2-100w panels / 20a MPPT cont / 12v 100AH batt - sound good?

MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭

I'm just starting to experiment with solar.

I'm thinking of getting (2) 100w monocrystalline Renogy solar panels and a 20a MPPT controller (EPEVER Tracer/2210A).
I want to use them to maintain a single 12v VMAXSLR100 100AH AGM battery. No specific power requirements, just want to see what I get. It'll be used primarily to maintain a 6a backup sump pump. Also will try and power some 12v devices, maybe try an inverter and see what I can power up.

The basic questions:
-Are all these components matched for safety and general compatibility? Are the panels overkill for the battery? (or the reverse)
-Should I wire the panels in 12v parallel or 24v series?
-Is a 25 foot run of 10AWG cable good for connecting the panels to the controller?
-Is the 12v output from the controller regulated enough to replace the 12v power supplies of various components such as Routers, computers and the like? Can I wire it directly to those devices? Or do I need additional power regulation to replace those individual power supplies.
-If I did get an inverter, what's the max wattage I should attach to this system?

Any other comments and help greatly appreciated! I know this is very newbie and also appreciate any suggestions for other reference sites that may shed some light on this situation.
thanks!

Comments

  • mike95490mike95490 Solar Expert Posts: 9,460 ✭✭✭✭✭
    With your panels (200W) and your smalish 100ah VRLA $$ battery, you risk easily overcharging the battery and venting precious electrolyte as gas. Sealed batteries, if overcharged, can vent (thats the VR -Valve Regulated part of the part #)
     I know nothing abut the charge controller you picked.  If it is a MPPT controller, you can wire the panels in series, if they stay well below the max input (max Voc) voltage of the controller.

    The battery, as it charges, will vary in voltage from 11V to 16V.  Your gear has to be able to accept that, or else you need to regulate your power with some sort of regulator, to protect the gear.  The LOAD terminals on the controller will NOT regulate to a 12.00V. Generally the LOAD terminals can only provide power for a  small light to prevent it from draining the battery completely.  Don't connect a inverter to the LOAD terminals, or you can burn out the controller.

    For  a small 12V battery, 300W or 500w inverter should be the largest you use.   You will learn how fast an inverter, even with no loads connected, will run down your battery, just keeping the inverter turned on (standby losses)
    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 ,

  • MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭
    Thanks Mike for a very detailed response! I should have mentioned that my panels won't have a lot of exposure - that's why I got 2. They'll probably get no more than 4-5 hours of direct sun per day. I'm surprised that a good controller would let the battery overcharge. Since the controller switches to a maintain/trickle charge when the battery is full - thought it would simply not use any additional power from the panels - just enough to keep the battery topped off. Perhaps you are saying in general practice this setup will stress the battery more than necessary and reduce its life - not so much "overcharge" the battery in an unsafe way? If I added another of the same 100AH battery does that sound like a better matched system? In that case should I connect the batteries in series (24v) and then run that into a 12v stepdown/regulator for my 12v components? I'm estimating around 20 amps of constant 12v DC load. (internet routers, security camera, etc.) Thanks for any further help you may have!
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    The CC shouldn't overcharge the battery provided it's setup right. AGMs are sensitive to overcharging, so it's important to check charging voltages and temp compensation, but generally the controller should only charge the battery with the voltage and current needed to reach a full charge.

    With an mppt controller you can wire in series or parallel, and with 25' between panels and CC and 10ga wire it may not make much difference. If panels get cold, you may get a bit more production by wiring in series.

    A 100w panel should give you ~4a of current, so 2 in parallel would be [email protected] or ~10a charging at 14.5v, which should be good for a 100ah battery in many applications, but we don't know a lot about the application.

    The questions about dc connected devices and inverter wattage are a bit more complicated.

    Very generally, dc connected devices will need a wide range of acceptible voltage ( ~10-18v) to account for the range between low voltage disconnect settings and cold battery/ eq settings in the controller.. Some devices can handle this, many can't. For running routers etc., I would suggest a variable input, constant output dc power supply.

    Inverter wattage is really a function of loads.

    If loads need a lot of current for a short time (like a pump), you want an inverter that has a lot of surge capacity and either a low search tare or the ability to turn on only when needed. Drawing large loads from a small battery will pull voltage down, which increases current needed to supply the load, which increases wire resistance, and so on, creating a practical limit on the size of inverter that can be used with a given sized battery (voltage and capacity).

    If the loads are small but steady, you want a smaller but more efficient inverter.

    Although you mentioned you have no specific power requirements, that's really where any system design starts. Without knowing what the loads are, it's hard to give useful opinions on things like inverter size or system voltage.
    Off-grid.  
    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
  • MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭
    Thanks Estragon for some very helpful advice. I've actually already ordered a DC power supply like you suggested. I won't be using an inverter for now, my pump is 12v DC. But I plan to power that direct from the battery without a low voltage cutoff in place because I can live with one full drain on the battery if it's keeping an emergency sump pump going. But I've decided to double my battery capacity to 200AH by adding another VMAXSLR100 100AH battery. I know batteries of different ages should not be combined into a bank but I've never really discharged my existing battery - it's been on standby/trickle for about a year and I've read that sort of situation shouldn't be a problem. Advice to the contrary welcome. I'd be wiring them in parallel to keep the voltage at 12 and double the AH. Any warnings comments on this idea welcome!
  • EstragonEstragon Registered Users Posts: 4,495 ✭✭✭✭✭
    One comment would be to make the parallel connections on the batteries with big wire (eg 4/0) to keep resistance low. I would also check specs on the pump to be sure it will be okay with the voltage range. A 12vdc pump probably will, but it wouldn't hurt to check.

    All battery positive connections (to pump, converter, and controller) should have overcurrent protection properly sized for wire sizes used. I prefer breakers as they can be easier to use as disconnects.

    With 200ah of battery and ~10a of solar charging you're about at the lower limit of being able to keep batteries properly charged in winter. I would definitely want a secondary means of charging (eg. generator).
    Off-grid.  
    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
  • MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭
    Thanks again Estragon! All makes good sense. I'm not going to put a lot of load on the batteries at first to see how much charging power I get with the limited sun. Right now it'll just power internet stuff and maybe a webcam and such. Looking forward to experimenting, thanks again everyone for the help.
  • myocardiamyocardia Solar Expert Posts: 118 ✭✭✭
    edited May 2017 #8
    Hi, Mark. Don't be offended, but you are making the same rookie mistakes that almost all rookies seem to make, when it comes to solar. You are going in reverse order. You need to start over. You buy batteries and solar panels to power what you're wanting/needing to power, not buy batteries and panels, and see what happens. That will just cost you a lot of needless spending and aggravation. See, you already know exactly how many watt hours per day that your sump pump uses, but you just don't realize that you do. See, power=watts. Watts= voltage times amperage. So, we now, finally, know how many watts per second that your pump uses, 6A @ 12V, so it uses ~80 watts.

    Now, and this is by far the most important of the information that you have yet to share, how many minutes at a time does said pump run, and how often/how many times per day does it run? If it runs for 30 seconds at a time, once per day, you'd be able to use a single 5Ah battery, and a 5 watt solar panel to recharge it. If it runs for 45 or 50 minutes at a time, once per hour, then it's going to require nearly an entire truckload (edit: pickup truck, not 18-wheeler :) ) of those very expensive AGM batteries that you have, since you have to be able to supply the pump with power 24 hours a day, not just the couple of hours per day that your solar panels will be charging the battery.

    I realize that you've said that this 12V pump is your backup, but do you really want to have your basement flooded, if/when your primary pump goes bad, and/or you lose AC power for a day or three? If I were you, I'd actually unplug the primary pump, and document how much the 12V pump runs, so you can have an actual, functioning backup system, not just one that will function for the first hour or two that your primary pump can't be used, or that you have no AC power, until your battery no longer has the power to run it.

    You most likely don't need a second battery, but we have no way of knowing for sure, since you still still have not given us enough info as to how much power per day that your pump will use. Oh, one last thing: doubling up your battery storage will require you to also double up your charging capability, i.e. the solar panels, since 200 watts of panels is about perfect for the battery that you already have, so for every one of those batteries that you add, you will need to add roughly another 200 watts of solar.

    Lastly, these are the type of converters that you need to be able to run things that require 12.0V, and not 12.0-15.5V that your battery will be supplying while the panels are charging it, such as routers, switches, and the like:

     https://www.amazon.com/DROK-Voltage-Regulator-Converter-1-2-36V/dp/B06VWT6CYF (fixed. -Bill B.)

    edit: Hmmm, anyone know why my link to the DROK DC to DC buck converters is linking only to the Amazon main page?
    edit #2: Thanks for fixing the link, Bill. You're a gentleman, and a scholar!
    DoD= depth of discharge= amount removed from that battery   SoC= state of charge= amount remaining in that battery
    So, 0% DoD= 100% SoC, 25% DoD= 75% SoC, 50% DoD= 50% SoC, 75% DoD= 25% SoC, 100% DoD= 0% SoC
    A/C= air conditioning AC= alternating current (what comes from the outlets in your home) DC= direct current (what batteries & solar panels use)
  • MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭
    No offense taken myocardia! Thanks for a great message with lots of info. Lots of good ideas here. Your experiment with the pump sounds very interesting - however during a heavy rainstorm when the power goes out it'll be running a lot more than any random period I might choose to test. But if it's just the power and no rain, your idea would certainly give me some good data to deal with on keeping my pump running normally til the power's back on. Yes I know I'm doing it backwards, seems that's always the case. I tend to set things up and see what happens. But i'm already with you on the DROK unit, I just got the one a bit higher up because it has a nice case: https://www.amazon.com/gp/product/B00C9UAE28/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
    Thanks again for the help!
  • jonrjonr Solar Expert Posts: 1,386 ✭✭✭✭
    Don't use any buck converter with a 12V source and expect to get 12V from it.  You want a boost/buck converter.  On the other hand, most 12VDC motors and 12V regulated electronic devices run fine with somewhat lower voltage.

    I am available for custom hardware/firmware development

  • MarkNewYorkMarkNewYork Registered Users Posts: 20 ✭✭
    Thanks for pointing that out jonr - double checked and both those units are boost/buck.
  • sayprogsayprog Registered Users Posts: 5 ✭✭
    Hello @MarkNewYork . A few months ago I had collected solar system the same as your,
    to achive a similar to your goal.
    I have two modules FSM-100M, Tracer 2210A, two flooded batteries 100 Ah and my old
    PowerCom BACK UPS-400-A, as inverter. I'm using NoteBook as load.
    First, I advise you to use a program Solar Station Monitor for the system monitoring.
    You can download it here http://www.epsolarpv.com/en/index.php/Technical/download .
    You will also need a cable CC-USB-RS485-150U to connect controller and PC.
    This will allow you to receive graphs of the system during the day. For example:


    And also, it will be easy to change any controller's parameters.


    Secondly, the controller has a very strange MPPT algorithm. While the PV array gives less than 1.5A, the controller
    does not even try to find the MPP and keeps the array voltage slightly higher than the battery voltage.
    Therefore, when the PV modules are connected in series in a 12V system, one of them is in the short-circuit mode and
    the total voltage of the array drops twofold. We have half the possible power.
    Thirdly, the controller has a three-stage charge algorithm. If the type of batteries is correctly selected in the settings,
    there will be no overecharge.
    Good luck.
  • mvasmvas Registered Users Posts: 384 ✭✭✭
    edited June 2017 #13
    @sayprog,
    Between 14:46 and 16:11 ...
    It appears the Charge Controller is in Float Mode
    And then the Voltage on your panels drops suddenly and sharply.
    The Controller drops out Float Mode and the Battery voltage drops.
    Is there a possibility that a shadow moves across one of the panels?

    The MPPT routine seems to work just fine with Low Amps in the morning.

    Do you have a device connected to the "Load" terminals of the Tracer?
  • sayprogsayprog Registered Users Posts: 5 ✭✭
    edited June 2017 #14
    @mvas said:
    Between 14:46 and 16:11 ...
    It appears the Charge Controller is in Float Mode
    And then the Voltage on your panels drops suddenly and sharply.
    The Controller drops out Float Mode and the Battery voltage drops.
    Is there a possibility that a shadow moves across one of the panels?
    You are absolutely right. My panels are oriented to the south (more precisely 170 degrees in azimuth).
    These graphs was recorded on May 30, 2017. On that day at 16:00 the sun was 260 degrees and did not fall on the panel anymore. Before this, partial shading occurs from various objects on the building wall.
    mvas said:
    The MPPT routine seems to work just fine with Low Amps in the morning.
    As you can see on the array voltage graph, MPPT starts between 6:06 and 7:21, when the array current increases to 2A.
     At lower values of the array current, there is no MPPT. The Battery current is equal to the Array current.
    mvas said:
    Do you have a device connected to the "Load" terminals of the Tracer?
    Yes, I have. This is a small comparator circuit and two relays. Consumption is not more than 100-200 mA.
    I expected to use only relays, but the controller designers do not allow me to increase the "Low Voltage Reconnect Voltage"
    parameter more than the "Boost Reconnect Charging voltage". Therefore, I had to do a comparator to disconnect
    and reconnect the load.

  • mvasmvas Registered Users Posts: 384 ✭✭✭
    sayprog said:
    As you can see on the array voltage graph, MPPT starts between 6:06 and 7:21, when the array current increases to 2A.
     At lower values of the array current, there is no MPPT. The Battery current is equal to the Array current.
    Yes, just after 6:06:14, I see a dip in the PV Panel Voltage.
     I think that dip, is where MPPT "searching" is actually activated.
    With very low insolation the Peak Power Curve is very broad and the Vmp point is very low.
    MPPT cannot improve much in that low power area ( 12 Watts ).
    I think, MPPT "searching" is not activated until the PV Panel Voltage > (approx) 1 Volt + Battery Voltage.
  • sayprogsayprog Registered Users Posts: 5 ✭✭
    edited June 2017 #16
    mvas said:
    Yes, just after 6:06:14, I see a dip in the PV Panel Voltage.
     I think that dip, is where MPPT "searching" is actually activated.
    With very low insolation the Peak Power Curve is very broad and the Vmp point is very low.
    MPPT cannot improve much in that low power area ( 12 Watts ).
    I think, MPPT "searching" is not activated until the PV Panel Voltage > (approx) 1 Volt + Battery Voltage.
    No, it's not the PV Panel Voltage, but the PV current. Look at these charts.

    The voltage of the open circuit reaches almost 20v much earlier than 6:37, but only after increasing the current of more than 1.5A MPPT is started.

    Until this time, the controller works like PWM.
  • sayprogsayprog Registered Users Posts: 5 ✭✭
    edited June 2017 #17
    This post must be deleted. But I have no permission.

  • LumisolLumisol Registered Users Posts: 374 ✭✭✭
    Estragon said:
    The CC shouldn't overcharge the battery provided it's setup right. AGMs are sensitive to overcharging, so it's important to check charging voltages and temp compensation, but generally the controller should only charge the battery with the voltage and current needed to reach a full charge.

    With an mppt controller you can wire in series or parallel, and with 25' between panels and CC and 10ga wire it may not make much difference. If panels get cold, you may get a bit more production by wiring in series.

    A 100w panel should give you ~4a of current, so 2 in parallel would be [email protected] or ~10a charging at 14.5v, which should be good for a 100ah battery in many applications, but we don't know a lot about the application.

    The questions about dc connected devices and inverter wattage are a bit more complicated.

    Very generally, dc connected devices will need a wide range of acceptible voltage ( ~10-18v) to account for the range between low voltage disconnect settings and cold battery/ eq settings in the controller.. Some devices can handle this, many can't. For running routers etc., I would suggest a variable input, constant output dc power supply.

    Inverter wattage is really a function of loads.

    If loads need a lot of current for a short time (like a pump), you want an inverter that has a lot of surge capacity and either a low search tare or the ability to turn on only when needed. Drawing large loads from a small battery will pull voltage down, which increases current needed to supply the load, which increases wire resistance, and so on, creating a practical limit on the size of inverter that can be used with a given sized battery (voltage and capacity).

    If the loads are small but steady, you want a smaller but more efficient inverter.

    Although you mentioned you have no specific power requirements, that's really where any system design starts. Without knowing what the loads are, it's hard to give useful opinions on things like inverter size or system voltage.
    I got these wires and they are 30' and 8awg. Might want to look at that if you have more than 25 feet to go.
    https://www.amazon.com/gp/product/B00DY85SDO/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
  • mvasmvas Registered Users Posts: 384 ✭✭✭
    edited June 2017 #19
    @sayprog,
    I agree, it sounds like the Buck-Inverter is initially running in "100% ON" mode just after the Charge Controller "wakes-up".
    As the sunshine increases, the PV Voltage increases and the Amps increase.
    When the sunshine is strong enough, then the MPPT logic begins searching for Peak Power.

    What happened between time 7:52:03 and 9:07:03 ?
    The PV Array voltage spiked to Voc and the Amps into the battery dropped zero.
    Was there a disconnection between the PV Array and the Controller or the Controller and the Battery Bank?
    It looks like it happened 4 times that day.

    What happened at 16:37:03, another shadow?
    And it looks like the Controller put the Buck Inverter into "100% ON" mode, again.
    Both amps are equal, just like the initial condition after "wake up".
  • sayprogsayprog Registered Users Posts: 5 ✭✭
    edited June 2017 #20
    mvas said:
    I agree, it sounds like the Buck-Inverter is initially running in "100% ON" mode just after the Charge Controller "wakes-up".
    As the sunshine increases, the PV Voltage increases and the Amps increase.
    When the sunshine is strong enough, then the MPPT logic begins searching for Peak Power.
    And there is! In my first post I talked about this. MPPT starts at an array current of more than 1.5A. Therefore, at low powers of the PV array, it is more advantageous to connect the panels in parallel. The threshold current value will be reached earlier. MPPT will start earlier.
    Because of this limitation in the autumn and winter there were many days when the MPPT does not run.
    The daily Eyergy Generation was about 0.03-0.04 kWh! :'(
    mvas said:
    What happened between time 7:52:03 and 9:07:03 ?
    The PV Array voltage spiked to Voc and the Amps into the battery dropped zero.
    Was there a disconnection between the PV Array and the Controller or the Controller and the Battery Bank?
    It looks like it happened 4 times that day.

    At these moments, the MPPT algorithm is restarted. I asked this question to the manufacturer. Here is their answer:
    Hello Sir,
    Yes, it should be Volt. Comp.

    About your doubt, it is becaue of the algorithm. Because we usually found the controller will not MPPT charging under unknown condition after years of applicaiton.
    So we improved the algorithm, the controller will restart MPPT charging every one hour to avoid some unknow condition.
    Thanks~!


    Best regards                                                                                  

    Wanderer 

    Technical Support Engineer 

    ———————————————————— 

     BEIJING EPSOLAR TECHNOLOGY CO., LTD. 

    E-mail:[email protected] 

    mvas said:
    What happened at 16:37:03, another shadow?
    And it looks like the Controller put the Buck Inverter into "100% ON" mode, again.
    Both amps are equal, just like the initial condition after "wake up".
    Yes, after 16:00 begins the time of shadows.By 16:37 the PV current dropped below 1.5A and the Buck Inverter goes into "100% ON" mode. Between 16:37 and 17:52 the MPPT started again.

    From all that has been said, it follows that the advantages of MPPT start at PV array power of more than 20-30W (for 12V) and 40-60W (for 24V). This should be borne in mind when selecting the PV-array modules connection scheme.
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