Solar gate motor

Solar panels facing east and west

Solar gate motor is really very simple to construct at minimal expense; small PV panels can be used to charge a 12V battery which then powers an appliance at any time of the day or night.

Build it yourself; you will need:

This page was last updated by Bernard Preston on 5 December, 2018.

By Bernard Preston

  • A 20-25W solar panel
  • A roughly 2m pole
  • A bracket to attach the panel to the pole; clamps.
  • 1.5mm wiring
  • An inexpensive diode
  • A second hand 45-60Ah battery from your dealer
  • A switch
  • No expensive charge controller is needed

Most gate motors use a small, roughly 10Ah gel cell battery which personally I find inadequate; they are neat because they fit snugly within the housing but just don't store enough energy to cope with inclement weather and overnight demand. They are also expensive, and rarely last more than a year or two.

The 2.2m aluminium pole is what you probably still have lying around from an old TV aerial.

Those brackets for the panels are very easy to weld up from some scrap iron; position them at around your angle of latitude; 30 degrees in my case.

So I recommend moving to a motorcycle or golf-cart battery; 45Ah or more; good second ones can often be picked up cheaply and they last because of the very low demand on them to drive the solar gate motor; they also love the slow trickle charge from the small PV panels.

I say panels as in my experience it's best to have two, one facing basically east and the other west; 15-25W each is ideal, depending on the number of times the gate must be opened and closed; usually they are used most early and late in the day, so one north or south facing PV is not ideal unless you have quite a large battery.

Start with one panel and, if it's not adequate, it's simple to add another.

Ideally the PV panels should be identical, otherwise you will need to use an extra diode to prevent the one reversing the current in the other; as I have had to do above.

It's rather less tidy as the battery will not fit into the gate motor assembly. Covering it with an ice-cream container, for example, protects it from the elements.

Classically one should use a regulator, but in practice charging a larger battery with around 15W all day does no harm.

It is wise if concerned to look out for tell tale signs of overcharging; the battery becoming overly warm, the casing swelling, and the terminals corroding badly.

The small gel cell batteries certainly will need a regulator; they are quite unable to cope with being overcharged and one of the terminals will corrode and literally fall off.

At this stage, because we have one of each, the wet battery that requires topping up periodically with distilled water, and a sealed type, I am not certain which to recommend; both seem fine.

The wet, unsealed type we've had for over a year; it's actually a 35Ah motorcycle battery, bought cheaply second hand and is perfect; but it requires topping up every few months with distilled water. 

The sealed battery from a golf cart I've had only for a few months; I'm watching it carefully for signs of overcharging. It's been fine to date, so I think you can use either, but I'm not altogether certain.

Obviously sealed batteries require no maintenance; I watch with interest to see if it lasts as long, or like the gel cell batteries is not suitable for a solar gate motor.

Solar gate motor

My recommended specifications:

  1. Two 15W solar panels facing NE and NW.
  2. One sealed battery, at least 45Ah.
  3. No need for regulator.
  4. Aluminium pole, say 2.2m
  5. Brackets to hold the panels.
  6. Switch.
  7. Two small diodes.
  8. 1.5 housewire.

If you can pick up a good second hand battery (I did for R150 and R200), then you can do this yourself for under R1000. I have two such installations, and they work perfectly.

If you gate opens and closes many times each day then increase those panels to 20 or even 25W.

You can easily pay double that from an online electronics company, but the cheapest I've seen is around R2000 when you've paid for the delivery; and you'll only have one of those nasty little expensive 7Ah batteries that will need to be replaced within a year or two.

Solar gate motor is particularly useful at remote installations where grid power is not readily available.

Supplying a mains voltage to any remote installation requires an armoured cable, and a qualified electrician to do the work. However, PV panels supplying direct current at about 25V, means that you can quite safely do it yourself, at a considerable saving in material and labour.

Also the solar gate motor then will not require a battery charger to turn the alternating grid current into DC at the required voltage, usually 12V.

Solar panels at night will radiate the energy from the battery back to space; it is necessary to put an inexpensive diode in each circuit; or switch it off every evening.

Solder or crimp it in series with the PV panel; if it's on the positive line, then the white band should be faced in the direction of the battery showing the allowed conventional current.

The diode will prevent electrons flowing incorrectly and discharging the battery.

The diode can either be placed in the circuit at the PV panel, or at the battery.

Connect the leads directly to the battery so that it will charge immediately there is enough light.

Then take wires directly from the battery terminals to the solar gate motor. In addition I find it wise to place a switch in either the positive or negative cable.

I have used 1.5mm house wire throughout to reduce heat losses which are high at the low voltage.

How diodes work may be of interest.

Solar gate battery

It's unfortunately not clear, but both cables from the two PVs feed into that negative terminal, and another out to the gate motor.

In short, this is easy to install, the battery is cheaper, and your electrical grid consumption will be substantially less; and is certainly a must if you are going off the grid.

The life of your battery will be extended if you place it on a block of wood to stop it shorting to earth.

In the unlikely event of total blackout, but which has already happened in Kenya and Uganda once in 2018 already, last week, you will be sitting pretty if you have a solar generator and your gate motor is energised by sunshine.

This has happened in other parts of the world too, in Italy for example, in the not too distant past, and in Atlanta where over 1000 flights were cancelled just before Christmas, 2018.

solar gate battery with ice-cream container cover

Protect your battery with some useful cover.

Power surges

Taking your solar gate motor off the grid will protect it from power surges.

We have three such motors; one at the gate and two on garage doors; the latter two are still on the grid. This week their mother boards were both blown by this mains power surge. My refusal to go off the grid must be revisited.

Power surge

Either because folk are becoming more environmentally conscious, or simply because it's cost effective, eco friendly homes are increasingly in vogue.

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56 Groenekloof Rd,

Hilton, KZN

South Africa