Re-purposing a panel for safety - patio lighting...

[Externet]

Good day.
If you have a spare ~40V/10A/400W solar panel leftover, how would you implement night lighting around your house, fully independent standalone from the house electricals ?
Charge three 12V lead-acid car batteries in series plus a DC-DC converter to make 12V to feed lights ? A DC-DC converter to charge a single car battery with 14V from the panel ?
12V LEDs are abundant as automotive gadgets for illumination. A dusk-to-dawn circuit is easy to make. What else would you consider to make it work ?

 

[highwaypirate]

I would use a deep-cycle battery as starter batteries will be destroyed after 10 cycles (I made the same mistake when I got on solar myself). The types of deep-cycle batteries you want to use can be any, depending on your preferences.

If your planning on keeping your battery voltage to just 12V, you wouldn't need a DC-DC converter; perhaps wire those lights with an install kit for vehicles with a rocker switch?

Keep in mind if you're planning on using lights such as your attached photo, determine how many amps they will pull. My SUV's lights eat 7.8amps per hour; I had to wire those directly to their own 50ah LiFePO4 (all of my other lights dimmed when they turned on).

 

[Q-Dog]

A Victron 75/10 or 75/15 Charge controller is less than $70.

 

[MidwestBest]

after all the cost is figured in wouldnt it just be cheaper/easier to buy a few solar lights?

 

[highwaypirate]

after all the cost is figured in wouldnt it just be cheaper/easier to buy a few solar lights?

While I've thought that same thing too, I can vouch those solar lights are terrible quality nowadays and fail/go dead after a couple seasons due to their tiny panels being baked.

My guess is he has a spare panel and wants to use it (400 watts is massive for night lights, but its an idea). I once repurposed a 50 watt panel as a jump starter just because it sat around. If he's going to use these lights for years, a small setup might work out to be smarter.

 

[MidwestBest]

While I've thought that same thing too, I can vouch those solar lights are terrible quality nowadays and fail/go dead after a couple seasons due to their tiny panels being baked.

My guess is he has a spare panel and wants to use it (400 watts is massive for night lights, but its an idea). I once repurposed a 50 watt panel as a jump starter just because it sat around. If he's going to use these lights for years, a small setup might work out to be smarter.

yeah you are right even the good ones only seem to last 2 years.. if you are lucky. and i have a spare 100w panel i want to use as a battery tender but havent yet figured out a cheap enough charge controller to justify buying.

 

[highwaypirate]

yeah you are right even the good ones only seem to last 2 years.. if you are lucky. and i have a spare 100w panel i want to use as a battery tender but havent yet figured out a cheap enough charge controller to justify buying.

If i may suggest... if you aren't picky on PWM or MPPT, I've installed a Voyager 20A controller on my boss's work truck. They're not too expensive ($44cdn; much cheaper for americans) but its been working out quite well on his truck.

 

[Externet]

you wouldn't need a DC-DC converter;

To bring down 40V panel to 13.8 V battery. Or, to bring down 36V battery series to 12V lights.
The 12V lights in the image take 1.2 Amperes each.

Will check for a charge controller that can accept a big 40V panel.

 

[Steve777]

Many of the cheaper/smaller charge controllers are designed for both managing a battery and running a load at certain times, like night time lighting. Some are also in weather proof cases. It seems one of those would be well suited to this project. I can't really say which ones of these would be good or bad, but there seem to be a lot of them to choose from.

 

[highwaypirate]

To bring down 40V panel to 13.8 V battery. Or, to bring down 36V battery series to 12V lights.
The 12V lights in the image take 1.2 Amperes each.

Will check for a charge controller that can accept a big 40V panel.

Sorry, I totally misread 40V panel lol. You might have to go with an MPPT controller; I know none of my PWMs could handle that high of voltage.