Panel power to charge 35Ah battery

[French_guy]

I've found 12V LED bulbs that draw 200mA each
I want to install 5 of them outside
I also have Yuasa sealed battery (35Ah) and want to know what is the recommended panel to charge the battery
Let consider the worst case: all lights ON for 12 hours/day in winter (from 7pm to 7am)
Thanks

[Sunking]

Where are you located?

First your battery is not really large enough to power the LED's 12 hours per day, 7 hours is about all it is good for daily usage. To get 12 hours you really need 60 AH

Panel wattage depending on location anywhere from 150 to 300 watts if you use a PWM controller or 100 to 200 watts with a mppt controller.

[French_guy]

I'm in Michigan...
35Ah @ 12V is 420Wh. If I take a 50% safety factor to prevent deep discharge, it gives me 210Wh
For the bulbs, 5 x 0.2 Amp = 1 Amp or 12W @ 12V
So 12W x 12 hour = 144W
Did I miss something?

[Sunking]

Yeah if you discharge 50% day means your battery last a year tops, and just one cloudy day means you are dark for two days to recharge. Discharge 20%/day and you get a 3 to 5 year battery life, and have enough to carry you through a cloudy day or two.

In Michigan you are looking at a 140 watt panel with a MPPT controller or 200 with PWM. That will generate 12 amps. 12 amps on a 35 ah battery makes it go Sizzle Crackle Pop Boom. Minimum requirement with 125 amp charge current is 50 AH on a AGM, or100 AH with FLA. Your in Michigan, solar really suks there as you have no real useful sun in winter. In December and January you are down to 1.5 Sun Hours.

So with your 35 AH AGM battery you are limited to a maximum panel wattage of 150 watts on a PWM controller and 100 watts with MPPT. Problem is in winter that only generates around 100 watt hours or less, not enough to do what you want.

Based on your location you must use AGM battery. To generate 150 watt hours a day means you must use 200 watt with PWM or 140 watts with MPPT. Minimum size battery requirement to meet a C/4 charge current and support your load is 62.5 AH.

[inetdog]

I'm in Michigan...
35Ah @ 12V is 420Wh. If I take a 50% safety factor to prevent deep discharge, it gives me 210Wh
For the bulbs, 5 x 0.2 Amp = 1 Amp or 12W @ 12V
So 12W x 12 hour = 144W
Did I miss something?

Mostly you missed that 144Wh will be 12AH at 12 volts, and 12 is ~1/3 of 35. Discharging the battery to 66% SOC every day will not let it last very long.
A more conservative discharge would be to 80% SOC, which would require a 60AH battery. (I seem to have heard that somewhere before.... Oh, yeah, Sunking!)
You can get away with discharging to 20% SOC or so with Lithium batteries, but with any king of Lead Acid cells you will use up your cycle life too fast at even 66% SOC as your daily target.

[French_guy]

So my best option is to move to Arizona....!!!!

[Sunking]

So my best option is to move to Arizona....!!!!

Yep in AZ you would only need a 40 watt panel and the same 65 AH battery. Location means everything. AZ gets 5 Sun hours in winter, you get 1.5.

Look on the bright side, on the 4th of July you only need a 50 watt panel, the other 364 days 150 watt panel.

[French_guy]

Mostly you missed that 144Wh will be 12AH at 12 volts, and 12 is ~1/3 of 35. Discharging the battery to 66% SOC every day will not let it last very long.
A more conservative discharge would be to 80% SOC, which would require a 60AH battery. (I seem to have heard that somewhere before.... Oh, yeah, Sunking!)
You can get away with discharging to 20% SOC or so with Lithium batteries, but with any king of Lead Acid cells you will use up your cycle life too fast at even 66% SOC as your daily target.

So ideally 2 x 35Ah in parallel.....This is what I already have for my sump pump (not connected to any solar panel though) They are brand new Yuasa batteries a friend gave me
I have to ask me if he could give me 2 more....

[PNjunction]

Your lack of solar insolation in the winter is the biggest problem.

To overcome that, forget the generic ups-style Yuasa agm's. You could accomplish this project for lighting just a few bulbs at great cost. That would mean changing your battery to one that is not current limited (within reason) and is voltage limited. That would be something along the lines of a 75ah Optima Blue Top deep-cycle (light gray case vs the black sli case), Odyssey, Concord high-end agm's, hundreds of watts of panel power, mppt controller etc.

Are you really willing to spend $1k or more on a system to light these bulbs? More if you plan to actually replace the battery which will be frequent since you will be hammering it in the winter with only 1.5 hours available.

At this level, it can be done, but for most it is just not practical.

[French_guy]

Of course I don't want to spend that much.....
But I thought solar energy was less "restrictive"
Only 20% of daily usage on a battery?......ouch!

[Sunking]

Of course I don't want to spend that much.....
But I thought solar energy was less "restrictive"
Only 20% of daily usage on a battery?......ouch!

Anything you take off grid is going to cost you around 10 times more than buying it for the rest of your life. Battery cost alone is up around 65-cents per kwh. You can buy it for 10 to 12 cents. Solar is extremely limited and restrictive. Sounds like you drank the Kool-Aide someone gave you.

[French_guy]

My battery is a Yuasa NPC38-12I / 12V 38Ah
In the specs, I've found this for the life span:
100% DOD down to 80% capacity 300 cycles
75% DOD down to 80% capacity 500 cycles
50% DOD down to 80% capacity 600 cycles
25% DOD down to 80% capacity 1400 cycles

I understand the % DOD, but not the "down to 80% capacity"...what does that mean exactly?

[Sunking]

That would be something along the lines of a 75ah Optima Blue Top deep-cycle (light gray case vs the black sli case), Odyssey, Concord high-end agm's, hundreds of watts of panel power, mppt controller etc..

Tell him what those battery cost and how often they need replaced.

[Sunking]

My battery is a Yuasa NPC38-12I / 12V 38Ah
In the specs, I've found this for the life span:
100% DOD down to 80% capacity 300 cycles
75% DOD down to 80% capacity 500 cycles
50% DOD down to 80% capacity 600 cycles
25% DOD down to 80% capacity 1400 cycles

I understand the % DOD, but not the "down to 80% capacity"...what does that mean exactly?

Capacity in AH. So a 100 AH at 80% capacity means 80 AH

[inetdog]

My battery is a Yuasa NPC38-12I / 12V 38Ah
In the specs, I've found this for the life span:
100% DOD down to 80% capacity 300 cycles
75% DOD down to 80% capacity 500 cycles
50% DOD down to 80% capacity 600 cycles
25% DOD down to 80% capacity 1400 cycles

I understand the % DOD, but not the "down to 80% capacity"...what does that mean exactly?

What it means is that at the end of that many cycles the capacity of the battery (in Amp Hours) will be 80% of what it was when it was new. For commercial applications that 80% mark is considered to be end of life for the battery and it would be replaced.
For solar use, many would hang onto the battery bank longer than that, since there is usually some extra capacity designed into the system, and we are cheap bunch.