Looking for General Plan Input and Questions on Charge Controllers

[GabeAteU]

I am currently budgeting and researching charge controllers for a new system. I have zero experience and therefore I don’t know what I should be looking for. I will be in alaska and therefore a cold climate with snow 2/3 of the year for this reason I chose bifacial solar panels. The biggest energy expense will be my high end computer which uses about 3.5kwh including the monitor and other peripherals. I need the computer for remote work so it is a non-negotiable The next biggest energy expense is my Starlink which will use about 1.5kwh per day. After that my energy use is very minimal using just lights, tool battery charging and the occasional water pump. I intend to use just over 6kwh per day. I will be fully offgrid without the option to tap into the grid. I will however have a diesel generator that I could use though I want to keep this at a very minimum(maybe a few hours a month in the winter). I feel fairly confident in most of the numbers but I am not certain of anything.

My biggest question is on charge controllers. Information online about brands is hard to come by and it seems like renogy is the go to brand. I am on a budget but if its going to break in a year or so I dont want to risk it. What are the viable option I have? Are LiFePo4 batteries my only option in that climate or could something else work as well?

These are the general numbers for the system I am designing(nothing is set in stone and I am open to all opinions):
12,000w 24V Batteries (Unsure on brand or specifics)
4x550w Renogy Bifacial Solar Panels
2000w Renogy Inverter
Charge Controller 100 amp

Thank you all for any opinions or advice : )

 

[rodrick]

With the new prices on the victron units on Amazon I would look at them and I personally wouldn’t buy one large scc I would by 2 or more smaller ones for redundancy just in case

also what is your plan for a charger from the diesel generator power does the renolgy inverter also charge?

 

[Solarcabin Channel]

Unless you can keep LFP batteries above freezing those will not work for your situation.

Sealed AGM deep cycle like the Vmax tank would work but keep in mind they are extremely heavy and capacity is half that of an LFP.

If you need 12k watt hours then you need 1000Ah of battery capacity.

 

[GabeAteU]

With the new prices on the victron units on Amazon I would look at them and I personally wouldn’t buy one large scc I would by 2 or more smaller ones for redundancy just in case

also what is your plan for a charger from the diesel generator power does the renolgy inverter also charge?

So after doing a bit more research I have decided to use a gas generator instead as diesel are quite a bit more expensive than anticipated. Most of the generators I have looked at already supply 110v electricity and therefore I will just connect via extension cords until the system is charged back up. Thank you so much for the advice on the victron units I will definitely look into those.

 

[GabeAteU]

Unless you can keep LFP batteries above freezing those will not work for your situation.

Sealed AGM deep cycle like the Vmax tank would work but keep in mind they are extremely heavy and capacity is half that of an LFP.

If you need 12k watt hours then you need 1000Ah of battery capacity.

I done a lot of thinking about the temperatures. My plans are to place the batteries into a very small, short, and insulated shed connected to my cabin. I also have plans to use low temp charging protection which on near all the batteries I have seen have been rated to go down to -5 F. My cabin is obviously heated by a wood stove and supplemented by a small propane heater for when I won’t be home for multiple day. Let me know if you think these precautions are enough.

 

[Solarcabin Channel]

I done a lot of thinking about the temperatures. My plans are to place the batteries into a very small, short, and insulated shed connected to my cabin. I also have plans to use low temp charging protection which on near all the batteries I have seen have been rated to go down to -5 F. My cabin is obviously heated by a wood stove and supplemented by a small propane heater for when I won’t be home for multiple day. Let me know if you think these precautions are enough.

What part of Alaska?

I would research the average night time temperature. Some (not all) LFP have a low temp sensor that will stop batteries from charging below freezing and they won't recharge until they warm back up to a set point.

I would also research the average sunlight hours for your cabin as Alaska is known for many days of low/no sunshine.

A genny can recharge batteries if you can get the genny to start in sub zero temps.

You are talking about an extreme weather system and I would just caution you that a system designed for that is not something I recommend for inexperienced people.

 

[Solarcabin Channel]

for when I won’t be home for multiple day

Is this a recreation cabin you will only stay at for short periods?

If so then a better option may be to get a large power station and genny. Charge the power station up to take to the cabin and if you need to recharge it use the genny. Keep the genny warm so it will start.

 

[GabeAteU]

Is this a recreation cabin you will only stay at for short periods?

If so then a better option may be to get a large power station and genny. Charge the power station up to take to the cabin and if you need to recharge it use the genny. Keep the genny warm so it will start.

The cabin will be a permanent residence and other than low temperature batteries what equipment would help the system perform better in extreme temperatures. Near Fairbanks where I will be living it can get down to -30ish for around a week or so but that is very rare. From what I have read there shiuldn’t be a problem with solar panels at that temperature and the only issues I could run into are the batteries. The batteries will be in a insulated shed connected to the cabin so I figured I should worry too much about them. Many people in my area have similar system setup that way.

Thats good to keep in mind about the generator. I will keep that in the shed or even in the cabin during the extreme temperatures and plan to use that during the dark weeks.
Do you think the wattage I have planned is enough or what changes to the wattage. numbers would you make?

 

[Solarcabin Channel]

The cabin will be a permanent residence and other than low temperature batteries what equipment would help the system perform better in extreme temperatures. Near Fairbanks where I will be living it can get down to -30ish for around a week or so but that is very rare. From what I have read there shiuldn’t be a problem with solar panels at that temperature and the only issues I could run into are the batteries. The batteries will be in a insulated shed connected to the cabin so I figured I should worry too much about them. Many people in my area have similar system setup that way.

Thats good to keep in mind about the generator. I will keep that in the shed or even in the cabin during the extreme temperatures and plan to use that during the dark weeks.
Do you think the wattage I have planned is enough or what changes to the wattage. numbers would you make?

Ok, that should work then. You have 1000Ah of batteries and 2200 watts of solar so if you can get 5-6 hours of decent sunlight that should recharge that bank and you only need the genny as a back up. Only run big loads in the day time when sun is shining and try to let your batts fully charge for overnight.

I would look at a 12/24 volt fridge that only uses 45 watts and I like the Alpicool brand. Get an electric blanket or sleeping bag and also rechargeable LI coat, gloves and socks are really nice.

I am not fond of the Renogy inverter and I had one fail on me and have had several people report same issues. Get a pure sine inverter from a better source would be my recommendation.

I live in a similar climate in the Rockies with about half that size system so you should be OK.

Watch out for bears and moose and be safe!

 

[MisterSandals]

I intend to use just over 6kwh per day. I

Looking at january with .88 solar hours per day:
6000Wh / .88h = 6818W array needed.

6818W / 28V charging = 243A charging (this is a LOT)

Assuming your computer and other loads run 24/7 at same power consumption:
6000Wh / 24h = 250W average load

In january you will have 23h running off of battery:
6000Wh x (23h/24h) = 5750Wh battery (usable so double for lead acid)

5750Wh / 25.6V nominal for LFP = 224.6Ah (actually quite reasonable)