Solar powered gate opener

pablito3
pablito3 Registered Users Posts: 16 ✭✭
Hi folks,
I recently bought an electric automatic gate opener and noted that the store sold, as an acessory, a small battery pack to operate the gate opener in the event of a power outage.
Well this got me thinking, if the motor can be operated by battery in an emergency why not all the time? Then I thought if it can be operated by battery how great it would be to recharge the battery with solar power.
I rang the manufacturer and they told me that yes it was possible but the emergency back up unit would´nt do the job for very long due to battery size.
Here´s my question to you experts. Is this feasable? What size battery would I require and what size solar panel to recharge it? The motor of the gate opener has a current consumption of 0.9-3.5 A. and the power is 40 W.
I dont want to throw money at this project but it would great if it were possible at a reasonable cost.
Any help would be gratefully recieved.
Regards, Paul.
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Comments

  • peterako
    peterako Solar Expert Posts: 144 ✭✭
    Re: Solar powered gate opener

    Hi there 40 w divided by 3.5 A gives you around 12 V.
    So any 12 V battery pack will do the job.
    If you have a opening time and closing is around 6 min. then 0.1 ( the 6 min.) times 3.5 A gives you 0.35 that is the reason that the manufacture installs around 1 to 2 AH and is asking you a 40 bucks for it.:grr

    Use a cheap lead acid battery 40 Ah used for small cars and if you put same nice LED lights on the gate you can run days on the battery alone.
    any small solar panel 12 V plus controller will keep the battery on level.

    Greetings from Greece8)
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Thank you for the reply and advice peterako. A further question what would be the minimum size solar panel that I could use in order to keep a 12V 40A battery
    in good charge.
    A little further information, I guess, on average , I open and close my gate four times a day. The specifications for the gate opener state that the motor operates at a speed of 10 metres a minute. My gate is four metres. So, one open and close would mean an operation of less than a minute. Therefore the motor would require, on average, four minutes of use per day.

    Regards,Paul.
  • sam c
    sam c Registered Users Posts: 16
    Re: Solar powered gate opener

    I did this a couple of years ago, used a car batt, and a 45 watt 12volt pv ck it every week for 3 mos never found the batt over 13v nor under 12v I havent looked at the batt for at least a yr, I just keep the panel clear of dust.
    I tried a small garden tractor batt didn't work, went flat in a couple of mos.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener

    stay away from using a car starting battery as they aren't meant for this type of use. you do use very little power overall so the factor may be the minimum current you would need to properly keep the battery charging and that would depend on the amphr rating of the battery. if you go with a 40ah battery for example you minimally need about 3% of that to charge it making the pv deliver 1.2 amps. many pvs will not consistently deliver an imp of 1.2a if they are rated at 1.2a imp so roughly add another 10% or more for real world results from the pv. 1.2a x 1.1 = 1.32a. charging losses can also come into play as well as resistive losses. keep in mind that 3% is low on a charge percent basis, but is workable in some low draw applications that the battery shall be able to become fully charged in some reasonable time. 5% is the bottomline we normally recommend and would represent for the same 40ah battery example 40ah x .05 = 2a from the pvs. of course a larger ah battery capacity would dictate a higher charge to the battery. it is doable in my opinion, but before you do it keep in mind you also need a charge controller and wires(properly sized), fuses, etc. work it out in your head and on paper how you wish to do this and run it past us before you buy anything.
  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    Re: Solar powered gate opener

    Most of the systems around here locally use something like an 8 to 15 amp-hour sealed motorcycle battery and a 5 or 10 solar watt panel. A 1 watt panel would work if only opened a couple times a day.

    Might Mule is the most popular brand, but a few others around.
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Gentlemen,
    I do apreciate your responses but can I just point out that your talking to a complete dummy here as far as batteries and chargers and all things solar are concerned.
    What is the difference between a car starting battery and a motorcycle battery? Is it even practical to use solar and battery power to power my gate opener? It seemed like a good idea to me as my gate is a fair old way from my household power supply and if I can use a sustainable system so much the better.
    Could I also ask, in anticipation of further comments, that they not be too technical. May I also point out that I live in Southern Spain so may not have access to some of the things you may have in other places.

    Regards Paul.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    A motorcycle battery is just a smaller lead acid storage battery--otherwise the same as a "car" or automobile battery.

    If you have a electric gate that is designed to work with a battery (low power drain while running the "remote control receiver", low power while opening / closing the gate) then running a solar panel and storage battery should be just fine.

    A 10 watt solar panel in the US will cost around $100 (plus tax and shipping).

    A 12-15 Amp*Hour sealed lead acid storage battery (like that used on a motorcycle) will cost ~£30 (in UK, including VAT).

    Here is some information on Mighty Mule Gate Openers and their recommendations for solar panel size for their models.

    Remember the battery may need to be replaced every 2 years or so. If you have access to electrical power within ~1000' (300 meters) it may be cheaper (over time) to just run utility power to the gate instead.

    You might also need a small solar charge controller to help extend battery life (prevent overcharging) for $30 USD or less:

    wind-sun_2041_25536697SunGuard 4.5 amp solar charge controller
    4.5 Amp, 12 Volt


    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Hi B.B.
    thank´s for your input. I´m more confused than ever. I´ll just state the original specifications of my opener. It´s not actually made to operate by battery there is the option to purchase a back up battery pack for use in the event of power loss. I rang the manufacturer and they told me it would be possible to run the motor permanantly from a 12 volt supply ie a battery.
    The current consumption is 0.9-3.5 A. The power is stated as 40W. ( does´nt mean a thing to me). The degree of protection is IP44, the limit switches are electromechanical. The opening speed is 10 m/min.
    As I said I´m a total dummy on all things electrical so!!!!! If it is possible to run this machine from a battery what would be my best option regards to type and size of battery? If it would be possible to charge the battery by a solar panel what type and size of panel would be best? What size and kind of cable would I have to use. Finally, if it is possible, how would I connect the power ie cables from the battery to the gate opener. Would I connect to where the household power would be connected or would I connect it to where the back up battery should be connected?
    As I´ve said earlier I live in Southern Spain where conditions for producing solar energy must be near perfect.
    Thanks, by the way for the link to the Mighty Mule site. Very interesting. We here in Europe are way behind the USA when it comes to hardware and consumer goods. I used to travel to the USA regularly and spent a lot of my time in places like Home Depot.

    Regards, Paul.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    Hi Paul,

    The reason it is difficult for us to help you is that there are two "numbers" that we need to know.

    The first number you provided is the "0.9-3.5 A" and "40W"... And lets assume the gate takes 30 seconds to open and 30 seconds to close.

    Watts are the same units used to rate Light Bulbs (as an example). 40 watts is fine running with a battery (even a "motorcycle" sized sealed battery). The larger the "watt" numbers, the more power the gate takes while opening and closing.

    The 0.9-3.5 amps from a 12 volt battery is just another way of stating the watts---using a little math:

    Watts=Voltage * Current = 0.9 amps * 12 volts = 10.8 watts
    Watts=Voltage * Current = 3.5 amps * 12 volts = 42 watts

    So, the "Watt" range is ~11-42 watts--close to the "40 watt" number they gave you. Since we don't know any better 40 watts is the number we will use--assuming a large/heavy gate and it takes the maximum power from your battery to move it. And we know that it takes 1 minute of this power at 40 watts.

    Our problem is this is only half of the information we need. The other half is how much power does the gate take when it is not moving.

    An analogy we can use is... You have a car, and you know how many miles per gallon (or km per liter) it takes while driving up hill in a headwind--but we don't know how much much downhill, highway, and city driving do you do--or how much it sits just in the driveway idling or turned off. So, we cannot figure out how many gallons/liters per day of fuel we need to put in the tank.

    If it turns out you drive the car 10 minutes per day and uses 1 liter per 10 minutes, and the rest of the time it sits in your driveway idling--how much fuel does it use the other 23 hours and 50 minutes a day.

    And that is the question you need to ask your gate manufacturer. "¿What is the current (Amps/Amperes) or power draw (Watts) of the gate electronics (radio receiver) while the gate is not moving?"

    It will probably turn out, in your application, that much (if not most) of the electricity (power) is taken from the battery while the gate is not moving.

    To make up an example--lets say that your gate electronics take 0.1 amps (at 12 volts) when the gate is not moving:

    Watts=Power=V*I=12 volts * 0.1 amps=1.2 Watts

    That does not sound like much power, and it is not when compared to the 40 watts the gate motor takes. However, the gate motor only runs 10 minutes a day (10 cycles in our example), but the gate electronics are drawing 0.1 amps / 1.2 watts 24 hour per day. And we need a way to "measure" that number... Sort of like how many gallons/liters a day do we need to put in your car's tank for a day of normal operation.

    The way we do that with electricity is to multiply Watts (Power) times Time (in hours). For example, that 40 watt light... Is it in the closet where it is used a few times (10 minutes) a day or is it in front yard lighting the door way 12 hours per day:

    Watt*Hours = Watts * Time = 40 Watts * 10 min / 60 min per hour = 6.7 Watt*Hours per day
    Watt*Hours = Watts * Time = 40 Watts * 12 Hours per day = 480 Watt*Hours per day

    In this example, we see that there is a huge difference in the amount of energy use per day--almost 100x more for the 12 hour a day use vs the 10 minutes a day use for a 40 watt bulb. This difference will define the size of solar panel and battery we need for this application.

    So, for our pretend example of 0.1 amps at 12 volts 24 hours per day:

    Watt*Hours = V*I * Hours = 12 volts * 0.1 amps * 24 hours = 28.8 Watt*Hours (standby gate energy used per day)

    And the operating energy per day (40 watts x10 open/close cycles at 1 minute each):

    Watt*Hours = Watts * Hours = 40 watts * 10 minutes / 60minperhr = 6.7 Watt*Hours (operating gate energy used per day)

    And the total energy used per day:

    28.8 watt*hours + 6.7 WH = 35.5 Watt*Hours per day.

    So, the "magic number" is 35.5 Watt*Hours per day (in this pretend model of your gate). And we can then easily pick a battery and solar panel to run this system. But I will save that for another post--because without your systems "standby" current/power draw, we don't know how to size the rest of your system (panels and battery sizes). And it would just confuse you when asking the question of the gate opener supplier.

    Do I make sense up to this point?

    Just to understand, you will be installing a battery, and connecting a solar panel (through a solar charge controller) to the battery directly.

    You will also need to tell us how many times per day you will be using the gate... 10 is probably too small of number--perhaps 50-100 times minimum. And we will suggest a design for at least 3 days of no sun (so you can open the gate in the rain)--making the solar panel and battery requirements larger.

    Do I make sense to you so far?

    -Bill

    Paul, since you have already purchased the gate--can you open the package and connect everything together and buy/borrow/have a Digital Multimeter (and an electrically aware friend--if needed) that you can wire between the gate electronics and the standby battery or use your car battery if you don't have the backup battery yet)?

    Set the DMM to 10 amp scale and measure the standby current--If the current is small (which it should be), you can move down to the 1 amp (or smaller) scale to accurately measure the current. Watch it for a few minutes and make sure you see the "average" current.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Wow, Bill that´s some answer you´ve given me there. It makes sense though to be honest I did´nt realise that the gate opener would be using power when it was´nt opening and closing the gate. My car uses no fuel if I dont drive it! Surely though the amount of power used when the motor is not being used would be a tiny fraction of the power used in operation.
    To add some detail, I doubt if my gate is opened and closed five times a day (yes OK I´m a bit of a recluse) so there is not a great usage.
    Would it not be possible just to go to overkill and use a battery and solar panel of a size that would more than enough.
    Sorry to try your patience. Paul.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    Paul,

    I may not be a "greenie"--but I am a conservative (read: "Cheap").

    Yes, you can overkill the system--but it may be a waste of money--or, in the worst case, still not large enough to work (depending on the design).

    In my analogy--I wanted to keep it simple--but imagine you left your car idling in your driveway all day/night long. That is what your "gate electronics" are doing--consuming a little bit of power to run the radio receiver (assuming it is radio controlled). And if you drive it 10 minutes per day vs sitting for 23 hours 50 minutes a day idling--you have to account for the fuel consumed for both modes of operation.

    If you use a key lock (on a post) instead to run the gate, there may be no standby power used at all (kind of the difference between your car idling in the driveway 24 hours per day, vs only starting it when you are going somewhere with the key).

    The problem with analogies, they are always simplifications and we can get into the discussion of making a better analogy (i.e., we can argue a gasoline/petrol powered car idling vs a diesel powered car--typically diesel cars use less fuel when idling so would be better for "off-grid battery" operations).

    But then we get lost in the analogy instead of the original problem. ;)

    Really, all we need is the standby current (battery draw)--and we are ready to "spec." your system. You could even purchase a "cheap" DVM or analog Volt/Amp/Ohm meter for you around your home--you will probably need one eventually as you go more RE.

    You might wish to look for a local or online basic electricity course/book/electronics kit. The basics are not difficult--I just fear with any "new user/poster" that I don't want them to do something dangerous by mistake from lack of knowledge (or anything dangerous).

    It is always difficult to describe what to do with people that don't have electrical experience. And I/we don't want to injure anyone. 120/240 VAC and large storage batteries are dangerous to work around if you don't know what you are doing. And we all have our burns, shocks, and scares from these little "mistakes" (OK, bone-head mistakes). :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener

    plabito3,
    i don't know if you have an answer for this or not, but you stated it came with a small battery backup in case the power goes out. just how big is this battery in ah or mah and do they state how long it will last during an outage? this will give a better indication as to what it will do during idle periods that it is on standby and a better idea of the battery needed for full time battery use.
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Hi Neil,
    the motor did´nt come with a back up battery it´s available to purchase as an extra. So I have´nt got a clue what specification it is. They did tell me that it will open and close the gate a minimum of five times without recharge.
    On the advice of B.B. I have bought a digital multimeter and the gate opener is atatched to my gate.
    But (there´s always a but is´nt there), I have´nt got a clue how to use the multimeter. I guess I put it between the battery and the motor to see what power is being drawn when the motor is on standbye but would that be between the positive lead and the motor or the negative lead and the battery. Also what scale do I set the multimeter to?
    I really do appologise for trying your patience gentlemen.

    Paul.
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Niel,
    I´m so sorry. I see I´ve spelt your name wrongly.
    Paul.

    edit to add by niel: your apology is not necessary as many misspell it, but thank you for your concern over it.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    Is there anyone nearby that can help?

    It is not difficult--but I don't want you to damage the DVM--and when working with AMP scale, it is possible to hurt yourself/meter (meter should have a fuse) on circuits with high current/voltage (car sized lead acid batteries have a lot of current potential and can vaporize wedding rings and such).

    Try reading through the first 4 examples on this page on how to use a DVM.
    1. Basically, wire the gate controller/motor to a 12 volt battery (per the instructions).
    2. Set the DVM to 10 amp scale and plug the wires into the base of the meter. The black lead to the "COM" connection, and the red lead to the 10amp connection (if present on your meter).
    3. Make sure the gate works on the battery (opens and closes).
    4. Lift the positive lead from the battery, connect the positive lead from the meter to the + post on the battery. Connect the black lead to the positive wire on the gate opener. (may be a tiny spark when you make the connection--that is OK. If you see a large spark, disconnect and regroup--something is wrong).
    5. You should now see a current on the meter (may be 0.100 amps, or as high as 4.xx amps when the gate motor runs).

    If the gate on standby read very low current (like 0.00 or 0.01 amps)...
    1. Disconnect the Red lead from the meter. Set the meter to ~1 amp full scale.
    2. Connect the Red lead to the meter's V/Ohm/mAmp connection (if it has one).
    3. Read the current (may be 0.010 amps or something).
    4. This is the reading we need (standby gate current).
    And you are done.

    Never set your meter up to measure "AMPS" and place it across the battery (+/- posts on battery) or into a wall socket/outlet/receptacle.

    The DVM/Meter when set to current is near a "dead short"--it would be the same as taking a wire and shorting out your battery or electrical mains... Injury, fire, or death may result.

    If done with a well designed DVM--you may just blow the internal fuse and/or destroy the meter--still not recommended.


    Questions? If not sure, ask for help first!

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • peterako
    peterako Solar Expert Posts: 144 ✭✭
    Re: Solar powered gate opener

    In Spain there are 9 solar panel production centers, so i think you will find local and yes your area is perfect for solar power.

    P.s. i am in Greece
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener

    i think that if he finds out how much current it uses while awaiting in standby for a signal that we could give better advice on the battery sizing. this is shaky when dealing with the inexperience of using a dmm because it could be done wrongly and that could give a false reading or create a short circuit which would either blow the meter and/or the internal fuse if it has one.
    although measuring it yourself may be the most accurate way of determining the needs of the opener, i think it would've been better to ask the manufacturer for that type of info firstly and then if they didn't provide it, then the dmm would be an option. know anybody that can teach or supervise the measurements?
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Thank´s guys, for your replies and advice. Bill your instructions for using the multimeter are very clear thank you. Just one thing, it´s obvious where the 10A scale is as it says 10A and is one of the positions for the central switch. However, which is the 1A scale?
    My DMM, which cost the grand sum of 5 Euros, has a section ACV with two stops 750 and 200. The next section is DCA and has stops 200, 2000, 20m and 200m. Then follows the 10A section.
    I´m must admit I´m a bit embarassed. I sound like a total idiot. Plumbing, woodwork, bricklaying, mechanics, I´m comfortable with them all. I just never got into electrics. Maybe it´s time.
    Anyway thank´s again for your help.
    Paul.
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Hi Guys,
    just to let you know. I thought I´d take the easy option and rang the manufacturer ( well the importer because, surprise, surprise, the gate opener is manufactured in China) I asked them what the standbye power consumption of the motor is and basically I dont believe they´ve got a clue. I might just have well asked to buy a ticket to see Elvis in concert!
    So I´m back to square one. I´m starting to think I may have to get in an electrician and hook it up to the mains. It aint easy to be green (or consevative Bill).

    Paul.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener

    it might be cheaper to have the electrician measure the 12v standby power of it. i wish i could advise you on a better option as this measurement is rather simple to those of us that know how to do it. another option would be to just go ahead with buying a 12v lead acid battery and size the pv to the battery and see how it works.(i'll bet it would work) for you to size the pv just be sure it is rated to output a current of at least 5-13% of the battery amp-hour rating. that amp-hour rating would not be cca or cold cranking amps that is seen of starter batteries.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    It sounds like your meter is like the one in the link I gave earlier. The scales "200, 2000, 20m and 200m" are really "200u, 2000u, 20m, 200m". The "u" is really a "mu" (fancy "u" or "μ" if it displays correctly on your computer with a tail below the line on the front).

    Mu μ stands for Micro or in this case microAmps, or 1/1,000,000 (one millionth) of an amp. Or 0.000200 amp full scale).

    So, 200μ would be 200 microamps full scale.

    But in your case, we want the 200m or 200 milliamp (1/1,000 or one thousandths of an amp). Or 200 mAmp full scale(0.200 amp).

    The 200mA / 0.200 amp full scale is fine to use if the 10amp scale is not sensitive enough (try 10amp scale first).

    Did the manual say how large of battery to use?

    I am sorry, I am really not trying to make this so complicated. Trying to do this right and figure out what you need without just throwing money at the problem (which may or may not work well--just don't know).

    You can do what Niel says and just get a 10-20 watt solar panel (get a 10 watt now, and a second 10 watt later if you need more power--or get a 20 watt panel first), and a 10-40 AH storage battery (or even use a used car battery if you have one laying around). The 40 AH battery would be better to use with a 20 watt panel. A 20 AH battery would probably be a bit more appropriate for a single 10 watt panel.

    I would also get an expensive 2-8 amp solar charge controller to ensure the battery is not overcharged.

    -Bill

    PS: I should add--regarding the battery--is there are two major types of batteries you can get. One is a standard flooded cell battery (you have to add water every so often). The other is to get some sort of sealed battery (Gel Cell, or AGM).

    For you application, get a sealed battery (and a solar charge controller). You will not have to check the water level.

    Also, you can use a larger battery with the smaller panel--the sealed batteries are more efficient and have less "self discharge".

    For example, you could use a 40 AH battery with the 10 watt panel.

    Motorcycle batteries are typically "no spill" batteries. They just have a vent tube and you still need to remove the battery caps and check the water/electrolyte levels.

    (Thanks to Solar Guppy for reminding me in his post--in another thread--this morning).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Gentlemen,
    today I connected the battery from my car ( 95 AH if that means anything) to the gate opener. It worked perfectly. Unfortunately I ran out of light before I could connect the DMM and get the reading you need to advise me on the size of battery and solar panel I need.
    I´ll do it tomorow. Please stay with me, I´m enjoying the experience!

    Paul.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    Paul,

    Sounds like you are moving forward just fine. 95 AH is a good sized car battery.

    For your permanent installation--you should try to locate a fuse and fuse holder (rated about 6-10 amps or so, depending on wire size--placed in the positive lead, near the battery) so that if there is a short in your wiring or the gate controller--your wiring doesn't catch fire (or--if you have grass lands--set them on fire).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sam c
    sam c Registered Users Posts: 16
    Re: Solar powered gate opener

    keep in mind paul, with the right size panel, the draw on the batt during the day will be zero
    my batt is 110cca, there has been no sun here for 6 days. the gate still works
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener
    sam c wrote: »
    keep in mind paul, with the right size panel, the draw on the batt during the day will be zero
    my batt is 110cca, there has been no sun here for 6 days. the gate still works

    to further explain this it should've read 'keep in mind paul, with the right size panel, the draw on the batt during the day will be zero because the panel could be providing all of the power to run it.' a 3.5a pv will be in the area of about 60w.
  • pablito3
    pablito3 Registered Users Posts: 16 ✭✭
    Re: Solar powered gate opener

    Hi Guys,
    I´ve just connected the DMM between my car battery and the stationary motor (as per Bill´s step by step instructions) and on the 10A scale the reading was 0.10 and at the 200m scale the reading was 1.
    Does that make sense? Hopefully now, Oh knowledgable ones, you can advise me on the size battery and size of solar panel I require. Also what size cable would be best to connect the battery to the motor. Should I use crocodile clips to connect the cable to the battery or would it be better to use the screw type connectors that attatch car leads to the battery? Bill you suggested a fuse in the power lead from the battery. Would a regular in-line car fuse and holder suffice?
    Finally (I think) is there an optimal distance for a solar panel to be situated away from the battery its charging.
    Be assured that your help and advice is really appreciated.

    paul.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener

    Paul,
    ...the 10A scale the reading was 0.10 and at the 200m scale the reading was 1.

    OK, it appears that these two readings are not the same... If they where, it should have been:

    10A scale: 0.10 amps
    200mA scale: 100 mAmps = 0.10 amps

    Instead, if I understand your meter's reading:

    200mA scale: 1 mAmps = 0.001 amps

    0.001 amps does not equal 0.100 amps

    And, you may have done everything correctly too... The 10Amp scale on the meter is very low resistance so that it can handle large currents (10 amps maximum). Whereas the other scales have a higher resistance so that they can measure smaller currents with more accuracy.

    But the problem is that, depending on what you are measuring, the meter may affect the actual current flow (so high of resistance,that the circuit stops working correctly and draws less current).

    So--At this point, unless your 200mA scale reading shows something different (like 114 mAmps=0.114 amps), I am going to trust your 10A scale reading of 0.10 amps...

    If you go back a few posts to my first detailed example--I used 0.10 amps as my "made up" number... So, the post is exactly correct for your system:
    So, for our pretend example of 0.1 amps at 12 volts 24 hours per day:

    Watt*Hours = V*I * Hours = 12 volts * 0.1 amps * 24 hours = 28.8 Watt*Hours (standby gate energy used per day)

    And the operating energy per day (40 watts x10 open/close cycles at 1 minute each):

    Watt*Hours = Watts * Hours = 40 watts * 10 minutes / 60minperhr = 6.7 Watt*Hours (operating gate energy used per day)

    And the total energy used per day:

    28.8 watt*hours + 6.7 WH = 35.5 Watt*Hours per day.

    So, the "magic number" is 35.5 Watt*Hours per day (in this pretend model of your gate). And we can then easily pick a battery and solar panel to run this system...

    Assuming the 0.1 amps (you understand that 0.1=0.10=0.100 -- I am not being exactly consistent in writing my numbers here :roll: ) and 10x 1 minute gates cycles per day--you would need 35.5 watt*hours of power per day.

    To size the solar panel, lets assume you live somewhere around Pinto/Madrid Spain. Use this program to look up the amount of sun for your area (can also use to size for on and off-grid solar systems)... This program is a bit confusing for a first time user because it uses/supplies so much information--but it you take your time, it is actually very clear and straight forward. It is in English only--but your English sounds better than my English (my only language :blush: )--so you should be fine.

    I will use use:
    • Madrid, ESP
    • 1 kw for solar panel (because is smallest number program will use--1kW=1,000 watts--we will scale later to your system needs)
    • 0.69 derating factor (0.77 * 0.9 for Charge controller * AGM/Sealed Battery efficiency--recommend sealed/gelled/AGM for your needs--don't want to keep checking/adding distilled water to battery every month)
    • Defaults for rest of questions (good enough for now)
    • Note panel tilt (from horizontal) of 40.45 degrees facing due south (180 degrees)
    The result shows that your worst "average" month is 46 kWhrs per 1kW of panels per month... Showing some math:

    46kWhrs per month/30days per month = 1.53 kWhrs per day per 1kWatt of panels

    Or, converting to watts (1kW=1,000 watts):

    1,530 Watt*Hours per day per 1,000 watts of solar panels.

    You need 35.5 Watt*Hours per day... So to figureout how much solar panel you will need:

    35.5 WH / (1,530 Watt*hours) * 1,000 Watts of PV panels = 23 Watts of solar panels for December. You will have way more power than you will need for the rest of the year.

    Battery size, normally, we recommend 3 days of no sun, and 50% maximum discharge (for long life):

    3 days * 1/0.50 = 6x daily load

    So, your daily load is:

    35.5 WH * 6 days = 213 Watt*Hour rated battery

    But, most times (in the US), batteries are rated in Amp*Hours:

    Amp*Hours = Watt*Hours / voltage = 213 WW / 12 volt battery = 17.75 amp*hours minimum 12 volt Battery

    So, your minimum would be:

    ~20 watt solar panel and ~18 Amp*Hour sealed battery of some sort. And you can use a car fuse+holder rated at least 6-8 amps. And probably 15 amp maximum.

    I will make a second post to discuss some options and details.

    1. to keep this post from getting any longer
    2. to keep from confusing you--the basics above are 100% correct for your application--but I want to suggest some changes separately to reduce confusion.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar powered gate opener

    meters differ sometimes and may even make the user plug the + lead in at a different place on the meter for the 10a scale(most meters). the inexperience of his using a meter was what i was afraid of as was evidenced by 2 possibly conflicting readings and even we can't be sure they are in conflict or is it just his reading error? we don't even know what meter he has or can be sure he is on the right section as he did not specify ma, just only m, and that could also mean m ohms or mv and the fuse or meter could have blown from such a mistep in ohms. also that in the 10a position and plugging into a special 10+ on the meter that many meters do not have that fused. you started this bill and you better go into depth with him on how to use his meter.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar powered gate opener
    pablito3 wrote: »
    Also what size cable would be best to connect the battery to the motor. Should I use crocodile clips to connect the cable to the battery or would it be better to use the screw type connectors that attach car leads to the battery? Bill you suggested a fuse in the power lead from the battery. Would a regular in-line car fuse and holder suffice?
    Finally (I think) is there an optimal distance for a solar panel to be situated away from the battery its charging.
    1. Wire gauge--If you have house wiring laying around--it will work fine (US gauge is 14 AWG for 15-20 amp). Using this handy table for AWG to mm^2; 14 AWG = 2.0 mm². However, your maximum current is only ~4 amps, and you could go as low as 18 AWG (0.8 mm²) if the run is short. Note, wire insulation degrades in sunlight unless it is rated for UV (ultra violet) exposure. Keep wire runs short to limit voltage drop.
    2. crocodile clips are not a great idea--they will eventually rust/corrode and fail. Use crimp on ring lugs or solder a loop on the wire end (you should be able to get crimp tool kits from local hardware/automotive stores). But--you can certainly use what you have on hand for now--they will work.
    3. Long wire lengths add resistance--keep as short as practical. Wire length from battery to solar charge controller should be kept short. Length from solar charge controller to solar panels--not as critical (controller needs to accurately measure battery voltage for proper charging).
    4. And adding any simple fuse holder from a car parts store will be fine.
    OK, now for some more details...

    Solar Charge Controller... Any simple 2.5 amps or larger charge controller will work fine as long as it has a "Sealed Battery" option (sealed batteries use lower charging voltage to keep from "boiling" the electrolyte away--which will kill a sealed battery in no time).

    The actual solar charge controller rating is in Amps--so depending on solar panel size, the charger rating will need to be:
    • 20 watt panel / 15 volts (min Vmp panel rating) = 1.33 amps of solar charge
    • 40 watt panel / 15 volts (min Vmp panel rating) = 2.66 amps of solar charge (need 3 amp or larger solar charge controller)
    Next, for the solar charger--any cheap unit will do... However, if you can find one with a LVD (Low Voltage Disconnect)--it might be helpful. If you have a period of bad weather and/or lots of gate opening/closing, it is possible to drain the battery dead. The first time you do this--the battery will be "basura" (trash). Some simple controllers that will work for you include (I know that buying from the US is not practical). The first does not have LVD and is ~USD$45. The second has LVD and is ~$53:

    wind-sun_2041_25542378SunSaver 6 amp solar charge controller
    12 Volt DC, 6 Amp

    wind-sun_2041_25546238SunSaver 6 amp solar charge controller with LVD
    12 Volt, With LVD


    You can also use a "simple" charge controller for ~$31...:

    wind-sun_2041_25536697SunGuard 4.5 amp solar charge controller
    4.5 Amp, 12 Volt

    All will work--And some may be overkill--partly depends on how much you spend on your battery... Better controller should mean longer battery life (assuming you have enough solar panel). Always mount the charge controllers in the same box with the battery. And keep the battery/electronics out of direct sun light. Batteries last longer if kept cool (25C or less is ideal. Above 35C, and the batteries will age faster and fail sooner).

    Regarding which solar panel--get one that is mono or poly crystalline and avoid Amorphous unless they are all you can get and/or very cheap. They only last about 1/2 or 1/3 as long, and will have a 20% power loss in the first 6 months (would need to get a 25% larger amorphous panel). Panel Vmp (voltage maximum power) should be at least 15 volt minium and 20 volts maximum (higher than ~15-17 volts will not help you--won't hurt either).

    ~20-25 watt solar panel should work fine... You could use up to 40 watt--but that would be way larger than you need for the rest of the year... If you hold lots of parties in December--then a larger panel would be called for... Otherwise, 25-30 watt panel should be more than enough.

    Battery type... Flooded / wet cell battery will work fine--but you will have to heck the water level every month or so--if not, they will probably boil dry. Getting a sealed battery for this application (assuming the price is good)--would be better (no maintenance required).

    Battery Rating... 18 AH is fine--but I would probably look for a ~35 amp*hour battery. It will carry you through bad weather better and, hopefully, help prevent a couple of days of heavy use in bad weather from killing your battery (since you are not going to be monitoring your systems--you want a little more battery, a little more solar panel, etc. so you can just "forget" about the gate for a few years).

    Use your DVM to measure the battery voltage once a month or so... During the day, it should be around 13.8-14.2 volts or so (fully charged and not overcharing). At night, above 12.5 volts or so.

    If the battery voltage is low, probably not enough sun/solar panel. If the battery voltage is high--then the charge controller is not working correctly.

    And like Niel said--it is possible that you did not connect the meter correctly (remember, you probably need to move the RED lead when you change from 10Amp scale to the lower scales). I don't think you damaged the meter (there should be a fuse for the smaller scales)--but if the RED lead was not in the correct meter location, you may not have a valid reading.

    If you have a small flashlight light bulb or even a resistor and battery pack (or DC power supply), you can play with the meter until you understand the setup and readings. Measuring the standby gate current should be "safe" for your meter (standby current should not be very large).

    Enough typing for now. :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • shastaron
    shastaron Registered Users Posts: 24
    Re: Solar powered gate opener

    This has been a great thread. Not just from the gate stand point! There is a lot to be learned in the discussion about meters, wiring, batteries, standby load, active load (or as we call it in hydraulics static and residual).

    My thanks to "pablito3" for starting this thread and B.B. for you patience and persistence in your detailed explanations. As another amateur I have learned and confirmed a lot and this is why I like this forum so much.