Need help getting 24v from solar - Fiberglass RV


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Old 08-06-2018, 03:34 PM   #1
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Need help getting 24v from solar

I am in need of some advice about building a solar system to operate a 24 volt gate opener. I know it is not for my RV directly but it is for the gate that encloses the carport where the Bigfoot will live while at home. Here is the gate.
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This is the shed where the Bigfoot will live. Ignore the ratchet straps, that was when hurricane Irma was coming and I needed proof for the insurance that I tried.



The gate opener is on its way so I need to figure out how to develop 24 volts using solar to charge deep cycle batteries. I know very little about solar and am hoping someone can point me to some products that will do the job without breaking the bank. The gate will not be opened a lot. Sometimes it will be days and days when it doesn't open, so I don't think I need large panels. I know I need to wire 2, 12v batteries in series to get 24v but other than that I have questions about the solar part. Like.....


__Should I have two separate 12v panels, each charging one 12v battery?


__Do I need a controller? What do they do?


__If there is no controller what senses when the batteries are fully charged and stops charging.

__Is there such a thing as a 24v solar panel that will charge both batteries while in series?



So you see that I am clueless, pretty much. If anyone can get me plumbed up on what I need I would sure appreciate it.
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Old 08-06-2018, 04:00 PM   #2
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there's lots of 12/24V solar charge controllers. to use them with 24V of batteries, you'll need to wire two sets of "12V" panels in series to feed the controller.

here's a typical generic chinese one.
https://www.amazon.com/ALLPOWERS-Cha...dp/B01MU0WMGT/

I'd imagine a pair of 18AH 12V SLA/AGM batteries in series would be sufficient for a gate motor, I can't imagine the gate being opened/closed more than a few times per hour... this would give you about 220 watt*hours /usable/ power before needing recharge. a pair of 30W 12V solar panels in series would provide about 2 amps typical, which should recharge those batteries in a few hours.

now, if you know how many watts or amps the 24V gate actually uses, and how often you expect to open/close it, and how long it takes to open/close each time, I could give you better numbers, I pulled those above out of thin air and wild guesswork.
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Old 08-06-2018, 04:08 PM   #3
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oh, your other questions, yes, you really should use a controller, they are cheaper than the panels anyways, they will prevent the batteries from overcharging.

I suggest getting the controller at about twice the amp rating you actually expect to have solar panels for. while 24V solar panels DO exist, they are large several 100 watt panels and would be way oversized for this application. 2 12V 30W to 50W panels would be plenty for the batteries size I'm guessing you need. if it turns out you need larger batteries, then you'd want bigger panels, like 2 x 100W for charging a pair of group 27 deep cycle, or 2 x 400W for charging 4 x 6V golf cart batteries in series (that would provide you with 220AH at 24V, at 50% discharge about 110AH usable, thats 2500 watt*hours, you could run a 1/4 HP (~400 watt) DC motor for 6 hours continuously before wanting to recharge the batteries).
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Old 08-06-2018, 04:22 PM   #4
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Thanks for the help John. I just looked at the specs. on the opener and it says it can draw a maximum of 735 watts. But then on another line it says "Rated power- 190watts". My gate weighs about 50% or less that the maximum weight recommended and it should take about 40 seconds to open. That would be 80 seconds run time for a cycle. a busy day for that gate would be 3 or 4 cycles. I am thinking2 batteries should be plenty???
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Old 08-06-2018, 05:03 PM   #5
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yeah, a pair of 12V 18AH to 20AH batts, such as Panasonic LC-X1220P (a personal favorite) should be plenty sufficient. lets see, thats 24V at 10AH usable (50% discharge) or 240 watt*hours... you should be able to cycle your gate at least 50 times before wanting to recharge, and twice that with the batteries going into damaged goods mode (for, say, emergency purposes).

those batteries are quite happy with a 2 to 5 amp charge rate. '30W' 12V solar panels provide about 2 amps, 60 watt ones, about 4 amps.

so... a 12/24V solar controller rated for at least 10 amps, and 2 30-60W 12V solar panels wired in series mount the panels on a pole facing south at about 45 degrees tilt for good solar exposure. put the solar controller in the weather proof battery box so the wires from the solar controller to the batteries are as short as practical.
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Old 08-06-2018, 05:37 PM   #6
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John, your the best! I checked with good old Mr Amazon and I found the Panasonic batts for $62 each, a 30w solar panel for $50 each and a 20amp 12/24v controller for $21. Other than the batteries this other stuff is no doubt China junk but it would get the ball rolling for about $250. Does that sound about right? I have a Batteries plus Bulbs store near me so I might check them as a source. Not sure what they carry.

For wiring these things together should I be using stranded copper as I would for wiring in my boat with crimped fittings or just wire nuts for future maintenance?
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Old 08-06-2018, 05:49 PM   #7
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I like using marine wire. 12/2 or 10/2 for high current DC applications like this. and marine crimps, tthat have heat shrink insulators. for the solar -> controller -> battery connections, you want 10 AWG for minimum voltage drop. for the battery -> motor connection, 12 AWG is likely fine.

solar panels tend to use MC4 connectors which are unique, you could get these to run from the panel to your solar controller in the battery box...
https://www.amazon.com/Awclub-Adapto.../dp/B078KX71ZK
note that unplugging a MC4 is a pain, there's a special tool to unlock them.

at the solar controller side, its a screw clamp fitting, so no fitting or connector needed. save a few feet of that same 10 ga wire to use for the solar controller to battery connector.

the Panasonic battery I mentioned has m4 lugs, you use a ring terminal, and m4 nut+lockwasher+bolt to secure the wires to the battery, ditto a short jumper wire of 10 AWG with 2 ring terminals to hook the 2 batts in series.

I'd get marine 12/2 to run from the solar controller 'load' outputs to your motor. like this stuff, https://www.amazon.com/Duplex-Tinned.../dp/B00MI5EOGG but you can get it by the foot at any marine supply.
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Old 08-06-2018, 06:15 PM   #8
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OK, I think I have a pretty good grasp of what I need. It appears I will need to buy a crimping tool to install those weird fittings onto the 10ga. to connect to the controller, will the controller have these fittings on its leads normally? Is this the connection you were saying I could just use crimp terminals with shrink tube and it will be fine? Maybe just the connection to the solar panels need the fancy connectors???


The gate opener is supposed to be here Friday and then I will need to pour a concrete pad for it. I will get the items we discussed on hand so I will know how big to make the pad. I will work on finding a good enclosure for the batteries and the controller beforehand also so I can be sure there is sufficient room on the pad.
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Old 08-06-2018, 06:25 PM   #9
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I've not crimped MC4's, but the pins of the ones I've looked at appear to be something you can crimp with a fairly generic large (10 ga) uninsulated crimper.... but that wire set I posted, the two MC4 connectors are each on a 10' piece of 10AWG already, so you don't need anything.

at the solar controller, you just strip 1/2", loosen the screw, insert the wire, and clamp the screw.

crimped on ring terminals would be for the battery side of things

the wiring is really simple... the solar controller has 6 connections. + and - to the solar panels, + and - to the battery, and + and - to the load (your gate motor thing), all 6 of these are screw-clamps...

re enclosure, if you're building a box/enclosure for the motor assembly, you can probably just make it enough bigger for the batterys + solar controller... they just need to be protected from direct rain... make sure the wires into and out of it go 'down' initially so rain doesn't run down the wires into the box (aka drip loops). I'd probably use some sort of risers so the batteries aren't sitting directly on the pad just to keep them out of puddles;
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Old 08-06-2018, 06:41 PM   #10
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I bought my panel from https://www.solarblvd.com/product-ca...?orderby=price
They have a 20W panel for $25 and a 40W for $35. But add shipping. Best deal on a 24v controller there is $59 but it should be decent quality. Note, make sure whatever controller you buy is waterproof for your outdoor use.
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Old 08-06-2018, 07:20 PM   #11
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Mike, Good point about making sure the controller is ok for outdoor. I will check out the supplier you mentioned and maybe step up to 40w for about the same dollars. That controller sounds better also. There is a lot of solar business here in Florida but it is all big stuff for whole house stuff.


John, Just to go over this vision you have planted in my brain.....I will get two panels, each will have 2 color coded wires, I will connect the negative wire from one panel to the positive wire of the other, using those weird connectors. I will run the remaining positive and negative wires to the controller and connect to the "in" connection points indicated in the manual or labeling on the unit. I will then connect the proper wires from the controller specified in the literature to the batteries. Then the positive and negative from the batteries to the motor. Hallelulya??
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Old 08-06-2018, 07:27 PM   #12
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Also, John, this is the opener I have coming.
https://www.ebay.com/p/SKC600DC-Gate...tor/1400119594


No place inside for the solar so I will be looking for some type of prefabricated enclosure. I am assuming that the small amount of gasses given off by the batteries won't harm the controller. I will have some ventilation. If you know of a good housing, I'm all ears.
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Old 08-06-2018, 09:23 PM   #13
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Quote:
Originally Posted by halfhitch View Post
Also, John, this is the opener I have coming.
https://www.ebay.com/p/SKC600DC-Gate...tor/1400119594


No place inside for the solar so I will be looking for some type of prefabricated enclosure. I am assuming that the small amount of gasses given off by the batteries won't harm the controller. I will have some ventilation. If you know of a good housing, I'm all ears.

huh, I found the manual for that model, and see nothing about 24VDC operation.
http://www.gatekeeperltd.com/SKC600DC_User_Manual.pdf
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Old 08-06-2018, 09:37 PM   #14
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Maybe I posted the wrong thing. This is what I am supposed to get.
SKC600DC Gatekeeper Sliding Gate Opener - Baldwin Pines
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