Outdoor Lantern Solar Solution needed

[Robaroni]

Originally Posted by BillG

Well, a 75% cutoff would then require (4) 24 series batteries. That is too many to safely wire in parallel, in my opinion. I agree that the battery will last longer, but suggest using batteries designed for the job, not car batteries. If he can live with 5 days of autonomy, then he could use two batteries set up for a 75% cutoff. It is my understanding that these are security lights, so it is important that they stay on at night. As I'm sure that you know, a big bird splat will all but shut off the output of a small panel, so that would give him 5 days to find it and squeegee it off before his security lights no longer work.

For what it is worth, my array has not produced more than 8 or 9 Watt Hours per day for the last 11 days according to its monitoring system, and I don't expect the snow to melt off of the array for at least another week, and probably two or three weeks.

First off, he lives in Ca, a very sunny place.

Secondly, I have no idea how big or small your array is. My systems, I have two, an intertie/off line that sends excess to the grid and backs up the house in case of failures and a strictly intertie that just feeds the grid. Total array is 10.4 Kw.
I don't run off grid because it's not a good idea, I only advise running off grid when individuals don't have the option. Why run through battery charge discharge cycles when you can simply have battery back up only at times when the grid is down? I'm several hundred dollars ahead on my Electric bill and haven't paid for electricity in over ten years and that's with charging my BEV, I don't pay for gas either. I also live in a very low sun area on the 42 latitude.

But back to Poor Man's request. He's only charging one 5 watt LED, should he be spending $500 plus to do that? So, being application specific, I took into account his needs and what would be feasible financially in his location. Even if we up his battery to 12v at 30 aH he still has 360 x2.5 hours a day or 900 wH. He probably has easily twice that where he lives, so I'm being very conservative. 25% of 900 wH will give him 225 wH for his 5 watt load which is over 4 days without charging.
If we use your two 75aH batteries we have (150a x 12v) x 0.25 = 450 wH. That's 9 days to 25% discharge. The battery cost is $90 for a deep cycle AGM 30 aH battery and $215 x 2 or $430 for two 75 aH deep cycle batteries. The difference is $340 more for 4 and a half days more(I used the same brand for both calculations). It's just not worth it.

https://www.ebay.com/itm/VMAX800-Gol...frcectupt=true

https://www.ebay.com/itm/VMAX-XTR34-...frcectupt=true

"Bird splat"?

https://www.ebay.com/itm/ACOPOWER-60...frcectupt=true

Here's a 60 watt module. It's 25" x 25", that must be some big bird! The price is under $100. The total cost of the solution I gave with charger, battery, module and LED is under $200, $140 less than just your battery choice. You still need modules, a bigger charger and a lamp.