Sizing a solar system

[Hextejas]

I am sizing a solar system to provide power for a refrigerator and freezer.
I started with the battery and I saw quite a difference in prices.
Any suggestions as to which way to go or who to believe ?
================================================
$160

Lithium Battery 12V 100Ah LiFePO4 Batteries with 100A BMS, Deep Cycle Rechargeable Lithium Iron Phosphate Battery, for Solar, Marine, Trolling Motor
Brand: Vinnotech
==========================
and then I see this one.

$309

Renogy 12V 100Ah Lithium LiFePO4 Deep Cycle Battery, 5000+Deep Cycles,Backup Power for Trolling motor, RV, Cabin, Marine, Off-Grid Home Energy Storage-Core Series


Gulp !!!

[nctnico]

Where it comes to batteries I like to check the warranty. Often this will say something about the cycles and / or total amount of energy a battery can store over its lifetime. The total amount of energy can be found by multiplying the number of cycles with the capacity in kWh. From there you can calculate the price it costs to store 1kWh by dividing the purchase price by the total amount of energy.

[tszaboo]

Any suggestions as to which way to go or who to believe ?

I believe Pluto is a planet, and I size it 30 trillion km or the equivalent in miles.

On a serious note, it depends what you want. Do you get terrible electricity grid with blackouts every year for weeks, which is apparently "normal" in the USA? Or you want to increase self-consumption.

[Hextejas]

I live in Houston and we just went through hurricane Berryl which left us with no power for a week. Had to trash the refrigerator and freezer, so i was thinking about a backup system. Initially I plan to power the fridge and freezer and some small fans in the house. And I dont know what else, probably a USB charging port for the phones.
Then I saw a device this morning which looks kinda good. It includes all the parts for $2000.00

[perdrix]

Solar system sizing - last one I did was about 121 AU (1.81×10¹⁰ km) from the sun to the heliopause 

D.

[CatalinaWOW]

Can't answer this for you.  This battery technology is growing rapidly.  Lots of new players and competition.  Prices are falling.

So, you have a high priced product from a company with a long history in the field, and a lower priced product from an player with a much shorter track record.  Is that lower price a reflection of better manufacturing scale, more factory automation, lower profit margin or is it lower quality.  I have seen people quite happy with the cheap ones, but those prices are only a couple of years old at best so there isn't really any field knowledge.

You are likely to have a light usage cycle (only a couple natural disasters a year at worst) and could break even on cost if the cheap battery fails twice as often.  Maybe even more if prices keep dropping.  It seems you might be a candidate for the cheap battery, but you are the one who decides how much risk you are willing to take, how much inconvenience in replacing batteries you are willing to accept and so on.

[Phil1977]

You should ask Magrathea, but I´ve heard they´re sometimes not so easy to reach...

[coppice]

You should ask Magrathea, but I´ve heard they´re sometimes not so easy to reach...

They do have an excellent warranty program. Blow up one of their products, and they'll make you a replacement, pronto.

[nctnico]

I live in Houston and we just went through hurricane Berryl which left us with no power for a week. Had to trash the refrigerator and freezer, so i was thinking about a backup system. Initially I plan to power the fridge and freezer and some small fans in the house. And I dont know what else, probably a USB charging port for the phones.
Then I saw a device this morning which looks kinda good. It includes all the parts for $2000.00

I'd get a small generator for such situations. Another option is to buy an inverter so you can run AC powered devices from your car. This may require fitting a larger alternator in your car though.

[Hextejas]

We do have a generator but it is a god awful noisy thing. The new solar system is to try and replace some of the local grid usage as it is frightfully expensive.
==============
Further to my solar system design there are a few questions or design issues that I need help with.
My original design thoughts were fairly simple or so I thought.
1) Solar DC output panels on the roof.
Feeding a battery charge controller to the batteries.
2) Inverter converting DC from the batteries to 120 VAC for use by the freezer.
=====////
And then I began hearing lots of suggestions which seem like really good ideas though I have no clue as to how to fit them into my simple design.
1) Apparently the solar panels can now produce AC, so would that mean that I would need 2 inverters.
2) I read where it is a good idea to have a device to be able to balance the charges on the batteries. Where does that fit into my simple design,
3) And more reading said that there is a battery charge controller/inverter that could simultaneously charge the battery and power AC devices Is there such a critter ?
=========
The mind reels.😳😳

[richnormand]

@Hextejas:
What you propose makes sense but here is another option that could meet your needs, although it is not an automatic switchover..

About 2 years ago we had an outage for about a week due to very high winds.

Waited about a day hoping the electricity would come back. It was eerily quiet in the neighborhood and dark at night. Nice in some ways.
Then everyone gradually powered up the generators and such. The noise at night and the stench of exhaust fumes started to be a real nuisance.
Problem is the generators were running 24/7 even if the electricity demand was low at times.

For us I just used the invertor option on the Ionic 5 in the driveway. Quiet and totally silent: we just wired the essentials like the fridges, a few lights and the internet/TV.
Only used slightly over 20% capacity in four days. If you get an EV consider getting this option and you can recharge by driving outside the blacked out zone too.

A much more environmentally civilized way of coping.
This could be an alternative to getting batteries and such as an EV will have a much greater capacity.

[nctnico]

We do have a generator but it is a god awful noisy thing. The new solar system is to try and replace some of the local grid usage as it is frightfully expensive.
==============
Further to my solar system design there are a few questions or design issues that I need help with.
My original design thoughts were fairly simple or so I thought.
1) Solar DC output panels on the roof.
Feeding a battery charge controller to the batteries.
2) Inverter converting DC from the batteries to 120 VAC for use by the freezer.
=====////
And then I began hearing lots of suggestions which seem like really good ideas though I have no clue as to how to fit them into my simple design.
1) Apparently the solar panels can now produce AC, so would that mean that I would need 2 inverters.
2) I read where it is a good idea to have a device to be able to balance the charges on the batteries. Where does that fit into my simple design,
3) And more reading said that there is a battery charge controller/inverter that could simultaneously charge the battery and power AC devices Is there such a critter ?
=========
The mind reels.😳😳

You have to split a few things here. Solar panels and batteries are DC only. To feed the grid or you own appliances, you need an inverter to turn the DC into mains AC. If you want to use your setup during a blackout, you need to buy a system which supports 'islanding'. https://www.energysage.com/energy-storage/islanding-and-batteries-what-you-need-to-know/
Be prepared that this could become costly though.

A quiet generator is likely to be cheaper. When buying equipment in any form, it is always good to look at noise levels and buy the most silent option (and/or accesoires which make it more quiet).

[Hextejas]

You have to split a few things here. Solar panels and batteries are DC only. To feed the grid or you own appliances, you need an inverter to turn the DC into mains AC. If you want to use your setup during a blackout, you need to buy a system which supports 'islanding'. https://www.energysage.com/energy-storage/islanding-and-batteries-what-you-need-to-know/
Be prepared that this could become costly though.

A quiet generator is likely to be cheaper. When buying equipment in any form, it is always good to look at noise levels and buy the most silent option (and/or accesoires which make it more quiet).

Whoa ! this is interesting from islanding and it makes sense.

In other words, solar inverters are explicitly designed not to allow your solar panels to continue to push electricity into your home in the event of an outage.

[CatalinaWOW]

As it states in the link it is important not to feed power to the grid.  Most inverters satisfy this safety requirement by shutting down when the grid shuts down.  Not all do, and that is what people are suggesting selecting equipment with islanding capability.