200w solar system expectations...

[Entwicklung34]

Hi.

I'm new to all this, but learning a lot and enjoying it. All advice appreciated.

So I have 2x 100w solar panels (and about to add a third) mounted on a South facing 15degree roof in parallel hooked up to a 30amp controller and 1200watt inverter. For storage I have two 110ah solar leisure batteries also wired in parallel.

I've been using the system to charge a couple of phones/iPads and run a small TV for a few hours of a night (pulling about 25watts) and my son's Nintendo switch. It has been brilliant for all of this - really happy with it!

I've also now wired some wall lights into the system (2 of them at 9watts each) and my wife has recently started using these of a day whilst working from home. She also charges her laptop on using the solar via a plug socket I put in for this purpose.

Looking at the wattage for all of the charging and lights I was expecting to have plenty of energy stored in the battery to cover a few shady days if needed and to be able to power more lights etc with this but today the solar cut out and the inverter turned off, I assume because of low voltage. The controller was showing 12.1 when I looked and it does charge up to 14.4 when full iirc.

I'm wondering if my expectations of this system are a bit too high?! I planned to add a couple of plug sockets upstairs just for lamps in a couple of bedrooms, but not sure whether it could handle any more at the moment.

I'm thinking I need to angle the panels up more to around 30degrees and add my third panel to get the batteries charged back up quicker.

Any other thoughts/comments I would really appreciate as I am really enjoying the mission of achieving some off grid power!

I'll add some pictures below of what I've got set up so far...

 

[Bud Martin]

So how many KWhr are you using in 24 hours?
What kind of SCC are you using?
Do you know how many KWhr the SCC is producing per day?

 

[rmaddy]

What kind of batteries do you have? What are their voltage?

If they are 12V batteries then 2 12V 110Ah batteries is 2640Wh. If they are lead based then you can only use 50% so you have 1320Wh usable.

Next you need to work out your total power usage in watt hours. For example, with 2 9W lights they use 18W. If you run those lights for 8 hours per day then the lights use 18W x 9h/day = 162Wh/day. Do the same basic math for all of your items and add them all up to get a total Wh/day.

If you want to be able to run your load for 3 days, for example, then your usable battery capacity needs to be at least 3 times your daily usage.

As for solar, you have 200W. You likely get less than 200W out of them. Let's assume 150W for the moment. If you get 5 solar hours in a day then that's 750Wh. That's about half of your usable battery capacity. It is likely less than your daily power usage.

 

[Entwicklung34]

The off-grid set up so far...

 

[rmaddy]

So how many KW/hr are you using in 24 hours?

You mean how many kWh are you using in 24 hours? It's not kilowatts per hour. It's kilowatt hours. Those are two very different things.

 

[Entwicklung34]

So how many KW/hr are you using in 24 hours?
What kind of SCC are you using?
Do you know how many KW/hr the SCC is producing per day?

Hi Bud... You might need to help me out with terminology - SCC?

 

[rmaddy]

See the following:

Commonly used Forum Acronyms & Abbreviations

Solar is befuddling enough! Why use acronyms? Well, we're lazy typists.... :LOL: xSyP - e.g., 2S2P, shorthand for how many cells in Series (S) and Parallel (P). A - Amperes or amps. A measure of current. See warning. AC - Air Conditioning, sometimes A/C. AC - Alternating Current, a waveform...

diysolarforum.com

In my earlier post I forgot to mention that your inverter is only about 85% efficient so that means you use more power than what the simple calculations indicate.

 

[Bud Martin]

You mean how many kWh are you using in 24 hours? It's not kilowatts per hour. It's kilowatt hours. Those are two very different things.

You are correct, it should be KWhr per day (24 hr).

 

[Bud Martin]

Hi Bud... You might need to help me out with terminology - SCC?

SCC = Solar Charge Controller
So you have 30A SCC?

 

[Entwicklung34]

What kind of batteries do you have? What are their voltage?

If they are 12V batteries then 2 12V 110Ah batteries is 2640Wh. If they are lead based then you can only use 50% so you have 1320Wh usable.

Next you need to work out your total power usage in watt hours. For example, with 2 9W lights they use 18W. If you run those lights for 8 hours per day then the lights use 18W x 9h/day = 162Wh/day. Do the same basic math for all of your items and add them all up to get a total Wh/day.

If you want to be able to run your load for 3 days, for example, then your usable battery capacity needs to be at least 3 times your daily usage.

As for solar, you have 200W. You likely get less than 200W out of them. Let's assume 150W for the moment. If you get 5 solar hours in a day then that's 750Wh. That's about half of your usable battery capacity. It is likely less than your daily power usage.

Hi rmaddy... Thanks for this - really useful.

Yes I have 2 12v lead acid batteries so your calcs should be spot on there.

So ok...
The two lights... 170wh
Small TV... 25w x 3 hours - 75wh
Nintendo switch... 10w x 3 hours - 30wh
Laptop charger... 50w x 5 hours - 250wh
Lamp... 5w x 3 hours - 15wh

Total 540wh / day usage.

I haven't been able to calculate what I'm getting per day from the two 100w panels... my controller says how many amps are going in but doesn't tell me how many watts... Am I right in thinking 1 amp is around 240watts? Normally it says something like 0.6 watts going in so this could be around 144watts an hour for maybe 3 hours a day (it's often overcast here) so roughly maybe 420watts going in?? In that case you'd be right in my usage being higher than my solar charging! I thought the battery would give me more days usage though with the amount of storage, but as you say you can only use so much and the controller is also set to protect the battery when it gets to a certain voltage as well. I'll try angling the panels up a bit soon so maybe I can increase their efficiency there, and add the third panel as well and hopefully that will cover the usage needs!

Thanks again!

 

[Entwicklung34]

SCC = Solar Charge Controller
So you have 30A SCC?

Ah great yes a 30amp SCC...

 

[Entwicklung34]

See the following:

Commonly used Forum Acronyms & Abbreviations

Solar is befuddling enough! Why use acronyms? Well, we're lazy typists.... :LOL: xSyP - e.g., 2S2P, shorthand for how many cells in Series (S) and Parallel (P). A - Amperes or amps. A measure of current. See warning. AC - Air Conditioning, sometimes A/C. AC - Alternating Current, a waveform...

diysolarforum.com

In my earlier post I forgot to mention that your inverter is only about 85% efficient so that means you use more power than what the simple calculations indicate.

This will be helpful for me!!

 

[rmaddy]

Total 540wh / day usage.

Since this is all being run via an inverter it's 540Wh / 85% = 635Wh from the batteries. Plus the inverter has an idle power usage simply being on even if it's not powering anything. So your batteries can power your loads for barely 2 days without any solar.

With a 30A SCC you can have 4 100W panels to make the most use of the controller. That will help some with the overcast days.

 

[Bud Martin]

So what is the make and model of the SCC?
Can you show us what are being display on the screen?

'Am I right in thinking 1 amp is around 240watts? Normally it says something like 0.6 watts going in so this could be around 144watts an hour for maybe 3 hours a day (it's often overcast here) so roughly maybe 420watts going in?
Those figures do not make sense.
How did you come up with '1A is around 240W'?
Where is the '0.6W going in' coming from?

 

[Rednecktek]

Am I right in thinking 1 amp is around 240watts?

If it's on your controller then 1a is only 1a @ the 12v of your batteries, or 12w. In a perfect world you should be seeing about 10a out of your controller if it's PWM, 16a if it's a nicer MPPT. Pro Tip: If there are USB ports on the front/side of your controller, it's PWM 99% of the time.

Normally it says something like 0.6 watts going in

That would be 0.6w @ 12v or 7.2w. Something is wrong or you live near me where the weather is horrible.

Even in a perfect world with 200w of panel and 5 full hours of sun you're not quite getting 2 days of charge. With 3 hours of sun that's only 600wh in a perfect world. If your controller is a cheaper PWM figure you're only getting about 75% of that 200w, or 150w per hour, 450Wh per day.

I don't see your inverter in your power list. If you look up the make & model you should find an entry for "No Load Draw" or "Standby Draw" or something like that. That's how much the inverter uses just to exist so take that number and multiply it by 24hrs and add that to your daily consumption.

You should think of Watts like Grams, it takes a lot to do much and nobody gets ripped by lifting 5000g weights.

 

[Entwicklung34]

Hi again - thank you a for your input, advice and questions... Really glad to have joined such an active forum.

I'll try to answer some of the questions and give some updates ...

Today I added the new 100w panel (so 300w in total now) and I angled them all up from the original 15degrees so perhaps now they're around 30degrees maybe a touch higher which should be better (I'm in the UK). And yes the weather where I am isn't so great, but we have had a bit of sun recently!

Today after the adjustments I checked the scc and the input from the panels was coming up as 3.6amps... and this was in the late afternoon so I'm excited to see what happens tomorrow earlier on if we have a decent weather day. I'll get some pictures of the SCC tomorrow to show what it's displaying.

I didn't mention initially that my wife plugged her hair dryer into one of my solar sockets and halfway through the drying process ? it went off... I assume she'd drained the battery to a level that the SCC cut out to protect the battery. For the record I did explain that the solar system is only for laptop/phone charging and little lamps etc!! The good news is the system seems fine now and the battery is charging up back as it should.

Hmm 1amp is about 240watts... How did I come to that conclusion? ? .... I've just had another look and it seems amps x volts = watts. So Google tells me that 1 amp at 230v (after inverter!) = 230watts . I wasn't too far off ay ?


Btw my inverter is a 1200w bestek inverter - I need to have a look at what the draw is while idle... I'll report back when I find this info! I had the inverter inside but a low humming noise was unbearable so I've got it in a discrete ventilated bench box outside that seems to work pretty well.

Thanks once again... Looking forward to some nice free energy tomorrow ?

 

[Bud Martin]

Well, without giving us the Voltage we have no idea what Voltage you are using for the calculation, but now we know you are talking about the AC output Voltage of the inverter, not the battery Voltage or the panels Voltage.

 

[Entwicklung34]

Well, without giving us the Voltage we have no idea what Voltage you are using for the calculation, but now we know you are talking about the AC output Voltage of the inverter, not the battery Voltage or the panels Voltage.

It's a 12v setup but the open circuit on the panels says 20v... I'm openly an amateur!

 

[Entwicklung34]

Some info on this overcast morning...

 

[Entwicklung34]

If it's on your controller then 1a is only 1a @ the 12v of your batteries, or 12w. In a perfect world you should be seeing about 10a out of your controller if it's PWM, 16a if it's a nicer MPPT. Pro Tip: If there are USB ports on the front/side of your controller, it's PWM 99% of the time.


That would be 0.6w @ 12v or 7.2w. Something is wrong or you live near me where the weather is horrible.

Even in a perfect world with 200w of panel and 5 full hours of sun you're not quite getting 2 days of charge. With 3 hours of sun that's only 600wh in a perfect world. If your controller is a cheaper PWM figure you're only getting about 75% of that 200w, or 150w per hour, 450Wh per day.

I don't see your inverter in your power list. If you look up the make & model you should find an entry for "No Load Draw" or "Standby Draw" or something like that. That's how much the inverter uses just to exist so take that number and multiply it by 24hrs and add that to your daily consumption.

You should think of Watts like Grams, it takes a lot to do much and nobody gets ripped by lifting 5000g weights.

Ahhh it's 0.6amps I meant going in! Today is 2.2amps in and it's overcast so that makes more sense - sorry! ?