate is pretty common and usually works well for our needs (a 6 hour rate is a faster discharge, and the "apparent capacity" will be less).

    Always good to browse the Battery Manual (and other manuals for your equipment) at least once:

    https://www.solar-electric.com/lib/wind-sun/Concorde_Lifeline_tech_manual.pdf

    A very handy tool is the Kill-a-Watt type energy meter. The standard ones work on 15 Amps @ 120 VAC (north American) voltages/current levels:

    https://www.amazon.com/s?k=kill+a+watt+meter&ref=nb_sb_noss_2

    And for larger loads, there are "whole home meters"... This is one (again, links are for information--I have not used this one myself):

    https://www.theenergydetective.com/

    Many others available... The Kill-a-Watt type meter is a great learning tool, as well has handy to measure the "real loads" of your plug-in appliances. For our needs, we need AC+DC clamp meters--There are AC only meters--And they are great meters, but don't work on DC/Battery Bus current).

    Also, you can estimate larger loads with an AC+DC current clamp meter (DMM):

    https://www.amazon.com/gp/product/B00O1Q2HOQ (less expensive, lower current levels)
    https://www.amazon.com/gp/product/B019CY4FB4 (more expensive mid-range meter)

    Note: to measure current, you need to clamp one wire at a time... If, for example, you need to measure the 120 VAC current, you need to "split the cord" or get a 120 VAC plug/socket breakout box so you can "clamp" the right cable.

    AC+DC current clamps are great--But you can only "estimate" total energy usage (they do not measure time and do not measure "real power"--AC math gets complicated very quickly).

    A Kill-a-Watt type meter is quick, relatively accurate, cheap, and great to measure loads on your genset/solar system so you can figure out what is really happening... Similar with an AC+DC current Clamp DMM.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    wellbuilt said:
    Your battery is 600AHs @12 volt most battery manufactures recommend 10% rate of charge so600AH = 60 amps
      

    Thanks wellbuilt, it's sinking in now.
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    I do have a killAwatt meter, and used it to do a couple surveys, but it's been a while, and needs have slowly reduced. I will definitely do one again when the move-in date gets closer to get current, thanks. I have also been semi-familiar with my manuals but will check that one again as I can take the hint that it's relevant. Thank you.
  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭
    Sounds like you have done a lot of research with your build. I've often recommended a berm shelter for people trying to have minimal energy needs. Sometimes it doesn't work out well, and sometimes it's good to talk with others in the area to see what they have done.

    I have a friend who grew up in Webb city MO in a berm shelter. I picked his brain a good bit. They kept air moving and avoided putting furniture against walls. I suspect southeastern Missouri is dryer than Memphis.

    I also would suggest you might be better off with a dehumidifier than an air conditioner at this point, other than needing the air conditioner to work in comfortable temps. The dehumidifier reduces the mister in the air and warms the air, warm air can hold more moisture than cold air so the percent of moisture in the air would be lower, I think... Also keeping air moving will help dry those moist things. I've run a dehydrator with and without fans, and with fans works better even if it's just a minimal breeze. I now use 2 laptop cooling fans in my solar dehydrator.

    Love the sound of your adventure! hope you will share phots sometime in the future! FWIW - this is the tiny home I built with 6" thick walls!


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    edited July 27 #14
    I've definitely done nothing but researching every angle for years, only time will tell if it was enough.
    While S.E. Missouri is close, nothing else seems to be as hot and humid.
    I also have dehumidifiers and mostly use them in the winter for the reason you mentioned, while less watts than the AC, they do produce warm air which just won't work in the summer.
    I also have plans to build a solar dehydrator. Any complaints with yours?
    Thanks! That's a cozy cabin, I'm sure that was an adventure too!
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Hope2Learn,

    No hidden hints... More or less just to confirm you have the correct set-points for charging (bulk/absorb) and float voltages (AGM batteries are generally set to charge below FLA batteries (typically 14.4 volts AGM vs 14.75 volts FLA for absorb set point).

    The "issue" with AGM batteries (sealed)--Is you cannot measure the state of charge with a hydrometer ("gold standard" for Lead Acid batteries--flooded cell type). You are left with monitoring battery voltage (charging/discharging/time on charge, etc.). 

    The Lifeline manual has lots of charts and tables at the end showing state of charge vs voltage (charging, discharging, resting, different discharge levels, etc.). That was what I was "hinting" too. You can monitor the bank voltage during different parts of the day and see how that bank was performing (as well as use Kill-a-Watt meter for AC loads, and possible a Clamp meter or even Battery Monitor System--To better understand how deeply you are discharging the battery (and/or if the batteries are in need of "help"--Such as elevated charging to help "Conditioning" the battery bank).

    If I was a little to "obscure" and supplying hints--My humble apology. I try to not do "hints" but absolute data/information/links (and being clear on when I do not have "answers").

    Understanding what is happening with your system--Voltage measurements, current draw/charging, etc... To ensure the system is operating "correctly". Measuring voltages under load and under charge--Looking for dirty electrical connections, too long/to small of AWG wire size for DC battery bus voltage (excessive voltage drop), bad cells/batteries, over discharging/under charging/etc.

    If you can tell us more about your hardware and wiring. At this moment, don't know if system is working OK or if there is charging issues (bad wiring, miss-configured MPPT charge controller). Or simply drawing more AC Watt*Hours (Amp*Hours @ 12 volts) than the system can supply.... Or too much AC Wattage and too small of DC wire from battery bank to DC inverter--Causing excessive voltage drop...

    More questions than answers at the moment.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,650 ✭✭✭✭✭

    I also have plans to build a solar dehydrator. Any complaints with yours?
    I'd plan on better venting and sealing over night and keeping a fan running. We reach the dew point most nights late summer and fall.

    I really like the curved glass 'ice cream' that mine is made from, but had to add solid aluminum screen to block the sun, It went from dehydrating to cooking pretty fast, I also need to add a thermostat and exhaust fan so I don't cook things...lol.

    Ice Cream Display Counter - Manufacturers Suppliers amp Dealers
    The front glass out of something like this with solid sides.


    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    BB. said:
    Hope2Learn,

    No hidden hints... More or less just to confirm you have the correct set-points for charging
    Got it. Yes, the first year I had the system I got fairly involved with fine-tuning. I did exactly this. I set those specific Lifeline values manually into the CC through the dongle/com port.


    If I was a little to "obscure" and supplying hints--My humble apology. I try to not do "hints" but absolute data/information/links (and being clear on when I do not have "answers").


    More likely it's me being slow.


    Understanding what is happening with your system--Voltage measurements, current draw/charging, etc... To ensure the system is operating "correctly". Measuring voltages under load and under charge--Looking for dirty electrical connections, too long/to small of AWG wire size for DC battery bus voltage (excessive voltage drop), bad cells/batteries, over discharging/under charging/etc.

    If you can tell us more about your hardware and wiring. At this moment, don't know if system is working OK or if there is charging issues (bad wiring, miss-configured MPPT charge controller). Or simply drawing more AC Watt*Hours (Amp*Hours @ 12 volts) than the system can supply.... Or too much AC Wattage and too small of DC wire from battery bank to DC inverter--Causing excessive voltage drop...
    All the wires connecting the batteries and then connecting them to the inverter are 4/0, and are as short as possible while also being of equal length.

    I will start paying attention to those battery soc values and seeing how they match to the current voltages as reported by the battery monitor.

    Thanks for the suggestions BB.

  • Hope2LearnHope2Learn Registered Users, Users Awaiting Email Confirmation Posts: 10 ✭✭
    edited July 27 #18
    That looks pretty fancy. And a little bit like a solar oven, so I can see it cooking. The diy ones I've seen were more like a tower made of plywood where the heat would rise up and out the top. Good tip on dewpoint.
Sign In or Register to comment.