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mattd
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# Posted: 3 Jan 2021 01:36pm
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Got my wife a wifi coop door last year, and a diy solar setup this year. Just got a 9ah lead acid battery and a 3.3w trickle charger.
The motor uses 3a, and runs for less then 10 seconds, twice a day.
I figured I can use half of those 9ah, so had 4.5ah available. The door, using 3a, and running for 20 seconds per day means that I’m using .017ah per day.
A x H = AH. 3a x (20sec / 3600sec per hour) = .017ah.
Was hoping the 3.3w trickle charger would be enough to keep up with that. Apparently not. Battery was at 8.8v after maybe 3 cycles.
It’s been cloudy and cold. And it’s likely the cold is having an affect on the battery, as well as making the motor work harder. But wondering if upping to a 20w panel and a proper controller would solve the problem. Obviously there’s a hole in my math somewhere. Or my wiring skills!
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Nate R
Member
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# Posted: 3 Jan 2021 02:51pm
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Are you just wiring the panel direct to the battery? Any charge controller?
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gcrank1
Member
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# Posted: 3 Jan 2021 02:53pm
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The formula is Amps x volts equals watts. It works forwards and backwards it you have any 2 of the 3 figures to work with.
Once you have the amps calculated you multiply that by 70% to find out what is really happening, on average, most of the time.
Assuming the battery is 12v and the panel 3.3w / 12v = .27amps (x 70% = .189) thats pretty puny amp per hour charging under the best conditions for only a few hours a day.
So, a 20w panel would give maybe 1-1.2ish Amps per hour for a few hours with good sun, way more likely to keep up with your load. A cheap pwm charge controller is all you need.
Btw, you Need To get that poor discharged battery topped up ASAP, staying in a state of discharge like that for any length of time will kill it.
A 9ah battery at a C-10 charge rate is .9amp charger, you could go a 1- 1.5 amp wall trickle charger safely. NO way use an 8-10 amp auto battery charger, it will heat/overpower the little thing.
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gcrank1
Member
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# Posted: 3 Jan 2021 03:01pm
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Fwiw, I have used both a 10w and a 15w panel with and without a cc to charge my old jump-start pac with an 18ah sealed wet-cell battery inside. A couple hours out in the sun, or even a partly sunny day, has topped it up from my night use for LED cabin lights, devise charging, etc. Way more use than your opener should use anyway.
I cant imagine what I could do with a 3.3w panel.
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mattd
Member
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# Posted: 3 Jan 2021 03:56pm
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Bigger panel it is then!
My brian works better in watt hours. 3a x 12v means the motor is using 36w. 36w at 20 seconds per day is .2wh.
the 3.3w panel x 70% is 2.3 watts per hour In perfect conditions. Isn’t that how it’s supposed to work? That’s why I thought this small panel might work. Is it just that small panels aren’t able to charge?
I do have a 1.8w solar maintainer on my skid steer. That works great. Battery’s always ready to go. But it’s not charging any.
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gcrank1
Member
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# Posted: 3 Jan 2021 06:16pm - Edited by: gcrank1
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The only tiny panel I have has a usb plug on it for small devices.
The small 12v 'maintenance' panels can only marginally charge, if at all, unless attached for a long time. They are to 'maintain' a full charge in an unused battery over time to counteract the self discharge. Any real charging takes place above and beyond that trickle 'charge'. Which brings up my thought, 'was that little battery really fully charged when you hooked it up?' 1.8w is really only about 1/10th of an amp; that 1/10th amp just cant do much. Fwiw, I wont even bother with a plug-in trickle charger unless it does a min. 3/4 amp (ie, Battery Tender Junior). Your 3.3w and 1.8w combined still only makes less than 1/2 amp.
Maybe try this:
Fully charge that little battery (that will hopefully still go to 12.8+v)
Run it on the opener, sans solar, over time and check the State Of Charge (SOC) voltage regularly. This will sorta indicate the draw. I dont like to go below 12.2v on my portable bat-pacs, it is way hard on batteries to cycle them hard. See and record how long it takes you to get from 12.8 to 12.6 to 12.4 to 12.2v. Keep in mind that the more you discharge the longer it takes to recharge (and that isnt a 1amp out, 1amp in, it is more like 1.1 in) so recharging asap after a use and before going to deep of discharge is important.
Consider if buying a bigger panel and charge controller makes sense or another battery that you swap out every day or two and charge on a wall plug.
I fully understand being intrigued by solar (I have been) and if you lived close Id let you try my 10w or 15w panel to see if it did what you want. Short that you end up like the rest of us, buying stuff that doesnt quite work out then what do you do with it as you continue to 'upgrade'?
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mattd
Member
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# Posted: 3 Jan 2021 06:48pm
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Ha! I’ve got lots of panels from diff projects and upgrades!
Think I have a spare 50w and 20w w controllers. They are allocated to other things (one charges a batt for an rv water pump that I can take back and forth to cabin, the other is planned to charge a deep cycle I leave at the cabin for led light, etc.). But I can use them for testing. If the 20w works I’ll buy one for the coop.
The 9ah battery was at 12.4v before I hooked it up. It’s on the Battery Tender junior now and I’ll try again while keeping an eye on voltage.
Thanks for your help!
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gcrank1
Member
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# Posted: 3 Jan 2021 08:05pm
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I think you are well set then Matt 
My interest in solar goes back to the early '80s but my cabin then was in the woods with no good exposure for panels even though it faced south. And info was hard to get and expensive components, too much for a po-boy that knew nothing other than I wanted to play with it. About 11 yrs ago I picked up the 15w panel, paid too much and got too little. I actually thought Id get 1.25 amps per hour out of it for every hour of sunshine in a day, LOL. It ended up sitting a box behind a door (NO solar exposure there!) for a long time. I finally hooked it up to my Aliner grp24 marine bat which got sun from sunup to noonish while parked in the driveway. It trickled it, often not even recovering the little bit of incandescent lights use of an evening, no way for any furnace draw. I stopped carrying it when camping, sites were often wooded/poor solar exposure anyway.
These past couple years with all the push for 'solar-generators' (market hype/misnomer) I started messing about again with my old, big jump-start pac and the panel and the whole C-rate thing. Now I had something that I could use as portable power and put in a position to recharge of good day. With a couple of those (found another being thrown away) I had some handy swap-out 12v power and one has a light duty 110ac inverter. With the bar clamps, a cig lighter and a usb adapter they are pretty handy. You can build similar with your little battery or two in a plastic ammo can, some plugs, clamps and wire.
Anyway, I found out I dont mind swapping out for stuff as long as the battery isnt too heavy, for me the grp 24 is about as heavy as I want to carry even if it has a handle. Funny, wasnt too long ago I thought that about the grp 27. The jump-start pac is pretty nice and if I replace the sealed wet battery with the same physical size LFP it would be WAY better.
Then with the new cabin came a hacked together 6 x 102w 12v panels, a 50amp 12/24vdc mppt control and 4 failing 10yr old 130ish ah ups batteries. And a learning curve.... Finally, after all these years, I have my solar system to play with, much more than I would have ever bought separately. It has been an interesting year. Big decision for spring: what to replace the failed by then batteries with; golf cart wets or lfp?
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Nate R
Member
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# Posted: 4 Jan 2021 11:09am
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If the battery was 8.8v after 3 cycles, even with NO charging, something isn't right...like it wasn't charged to begin with?
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mattd
Member
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# Posted: 6 Jan 2021 05:01pm
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An update. Got the battery fully charged on the battery tender. It was 12.8v.
The door actually runs for 32 seconds each cycle. After 1 cycle the batt was 12.7v. After a second it was 12.6v.
But whe I hook up the 3.3w panel it has an led light that gives you an indication of what it’s doing. Green mean battery is hooked up properly and it’s charging. Red means something’s wrong.
With this coop battery it won’t turn green. I tested other deep cycle batteries and the light is green. Do panel is good.
Guess maybe battery is bad? It charges fine from the wall. Just dosent like this panel I guess.
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gcrank1
Member
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# Posted: 6 Jan 2021 05:59pm
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My two small panels have the same type SAE connector and surprisingly (to me) the polarity of each connector is Not The Same +/- !
Whatever you have for a connector check the polarity output to ensure you get it hooked to the battery posts correctly.
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