Interim solar build

ianleu

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Joined
Mar 10, 2022
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4
thanks for the ad to the forums.. first time poster.. first time solar builder.. please be gentle!

Would greatly appreciate any input on the below setup..

Aims of the system are pretty modest.. we want to power up a Starlink internet satellite system on our off-grid farm to give us some communication with the outside world. Starlink is estimated to consume 90 – 120Watts. Ideally we would just let the Starlink run 24/7 however we can cycle down (at night for example) to reduce power consumption as necessary. Aside from Starlink a couple of other devices bring our power needs up to around a max of 300watts or average of 150.

We already have a petrol generator (Honda e20i) so if we are unlucky with bad weather we can charge up the battery with the generator.

The build is an interim solution for the farm as eventual (2-3 years) plan is to build a house and build a very large solar system capable of powering a family home indefinitely. While it would be nice for the components of this build to have some future use, it is understood that the future build is likely to be a 48V system and this is mostly 12 volt kit.

Farm is in the Hawkesbury region of NSW, Australia. Panels will have good access to the north.



The system components thus far:

Panels:

2 x LG 350N1K-N5 350W NeON2 Black panels

34 V MPP 10A max per panel

Wired in series so max 68 Volts max 20

PV array isolation switch




Solar Controller:

Victron MPPT 100/50

Nominal PV power 700W rated 50A charge current Max PV open circuit 100V.




Battery:

VoltX 100Ah Prismatic Lithium ion Battery




240V Inverter:

Victron Phoenix Inverter 12/375 300Watt inverter




AC charger to use generator to charge battery:

Victron Blue Smart IP65 Battery Charger 12/15(1) 230V AU/NZ 15-Amp waterproof

https://www.victronenergy.com/upload/documents/IP65_A4_2022_smart_230V_web.pdf



Will add in isolators for the Panels and Battery.. as well as a fuse on the battery.

Happy to start with the Bluetooth monitoring.. may add something like the BMV-712 if I want something visible on the panel.


What are your thoughts? Anything obvious i am missing or have screwed up? Any constructive feedback welcome!

Cheers
Ian
 

sunshine_eggo

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150W * 24h = 3600Wh.

Your battery has:

12.8V * 100Ah = 1280Wh

1280/3600 * 24 = 8.5 hours - you can run your stuff for about 8.5 hours/day without charging.

You use Voc to compare against MPPT rating. 82.8V vs. MPPT 100V PV limit. You should be good down to about -38°C.

"good access to north" = unshaded exposure from sunrise to sunset? If so,

1647318510274.png

Multiply .7kW by the "solar radiation" number, and that's your average daily kWh for that month, e.g., in March, 5.44 * .7 = 3.808kWh/day.

Being limited to 50A means you might loose just a bit of that.
 

Hedges

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Mar 28, 2020
Messages
11,686
What are your thoughts? Anything obvious i am missing or have screwed up? Any constructive feedback welcome!

Temperature. Lithium Battery doesn't want to be charged below freezing.
Alternatives include heating it, insulating it, using lead-acid (or a different lithium chemistry.)

Given a battery that can't provide 12 hours power, shutting off some time in the evening could be better. To work 24/7, double the battery size.
That assumes no days without sunshine.

Check an insolation calculator for your location. Winter, might be 2 hours equivalent sun, so 3600 Wh/day would require about 1800W of panels.
So about 3x the 700W you're considering.

Having the system power up occasionally would reduce power consumption. But compared to the cost of Starlink, you'll probably just want more panels and more battery.
 

sunshine_eggo

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Messages
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Location
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Couple things I forgot:

On good sunny days, you can basically power your loads with the sun and continue to power them for 8.5 hours after the array stops producing 150W.

Your charger... 15A charger will take 100/15 = 6.7 hours to charge your battery. That's a lot of generator run time.
 

ianleu

New Member
Joined
Mar 10, 2022
Messages
4
150W * 24h = 3600Wh.

Your battery has:

12.8V * 100Ah = 1280Wh

1280/3600 * 24 = 8.5 hours - you can run your stuff for about 8.5 hours/day without charging.

You use Voc to compare against MPPT rating. 82.8V vs. MPPT 100V PV limit. You should be good down to about -38°C.

"good access to north" = unshaded exposure from sunrise to sunset? If so,

View attachment 87377

Multiply .7kW by the "solar radiation" number, and that's your average daily kWh for that month, e.g., in March, 5.44 * .7 = 3.808kWh/day.

Being limited to 50A means you might loose just a bit of that.
Thanks Sunshine_ego.. yeah i am skimping on battery a bit aren't i.. trying to keep costs down.. Looks like i should figure in some mechanism to gracefully shut down and restart the Starlink throughout the day..

yes we have options on the panel placement so should have direct sun on them all day..

good point on the AC-DC charger.. hard to find 30A chargers that dont cost a fortune here in Australia. I will look again.

annual temp range here is something like +4 C to +35C so more worried about too hot than too cold..

thanks for the feedback
 

ianleu

New Member
Joined
Mar 10, 2022
Messages
4
Temperature. Lithium Battery doesn't want to be charged below freezing.
Alternatives include heating it, insulating it, using lead-acid (or a different lithium chemistry.)

Given a battery that can't provide 12 hours power, shutting off some time in the evening could be better. To work 24/7, double the battery size.
That assumes no days without sunshine.

Check an insolation calculator for your location. Winter, might be 2 hours equivalent sun, so 3600 Wh/day would require about 1800W of panels.
So about 3x the 700W you're considering.

Having the system power up occasionally would reduce power consumption. But compared to the cost of Starlink, you'll probably just want more panels and more battery.

Hey Hedges - thanks for the feedback..

Luckily here in NSW Australia our lowest temps are something like +4C at worst.. so not as concerned about freezing as over-heating.. it can get to high 30's C

I will look into the winter sunlight in our location.. Thanks for suggesting the isolation calculator..

Cheers
Ian
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
11,686
The battery says max 50A charge current (which would be at nominal 25 degrees C, reduce that if very cold or hot.)

Two batteries would be 2400 Wh. Max charge current 1200W.
The 1800W panels I suggested would be a bit too high. More batteries could handle it. Two 900W arrays, aimed NE and NW, would reduce peak to 0.7x as much, 1250W, a better match. It will also keep battery full later in the day before it starts discharging.

Your Victron 100/50 would limit current to 50A, good max for a single battery. You could use two, or a 100A charge controller. Or a 24V system.


Wait a minute! Why an inverter? Starlink doesn't run on AC, at least not internally. Whatever AC adapters it uses, see what DC the produce and try to feed that directly.
 

ianleu

New Member
Joined
Mar 10, 2022
Messages
4
Good suggestion re two different arrays in different directions. given the relative cheapness of panels v's batteries this is worth a look.

Yeah agree with you entirely on running the starlink on DC and that is def on the cards.. this is what i know about that so far:
You can set-up starlink and bypass its internal router and wifi hotspot.. So at a minimum i could move that to a separate 12 volt powered device.. ( no idea what the actual power saving will be but worth a try). To do this we have to get the now optional external ethernet port.

In terms of running starlink itself on DC it looks like it uses some type of overpowered/proprietary power over Ethernet (poe) to power the dish.. 56 volts instead of 48.. unfortunately in the new version not as easy to separate the powersupply as in previous models.. But still may be possible. Looks like there are a bunch of folks who have done this with the older style round dishes.. haven't found anything yet like this with the new rectangular ones..

Elon Musk has apparently made some promises to the Ukrainians to make running the system off 12 volts easier for those who need to.. maybe that will happen sooner rather than later..

Lastly, the satelite dish includes some system to heat it to remove snow in colder climates which we will never need, so i am hoping that we will see lower power usage in any case.

Thanks again for the responses..

Cheers

Ian
 
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