ATS + generator = ac power + battery charge? possible?

Apologies for my silly topic I was trying to convey my question in as short manner as possible. 

I am planning my off grid solar system and was trying to figure out how to incorporate as seamlessly as possible my honda generator and iota converter charger (inverter will be a magnum standalone - not charger). 

Ideally, I will always run off my inverter for ac and batteries for dc but I am confident that I will need to boost my batteries every so often especially in winter (NY upstate.. snow).

It will be best if I can just start up my generator, plug it in, and it will automatically (via an automatic transfer switch?) run my ac power and charge my batteries - at the same time. 

I cannot tell if Go Power TS-30 indeed does that. And if it does - do I need to also disconnect the panels and mppt (via disconnect switch?) when I am doing so? 

If this ATS won't allow me to do that then any other one will? 

Comments

  • mcgivormcgivor Solar Expert Posts: 3,403 ✭✭✭✭✭
    An auto transfer switch can be used, the inverter output would be connected to the backup power input of the ATS, the generator connected to the prime input of the ATS  and the output of the ATS goes to the distribution panel, I know it sounds backwards but it will work.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    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.
  • mike95490mike95490 Solar Expert Posts: 8,761 ✭✭✭✭✭
    Often, the high end inverters, will manage both AC pass-thru loads, and charging batteries from the generator

    Top of the line inverters will adaptively charge batteries till the load exceeds the generator rating, and then switch to inverting to assist the generator. (for those times when the heat pump is on, the sump pump is on, and then someone turns the blowdrier on.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || 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 ,

  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    mcgivor said:
    An auto transfer switch can be used, the inverter output would be connected to the backup power input of the ATS, the generator connected to the prime input of the ATS  and the output of the ATS goes to the distribution panel, I know it sounds backwards but it will work.
    And this assuming a standalone inverter and charger and not an inverter/charger unit? 

  • mcgivormcgivor Solar Expert Posts: 3,403 ✭✭✭✭✭
    edited May 15 #5
    minisolar said:
    mcgivor said:
    An auto transfer switch can be used, the inverter output would be connected to the backup power input of the ATS, the generator connected to the prime input of the ATS  and the output of the ATS goes to the distribution panel, I know it sounds backwards but it will work.
    And this assuming a standalone inverter and charger and not an inverter/charger unit? 

    Correct, the charger would be connected to the generator output before the ATS 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    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.
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    edited May 16 #6
    Thank you. 

    Sorry for being redundant - if I set it up correctly as you mentioned  - then when I plug in the generator it will charge my batteries via my IOTA charger but also keep my ac load (and dc?) going - automatically and once I unplug it go back to normal inverter power?

    They give this diagram for this ATS I found: https://gpelectric.com/wp-content/uploads/Using_a_Prewired_Transfer_Switch.jpg
  • mcgivormcgivor Solar Expert Posts: 3,403 ✭✭✭✭✭
    edited May 16 #7
    That diagram is for a RV type setupi which will lead to confusion.  Below is a picture of my ATS on the top N is prime input, R is backup input the lower terminals are the output. The drawing is a single line example of the layout I had in mind, the battery to inverter and charger are the DC side, this will allow AC loads to run on generator when running then transfer to inverter when not. The charger must be connected to the generator output before the ATS, it will only charge when the generator is running.

    PS....the wiring colors are what is used in Thailand, red is live, black is neutral 220VAC, it's not DC
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    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.
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    edited May 16 #8
    Wow. I can't believe it but I think I got it! then the ATS I mentioned will work if I wire it your way? I will order one today. I am starting to collect parts for my system. I am working on my diagram for my system and will post it soon.
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    I just posted my diagram. Can you please look it over and tell me what I am doing wrong, missing, and how you would have done it differently? https://forum.solar-electric.com/discussion/355740/please-critique-my-plan-diagram/p1?new=1
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    I did post a comment on your other thread--But I suggest that you keep all similar posts in one thread--Saves us splitting discussions in different locations.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    Sorry about that Bb. I'll just keep using this thread. I just found 250watt paneles, mono, brand new, manufactured in 2015 for $100. He has two different models I'll post it.

    $0.4 a watt is good? The 60amp epever will take 750 watt max so I can get 3 of these, right? 
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    $0.40 a watt.. Sounds better than the $5.00 a watt that I paid 15 years ago for my GT system.  :)

    Pricing is what you can get delivered to your front door. And it is possible to get new panels for $0.50 a Watt or so (+shipping?).

    Need to see the specifications for the panels (Vmp and Imp), a link to the EpEver you want to use, and the voltage of the battery bank--Usually need to know all of that to configure the array/charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    mcgivor said:
    That diagram is for a RV type setupi which will lead to confusion.  Below is a picture of my ATS on the top N is prime input, R is backup input the lower terminals are the output. The drawing is a single line example of the layout I had in mind, the battery to inverter and charger are the DC side, this will allow AC loads to run on generator when running then transfer to inverter when not. The charger must be connected to the generator output before the ATS, it will only charge when the generator is running.

    PS....the wiring colors are what is used in Thailand, red is live, black is neutral 220VAC, it's not DC


    I am going to only buy a battery bank (six 12V AGM batteries with 105ah each wired in parallel) and inverter fro now to learn my load usage. Can I use the ATS in a way where when I plug the generator in it will charge batteries and power distribution panel at the same time and when I unplug it will let inverter feed distribution instead? 
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    My personal suggestion... 2x 6 volt @ ~200 AH batteries in series, x 3 parallel strings (12 volts @ ~600 AH battery bank).

    Instead of 6 cells (12 volts) * 6 batteries for 36 cells to check, you only have 18 cells to check with 6 volt golf cart batteries in series parallel. Also, it is very quick and easy to check the voltage of each 6 volt battery for battery health... With 12 volt batteries all in parallel, you cannot check the "health" of each battery with a voltmeter without disconnecting each one, and measuring individually.

    Also, I am not a big fan of going over 2-3 parallel strings of batteries... In any case, if you do parallel batteries, here is a quick read on how to optimize the connections:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    BB. said:
    My personal suggestion... 2x 6 volt @ ~200 AH batteries in series, x 3 parallel strings (12 volts @ ~600 AH battery bank).

    Instead of 6 cells (12 volts) * 6 batteries for 36 cells to check, you only have 18 cells to check with 6 volt golf cart batteries in series parallel. Also, it is very quick and easy to check the voltage of each 6 volt battery for battery health... With 12 volt batteries all in parallel, you cannot check the "health" of each battery with a voltmeter without disconnecting each one, and measuring individually.

    Also, I am not a big fan of going over 2-3 parallel strings of batteries... In any case, if you do parallel batteries, here is a quick read on how to optimize the connections:

    http://www.smartgauge.co.uk/batt_con.html

    -Bill
    Thanks Bill. 

    I thought that AGM batteries are maintenance free so no need to check anything? I picked them over the much less expensive flooded because I read that they are much better for installations where you aren't near batteries a lot so you can't check on them often - like my installation. 

    Sam's club AGM 12v 105 x 6 = $1078
    amazon (cheapest I found so far) AGM 6v 225h batteris x 6 = $1394

    Or 

    Sam's club 6V flooded golf cart 205ah batteries x 6 which will cost $ around 540....  

    So to have less parallel and still have AGM  I need to pay another $310 or pay less but have flooded instead of AGM. Keep in mind that these won't be solar charged for the near future but just generator charged. Also the ones from sam's club come with 18 month warranty free replacement while the amazon is 12 month if defected so not sure how that will be decided. 

    If you think it is worth the extra money or I am better off with the cheaper flood - to make it a healthier and less problematic system - I will do it. 
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    With AGM, all you can check on them is the voltage (and how warm they are)... No caps/specific gravity to check.

    For your battery bank, checking voltage (and if FLA, specific gravity with a hydrometer) is the only way to quickly and easily verify the (estimated) state of charge of the batteries. With 6x 12 volt batteries in parallel, you only get the "bank average", not the per battery average (old batteries, you used to be able get at the inter cell buss bars and measure per cell voltages--But not most modering batteries--other than large Forklift/Traction batteries that are built out of individual cells).

    You can use a DC Current Clamp DMM and measure charging/discharging current--Which is very helpful to make sure all is balanced--But can be a bit of a pain depending on how you parallel connect the batteries (each battery back to a central bus bar, vs daisy chain from battery A to battery B to battery C, etc..). It is nice to be able to clamp onto one wire, and measure the current for that one string... Vs measuring 20 amps in and 15 amps out, and getting 5 amps going into the one string.

    I am a big believer in keeping things simple... 6x 6 volt @ 200 AH batteries is 1/2 the number of cells vs 6 12 volt @ 105 AH batteries, 1/2 the number of parallel connections, few larger cells vs more smaller cells... But for all my concerns, your average electric car has a 1,000 or more 18650 batteries in series/parallel and they work.

    AGM batteries are a much nicer version of the Lead Acid chemistry. Much cleaner, no fumes during normal operation (but AGM batteries that are over charged, or near the end of their life, do vent--So you still need to take precautions). They have much lower self discharge (~6 months between charging, vs ~1 month between charging for FLA), no cells to fill, higher surge current support, easier to ship (no pallets of batteries that tilted and spilled acid all over everything). Besides not being able to measure SG (which is the "gold standard" for FLA battery State of Charge), AGM batteries seem to last 1-2 years less than similar quality FLA batteries (that have been taken care of).

    You are between a rock and a hard spot... If you go 6 months between visits, AGM is the way to go. If you visit every 1 month and can recharge, that works fine for FLA. And, many (most?) people do "murder" their first battery bank or two because of mistakes (forget to turn off AC inverter when gone, spouse/friend leaves everything on and goes out for a day or two, and takes the bank dead... Have an emergency back home and don't have time to recharge the bank, etc... Will you "murder" your first bank or two--I have no idea.

    There is an option--You can install a 1% to 2% rate of charge solar array and a small charge controller... It will not recharge your bank, but will float it and keep the batteries "happy" while you are not up there:
    • 600 AH * 12 volts * 0.02 rate of charge = 144 Watt array (panel)
    For folks that have snow--They have been known to mount the "float array" on the side of the building vertically (or winter vertical, summer at 45 degrees--or whatever is correct for your location). The panel is above the drifts, and mounted vertical--Keeping it clear of snow. And FLA batteries kept "COLD", do have lower self discharge if the array is covered by drifted snow...

    Set the charge controller to float your battery bank (~13.6 volts or so), and you can leave the site and not have 1,200 Watts of solar panels and an expensive charge controller left to be damaged/stolen.

    If you are 5 years in the RV, $1,000 for 5 years for AGM vs a $500 bank that you replace once ($1,000 total for 5 years)--Assuming that no big issues (theft, "murder" of the bank, etc.)... Either seems to be a similar cost solution. With a small 1-2% float array, could you get 5 years out of the FLA bank made from cheap Golf Cart batteries? It is close, but a weekend place, cooler climate (cold batteries age slower), maybe.... 

    If the batteries are in the RV space (not vented directly outside), then AGM will probably make you happier. Some folks are very sensitive to the "rotten egg" smell of charging FLA batteries (sulfur based electrolyte).

    You can get a battery monitor... The shunt based monitors can accurately give you the AH in and AH out of your battery bank. And give relatively accurate state of charge estimates (they can drift--So you have to watch for that):

    https://www.solar-electric.com/search/?q=battery+monitor

    The Bogarts are the least expensive shunt based (from our Host)--A bit cryptic to setup (not a nice graphical interface).

    The Victron and Xantres are really nice with additional features (like a remote alarm output). The Victron even has Bluetooth.

    Then there is the "simple" and less expensive Voltage Only monitor. Such as the one from Midnite. Estimates state of charge and warning if not fully charged in the last week:

    https://www.solar-electric.com/midnite-solar-mnbcms.html

    What is best for you--I cannot say--And it is not my money. Best I can do is give you the reasonings. And the experiences of others here.

    I am still questioning--If you buy the RV, can you run it in your driveway for a few days/weeks and measure the energy consumption, weigh propane bottles before and after, etc.?

    Good luck,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    Bill I love reading your posts. Very detailed and well made. 

    I have started a search for well priced 6v AGM. I am confident I will find some and then we will have best of both worlds. 

    This summer we will go, hopefully, every week for a few days which means I will be able to maintain FLA. But in winter, when we have a ton of snow and freezing temp, we will go less for sure and maybe note at all as I have two very young kids and I don't want to be without running water with them. We might have a solution to that but I won't know yet. Your idea of vertical - keeping batteries alive is a great idea but again as you said - AGM will most likely make me happier (I also have a very keen sense of smell)... 

    I will find 6v AGM for reasonable price. 

    Thank you for the links on battery monitors. I saw this one taht comes with a shunt: https://smile.amazon.com/bayite-6-5-100V-Display-Multimeter-Voltmeter/dp/B013PKYILS/ref=sr_1_6?crid=1RYMNH3AVJM95&dchild=1&keywords=digital+battery+monitor+12v&qid=1590322811&sprefix=digital+battery+monitor%2Caps%2C165&sr=8-6#customerReviews

    Pretty cheap and reviews are good. This one will work?

    I now have two other minor issues: I was told (photowhit) that the batteries won't charge at full speed until 100% but instead will slow down charging at either 80% or 95% which is a huge difference. AGM are supposed to perhaps go to the 95% (another vote for AGM). 

    When I find my 6v AGM source I will call manufacturer of said batteries to find out. Also, IOTA makes these modules that is a most purchase because if you don't use it and aren't careful it will let generator over charge. They have an AGM (and FLA btw) specific modules so I sent an email to IOTA to see if their module will go to 95% before slowing or less... 

    So this 80-95% charge is indeed a bummer but not a killer then the 2nd minor issue is the length of time to charge.. I was thinking 3-4 hours but 10 hours is a different ball game to use generator. I ordered parts yesterday to extended generator run from 6 gallon tank and started planning a good silencer box for it as well. I am thinking that I will actually let the generator run at night - a hum at night will bother us less when we are indoor and the AC will run continually so the biggest battery drain will run off generator while it charges so in the morning we will be fully charged and AC off. 

    This is why I like this idea of no MPPT and array until we figure out our usage. I will just keep tracking usage but regardless I feel like in winter my array will not do much and will need this generator charging system for winter so I don't feel like I am doing work for nothing - which I hate. 

    I have no option of keeping RV.. no driveway. I live in NYC haha. at 34ft it is the size of many apartments here. 

    Another important question: the inverter I am getting magnum CSW2012 will automatically shut off due to low voltage which is great but.. the cut off is 10.5VDC. which at that point batteries will be 'murdered' right? anyone knows if I can change that setting to shut off when they hit 50% instead (whatever the voltage fro this is) 
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    The energy monitor you linked to is not a Battery Monitor... It only logs the current in one direction (counts up when current is flowing + to -, does not count when current is flowing - to +). You can use two meters (on one battery shunt), have one count the discharge current, and the other the charging current (as an example). And you push the reset button when the battery is full.

    It also has a 100 Amp limit--That is roughly 100 amps * 12 volts = 1,200 Watts... A 2 kWatt AC inverter will draw more current than the shunt is rated to carry and possibly burn it out.

    A true BMS is designed to measure current both directions, and you program the size of the battery--So it can give you and estimated state of charge... And the meters typically reset to 100% SoC when the battery is held at 14.4 volts (for AGM) for a couple of hours (the BMS also have other efficiency factors and such to make it more accurate when estimating SoC).

    It does not look like the CWS inverter family has a programmable LBC (low battery cutout).

    There are other models (more expensive, more features, etc.) that do have programmable LBC (Note that this 2 kWatt inverter is actually an inverter+AC Charger):

    https://www.solar-electric.com/magnum-ms2012-2000-watts-12-volts-inverter.html

    And you need a remote meter/control to do the programming (there are lots of inverter and meter models, don't hold me to that the above inverter mates correctly with this meter--I think it does, but you need to confirm):

    https://www.solar-electric.com/mameadrecofo.html

    As an alternative--I would really look hard at bringing utilty power to your site now (for $15k?) vs setting up and running genset/solar power for A/C, fridge, etc. for 5 years, then bringing in Utility Power later... I know the cost of running the power lines and monthly bills are not something to cheer about--But, I fear, that you will be spending lots of money and time over the next 5 years of RV living--And not getting what you really want (lots of power, quiet time, and low maintenance).

    Another issue is that the cost of bringing in Utility Power will probably go up in 5 years, and sometimes regulations/state PUC/economics may mean that the utility could refuse connection 5 years in the future (I don't trust the government+PUC, they make political based decisions all the time), or charge even a bunch more.

    If your system was just LED Lights, RV water pump, Cell phone and laptop charging, Solar could be a good fit (run the fridge/cooking/hot water/etc. from propane)--I.e., a ~300 Watt AC inverter+battery bank+solar/genset. And run just the AC (and a little winter battery charging) from the small genset--Can be OK.

    A 2 kWatt solar (or genset+solar) battery system... That is asking a lot from a "small" off grid system. This off grid power stuff adds up quickly.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    Sorry about the wrong monitor. I will stick with the one you linked to. 

    I hope I am not frustrating you too much that you are trying to get me off solar haha. I haven't checked the cost of bringing power to my land and will indeed check but online they say 25-50$ a ft so in my case it is between 25-50k so I guess I will stick with generator and solar for the next 3-5 years. 

    "If your system was just LED Lights, RV water pump, Cell phone and laptop charging, Solar could be a good fit (run the fridge/cooking/hot water/etc. from propane)--I.e., a ~300 Watt AC inverter+battery bank+solar/genset. And run just the AC (and a little winter battery charging) from the small genset--Can be OK."

    I think I finally realized why you are saying my 2000 watt inverter is wrong and what is the issue here. looking at your estimated loads for me, and removing the AC - the largest consumer of energy, I will use around 1800WH a day. Which means on 645ah bank fully charged I will have only 2 days and a bit more - without AC. So really if I want to run the AC on my bank I will need a much much bigger bank. So going back to what you said originally - starting from the loads you build a system.

    Realistically I have to run AC on generator. Then if that is the case... maybe I will never go to array and mppt since my generator will run every time I am there from around 7 pm until 7 am - powering everything and charging batteries. So my bank only needs to support day time usage which is very low around 1000-1100wh - and only fro one day since at night - it will be charged again.. Therefore I should be good on around 183ah... huge change. So using two 105 ah AGM 12v batteries in parallel... will be more than enough - right? Don't even need to find another source for AGM ahah. 

    Now the question of inverter. Only jump is the microwave.. 700 watt for a few minutes which with fridge and other usages can reach 900-1000 watt for a few minutes. The 400 watt magnum has a peak watt of 900 watt but not sure for how long  can run that but for another $60 I get the 1000watt magnum and then I should be more than good.

    To reduce my risk of murdering my batteries I really want a low voltage automatic shut off... Magnum doesn't have it. Any other device I can use for that? Or maybe you can recommend a good inverter that will do that?




  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    MiniSolar,

    No problem on my side... I hope I am not causing you grief as I keep harping on the issue of loads vs battery vs inverter vs genest vs etc...

    The other "big(ish)" load is typically the refrigerator... But there are so many choices here--There are small 12/24 VDC (no inverter) refrigerators, converting a chest freezer to refrigerator (~250 WH per day). and simple 120 VAC refrigerators that can be down towards 1000 WH per day. Or if you get an RV with a propane fridge--Very little 12 VDC power for the fridge controller.

    And I keep harping on 2x 6 volt @ ~200 AH golf cart batteries in series, vs 2x 12 volt @ 105 AH batteries in parallel. AGM or not--Either will work. Next figuring out how much "useful" energy per day from such a bank:
    • 12 volts * 210 AH bank * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 535.5 WH per day (for 2 days of no sun, 50% max discharge).
    You could go with 1 day of storage, which would give you 2x more energy (1 day) of ~1,071 WH per day (or overnight)

    If you want 1,800 WH per day, and only use 535.5 WH overnight--Rest of the power during the day is supplied by the solar array--Both to the loads, and charging the battery bank. Using a simpler solar calculator for Burlington VT, fixed array facing south:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Burlington VT
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 46° angle:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.08
     
    4.00
     
    4.49
     
    4.51
     
    4.50
     
    4.72
     
    JulAugSepOctNovDec
    4.89
     
    4.77
     
    4.33
     
    3.41
     
    2.46
     
    2.40
     

    Use October as the break even month @ 3.41 hours of sun per day:
    • 1,800 Watt load * 1/0.52 off grid AC system eff * 1/3.41 hours of sun per day = 1,015 Watt array (break even)
    Rate of charge for 12 volts @ 210 AH battery bank 5% to 13%:
    • 210 AH * 14.5 volts nominal charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 198 Watt array minimum
    • 210 AH * 14.5 volts nominal charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 395 Watt array nominal
    • 210 AH * 14.5 volts nominal charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 514 Watt array "typical cost effective maximum"
    So, large load, large solar array, and a small battery bank... Typically to run a standard 120 VAC energy star rated fridge, a 1,200 Watt inverter is suggested (standard fridge starting current). And the suggested battery AH rating would be (using our simple, close enough rules of thumbs):
    • 1,200 Watts * 100 AH (at 12 volts) * 1/250 Watts (at 12 volts) = ~480 AH @ 12 volt battery bank... 
    And if you have a 12 volt ~ 420 AH @ 12 volt battery bank (close enough for solar...):
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 395 Watt array minimum
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 791 Watt array nominal
    • 420 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,028 Watt array cost effective max...
    So, I would be suggesting a 1,200 Watt AC inverter, ~1,028 Watt array, and a 420-480 AH @ 12 volt battery bank for a relatively "balanced" system design based on your (guessing) loads... And counting on sunny weather for daytime loads/backup genset, only being there 2 days in a row (especially if there is cloudy weather--Needing the genset).

    But I am still guessing, and trying to get the minimum hardware needed to have a "functional" solar power system...

    The question of MPPT controller or PWM charge controller, not really an issue at the moment, at least until we nail down the rest of the loads/hardware paper specs./etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    edited May 26 #21
    Thank you Bill.

    I found batteries I think - https://www.interstatebatteries.com/products/gc2-hd-agm

    6v 200ah agm. Got a good price - $180 each with deposit.

    I would like to start with 4, making a 12v 400ah bank, then if need be increase it later on. By later on I mean 2-3 months which is probably when I learn my usage. Will that be an issue of combing brand new with 2-3 months old? 

    Also these batteries only have 6 month warranty.. Is that on pat with other agm in this price range?

    The current fridge in the rv is a dual fuel 12v dc  /propane... That means it is a big consumer or it might be good? If it might be good, then how do I check its usage? 

    I'm building a silence box this week for my generator so I immediately start staying there and tracking my usage. 
  • BB.BB. Super Moderators, Administrators Posts: 30,503 admin
    Batteries are easy to kill if not charged correctly, under charged/over discharged. With a good charge controller, there is usually little to fear from over charging.

    Adding more batteries in 2-3 months, should not be an issue.

    I really do not have much to say on brand/warranty questions. Short warranties and low prices put some of the risk on you. Longer warranties and higher prices--Put more risk on the company, but some of the cost on you... If you are happy with them lasting 3-5 years, you should be fine (they can last 6-7 years--But I would not bet the bank on it).

    Duel fuel propane fridge--Run on propane. The 12 VDC powered cooling (vs just powering the electronics) usually is not financially viable for a solar power system (that was my earlier post in your other thread (?) that showed his mid-size propane fridge taking ~5 kWH per day on 120 VAC vs 1-2 kWH per day for an efficient full size standard refrigerator). Generating heat from solar electric power is usually not very cost effective--Vs running a small burner from propane for the absorption refrigerators.

    Measuring energy usage... Lots of things out there. From standard BMS monitors, to relatively cheap Amazon (and similar) DC AH/W\H meters, 120 VAC Kill-a-Watt type energy meters, to DC Current Clamp DMMs.

    https://www.amazon.com/s?k=DC+AH%2FWH+meter&ref=nb_sb_noss (cheap DC power/energy meters)
    https://www.amazon.com/s?k=kill+a+watt+meter&ref=nb_sb_noss_2 (cheap 120 VAC power/energy meters)
    https://www.amazon.com/gp/product/B019CY4FB4 (mid priced AC+DC Current Clamp DMM)
    https://www.solar-electric.com/search/?q=battery+monitor (Battery Monitors--Not cheap)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • minisolarminisolar Solar Expert Posts: 57 ✭✭
    Got it. So that fridge has got to go and I'll get the one you recommended. 

    I found another battery, same as this interstate ones only slight bigger 224ah vs 200ah, with a price of $300... But... It comes with 5 year warranty which is a big difference. I'll look into how they honor that before I make the decision. That brand is Full line.

    Thank you Bill. 
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