Off-grif solar system

[compact72]

Hi,

Doing this post for my neighbor who is building an off-grid system for his cabin.



Above is a diagram is what he has at the moment, is there anything that can be improved?

Do get the sun on the panels for about 75% of the day

Thanks

 

[BentleyJ]

A 3000W inverter at 12V is going to pull up to 300Amps. A 24V or better a 48V inverter would be a better choice.

As far as maximizing solar output, there are solar calculators online that will give you optimum Azimuth and tilt for your geographic location.

Here is one: http://www.solarelectricityhandbook.com/solar-angle-calculator.html

 

[Bud Martin]

May I as why choosing 50A Solar charger when you have 1000W (not 1000W in real world) of Solar power?
1000W/12V system = about 80A of charging.
I run my system at about 85 ~ 90% of the max spec for long term running.

 

[compact72]

A 3000W inverter at 12V is going to pull up to 300Amps. A 24V or better a 48V inverter would be a better choice.

As far as maximizing solar output, there are solar calculators online that will give you optimum Azimuth and tilt for your geographic location.

Here is one: http://www.solarelectricityhandbook.com/solar-angle-calculator.html

Would it be better to use a 1500W inverter?

Thanks for the link!

May I as why choosing 50A Solar charger when you have 1000W (not 1000W in real world) of Solar power?
1000W/12V system = about 80A of charging.
I run my system at about 85 ~ 90% of the max spec for long term running.

The 50A is an old one and has since gotten extra panels since it was originally purchased.
Would it be better just buying a 100AMP solar controller? Something like https://au.renogy.com/renogy-rover-...4y5dPiwF1ZlVPOCsBKKMnotbYckEz2URoCQT0QAvD_BwE

 

[Bud Martin]

Would it be better to use a 1500W inverter?

Thanks for the link!

The 50A is an old one and has since gotten extra panels since it was originally purchased.
Would it be better just buying a 100AMP solar controller? Something like https://au.renogy.com/renogy-rover-...4y5dPiwF1ZlVPOCsBKKMnotbYckEz2URoCQT0QAvD_BwE

It depends if the 50A charging will be enough to charge the battery backup enough or not, once the batteries are drained down during the night the charger has to be able to charge the batteries and supply the power to the load at the same time the next day.
Did you do power audit to find out how many kWh you typically use per day?

 

[compact72]

It depends if the 50A charging will be enough to charge the battery backup enough or not, once the batteries are drained down during the night the charger has to be able to charge the batteries and supply the power to the load at the same time the next day.
Did you do power audit to find out how many kWh you typically use per day?

Nope. By the end of the day, need to connect a battery charger/generator to keep the power going.

Not sure if the solar charger is being a bottleneck and not charging the batteries to the top? They normally sit around 13V when the power hasn't been used. With the battery charger/generator, the batteries will go up to 14V

https://www.jaycar.com.au/12v-24v-3...-for-lead-acid-and-lithium-batteries/p/MP3745 is being used at the moment. Looking at the specs, it will only take in 700w.

 

[Bud Martin]

Well, if you use 1500Wh per day but you only produce 1000Wh per day then that will be a problem.

 

[compact72]

Yeah - do you think the panels and batteries running in parallel are fine?

 

[Bud Martin]

Yeah - do you think the panels and batteries running in parallel are fine?

Battery is also a load to the charger when it is being charged, and if you running the inverter which is a load and connected in parallel with the battery, then the charger has to be big enough to charge the battery and also supply the power to the loads at the same time.

 

[djnorth]

Parallel panels is good if some get shaded during the day.

Series will reach the turn-on threshold voltage of the solar charge controller sooner and subsequently start charging the batteries earlier.

 

[MichaelK]

You are really better off going with 24V for a couple of reasons. First, you will never be able to tap the full output of your 1000W of panels with that 50A controller. As Bud mentions in post #3, your panels will put out more than 50A. I personally would use the math [(250W X 4 panels)/12.5Vcharging] X 85% fudgefactor = 68A. Switching to 24V would bring the charging amps down to 34A. That means cheaper copper wire!

Secondly, four batteries in parallel is poor design. It will always be problematic keeping the strings evenly charged. By switching to 24V, you have only two strings, not four.

I suppose a third reason is that the really high-quality electronics start at 24V. Easy to find a whole-home inverter that offers far more bells and whistles. My Conext SW4024 for example is split-phase (yeah, I know, you are in Australia), built-in transfer switch, generator charging circuit, grid support.

 

[Rednecktek]

48v is also a good option. Smaller fuses, 3kw is easy to find, and gives you an upgrade path later. Plus you get to use a lot more panels on the same size SCC.

 

[jjchvl]

Is 1000watts of solar panels getting sun only 75% of the day enough to keep 1100ah of frequently drawn from batteries charged? Im asking out of my own curiosity as well as for the sake of the OP. My unqualified and probably clueless instincts tell me that the OP doesnt have enough charging power regardless of whether he goes 24v, 48v or stays at 12v.

 

[farmhand]

Is 1000watts of solar panels getting sun only 75% of the day enough to keep 1100ah of frequently drawn from batteries charged? Im asking out of my own curiosity as well as for the sake of the OP. My unqualified and probably clueless instincts tell me that the OP doesnt have enough charging power regardless of whether he goes 24v, 48v or stays at 12v.

I'm with jjchvl, I would double up to 2kw (along with all the great suggestions above.

 

[jjchvl]

I'm with jjchvl, I would double up to 2kw (along with all the great suggestions above.

I was thinking he should double up as well but wasnt sure enough of myself to say so ?

 

[50ShadesOfDirt]

I think I would clean-sheet the design for the neighbor, as it cuts out the befuddle of existing components, limitations, etc. Get the audit done, and get to something like this design right from the start:

48v inverter (AIO)
48v battery bank
right-sized panels
generator

The audit helps determine which of the old components could then be drawn in to supplement the clean sheet design, and which just don't measure up any longer. Now just head over to the "diy solar products and system schematics" portion of this forum, and download that 48v design, and go from there.

Clean-sheet means you won't drag all the old componentry and limitations into a modern design, but you could choose to temporarily reuse some components until you get everything modernized (batteries, panels). For example, while getting to the new LiFePO4 battery bank, the 4 existing AGM batteries can be reconfigured to support a 48v bank design ...

When everything is modernized, sell off the old stuff, which is (seems to be) a working 12v system.

Generator is always there as backup power to replenish battery-bank until new solar panel design fully takes over the load.

Hope this helps ...

 

[Mattb4]

Math time:

1000w worth of panels depending on location and average amount of hours of full sunlight will produce so much watt hours. If when looking up the area and Season this comes to 5 hours than 1000w X 5h = 5000wh
Batteries rated in amp hours can be converted to watt-hours by simply multiplying the volts by the amperage-hour Thus 275ah X 4 X13vDC = 14,300wh Of which since you only want to use 50% of LA capacity gives you 7,150wh to work with.
Since you at best (and there is losses to account for) can gain 5,000wh in a day from PV this must account for daily loads and also the extra for battery charging.

As you can see there is inadequate charging capacity if you draw more than around 2000wh per day for loads.

 

[farmhand]

I was thinking he should double up as well but wasnt sure enough of myself to say so ?

I'm just week 4 here, and maybe you saw my 300% overpanel post. But here's what 2.4kw gets you this morning.

https://imgur.com/a/pobhWxM

 

[jjchvl]

I'm just week 4 here, and maybe you saw my 300% overpanel post. But here's what 2.4kw gets you this morning.

https://imgur.com/a/pobhWxM

Hah! Imagine what you (not) be getting if you werent overpanelled!

Im overpanelled too but Id rather be over panelled than under panelled!!

 

[farmhand]

Hah! Imagine what you (not) be getting if you werent overpanelled!

Im overpanelled too but Id rather be over panelled than under panelled!!

At this rate the Eco Max will need 10hrs, which isn't bad as a full charge averages us 11hours (If we don't use that air fryer!). I'm really blessed we ended up with so many panels, really ticked at SOOOooooo many youtubers showing 400w arrays or even 800w arrays and selling people on this! There must be hundreds of these videos. Why not an honest reviewer that's like "If you don't plan on having a TON of panels don't bother with it." :D