Tiny Solar Project

[Steve777]

I have been kicking around ideas for a tiny (maybe even a nit) solar project, and was looking for ideas/suggestions. We have a chicken coop on the property, and I put in an automatic door opener, which has been working fine. It runs off of a 6v lantern style battery which typically lasts just under a year. Most recently I put a 6v AGM LA lantern battery in. I had been charging it every 5-6 months with an AC charger but this seems like a perfect situation for adding a tiny PV panel to keep the battery charged.

What I was thinking of was a tiny (like 1W or less), flexible, stick on PV panel. I thought they made nominal 12v ones. I would put a diode in line with it, to prevent it draining the batt at night. And was thinking that between the diode voltage drop running a 12v nominal panel into a 6v batt would be fine, not ideal power xfer, but I am really only trying to keep the AGM batt charged. My thought (hope) was that I could do without a charge controller, as long as the PV output was low enough that it would not overcharge the batt.

My question is does this sound like a workable idea? How low an input current would it need to not overcharge the batt? And idea ideas/suggestions for a suitable tiny PV panel?

Thanks

 

[2009Bounder2020]

why not just do like everyone else and use a charge controller, you just need panels and a charge controller

 

[Short_Shot]

why not just do like everyone else and use a charge controller, you just need panels and a charge controller

Because that's expensive, relatively speaking? Though I agree for the most part.

OP, keep in mind that a 12v nominal panel may output 17 to 20v or more. Especially when cold.

You won't be charging a 6v battery with that. You'll nuke it.


Try this.

Amazon.com: ZEALLIFE 6V 1w Solar Panel to Recharge Deer Feeder Battery Waterproof Outdoor Solar Charger with Mounting Bracket (6v Deer Feeder Solar Panel 1W): Garden & Outdoor

Amazon.com: ZEALLIFE 6V 1w Solar Panel to Recharge Deer Feeder Battery Waterproof Outdoor Solar Charger with Mounting Bracket (6v Deer Feeder Solar Panel 1W): Garden & Outdoor

www.amazon.com

 

[Short_Shot]

In fact there's even a review on there from someone specifically using it for a chicken coop door @ 6v.

Another review claims it's "sucking down the battery" so make sure you put a diode on it if it doesn't have one.

 

[kshaw]

We have a very small solar system to keep the battery charged on our mower. Ours is a 12 SLA battery. We put a molex connector on the mower which goes to the mower battery. We just flip a switch turning off power from the solar panel, plug in the molex connector, then flip the solar panels back on. The system works very well.

 

[Woody]

A micro solar system is a perfect use for something like this. 12v is a more common approach but they make 6v systems. Just Google “6V solar charge controller “. Here’s a couple examples of what could be of use.

Amazon.com : 6 volt solar battery charger

3A 6V-12V PWM Solar Panel Light Controller Battery Charge Regulator SX01

PMW solar charge controller multifunction for intelligent control is realized by using microprocessor and dedicated control calculation. Through the computer chips, the controllers take samples from the parameters of storage battery voltage, solar battery, discharge current and environment...

directvoltage.com

I have/do these micro solar systems all the time from keeping batteries on trailers charged, power for irrigation controllers, power for security cameras, remote lights, gate power, power for field rf bridges, … solar is perfect for small remote power! All you need is a panel and charge controller to keep the battery filled up. Toss in a small cheap inverter and you have a remote ac power system. Lastly, I use CHEAP panels and charge controllers. They are not the most efficient or highest quality but they work and they are cheap. So not the end of the world if they fail or go missing.

 

[circus]

I'd buy a $15 6v solar battery charger.

 

[Woody]

Here’s the last micro solar system I made a few months ago for the garden area. I wanted a radio and lights out there while I was working in the garden. I used an old car battery (wouldn’t turn over the car on cold days), a cheap pulse style charge controller and three 10 watt solar panels (all purchased off eBay). Plenty of power for the radio and nine 10w flood lights. Hope this help you see how simple it can be.

 

[Steve777]

Thanks to all. A lot more answers and ideas than I expected. A charge controller probably is the right way to go, to prevent overcharging the batt. However I was trying to avoid having to put another water tight box out there, and space is somewhat limited inside the door mechanism. Plenty of room for some wires and a diode, but not a whole lot more. A fully contained 6v solar batt charge would work well, other than finding room for it. The 6v panels might be a good solution, designed for outside use and the right voltage; but need to find out if they have a built in blocking diode, and check with the batt manufacture to see how much current it can safely dissipate. These are some good directions to check out.

 

[Short_Shot]

need to find out if they have a built in blocking diode, and check with the batt manufacture to see how much current it can safely dissipate. These are some good directions to check out.

If it has a charge controller that sorts itself out.

 

[rin67630]

OP, keep in mind that a 12v nominal panel may output 17 to 20v or more. Especially when cold.

You won't be charging a 6v battery with that. You'll nuke it.

a tiny (like 1W or less), flexible, stick on PV panel. I thought they made nominal 12v ones.

Those toy panels are more likely to even get badly exaggerated specs, frequently by factor 2 or 3...
So expect 300mW to be realistic.
Mainly your idea will work of the battery has ~10Ah with less than C/100 you won't nuke anything.
But if you are living in a region with less sun it may not have been enough to keep the charge.
An AGM battery needs a full charge from time to time.

 

[Short_Shot]

Those toy panels are more likely to even get badly exaggerated specs, frequently by factor 2 or 3...
So expect 300mW to be realistic.
Mainly your idea will work of the battery has ~10Ah with less than C/100 you won't nuke anything.
But if you are living in a region with less sun it may not have been enough to keep the charge.
An AGM battery needs a full charge from time to time.

Well. Maybe.

But I can't see how putting 15 to 18 volts into a 6 volt battery can be conducive to long life even with extremely limited current.

Hence the reason for suggesting a specifically 6v panel rather than messing around with trying to drop voltage on a "12v" one.

There are larger 6v panels out there.

 

[rin67630]

Well. Maybe.

But I can't see how putting 15 to 18 volts into a 6 volt battery can be conducive to long life even with extremely limited current.

If you want to do it 100%, this tiny module should perform the voltage conversion and current limitation while keeping the panel voltage close to its MPPT.
https://www.ebay.de/itm/272508358482

 

[Short_Shot]

If you want to do it 100%, this tiny module should perform the voltage conversion while keeping the panel voltage close to its MPPT.
https://www.ebay.de/itm/272508358482

Or you can just buy a ~6 volt panel lol