DIY solar flood lights?

RobA · Nov 6, 2015

I want to put some spot lights on posts but would rather not have to run electricity to the area. I have not had good luck with solar powered lights in the past. Has anyone ever used 12 volt LED spots lights hooked up to a 12 volt car/marine battery and a solar panel to keep the battery charged?

charlz · Nov 6, 2015

For intermittent use or like a security light (on all night every night)?

RobA · Nov 6, 2015

With a motion detector, so intermittent use only.

JRobyn · Nov 6, 2015

Take a look at my thread regarding either rechargeables or solar/battery for a Dakota Alert - http://www.tractorbynet.com/forums/rural-living/347552-r-cr-123-batteries-dakota.html. I am drawing the conclusion from that, that a 5-9aH gel or sealed lead acid battery plus a small solar panel is the way to go for this kind of application. I'm still kinda surprised that there is not an abundance of ready-made packages in various capacities for this sort of application. Maybe because it is hard to determine exactly what sort of capacity will provide good results for various applications?

- Jay

RobA · Nov 6, 2015

I responded to your thread. I already converted my Dakota sensors to sealed batteries and solar panels. Very simple to do. That's what made me think of doing spot lights too. I wasn't sure if the smaller battery would power an LED spot.

These might work with that setup:
GLW® 10W 12V AC or DC 700lm LED Motion Sensor Flood Light, Smart PIR Decector Outdoor Security Floodlight 6000k Cool White, Waterproof Basement Light 100cm Cable, 80W Halogen Bulb Equivalent - Landscape Spotlights - Amazon.com

Bengineer · Nov 6, 2015

Some "back of the napkin" parameters to think about:

o You probably want more of a deep-cycle battery for this application than a starting battery. Think motive/fork lift/industrial vs auto starting. Marine deep cycle might work.
o Sealed lead-acid batteries would be one choice - compact, commonly used in gate openers, UPSs, mobility scooters.

Lead acid batteries:
o Are only good for so many cycles - think 100's. If your lights are on every day, you might be replacing batteries yearly.
o Have less capacity in cold weather. You'd need to oversize.
o A discharged LA battery will freeze -- a charged battery will not freeze. A battery that has been frozen is very likely a dead battery.

One spot fixture might be 2 90w equivalent LED bulbs @ ~ 20w each = 40w @ 12v = 3.3A. So you'd need 3.3Ah of battery at a 3.3A discharge rate per hour of lights on. Scale by the number of hours a night x cloudy days and add some.

On the charging side, You'd need a solar panel & charge controller that would have enough capacity to charge the battery on an average day. It would need to charge at the appropriate rate for the battery.

I think my biggest concern would be keeping (the potentially discharged) battery from freezing.

forgeblast · Nov 6, 2015

What about the harbor freight set ups, I have the 2 of the 31 (I think) led and it lights up an area nice, comes with a panel to recharge the battery.