Choosing and wiring the components of a solar-powered driveway gate

[JBlizzard]

Hi all, I am neither an artist nor an electronics person but I'm giving it my best shot today and every day.

I have a battery-powered driveway gate which charges by a solar panel. I chose to get the cheapest system possible and then spent almost an equal amount of money upgrading it, and getting out of my car dozens of times, always in the rain, when it failed in a truly surprising variety of ways.

Recently the board burned up and took the marine deep cycle battery (Product Link) with it. I replaced the board and battery but now the new battery only charges up to 12.3v or so, and this gate company designed their actuator to run on 12.5v to 13.5v with a solar controller that outputs 11v to 13v. I would've expected it to at least run slower at lower voltages, but it doesn't run at all if the battery is sitting at 12.49v or less - the control board won't tell the gate to open. I could exchange the battery but I'll just be facing the same problem in a year anyway when it gets to 95% service life and can't hit 12.5v anymore. It seems crazy to me that the control board would demand the top sliver of performance or else refuse to work at all, but anyway.

My solution, and what I would like help with, is: Get a second identical battery, hook it up in series to provide roughly 24v, then regulate it down to 12.5v - 13.5v so that the gate opener gets what it wants and my batteries should last a long time. Is this a good solution, and how do I hook everything up? I expected a Battery Isolator to only have 3 connections and a Regulator to only have 2 connections, but I'm not sure if this is correct: I keep seeing DC-DC Converters with 4 connections. (Is that the same thing as a regulator?)

This is a picture of my current setup:

This is my proposed solution:

And this is how the wires would be hooked up at the battery(s):

Is this correct? Here are the products I was thinking of using but I am definitely open to suggestions.

Regulator: 24v to 12v DC-DC Converter
Battery Isolator

 

[ZipZapOuch]

This is a mess. You would be money ahead by just changing your controller. Buying a second battery, a dc-dc converter to make your controller work? It would be much cheaper today and the next time you need two new batteries to buy a controller that works down to 9V.

 

[JBlizzard]

This is a mess. You would be money ahead by just changing your controller. Buying a second battery, a dc-dc converter to make your controller work? It would be much cheaper today and the next time you need two new batteries to buy a controller that works down to 9V.

The board for this gate system costs $319, so I have to imagine a higher-quality board would cost more. The extra battery, converter, and isolator total $228 so I'm ahead $100 or so. If I had known to call all the consumer gate companies and ask their minimum voltages, I would, and if I ever install a second gate, that's definitely the plan.

 

[Diver300]

You need several switching elements if you are going to connect two batteries in series at some times and in parallel at others, so that isolator won't work. It is also quite difficult to have a 12 to 24 V converter that can run in either direction.

To run the gates from two batteries in series, you need a 24 V to 12 V converter that is sufficiently powerful to provide the peak current that the gates take.

To charge the batteries there are several ways it can be done.

1) You could have a completely separate solar panel designed for 24 V.
2) You could have a 12 V to 24 V converter and charging circuit running from the existing 17 - 21 V solar panel
3) You could have the batteries in parallel when being charged and in series when being used.

For 1) and 2), you would not need to have any switching devices.
On 2), the 12 V to 24 V converter needs to work nicely with a solar panel, which isn't that easy to do.
On 3), there has to be something to detect when the gates are in use to change the configuration.

The circuit would be something like that. The three switches marked "A" would be closed when the battery is charging, and the two switches marked "B" would be closed when the gate is being used.

 

[JBlizzard]

Diver, thank you for showing me some different options, I still have a ton to learn about this. My thoughts were that the isolator would basically be a check valve to ensure a high battery doesn't charge a low battery, but you're completely right, I forgot to reconcile the 11-13v coming from the board toward the batteries being divided into two batteries; 6v into each would not work.

If I tried your option #1-2, could I buy an additional solar panel, hook that up in series, and bypass the control board for charging so that the solar panels would send 34-42v to the batteries (presumably with another voltage converter or some other over-voltage safety device?) Is there not a device that just limits the voltage to 24v from whatever it starts at? -- Or just buy a 24v panel and still use an isolator?

For option #3, I'm not sure that I'm ready to introduce some huge multi-pole relay or however that would work. I'd prefer it work passively, without the need for switching. I think it would be better to do option 1 or 2, given that the parallel 12v batteries can't charge from the 11-13v source coming from the control board.

 

[rjenkinsgb]

Both the battery charging and actuator system are fundamentally wrong, unfortunately.

11 - 13V is far too low to actually charge a 12V lead-acid battery to full capacity.
The correct charging voltages are 13.8V, if the charger is permanently connected, or 14.8 - 15V for intermittent charging. That should be reduced to 13.6 - 13.8V once the current drops to 5% of the AH rating.

The valid voltage range from a 12V lead-acid battery when off charge is from a max of 12.9V fully charged, down to around 11.6V fully discharged. They reach 12V at about 40% charge!

The 12.49V you mention would be reached at somewhere between 60 - 80% capacity, while off charge, IF the battery was properly charged beforehand.

With only 13V on charge, it will only ever part charge and will degrade quite quickly.


The charging system needs to be working correctly before anything else can be fixed.

 

[JBlizzard]

Everything you mention is information that I would've liked to know before buying from this company. Unfortunately all the values we have here are nominal, and the solution the company provides is to replace the battery every 2 years, which is a garbage response. I'm leaning toward buying a 24v solar panel and charge controller to bypass the board's charging circuit, then regulating the electricity to the board down to 12.5-13.5v. Then I should have a nice, robust, passive system that will last the actual life of the batteries.