Solar panel system shutting down

Posted on 2011-10-18
Last Modified: 2012-06-22
Hi guys

I installed a solar panel system to run 16 surveillance cameras.
This is my calculation
1 DVR  -  15Watts = 12Volts * 1.25 AMP
16 cameras = each camera use 12V with 0.3 AMP, so 12*0.3=3.6Watts * 16 cameras = 57.6
Internet device -> around 15 Watts
So per hour we need 15(dvr) +  60(cameras) + 15(internet) = 90Watts per hour
Now this is the tricky part, we need to run the system 24 hrs
So, we need 90Wats per hour * 24 hours = 2160 Wats per day - This is what we need to keep the system runing per day.
Solar panels, we currently have 2*45 watts and 4*100 Watts 12v solar system, that generates
490 Watts / hr
5 hrs(sun power per day) * 490 = 2450, enough to recharge 2160 used per the system
again we need batteries to support a demand of 2160 watts a day, but if we have 2 days with bad weather and no sun, the battery bank should support the double(mostly everybody use 3 days)
2,160 watts * 2 days = 4,320 Watts divided by 12 V(batteries comes in 12 V) = 360 Amps
Batteries comes 12Volts 105 Amps
So we need 4 Marine Batteries Deep Cycle 12V 105 Amp
I have 8 marine batteries 12 V 115 amp.

The system shut off after 2 weeks, what am i doing wrong?
what do i need to change or add.

I am a rookie on this and have invested a lot of money on thsi system?

I am also using a 45 Amps charge controller and 1200 W inverter.

can the inverter run continuosly?

Please advise
Question by:titorober23
    LVL 30

    Accepted Solution

    Perhaps you need to revisit your calculations allowing for losses in the system and lower efficiencies of the panels at different times of the year . I suspect that you are running things a little close to the wind in that you're consuming 90 Watts, leaving a maximum of 400W to charge the batteries - but you'll only get 400W for a couple of hours around midday assuming your panels are at the correct tilt for your latitude and oriented due south (or north - depending on where you are). The panels will also produce less than the theoretical maximum in spring, autumn and winter. To put that in perspective, I have a 4.9kW system that is generating about 3.2kW at this time of year. I don't expect it punch out the full 4.9kW until summer.

    To solve your issue, you'll need more panels to maintain the battery charge. For example, for a 115A/h, a 10 A charge rate will take 14 hours to charge the batteries (assuming 20% efficiency loss). If you can actually pump in 33A from the charge controller (which is the maximum theoretical output from the panels allowing for running the surveillance system) , then you could charge the batteries in 4.2 hours - so there's your issue I suspect. You need more solar panels to charge the batteries. You'll need sufficient capacity in the solar system to generate 33A year-round, which will take more solar panels than you have now.

    First - what is the amp-hour rating of your batteries?
    Second - where are you? City and country is sufficient.

    Author Comment

    The battery bank size is correct?

    would you include extra batteries?

    How do i handle the Amps if i add more solar panels, the charge controller that i currently have  handles up to 45 Amp?
    If i add 2 100 Watts panels, they would be around 18 Amp extra.
    How do i calculate the number of days that i can run the ssytem only on batteries

    thanks for your help
    LVL 30

    Expert Comment

    by:Duncan Meyers
    What is the amp-hour rating of the batteries? You said in your question that the batteries are 12V 115A - but that could mean maximum drain or it could be amp-hour.

    Author Comment

    they are
    Everstart Marine" battery #27DC-6. ... 115 Amp Hours, 720 Marine cranking amps, 600 cold cranking amps.
    LVL 46

    Expert Comment

    Even w/o doing any math, it is obvious that you are using more power then the system is capable of generating and storing.  You need to contact an engineer that works for the inverter vendor to run your setup by him or her.  They have access to the additional specs like efficiency, duty cycle, and how ambient temperature would affect it.   (Same for the batteries)

    Everything *looks* good on paper, but as a professional engineer, I can tell you that there is a big difference between theory and practice.  Step back and make some phone calls to your vendors and perhaps they have an applications engineer who can suggest a modification to your design or pinpoint the problem.

    LVL 30

    Expert Comment

    by:Duncan Meyers
    ...exactly. Take a look at this image. It shows the output from the solar system on my house that's made up from nine 240W polycrystalline panels:

     Solar system output, 19th October
    It was a lovely cloudless day on the 19th. The theoretical output is 2160W, but as you can see from the graph, the system didn't even hit a peak output of 2kW - and that's due to the time of year and the tilt of the panels. As you can also see, it was generating above 1.5kW for only 5 hours from about 10:00AM to 3:00PM.

    Bottom line is you don't have sufficient generating capacity to keep the batteries charged - especially if you have a dull or cloudy day.
    LVL 30

    Expert Comment

    by:Duncan Meyers
    For comparison, here's the graph for a day that had intermittent full sun. You can easily see when the clouds covered the sun:

     Solar system output, 16 October
    BTW - it would seem that you have sufficient battery capacity as the system ran for 2 weeks before expiring, although I don't have the necessary maths to confirm that (you need to allow for natural discharge rates, inefficiencies etc). At a very high level, 115A/H means that the battery can supply 115A for 1 hour, 11.A for 10 hours, etc. Your consumption is approximately 90W or 7.5A, so 15 hours per battery or
    about 15 x 4 = 60 hours = 2.5 days with zero charge.

    Author Comment

    I purchased the inverter online, I am not sure who to contact.
    I need to double check the math and even if i am off for a bit i would like to be in the safe side and probably buy more panels, but now as far as i understand if i add more panels i should do another independant connection because my charge controller only support up to 45 Amps.

    I am trying to do this on my own to save some money, I already put a lot into it and cant afford more, so i need to buy what is really need it.

    how do i know how many more panels do i need?
    Can inverters run 24/7?

    if i am generating 500W at 12 volts, does this mean that i receive through the charge controller 500/12= 12vols 41 Amps
    is that how this work

    I know your advice would probably be find an engineer, that they will charge me more and i know i am pretty close.

    Please help
    LVL 30

    Expert Comment

    by:Duncan Meyers
    how do i know how many more panels do i need?
    That's hard to work out, but at a guess, I'd suggest you need to double or even triple your solar capacity, or you can add an alternative power source such as a wind generator (if the location is windy enough) as they generate whenever the wind is blowing. Be aware too that the solar power output will drop dramatically as winter approaches (I assume you are in the USA). Try contacting a RAPS (Remote Area Power System) supplier in your area as they will have experience with local conditions. Even if you have to buy your additional solar panels, charge controllers and inverters from them...

    Can inverters run 24/7?
    Yes - provided they are rated to do so.

    >if i am generating 500W at 12 volts, does this mean that i receive through the charge controller 500/12= 12vols 41 Amps
    >is that how this work
    Yes - Power = Volts x Amps, so Amps = Power/Volts
    LVL 25

    Assisted Solution

    I've been away this past week and did not see your posts till yesterday.

    From the original question I had recommended at minimum 600 watts of panels if you needed to operate 24 hours a day.  Even at that I suspected it would not be enough all year round and that it would be good to be sure your equipment could add panels as needed.  Sorry if that was not clear.

    What make and model (or a link to the one you bought) of charge controller/regulator did you get? Also what panels?    Any chance you can trade up the charge controller?

    If you are getting about 14 days from your batteries you can back figure roughly how much you are short on power daily on average,

    115 Ah * 12 volt * 8 batteries = 11040 watts total / 14 days = 789 watts daily on average

    If the charge controller can shut down everything if the batteries go too low (before a full drain) the shortage figure might be 15-20% lower.  This is a helpful feature as draining your batteries dry is hard on them.  Also that calculation is assuming the batteries were fully charged at the start.  New batteries are not usually topped up and if they sat around could have been pretty low to start if you didn't charge them up before installation.

    Since you have this stuff up and running you can do some testing with a ammeter to verify that you actual loads are in line with calculations and show roughly what sort of efficiency you are getting.  Even better if you could actually get any data from the solar gear to show what you actual production is though the day.  If you could get a amp rating at day peak it would be enough to ballpark your actual panel production.  Or even if you could get hourly readings through a day.

    Also you could do some run tests to check on exactly whats going on.  Once you know your load for the camera's etc.  from a full battery charge run down you batteries with the solar panels disconnected.  This will tell you how much you are really getting from the batteries to your equipment.

    Then disconnect all the video and charge up the batteries on solar.  Keep an eye on the weather so hopefully you get kind of average weather for this.  So because you know from the prior test what you get in total out,  now you can find out just how much you have to put in to get that output - this will include all the losses etc involved with your current setup.

    Right now you have a decent idea of the load and it should be fairly steady but not so much on losses and on what you are really getting into the batteries.  So by doing the tests we can get a fairly good idea of what is really going on including battery loss,  wire loss, inverter loss, charge loss and actual panel production.  These results do not duplicate the daily charge/discharge cycle but are going to be a better place to start than working from strictly 'on paper' figures and should allow for a more accurate scale for the system.

    The inverter should be fine for 24/7 but what is being powered through it?  It is significant point of loss so the less you have going through it the better.  If you can link it or provide make/model likely can confirm suitability.  Given the stuff you are running could all be run right off 12 VDC you could completely avoid using a inverter (and be better off).

    One other possible issue,  how long are the wire runs between the panels and the controller and the batteries and the controller,  and what wire gauge did you use?  Because of the amperage, if the wire is too small it can be a significant loss of power.  Improperly sized wire could be a loss of 5 - 10% alone.

    If possible,  adjusting panel angle seasonally can get a significant gain in production.

    We really need the specs on the equipment/installation and how things are connected to see if there is anything that can be done to improve the efficiency without you needing much more or different equipment.  Though 490 watts of panels is certainly not enough.

    The 45 amp limit on the charger is a issue as that limits you to below the panels potential during peak times.  If the controller has protection against overloading it is not a problem to hook it up.  So any possible production above ~540 watts is lost as it will stop at 540.  If you added 2 100 watt panels for 690 total,  you would cap out at about 78% of the rating.  

    BUT as the graphs meyersd posted show,  the amount of peak time is fairly short and for much of the year the daily peak is only around 80% of the panel rating anyway.  When you check on the actual production this will be apparent.

    Don't get me wrong this is not good design as it impacts the annual overall efficiency.  I just imagine that for this application it is more important to keep things running in off seasons than getting a bit more power in the summer.  When everything is figured its not going to be as bad as it sounds because the actual time when the panels get that much light is fairly short each day and only for part of the year and you will still do gain more power at off peak time than you would with 490 watts of panels.  It does limit the top end though,  so as you add more panels you will start losing too much and once off peak seasons are impacted it becomes impractical.

    Did you check the solar maps I had linked,

    Which area do you fall into on the December map?

    The January map is for a tracker - a motorized solar panel array that follows the sun.  Big cost so don't even look at that map.

    It looks like you have a handle on the calculations but are just not taking into account losses and possibly working from a best case scenario on the solar output when you need be working from the worst case.

    Oh if you solar equipment does not have any data output but has a display you could point a camera at the display to capture data and allow you to see live data remotely.  Same applies if there is not a display but you hook up a meter to show amps or volts etc.  The voltage during battery discharge will show if the batteries are declining daily or not.

    Author Comment

    This is the charge controller i got
     Morningstar TriStar Charge Controller, MPPT TS-45

    This is the inverter
    Whistler Pro-1200W 1,200 Watt Power Inverter

    I bought the panels on ebay
    400W solar panel for 12V DC ,Low Price, High Efficiency
    4PCS 100W Solar Panels

    Item Description:

    --Brand new 100W 17.5V solar power module panel.
    --Aluminum frame surrounds and protects the glass and solar cells.
    --Weatherproof and can withstand extreme heat and cold.
    --Made by solar grade A silicon material.
    --High anti reflective and transparency tempered glass.
    --Junction on the back of panel with - / + leads and backward diode.
    --3 ft cable with multipal connectors


    - Type(Module): 100D
    - Power(Wp): 100
    - Module Size: 46.1 x 26.4 x 1.4(inch)
    - Weight: 22(lb)


    Operatine Voltage: 17.5V
    Operatine Current: 5.71A
    Open-Circuit Voltage: 21.8V
    Short-circuit Current : 6.2A
    Max-Power: 100W
    Max System Voltage: 1000V

    I live in Edison, NJ - December map shows 2 to 3

    I would like to add 200 Watts more, but do not knwo how to handle Amp with the same charge controller, i think i should add another.
    Please advise
    LVL 25

    Assisted Solution

    Yet another busy week ...

    Good news is you have a decent charge controller.  If you need to you can put more than one of these units on the same battery bank.  Also because it is a MPPT style unit you can also run different voltages on panels vs the battery bank.

    It might have been nice to have the 60 amp model with the built in networking and if you could trade up I would think its cheaper than a second 45 amp unit.

    That said the unit is rated to handle 45 amps at 12, 24 and 48 VDC so by increasing the system voltage you can get more power.  In a 12 volt configuration it is limited to 12 volts x 45 amps = 600 watts,  but at 24 volts that becomes 1200 and at 48 2400 watts.

    Morningstar have a calculator on their website you can use to do calculations for panel configurations.  MPPT calculations are pretty involved and things like the temperature do factor in but you can plug in the numbers and it will tell you the results for different  panel arrangements for the controller.

    So if you had 6 100 watt panels you would likely be looking at 2 'strings' of 3 panels each.  A string is a set of panels connected in series.  Then each of these series sets is connected to the controller in parallel.  The two big limits with the controller is that the total voltage of any string cannot be more than 150 VDC and the total short circuit amperage (Isc) cannot be more than 36 amps.

    The same goes for batteries,  you just group them into pairs to get a 24 volt battery configuration then connect each set in parallel.  Doing this doubles the power capacity of the system without exceeding the amperage limit.

    Now one thing you have not got and really must add is a low voltage disconnect or a load controller.  The purpose of this is to shut down the load if the battery voltage gets too low.  I had mentioned this before,  basically fully drained batteries = shorter battery lifetime.  Because this solar system is to operate more or less on its own this is pretty important to have because the system is fairly likely to run down several times a year.  

    On top of being good for the batteries it is also better for the camera's and other equipment.  Having too low a voltage can be hard on power supplies in equipment but in this case it can cause a sort of 'lock up' with camera's.  Often when the power is not turned off and on cleanly cameras can just stop working.  Simply powering them down and back up normally clear the problem.  But again if this system needs to run on its own the load controller/disconnect will get you a clear off/on situation.

    Also as the power input gets farther off spec the efficiency of power supplies and inverters is likely to get worse.

    Morningstar have a suitable relay driver that con be combined with a relay to switch all your camera gear's power off and low and back on when enough power is restored to the batteries.

    Also this unit is a load controller and provides some data recording for power used and has some other programmable features.

    There are also general purpose disconnects/load controllers.  Exactly what you get is not that important,  just that you do get something setup to help keep the batteries in good shape.  As it is you may find that you may end up having to replace batteries every 2 to 3 years.

    One catch to all of this is that your inverter is not going to work with a 24 volt system,  and you also cannot directly connect all the 12 volt camera gear to the battery bank either.  You never did say if all the camera's are going through the inverter or if they are directly connected to the batteries.


    Author Comment

    So, with this type of unit, I can run the panels on 24Volts and charge the batteries on 12 Volts?

    does my inverter shut off and backm on by itself?

    all the cameras are going through the inverter.

    thanks for all your help, but what do i need to do to keep the system runing, let's say
    add 4 more panels with a couple of more batteries?????
    ruin them on 24 volts?

    what should i do

    please advise

    LVL 9

    Expert Comment

    by:My name is Mud
    add a wind turbine... 1k... might compensate for cloudy nights...

    Author Comment

    what about panels, how many more???
    LVL 25

    Assisted Solution

    Yes MPPT style charge controllers allow you to configure the panels at a higher voltage than the battery bank and still charge properly.

    That said you are still limited to 45 amps,  so 45 amps at 12 volts = 600 watts.  If you  do a 24 volt battery setup it doubles upper limit of the power you can put into the batteries.  So 45 amps x 24 volts = 1200 watts.

    Probably 4 more panels would be a decent point.  The December/January months can be pretty rough.  I would not be surprised if you end up needing around 1000 watts.

    Because everything is going through the inverter you are losing ~ 15% in the conversion.  So to get 90 watts you need to put up around 100-105 watts into the inverter.

    Most inverters will shut down when the voltage gets too low.  The problem is this is usually set too low,  down to 10.5 volts which is a full drain and not good for your battery life.

    The advantage of a proper shut off arrangement is it will shut off at about 11.5 volts when still has about 15-20 % left.  Then it will keep it off until the voltage comes back up to a higher charge level.  Typically this would be ~ 12.5 volts which is around 90% capacity.

    Ideally something with programmable voltage and timer settings that will allow you to tune the setup to your needs.  The whole idea is to not flip off and on with batteries wavering around a low voltage.

    You don't need a big capacity inverter either,  it only needs to deliver power for the video and network stuff so 150 watt capacity is lots.

    You were not too bad on the batteries.  Between a disconnect at 15-20% capacity and also loss of capacity from low temperatures you may find you need a few more batteries to get operation for 2 days without sun.

    You should expect to lose 20-30% capacity from low temperatures,  you might have a data sheet on your batteries to give a better figure for this.  In general for lead acid batteries a figure of 1 % capacity loss per degree C below 20 C.

    It's pretty easy to add more batteries as you don't need to resize any other components to handle the extra batteries.


    Author Comment

    excellent information

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