Proper battery for gate opener? Did 12 volt light kill it?

firemediceric · November 2015

I have a Mighty Mule gate opener that I installed 2.5 years ago. At the time I used a Marine type battery and connected a 50 watt (IIRC) solar panel to keep the battery charged. No issues until this week.

In an effort to add lighting by my gate I installed from Amazon a GLW® 10W 12V AC or DC 700lm LED Motion Sensor Flood Light, Smart PIR Decector Outdoor Security Floodlight 6000k Cool White, Waterproof Basement Light 100cm Cable, 80W Halogen Bulb Equivalent. I reasoned that the large marine battery had more than enough power to both power the gate open/closed half a dozen times per day and to also illuminate the light in the evening as circumstance may trip the motion detector to cause the light to come on for 6 minutes at a time. I think I was wrong about the battery being up to the task.

On the first night when the light was activated the gate opener began sounding its audible beeping to inform me that the voltage was too low to power the gate opener, even though the opener was not in use. I did a little observing and realized that without any draw on the battery there was 13 volts present, even at night. When the light comes on that drops to just over 10 volts. I was very surprised by such a large drop in power from such a small light. I disconnected the light.

I tried to activate the gate opener the next morning, but without success. Now when I test the battery I see 13 volts without a load placed on the battery, but when I use my battery tester to apply a load to the battery the needle goes all the way to the left telling me there is not any voltage or that there is a short.

My first question is what type of battery should I use to replace this failed battery? Another marine type or something else?

Is it purely a coincidence that the battery failed at the same time the light was installed or did the light put too much of a demand on the battery, especially without the sun shinning to recharge the battery at night?

I'd like to have the benefit of that 12 volt light, but I don't want to be replacing the battery prematurely.

Aguarancher · November 2015

How is the water level in the battery and is the solar panel able to have full sun with no shading? Also what size is the battery?

firemediceric · November 2015

Water level was good. Solar panel is exposed to full sun for the entire day. I don't recall the size of the battery, but it is a good size marine battery that is listed as a "Marine Starting" battery. As mentioned, all has been fine for a couple of years until I hooked up the 12 volt light and then things went to hell.

Johann · November 2015

Check your chemical levels with an hydrometer, cell by cell.
You have the voltage without a load and with load the voltage goes down very fast. Looks to me that you have a sulphated battery or just a bad battery with eroded plates or a battery with one bad cell.

And using that light and that battery goes bad was just coincident, it just gotten noticed now since the sun hours are less now and the battery may get less power. On the other hand, that light may put a small standby load on the battery. You may want to check what the constant draw on the light is, even when the light is not energized.
Make sure that the solar panel is actually putting power out.
A marine starter battery is just a starter battery like a car battery and may not even be a hybrid deep cycle battery and is running short being a true deep cycle battery. Usually starter batteries do not last long in solar applications.

firemediceric · November 2015

Johann, You have provided me with some good food for thought. So I will choose to NOT go with a starter battery tomorrow when I purchase a replacement. Is a standard deep cycle the best for my application?

Without the light illuminated, the voltmeter that is continuously on the battery reads a solid 13 volts. That makes me think there is not a draw on the battery when the light is not illuminated and the gate opener is not running. On the other hand, even though the motion detector light is set to come on just when it is dark outside, maybe the motion detector is constantly drawing power, yet even at night without the benefit of the solar panel charging the battery the voltmeter reads 13 volts.

Before hooking a new battery up tomorrow I will confirm that the solar panel is indeed producing volts. Given the facts above about the battery being at 13 volts at night without the benefit of the solar panel during that time of darkness, I tend to think that the solar panel has been/is doing its job. The gate opener is used several times a day and until this incident has run flawlessly without a sign of reduced power. As mentioned above, the gate opener makes a beeping sound when the voltage is low, even if the opener is not in use. When the light kicked on, the beeping started. When the light timed out and shut off, the beeping stopped.

My take away from your post is to get a new battery that is not listed as a "Starter battery," confirm that the solar panel is indeed putting out power and then to re-attach the gate opener and the 12 volt light. Have I got it correct?

firemediceric · November 2015

In doing some more research, I plan to add this to the mix:
Sunforce 7 Amp Charge Controller
http://www.amazon.com/Sunforce-7-Amp...FGWK4K8SNAPAEC

inetdog · November 2015

Before you go out and get a new battery, you can also test by measuring the terminal voltage while the gate is opening and shortly after a gate cycle.
BTW, my Mighty Mule gate is hooked up with an AC trickle charger and there is a circuit built into the gate opener that uses a shunt relay to keep the battery voltage from going too high. That may be the reason that MM does not require you to use a Charge Controller (CC) with a small solar panel.

vtmaps · November 2015

inetdog said:

Before you go out and get a new battery, you can .....

It's a 2.5 year old starting battery being used as a deep cycle. The battery is scrap. OP needs a deep cycle battery. OP needs to (in this order) figure out his daily load in watthours, then choose the correct size battery for that load, then make sure he has enough solar panels to charge the size battery he has chosen.

Anything else is guessing. If he guesses the battery size or solar panel size wrong, he will be lucky to get 2.5 years from his next battery.

--vtMaps

BB. · November 2015

Watch how much the light is on at night... I have motion detector lights and during April (our windy at night season), the moving trees/leaves off to the side of the motion sensor keep the light on for hours at a time.

More than likely, your battery is probably near dead, and the lights may have added just enough load to pull the surface charge off the battery--And then nothing works.

10 Watts (near 1 amp) is not a big deal--But if it is on for many hours per night (say 10 hours)--That is 10 AH from the battery and about 10% to 15% of a typical starting battery--And if the battery is weak/old/near death, that is more than enough to kill it the rest of the way.

Your present 50 watt panel in full sun (assuming Vmp is ~17.5 Volts or so) with a decent solar battery charger on a 30-80 AH deep cycle battery should be a good solution.

-Bill

firemediceric · November 2015

Thanks for the input. Headed to purchase a deep cycle battery now. The charge controller listed above should be here tomorrow, then I'll put it all together.

Regarding how long the motion detector light is on, sometimes passing traffic will activate the light, but being on a dead end road keeps it from being activated often.

firemediceric · November 2015

Thank you all for the direction. The charging control showed up yesterday evening. I wired that place in between the solar panel and the battery. I then connected the gate opener and the 12 volt LED light as well as a digital volt meter. The sun had set by the time I was done. The battery was reading 12.5 volts and at that time of the evening was not going to get any help from the solar panel. With either the gate opener running or the light shinning, the voltage dropped to only 12.4 volts. With both the gate opener running as well as the light shinning, voltage dropped to 12.3. I have no idea how many times the light may have been activated overnight, but this morning the gate opener functioned just fine.

Thanks for the recommendations of the deep cycle battery, the use of a charge controller and setting me straight that the failure of the battery with the initial connection of the flood light was simply coincidence.

PNjunction · January 2016

Well, hope it is still working for you at this point... but ....

That Sunforce charge controller is right from the 1970's - basically a poor controller that relies upon the hysteresis of the battery, and when it sulfates, things just get worse and worse.

May I suggest an upgrade to something more modern - like a Morningstar Sunsaver SS-10-12V pwm for your application. It is WAAAY more efficient than that 70's "ping pong" controller - and built much better to boot. Even though it costs more than that cheap controller up front, your battery will thank you.

Proper battery for gate opener? Did 12 volt light kill it?

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