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deerslayer
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# Posted: 18 Aug 2022 04:37pm
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Hello all- I have been trolling this site for years gaining tricks and tips for my little slice of heaven. I am looking to add solar and want to start on something simple at home before taking my knowledge "up north". What I want to do is to maintain the batteries in my atv and lawn tractor in my garden shed, which is far enough from the house that running wire is impractical. So, my question is how do I maintain two separate batteries from a panel? Thanks, I will hang up and wait for an answer to my question...... 
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paulz
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# Posted: 18 Aug 2022 09:08pm
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I do this at my shop, but with a separate panel and charge controller for each battery. You could connect the batteries in parallel, as is done in typical solar situations, but they are usually of the same size, style and age batteries. Not sure what would happen with unmatched batteries.
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gcrank1
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# Posted: 18 Aug 2022 11:13pm - Edited by: gcrank1
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Guessing you want to charge the bats while still in the units just to 'keep them topped up'.
Do you have good solar exposure? Solar charging time averages at best about 5hrs if the sun is out and hitting the panels, but poor exposure, shadows, etc can kill it.
What latitude are you at? That will affect your harvest too; ie, Arizona is far better than Quebec.
Batteries for an atv and mower/lawn tractor are typically kept charged/maintained at a relatively low rate with a plug in charger, like 1 to 2 amps. They dont care what charges them so any small solar panel that puts out similar to that, and assuming 12v, will work, but only for 4-5hrs a day, not 24/7 like a plug in charger. If your bats are good and the charging system on the units is good to solar maintainer will keep them topped between use.
But panels are rated in watts, not amps.
Amps x Volts = Watts.
So, a 2 amp output x 12v = means you need a 24w panel right? Not really, there are inefficiencies and losses. Id prefer a 36 to 50w panel. Reality is that if you can get 70% of a panels rating (rate under 'ideal' lab conditions) you are lucky.
And you need a charge controller to take a typical '12v' panel's unregulated 18-21ish volts and turn it into 14-16ish volts to pump the amps output into the battery.
That is to say that a 12v battery isnt. They are closer to 13v but we 'say 12v' because its convenient. We need to be pushing higher voltage than the nominal battery voltage to actually get a charge.
Im actually doing something similar at my off-grid toolshed, a small panel feeds a spare 12v battery to power my modest lighting needs. It could just as well be a battery in an atv. The output leads from the charge control just hook up to the bat.
For your purpose with 2 units Id run the charge control leads to the closest unit (close matters, there are 'line losses' the farther you go so use as large a wire gauge as you can) and Id jumper to the 2nd unit. They will equalize enough, I think, to stayed topped up.
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darz5150
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# Posted: 18 Aug 2022 11:26pm - Edited by: darz5150
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They have solar battery maintainers on Amazon and harbor freight. I use one to keep the battery on my 5 the wheel topped off. They won't charge a dead battery, but still puts enough back in the battery after a little use. Not sure if that's what your looking for, just another option.
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ICC
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# Posted: 18 Aug 2022 11:39pm - Edited by: ICC
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The easiest and best for the batteries trickle charging would be to have a separate solar panel trickle charger for each battery . This is just to keep a battery charged as it sits with the vehicle not being used for months at a time, not for recharging a depleted battery. That is a whole other thing. There are many on the market. I have a few, but have had them for years. I don't have a present recommendation for a specific unit.
A rough rule is if the panel puts out 2 watts or less for each 50 amp-hours of battery capacity you do not need a charge controller. More than 2 watts per 50 amp-hours of battery should have a simple PWM controller. There are some very inexpensive units.
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gcrank1
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# Posted: 19 Aug 2022 10:18am - Edited by: gcrank1
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Your batteries, lead-acid of all types, sealed or not, want to be kept fully charged all the time.
If they get depleted they need to be charged to full asap. Today is good, Not 'tomorrow', def Not next week. A battery left at partial charge will sulfate and diminish in capacity and life span. A very basic, cheap, maintenance type panel will not recharge but verryyy slowly, especially at 4-5hrs/day of sun.
If they crank over slow they are depleted, maybe nearing end of life, and need to be recharged asap, not slowlyyyy. If your battery is getting like that pull it out or run the rig over to grid power and get it on a real charger.
A very basic, low output 'maintenance' panel will not recharge fast enough, that is why I recommend bigger panel(s) and a charge controller.
That said, for a 'maintenance/light duty' imo a minimum might be the Harbor Freight 25w 'Thunderbolt' (lol) panel @ $70 and their 100w controller @ $20. Plug & play for under $100.
Note that the '100w' controller can only provide a max of that; ie, nominally 8amps, IF the panel can produce that much. A 25w panel Wont, a 100w panel wont likely either but under ideal, and cold, conditions might spike there (remember the inefficiencies and losses thing).
You can run 2 controllers off one panel, one for each battery, by using a Y adapter, but they will share the output from the panel (so, again, remember more panel wattage is a good thing).
I dont suggest the smaller panels, they are toys that take your money and provide very little.
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ICC
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# Posted: 19 Aug 2022 11:51am
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My assumption is/was that the ATV, small tractor, whatever are used similarly in the way I use my actors, graders, skid steer, etc. That is when I use 'em they get started up and run for a while; long enough to recharge the small amount of energy that is used to start them. Then they may sit for a month or, in my case, some things sit for months without being looked at, let alone be started.
For that type of scenario, all that is needed is to maintain a charge. If a small panel can not keep the battery floated then the battery probably needs replacing, and if a battery is not able to hold a charge for at least a week or two I replace them rather than mess around. To each their own, though.
OTOH if an actual battery charging system is desired or needed, my solution does not apply.
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paulz
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# Posted: 19 Aug 2022 02:01pm
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About a month ago when I started building my carport, I put an MP3 player and 2 way radio to the cabin on my UTV. Much nicer working to music. But after several hours they were running the battery down, so I stuck a spare panel on the roof and a $10 PWM controller. Problem solved, plus it keeps the battery topped up when I'm away.
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deerslayer
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# Posted: 19 Aug 2022 02:21pm
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I am at 45 deg N lat (WI). Yes, what I want to do is to keep the batteries in those two vehicles topped off so that they are ready when I need them. For instance, in the fall I may not mow for a month and then want to use the tractor to haul leaves or whatever- and with the falling temps and weeks of sitting, the battery has become weak. So it sounds like two separate solar chargers are what I need. I also do not have the best sun at the shed during leaf-on season- but am not looking to run a house, just maintain a couple small batteries.
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gcrank1
Member
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# Posted: 19 Aug 2022 04:36pm - Edited by: gcrank1
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Im at 44deg in WI too.
Solar
Means the sun has to get to the panel(s) to work. If you dont have good sun for the peak production hours of 10-3ish, southerly oriented and at about your latitude angle the output will be greatly diminished.
In that case you can make it work by 'overpaneling'; ie, using more panels than 'if ideal located' to collect more irradiance.
Locking yourself into components that cant be expanded to increase production (once you find out you need/want to) will just be lost money.
Doing an expandable system that can grow over time and produces a bit more power for you than barely (if) adequate can allow you to also run a LED light or two in the shed and even a USB charger; all good. Paulz uses a bunch of usb powered stuff, iirc.
Btw, Harbor Freight often has discount coupons. Their solar stuff is not top-drawer but is cheap and available.
If by chance you decide to just get a couple of their low-end 'maintenance' panels get the most wattage panels you can and play with them to learn some stuff.
Btdt years ago. Fwiw, my old 15w panel realistically, at best, under ideal conditions, can output about 3/4-1 amp to my 12v battery. At 4hrs a day that is at best 4amps.
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Steve_S
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# Posted: 21 Aug 2022 06:21pm
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As you folks know, I am a solar guy & live on Solar... So I have big stuff BUT I have a small "Maintainer" which maintains the battery for the little Propane Furnace in my powerhouse which runs off a 12V Sealed Battery. It's actually a 40W Coleman Kit with PWM Controller, nothing special simple & cheap. It's worked great for that purpose for 5 years now.
Their equipment is strictly for 12V, it's all "Plug & Play" simple and they have a variety of kits. Even small Inverters if you need 120V (lights or similar).
They've expanded their products into very convenient packages, they do cost a bit more than if DIY with the commercial products but there's No muss & fuss and good warranty if ever needed. I also have to say their stuff is well built & toughened. (more idiot proof & friendly).
Have a look through their site and check it out. They even have kits just for car storage, and more.
https://sunforceproducts.com/
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travellerw
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# Posted: 21 Aug 2022 08:27pm
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Once upon a time you used to be able to go to a Volkswagen dealership and they would give you a small 12V panel. All Volkswagen's used to ship with a panel (5w) in the window to ensure the battery was maintained during shipping and storage. They had so many that they just gave them away..
I have no idea if the still do that.. but places like Canadian tire, Princess Auto, Tractor Supply, ect all sell 5W maintainers fairly cheap.
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gcrank1
Member
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# Posted: 21 Aug 2022 10:00pm
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Steve, thanx, Coleman/Sunforce looks like a better selection of stuff than H.Frt. for this thread.
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gcrank1
Member
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# Posted: 22 Aug 2022 08:04pm - Edited by: gcrank1
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Ok, I pulled my old Coleman maintainer out, its label says 9W, 15v-21v, .4xx-.6xx amps. It was free, I found it in the weeds! Figuring this stuff likely doesnt make peak my guess is .4-.5a; 1/2 amp per hour over how many good solar hours a given day gets. An average 4hr day at .5a is 2amps in.
Depending upon the battery size and any ghost loads it may or may not keep up with the self discharge of a lead acid battery.
Ive got it hooked up to an old 20ah jump-pac battery in my off grid shed; no charge control/direct hook up.
I saw the v-meter hit 18+ volts off and on as the light changes on the panel inside the shed window facing pretty much east at mid-day. That much voltage would kill a battery IF it was pushing high amps! On this one and with limited hours it 'should be ok'. It wasnt even warm after the light left the panel about noon and the battery voltage settle out quickly to 12.9.
I hooked up a little battery de-sulfate/surge device to pulse load it full time; see how it goes.
Intention is to have this run a small inverter that when switched on will run a 120v led 60w equiv bulb over the workbench.
None of this is critical, and the old bat is pretty much sacrificial for the experiment. If this tiny panel keeps up with my wants and needs it will be the most micro system Ive put together. We are getting there about every couple days so I can keep my eye on and let you know.
The other old panel (maybe 15yr) is a 15w rated Sunforce, my 1st solar panel I ever played with hoping to add some amps into our pop-up camper battery. It never did much and I mostly gave up on it; it has sat in the box a lot, lol. That is the one I said might make .75 to 1 amp output. It was money poorly spent, imo, though if the Coleman doest cut it for my shed I'll hook this one up and maybe get some use of it.
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