Battery Charge from solar panel for automatic gate opener

[DeanKC]

The battery for my automatic gate opener is a 12-volt Duralast 24MS-DL Marine Starting Battery. It has been in service over six months and has never needed to be charged even though the gate is operated several times every day. In other words, everything about my Ghost Controls opener has been extremely satisfactory.
Today, I decided to check the state of charge since we have not seen sunshine for about a week. The battery seems just fine but the state of charge as indicated by the output voltage is what I don't understand as it is over 14 Volts. See photo.

 

[MAX-24-Dean]

When I worked in an industrial battery shop, we used hydrometers and cross referenced specific gravity charts to determine voltage and state of charge. The reason was that using a volt meter to find state of charge required us to let the batteries rest (no charge voltage being applied) for several hours for the voltage to stabilize to use the voltage cross reference chart.

2.3 volts per cell is typical for lead acid chemistry on charge, so 14.0 volts for a ball park while on charge is a normal reading.

A solar charger will still function in an overcast cloudy enviroment, just not at full capacity. So it appears in your case that the solar produces more than the demand on a consistant basis.

I have had several cloudy days in a row here in Washington state with 100% overcast, I was still able to produce approximately 4Kw total per day from an 8Kw system for three consecutive days. Usually producing 20Kw a day.

 

[DeanKC]

Thanks Max. Having always known about 2.3V, it was the chart that confused me. Had I disconnected it and delayed several hours, the chart might have been applicable.
I learned something important today. Thanks again. Dean

 

[CH4Ohio]

Looks like you were really checking the output from your solar charger at that instant. The battery could be quite weak but you'd still get a high reading if you're checking with the charger connected.

(Just like checking across your car battery while the car is running. If the alternator is good, you'll see ~14 volts. This doesn't tell you anything about the condition of the battery except that it still has continuity.)

 

[Fuddyduddy1952]

I'd cover solar panel with a cloth then measure battery, cycle the gate a few times taking surface charge off of battery seeing what voltage is.

 

[MAX-24-Dean]

I'd cover solar panel with a cloth then measure battery, cycle the gate a few times taking surface charge off of battery seeing what voltage is.

Always a good rational thinker in the crowd!

 

[DeanKC]

Looks like you were really checking the output from your solar charger at that instant. The battery could be quite weak but you'd still get a high reading if you're checking with the charger connected.

(Just like checking across your car battery while the car is running. If the alternator is good, you'll see ~14 volts. This doesn't tell you anything about the condition of the battery except that it still has continuity.)

Thanks. Will disconnect and see what happens.

 

[DeanKC]

Always a good rational thinker in the crowd!

I'd cover solar panel with a cloth then measure battery, cycle the gate a few times taking surface charge off of battery seeing what voltage is.

Thanks. Every response has been a very informative. Now I'm really interested in seeing the results.

 

[DeanKC]

Operated the gate a couple of times, then disconnected the battery. A while later I tested with the battery disconnected. SE Louisiana has not seen much sunshine for the past week or so. Today's reading should be accurate. If I am still missing something, please let me know.

 

[Fuddyduddy1952]

Battery is wet. Is that rain?
I'd use that meter on any car, truck, tractor. Check battery then start it. Voltage not running then running & charging...see how it compares.

 

[DeanKC]

Water gets into the battery box thru the vents. Going to make a roof over it as it is partially exposed to the elements. See

 

[Fuddyduddy1952]

Check other batteries with that same meter, simply off then running/charging.

 

[DeanKC]

Here's the results: Outside temp is mid-40's. Truck built 5-yr ago. Factory battery. Not started for 22 hours showing 80% charge. 2nd reading is with engine running.

 

[Fuddyduddy1952]

To me, I wouldn't be too concerned, however, I would either unplug solar panel or throw a towel over it (cover completely). Open & close gate a few times with just battery not being charged. The higher voltage apparently is because the charge exceeds the intermittent gate motor load. Even cloudy panel is still charging some.
Just looking at pictures to me it's a nice set-up but maybe a little overkill...the solar panel & battery exceeds use time cycles.
Me, as an electronic technician, I would probably try a temporary experiment like a 12 volt landscape light or two, especially with a photocell (dusk/dawn). That gives a 1 or 2 amp load on battery.
Most likely it's designed the way it is because some applications the gate may be used every 5 minutes!
I have a landscaping friend who changes gate batteries a lot and thinking about it, it's probably from overcharging.
I think you'd certainly have higher voltage readings on your truck battery if it was on a charger 9 hours a day.

 

[DeanKC]

To me, I wouldn't be too concerned, however, I would either unplug solar panel or throw a towel over it (cover completely). Open & close gate a few times with just battery not being charged. The higher voltage apparently is because the charge exceeds the intermittent gate motor load. Even cloudy panel is still charging some.
Just looking at pictures to me it's a nice set-up but maybe a little overkill...the solar panel & battery exceeds use time cycles.
Me, as an electronic technician, I would probably try a temporary experiment like a 12 volt landscape light or two, especially with a photocell (dusk/dawn). That gives a 1 or 2 amp load on battery.
Most likely it's designed the way it is because some applications the gate may be used every 5 minutes!
I have a landscaping friend who changes gate batteries a lot and thinking about it, it's probably from overcharging.
I think you'd certainly have higher voltage readings on your truck battery if it was on a charger 9 hours a day.

 

[DeanKC]

When you mentioned landscape lighting, that was exactly what I had decided to add to the setup. BTW, I went to 6-mo Coast Guard ET school 60 years ago. Right after, I was transferred to New Orleans where I spent 3 years investigating ships requesting to enter US waters. It was never my occupation but you don't forget some of the training (e.g. resistors BBROYGBVGW).
I have never had to charge this battery. The setup across the road uses a smaller solar panel and two of those batteries that go in UPS (Uninterruptable Power Supply). He keeps two on charge and needs to swap them out 2-3 times a month.
I'm happy with my setup.
With the truck battery showing 80%, it might indicate that it is almost time for a new one. I've had my current tractor for 22+ years. Batteries lasted 8 - 7 - 6 years in that order.
Thanks for all of your suggestions.

 

[JudeSaunders]

Great setup, and thanks for sharing your Coast Guard background—impressive! Your experience with the solar panel for the gate opener and landscape lighting sounds solid. It's fascinating how different setups affect battery life. Have you ever considered solar panels Cork? Seems like your expertise could be valuable in exploring those options!