New member , advice please/show and tell

[Richiepettifer]

Hello . New member ,

I am new to solar and just wanted to check a few things and learn more .

I have installed 2x 100w solar panels on the roof of my summer house . To power my outdoor lighting, ventilation etc

I have made a diy box with timers etc to run the lights . (Don’t judge if it’s not up to scratch, I’m a mechanic by trade lol)

I am using a 12v 100ah efb battery ,
But I’m never sure what the solar charger voltage should be . Can I assume if it’s only running at 12.8 volts , that the battery is charged and the controller has dropped voltage down because of this ?

What should it drop to at night when all the lights and vents are on ?

Here are some pics . And some feedback would be helpful , as I didn’t get much instructions with my solar kit . It was only about £200 on Amazon , I just got fed up of unreliable outdoor solar lights .

Thanks

Richie

 

[sunshine_eggo]

How many Wh are you consuming?

Compute by compiling:
Device: X watts used for Y hours/day; X * Y = Z Wh/day
Find your total daily Wh for all devices.

Your panels wired in parallel?
You are in a region with poor solar?
Winter sun well to the South right now?
Panels are tilted mostly East/West? Optimal Winter tilt for you yould likely be about 50-60° from horizontal facing South.

AGM battery?
Charge controller is set to AGM or SLA (Sealed lead acid) setting?

Your AGM should be charged to somewhere between 14.0 and 14.6V - depending on battery specification. If it's not listed 14.4V is a decent number. Once that voltage is reached, it should stay there for a couple hours. It should then drop and hold 13.6V as long as there is enough solar to hold it there and power any loads.

Assuming you're in the UK (£200), I'm guessing you and the ball of fire in the sky don't see each other much. If that's the case, then your system is not likely to harvest enough energy to meet your needs.

Concerning your installation: Wow. You're meticulous. I've never seen so many of those used. Truth be told, I'd have zip-tied related wires together and MAYBE have secured them in 3 places. Whatever kind of "mechanic" you are, if you apply that level of effort to your job, you're a good "mechanic."

 

[Richiepettifer]

thanks for the reply . And thank you for the compliment on the install

I am still to work out what I’m using , I don’t think it’s going to be major , I’m running about 15 meters of outdoor led strip , 30 meters of string lights . Lights to the shed that only get used every now and then .
2x small extractor fans above the hot tub which are on for an hour ish ever other night .
From what I can work out . The lights are all very low amps . I need to add it all up and check back with the answer to that one .
The lights are set on timers for 6 hours a night

I was running a 95ah agm battery but I think it’s faulty so today I replaced with a 100ah leisure battery I got from halfords . Which is not agm
It is a flooded , but I figured being an actual leisure battery it would be better than the other that I got off of a transit lol

When I first had it on . It was charging at 14.2 , then while in use the battery icon flashed empty on the controller screen

With this new battery it’s only charging now a 12.7 but I can only assume that is because it’s new and is charged .

The controller setting for the battery is 601 and. Can’t find what that corresponds too . As the instructions are terrible .

I’ve been monitoring it loads . But just not too sure what to expect

With regards to sun . Just fitted them with the tilt of the roof . Maybe I should adjust them .

We aren’t having much sun at the moment as usual .

I don’t mind if I have to charge the battery manually every now and then .

I think I’ll work out what I’m actually using.

The solar panels , both solar panels go into one cable . I can’t think if that’s series or parallel lol

Thanks
Richie

 

[DJSmiley]

I would suggest adding a Victron Batteryprotect or similar.

If there isn't sufficient solar to keep the battery up to charge, you're risking overdischarge the battery. That will kill it pretty fast.
A BP will prevent that

For the switches/fuses: Fine for small loads, but those 'car audio' style fuses and breakers are not recommended for long-term high current use.

Also, usually fuses are installed as close to the source (battery) as possible. I'd recommend placing a decent fuse as close to the battery as possible. (And cover the terminals of the batteries)

 

[Richiepettifer]

Hi , thank you

I was led to believe that the controller has over discharge protection . But I’ll check into the battery protect for sure

The car Audio brakers are rated at 20amps so I figured that as that’s the same voltage the controller is rated it , I thought it would be ok . And I thought it’s an easy way to kill the power if I have to replace anything . There are fuses at the battery too .

I figured it’s all a 12v system , the same as a car so I was thinking what I’ve done would be ok .

Yeah I’m still waiting for some covers to arrive from Amazon .

Thanks

Richie

 

[sunshine_eggo]

thanks for the reply . And thank you for the compliment on the install

I am still to work out what I’m using , I don’t think it’s going to be major , I’m running about 15 meters of outdoor led strip , 30 meters of string lights . Lights to the shed that only get used every now and then .
2x small extractor fans above the hot tub which are on for an hour ish ever other night .
From what I can work out . The lights are all very low amps . I need to add it all up and check back with the answer to that one .

Yes you do. Without this information, we can't determine if your system will work at all.

Watts = Volts * Amps. Devices may list the amp draw.

Once you have Watts for each item, multiply by the daily hours of run time.

I was running a 95ah agm battery but I think it’s faulty so today I replaced with a 100ah leisure battery I got from halfords . Which is not agm
It is a flooded , but I figured being an actual leisure battery it would be better than the other that I got off of a transit lol

Whatever the case, you should avoid discharging below 50%, so consider that you only have 50Ah available. 50Ah * 12V = 600Wh - your daily usage need to be under this.

When I first had it on . It was charging at 14.2 , then while in use the battery icon flashed empty on the controller screen

That strongly implies the load was so high that it pulled the battery voltage down too low. Could also be a bad battery.

With this new battery it’s only charging now a 12.7 but I can only assume that is because it’s new and is charged .

I would draw the conclusion that it is either not fully charged, the solar is unable to fully charge it (insufficient sun), or you are over-using the system and not replenishing nightly use.

Recommend you NOT use the system at all until you see 14.X on the voltage.

The controller setting for the battery is 601 and. Can’t find what that corresponds too . As the instructions are terrible .

This is important information.

I’ve been monitoring it loads . But just not too sure what to expect

I don't really know what you mean by that. It seems you can't supply any numbers, so I don't know what "monitoring loads" means in that context.

With regards to sun . Just fitted them with the tilt of the roof . Maybe I should adjust them .

If you do, you need to adjust the orientation/tilt for your location.

We aren’t having much sun at the moment as usual .

This will DRAMATICALLY inhibit the power you can collect each day. 200W of solar panels likely can't top off your 600Wh usable battery capacity in a day.

I don’t mind if I have to charge the battery manually every now and then .

I would do it daily until you can determine if your system will work at all. Otherwise, you risk battery damage.

I think I’ll work out what I’m actually using.

Please. That's critical info.

The solar panels , both solar panels go into one cable . I can’t think if that’s series or parallel lol

Sounds right.

 

[Richiepettifer]

By monitoring it . I just mean I’ve been checking the voltage etc a lot . But unsure of what i should be seeing . So of the battery I put on is charged . Will I still see 14volts or is it ok to be at 12.7/8 which Is what I can tell it should be at when charged fully . So would the solar charger just cut off and trickle it maybe ?


When I checked the voltage . On a day with no less sun than today . It measured 14.3v , so my thought was the battery must be charged and hence doesn’t need 14.3volts any more :/

 

[Richiepettifer]

 

[Richiepettifer]

This is what I am running , (not yet the string lights but soon)

So I think I have to narrow down the time I use them for ?

 

[sunshine_eggo]

This is what I am running , (not yet the string lights but soon)

So I think I have to narrow down the time I use them for ?

Yes.

By monitoring it . I just mean I’ve been checking the voltage etc a lot . But unsure of what i should be seeing . So of the battery I put on is charged . Will I still see 14volts or is it ok to be at 12.7/8 which Is what I can tell it should be at when charged fully . So would the solar charger just cut off and trickle it maybe ?


When I checked the voltage . On a day with no less sun than today . It measured 14.3v , so my thought was the battery must be charged and hence doesn’t need 14.3volts any more :/

Per my above post:

Your AGM should be charged to somewhere between 14.0 and 14.6V - depending on battery specification. If it's not listed 14.4V is a decent number. Once that voltage is reached, it should stay there for a couple hours. It should then drop and hold 13.6V as long as there is enough solar to hold it there and power any loads.

FLA should also work to similar voltages. This SHOULD OCCUR EVERY DAY if a battery is being fully charged. If an unloaded battery on the charger is less than ~13.6-ish volts, it means it's not being floated - insufficient solar or improperly configured charger.

Lead-acid needs to be fully charged every day between uses. Failure to do so will decrease its service life. Again, I recommend you manually charge the battery to full every day until you can conduct the aforementioned analysis.

Use https://pvwatts.nrel.gov/pvwatts.php to simulate your system. Here's Leeds, UK for 200W of panels mounted 20° tilted facing East/West:



Looking at December, 0.42h means your 200W panels can produce, 200W * 0.42h = 84Wh of energy per day = about 15% of your usable battery capacity.

The Solar Radiation numbers also include average daily weather conditions.

Every time I've interacted with someone from the UK, solar has always been a losing proposition - Northern latitude and weather make for crap solar harvest.

 

[Richiepettifer]

Oh bloody hell . I didn’t realise it was that bad !

I might not have bothered if I’d known it was like that . I shall order a charger , thank you . Your info has been very helpful

 

[Richiepettifer]

What amp charger would be recommended for my battery ?

 

[sunshine_eggo]

I downloaded the hourly data for December and plotted your output:




Each peak is a day and the gaps between them are nights.

You have HORRIBLE winter solar. Should be great March to September.

10A charger (10% of capacity is recommended for lead-acid)

 

[Richiepettifer]

Thank you very much .

From what I can work out tho . Even with good sun and fully charged battery , I can’t run my lighting for much more than 4 ish hours a night which isn’t great , bigger amp battery maybe ?

 

[sunshine_eggo]

Thank you very much .

From what I can work out tho . Even with good sun and fully charged battery , I can’t run my lighting for much more than 4 ish hours a night which isn’t great , bigger amp battery maybe ?

The battery only determines how long you can power loads between charges. Right now, you can use 600Wh.

Assuming you use the four listed items 4h/night: (36W + 36W + 60W + 60W) * 4 = 768Wh

 

[Richiepettifer]

So they wouldn’t last much more than a couple of hours a night even at full charge ?

 

[sunshine_eggo]

So they wouldn’t last much more than a couple of hours a night even at full charge ?

600Wh / (36+36+60+60) = 3.125 hours

100Ah is based on a 5A load. Using more than 5A means you'll get less. I would expect around 2.5 hours on that basis.

This assumes you're running ALL of those items for the duration. Your prior post implied some variability. I would break them out individually and compute actual Wh per items. Weren't there vent fans in there too?

 

[Richiepettifer]

yeah the vents are on if we’re in the hot tub . Only for an hour tho .

So can I assume that even in summer , my solar panels being 200w wouldn’t fully charge a bigger battery ?

 

[Rednecktek]

Just to give you a point of reference, my shed has 2x 100w panels and a 20A MPPT controller feeding a 120Ah FLA battery. The 300w inverter I have has a 5w standby draw.

I had to replace my battery the other day as it was dead again. I don't get enough sun in Western Washington to offset the 5w draw of the inverter and I haven't seen the sun in about a month for more than an hour or two... and I mean if you add all the time I've seen the sun in the last month it might add up to an hour or two.

You're going to need more battery and a LOT more panels, which makes a MPPT controller beneficial as well.

 

[Richiepettifer]

Oh bloody hell. I wouldn’t have started all this if I knew I’d need that much . It’s already cost me a fair bit of money . I just wanted more reliable lights that lasted longer , what a pain , might be time to send back what I can