Need guidance on my shed set up,something is not right ?

[johnnyhavana]

HI there, first post , hoping someone can shed (get it ) some light on my set up.

I have a renogy 50w panel
12v, 18 amh golf cart battery brand new.
10w control charger
400w intervter.
small ac timer to turn on the lights.

I get about 4 solid hours a day of direct sunlight on the panel and aside from that light through some massive trees, so an additional partial sunlit 4 hours as well.

I am currently running 2 -120v outdoor light fixtures through the inverter with 5w LED bulbs, so basically drawing 10w per hour for 4 hours a night or 40 watts.
after 3-4 nights i notice the battery in the morning is very low around 11.8volts.

When i've left it for a few days (turn off the inteverter and timer), it'll charge upwards of 13.4 volts or maxed out


My questions

1 - with these specs, how many hours should i be able to get with the battery, ( i suspect its too small and not enough storage ?) dont know how to calculate this ?
2 - is the 50w panel enough to charge daily with 4 solid hours of direct sunlight ? ( my other assumption here is not enough draw from sun, so larger penels or more time in direct sunlight per day)

Ideally I'd like to convert the whole shed lighting ( 16ft dc led strips x 3 inside used occasionally / 2 ac motion detectors running at night, motion only for 30 second light blasts with led lights ( 4 9 watt lights in total) as well )

Not that much but would like to steadily have the 2 outdoor lights work everyday and not damage the battery.

any guidance would be greatly appreciated
have a great day
Johnny

[SunEagle]

Using a napkin calculation, with an 18Ah 12volt battery you can safely get about 54 watt hours a day. (18Ah x 12v x 0.25 = 54wh).

My guess is that you are using more than that amount or you are not getting the battery back to 100% SOC.

That 50 watt panel might provide maybe 150 watt hours (50w x 4hr x .75 = 150wh) although as we get toward Winter that amount will go down.

Oh I almost forgot. Your inverter consumes a % of that 400w nameplate rating which you will need to add to what the lights are using.

[max2k]

...
I am currently running 2 -120v outdoor light fixtures through the inverter with 5w LED bulbs, so basically drawing 10w per hour for 4 hours a night or 40 watts.
...

are those lights on some kind of timer- how do you know they don't stay 'on' longer than 4 hrs?

[AzRoute66]

Agreed. Between the lights themselves, the timer, and the inverter self-consumption I suspect you are underestimating the load.

Try throwing an ammeter on the battery and confirming it with the lights on and lights off.

[johnnyhavana]

Using a napkin calculation, with an 18Ah 12volt battery you can safely get about 54 watt hours a day. (18Ah x 12v x 0.25 = 54wh).

My guess is that you are using more than that amount or you are not getting the battery back to 100% SOC.

That 50 watt panel might provide maybe 150 watt hours (50w x 4hr x .75 = 150wh) although as we get toward Winter that amount will go down.

Oh I almost forgot. Your inverter consumes a % of that 400w nameplate rating which you will need to add to what the lights are using.

Thank you for that, you are correct i need to figure the draw from the inverter as well as the timer, will do so and get back.
But your calculation of 54wh on a full charge is that based on 4 solid hours of sun a day ? just checking and thank you for the reply

[johnnyhavana]

are those lights on some kind of timer- how do you know they don't stay 'on' longer than 4 hrs?

Yes as mentioned in my equipment, i have a small ac timer thats turning on the lights at 8:30 and off at 11:30 so actually only 3 hours a night not 4 as previously mentioned.

[johnnyhavana]

Agreed. Between the lights themselves, the timer, and the inverter self-consumption I suspect you are underestimating the load.

Try throwing an ammeter on the battery and confirming it with the lights on and lights off.

Thank you I will try that, but will also try to figure out the load with the invereter and timer as well.

[Mike90250]

I would guess, that a 400w inverter, would self-consume 10 - 30 w from the battery, waiting for something to happen, When the timer activates lights, I expect the same self-comsumption to be ongoing, and adding 20% loss, so a 30w load, would be 10W inverter, 30w load, 6w losses= 46w burned.

[SunEagle]

Thank you for that, you are correct i need to figure the draw from the inverter as well as the timer, will do so and get back.
But your calculation of 54wh on a full charge is that based on 4 solid hours of sun a day ? just checking and thank you for the reply

My 54wh calculation is based on your 18ah battery at 100% SOC being discharged 25% after the sun goes down. With 4 hours of "good" sunlight including losses you should be able to generate 150wh and put back more then you should be taking out of the battery.

I believe the problem is that you are using more than 54wh after the panel stops charging the battery which could mean you are not charging it back to 100% each day.

[johnnyhavana]

My 54wh calculation is based on your 18ah battery at 100% SOC being discharged 25% after the sun goes down. With 4 hours of "good" sunlight including losses you should be able to generate 150wh and put back more then you should be taking out of the battery.

I believe the problem is that you are using more than 54wh after the panel stops charging the battery which could mean you are not charging it back to 100% each day.

HI SunEagle, thank you for clarifying.

I had a look at the two other items drawing.
300w inverter (thought it was 400, sorry) , says - Output max 300w / 2.6a continuous - it also says 115vac 60 hz
- i would assume im burning 2.6amps per hour while the lights are not on?

The Woods 50027 timer: Rated for 125V ac, 60 Hz 10A, 1250W Resistive/4A, 500W Tungsten/4A Ballast, CSA Certified C/US, CFL Compatible
- so does this mean its burning 4amps/h ??

sorry new to all of this but can you break this down for me, so i have a better idea.
thank you

One additional question, i can move the panel to a 3rd floor balcony to get about 7 solid hours of sunlight but i'd have to run the cables about 45 ft, would the cable run reduce the draw? right now its only on a 15 ft cable to the controller and the battery is 18 inches from that ?

thank you in advance

[johnnyhavana]

I would guess, that a 400w inverter, would self-consume 10 - 30 w from the battery, waiting for something to happen, When the timer activates lights, I expect the same self-comsumption to be ongoing, and adding 20% loss, so a 30w load, would be 10W inverter, 30w load, 6w losses= 46w burned.

wow ok thank you for that, i have more detail info on the other two components as i mentioned to SunEagle as well.

300w inverter (thought it was 400, sorry) , says - Output max 300w / 2.6a continuous - it also says 115vac 60 hz
- i would assume im burning 2.6amps per hour while the lights are not on?

The Woods 50027 timer: Rated for 125V ac, 60 Hz 10A, 1250W Resistive/4A, 500W Tungsten/4A Ballast, CSA Certified C/US, CFL Compatible
- so does this mean its burning 4amps/h ??

sorry new to all of this but can you break this down for me, so i have a better idea.
thank you

[Mike90250]

The timer specs are for the load the switch inside can manage, up to 4amps. The timer would consume maybe 5 watts, [ 5*24=120 watt hours daily ] Somewhere on the inverter paperwork, it should state what it's idle (standby) power is, and what it's efficiency is.

[SunEagle]

HI SunEagle, thank you for clarifying.

I had a look at the two other items drawing.
300w inverter (thought it was 400, sorry) , says - Output max 300w / 2.6a continuous - it also says 115vac 60 hz
- i would assume im burning 2.6amps per hour while the lights are not on?

The Woods 50027 timer: Rated for 125V ac, 60 Hz 10A, 1250W Resistive/4A, 500W Tungsten/4A Ballast, CSA Certified C/US, CFL Compatible
- so does this mean its burning 4amps/h ??

sorry new to all of this but can you break this down for me, so i have a better idea.
thank you

One additional question, i can move the panel to a 3rd floor balcony to get about 7 solid hours of sunlight but i'd have to run the cables about 45 ft, would the cable run reduce the draw? right now its only on a 15 ft cable to the controller and the battery is 18 inches from that ?

thank you in advance

IMO whatever you might gain from that 3rd panel you would probably lose due to the extra distance from it to the CC. It is best to keep your panels close together and the wiring as short as possible or big enough so that there is very low voltage drop which reduces the losses.

If you need more solar production then purchase another panel with the same specifications as your existing. That is the simplest action to take.

[johnnyhavana]

The timer specs are for the load the switch inside can manage, up to 4amps. The timer would consume maybe 5 watts, [ 5*24=120 watt hours daily ] Somewhere on the inverter paperwork, it should state what it's idle (standby) power is, and what it's efficiency is.

Hey Mike the manufacturers replied back and said

Hardwire timers - .08 watts to 1.2 watts(minimal) this is the draw when installed whether turning device on or (sleep mode). There is not really a battery in timers

[johnnyhavana]

IMO whatever you might gain from that 3rd panel you would probably lose due to the extra distance from it to the CC. It is best to keep your panels close together and the wiring as short as possible or big enough so that there is very low voltage drop which reduces the losses.

If you need more solar production then purchase another panel with the same specifications as your existing. That is the simplest action to take.

Hey SunEagle, so then a 50foot run of cable from panel to CC would have loss in that cable so going from 4 to 7-8 hours pure sun might be eaten up by the length of cable ?

- i actually found a 100 w panel today online, same make, just twice as large so i'll end up with 150w (combined), that should definitely draw enough, i guess I'll see what my charge is at the end of the day with 3 times the solar. I'll keep you posted.
thank you for all your guidance.