• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education skip experiences global resources cider press projects digital market permies.com private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Anne Miller
  • Pearl Sutton
  • Nicole Alderman
  • Mike Haasl
  • r ranson
  • paul wheaton
master gardeners:
  • jordan barton
  • John F Dean
  • Rob Lineberger
  • Carla Burke
  • Jay Angler
  • Greg Martin
  • Ash Jackson
  • Jordan Holland

Solar 12 volt power and motion sensor lights / lights don't work

  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I set up a solar system using two 100w solar panels and a 125 hour deep cycle battery with a 1000w cobra inverter. It works fine for powering plugs. But, when I ran power to a motion sensor security light it works for a couple of days then stops working. Any ideas why?
[Thumbnail for image.jpeg]
[Thumbnail for image.jpeg]
Posts: 525
Location: Northern Germany (Zone 8a)
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
hey... welcome to the forums!

i am just guessing here.
my inverter will stop working when the battery voltage reaches 11V. maybe your lights are more sensitive and stop working at 11.9V or so.

i assume that your lights are 12V here. this thread https://permies.com/t/56779/solar/Automotive-LED-lights-grid-lighting  talks about constant current controllers in the last post. maybe that is the solution

if your lights are 220/110V through the inverter, then it is a different thing. but i guess, that your battery is running low. did you check the voltage of the battery, when the lights go out? does the inverter shut down? they normally give a sound signal, when they reach low voltage and shut down.

good luck and blessings
Posts: 68
Location: Zone 2b, Canadian Rockies
hugelkultur forest garden solar
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Inverters draw current if they are on, even if you draw no power. Efficiency is very low if you draw small amounts of power, and rises as you reach your inverter's peak operating point. If you are running an AC motion sensor and lighting, it will rapidly drain your battery. Simply flip to a 12V DC motion sensor and light; you'll gain a tremendous level of efficiency. You could leave the inverter connected to power outlets, provided its current draw is minimal when AC power usage is zero. You should turn the inverter off when you are out of the building.

You can actually wire an inverter to only supply current if the emergency lighting triggers. This will save you money if your emergency lighting is AC. Simply install a DC motion sensor and wire it's output to the switching side of a relay. Wire the high output side of the relay to an inverter and when the motion sensor triggers, it will activate the relay to enable AC. Relays with a DC activation circuit and high amperage DC power output circuit are available and cheap... about $10. Use a small inverter for this so that you at its efficiency point. The large inverter would remain directly connected to the battery so you can have outlet power.

Along with the power utilization issues mentioned above, look at your energy production. I see shading very near to your panels in the picture. Do shadows cross your panels throughout the course of the day? Even a small amount of panel shading (a few percent) will significantly decrease panel output.

As a final suggestion, you might invest in a DC power analyzer. Connect it inline in different places to test power input and power draw when the system is in use. I use one by RC Pro; Watt's Up is another brand you can look at. If you shop around, you should get one online for about $30.
6 Ways To Keep Chickens - pdf download
will be released to subscribers in: soon!
    Bookmark Topic Watch Topic
  • New Topic