Solar + battery garage door operator

[MintJulep]

A colleague just asked me if I thought it was technically feasible to run a garage door opener from a battery powered system charged by a solar cell.

My quick Google analysis went like this:

Small garage door opener is rated "1/2 horsepower".

1/2 horsepower is roughly 400 watts.

12 volt DC to 110 volt AC inverters of appropriate output are readily available.

12 volt solar batter chargers are readily available.

400 watts from 12 volts requires about 33 amps, plus a few extra for inverter loss.

An open/close door cycle is about 30 seconds.

So my conclusion was "It might work."

Did I miss anything?

 

[Eltron]

How many times does it operate per day? Is there enough sunlight in the area to power the charger? Why not switch to a DC motor?

Dan

http://www.eltronresearch.com

Dan's Blog

 

[CorBlimeyLimey]

Economically, is it worth doing? How much does running a garage door cost?

 

[Compositepro]

Such a project will easily work. Using off-the-shelf components will keep cost down. Why you would want to do this is separate question. It would only make sense where grid power is not available.

 

[VEBill]

Probably need a bigger inverter to account for motor start.

Given a normal (car sized) deep cycle battery, the rest should be trivially easy. Even a cloudy day will recharge the battery enough to keep up with any reasonable use pattern.

Watch out for the steady state stand-by current draw. It'd be annoying if the stand-by current was half an amp to run the receiver and safety system LEDs (etc.).

 

[MintJulep]

Figure 2 cycles per day.

That's about 7 watt-hours. Solar battery chargers seem to come in flavors between 5 and 15 watt output, so just a few hours of sun should top the battery up again.

Trying to stay with commercial off-the-shelf products, just wired together. Don't want to tear apart a new opener and modify it to take a DC motor.

 

[MintJulep]

The garage in question does not have power and the quoted cost for running power to it are exorbitant.

Seems like a suitable inverter, charger and battery would only be a few hundred dollars.

 

[VEBill]

Measure the stand-by current. It will probably swamp out the in-use watt-hours.

 

[TheTick]

Make sure doors have adequate torsion spring system to reduce motor load.

 

[zdas04]

I want to know how you keep the cycles to two per day. I'd be happy if my door stayed in the same position for an entire hour. Everyone opens the big door to keep from having to deal with a regular door and storm door (and my kids know the code and don't carry keys to the house any more). Damn thing is always going up and down.

David

 

[MintJulep]

Detached garage.

Take the car out in the morning, put the car in at night.

At least that's what I do.

 

[VEBill]

...about 7 watt-hours...

What if, for example, it draws just 5mA (120vac) when in standby?



It might easily draw many times that, depending on how careless the designer was.

 

[VEBill]

By the way, I'm assuming it's the type that has a radio receiver for remote control and/or a keypad. I've never seen one without such features.

 

[MintJulep]

Well, I don't have a power opener, so I can't measure the stand-by draw.

Any volunteers?

 

[KENAT]

Funny, we refer to the remote as the 'garage door opener' so before I read the OP I was thinking, of course you can run a little remote off of a solar panel.

Oh well.

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[LionelHutz]

VE1BLL - That inverter won't be running for free either. It'll constantly be using power and I'd bet it'll use more than the stand-by current of the opener.

It wouldn't make sense to turn the inverter on and off for each use. By the time you enter the garage and turn-on the inverter so that you can operate the door opener you might as well just quit being so damn lazy and open the door manually.

It really would be much better to build/use a DC opener controlled by switching on the motor with some sort of limit switches to stop it. Some sort of 12VDC remote signal receiver could be used which would have a very low standby current.

There are garage door openers available with battery backup. One of those may be suitable if the battery is charged from solar panels.

 

[VEBill]

Maybe the system needs a couple of power switches (3-way electrical switches) so that the user can reach out the car window to turn the system on, and then turn it off again once inside.

 

[jraef]

Totally feasible. A 115VAC solar inverter capable of starting and running a 1/2HP motor will be around 1500W, maybe 1250W if it has "surge capacity" (an ill defined marketing term, so be carefull).

Size the battery (...ies) based on how often you plan on using it and especially how often you might want to use it in the dark or on cloudy days when the solar array isn't going to contribute to recharging, plus how big your array can be in terms of providing recharge energy. In other words if you only have room for a small array and you and yous get home after dark quite often, use a LOT of batteries. There are on-line calculators available from the Home Power industry that will help you select the components based on your predicted use.

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