One of my weak points in preps is no solar. I have several inverter generators and store fuel. I figure with 60 gallons in cans / drums and another 100-120 in vehicles I could run 3-6 months in a grid down scenario. I am a Master electrician, have experience in controls and PLC as well. So, I can do the wiring for solar. I have kept 6-12 batteries (8D) to use inverters with. I have multiple - multi bank chargers. Figured I would charge batteries while running generator a few hours for fridge/freezers. I know that idea sucks, but it is what I had / have.

Now, I want to be able,to,power 2- freezers, 1- fridge and POE NVR with cameras, charge AA/AAA batteries without running a generator. I have a shed / shop in backyard I would put it all in. I have power from the house in shop. I have it set up to run generator in the shop, to power the house. So, I could use that to give house solar power input. I watch Will Prowse and others on YouTube. I want to slowly build a small system over a few months. I can spend $200-600 a month to do this over time with all cash.

The cheap Renology kits only have 100W or 200W panels, but is mini system in a box. Would a 60A MPPT charge controller be okay for a starter system? How would you start piecing a small system together? Panel(s) with a MPPT first and use the 8D batteries I already have? My thought on that is I could keep grid power and solar to keep batteries charged. In a quick outage act like a big UPS to keep freezer in shop running. As time and money allows switch to Lithium Iron batteries and grow system to 24 or 48V. I want to move to a more rural home in 3-4 years, so I have been putting this off. But I really want the ability now.

Any thoughts or ideas would be helpful, so I don’t waste money. Any input from projects you have or pics would be great. Others here could learn and get ideas as well. Maybe with others help, we can help people,like me cobble together something useful.

The important part is to run your panels in series, not parallel.

For example, our camper.  We upgraded from 1 100w panel to 4 100w panels.  When run in series, they max out at 100v total, but the current is still the same as it would be with 1 panel, our 40A Renogy controller can support 100 volts.  The upside to this is less wiring, smaller gauge wiring (we used 12ga wire) and less voltage drop as a percentage of total voltage.  You also can still make usable power with less light.  Think of it like a flashlight, I suppose.

When we were camping last October, sunlight wasn't that plentiful, and we were making more usable power with our 4x100w panels than our neighbor was with his 2x200w panels.

Two things to note about your approach:

First is that it’s best to buy batteries or cells at the same time so they have very similar internal resistance and to run them together for long life.   Adding new to existing batteries is possible but definitely suboptimal.

Second similarly it’s best if panels run in series are same. You don’t want to mix panels like having a a couple 160 watt and then a year later you want to add another and the mfg discontinued it and you can only find 180 watt or something.  I’ve had this happen. It’s annoying. It’s not the end of the world it works but is limiting.  

Ive found a good strategy is using multiple small mppt for redundancy and then you only need to match panels on the mppt.  For instance I have 460w panels on one mppt and 490w panels on two other mppts.

I’ve also found used panels to be a great bargain. I was very hesitant because I like buying new but I tried it and I doubt I’ll go back to paying full price as long as decent used ones are available. They sell cheap panel testers which are like a multimeter designed for testing panels.  Worth it.


I say the above because you’re planning to spend a few bucks each month instead of saving up and buying at once.  For batteries I’d really recommend waiting and saving because it’s best to buy what you need at one time and the price of lifepo4 is still dropping.

Buying multiple mppt is easy.   It’s nice if they work together but less critical for lifepo4.  There are some inverters designed to stack. As I’m sure you know they have to talk to each other to make sure they’re in phase and most inverters (incl mine) won’t do that.  So I have a SPOF there.  

But generally it’s a challenge to incrementally upgrade these systems.  You’re really better off doing your homework on requirements and getting what you need at once.

Regarding sizing…  
What are your loads? I know you listed fridge and freezers but look at their energy star ratings and see how much they draw per day)
Now add a fudge factor for converting from dc to ac. I’d recommend 10%
Next how many days do you want to be able to run with no sun?  Multiply and that’s how much battery you need.
Then how much sun do you get and how fast do you want to be able to recharge?  That’s how you size mppt and panels.

In addition to what others have said, just go straight to 48V and avoid replacing under-sized charge controllers/inverters later.

This.

X being the number on your Energy Star sticker

X kWh/year DIVIDED BY 365 days/year = Y kWh/day

Y kWh/day TIMES 1000 watts/kWh = Z watts

I'm far from an expert but I built a system to do exactly what you're wanting to do last year.  I bought Watt Meter to see how much each device was using.  My small freezer used 800 watts and our fridge used 1300 watts over the course of 24 hours.

I bought 4 used 330  235 watt panels from facebook marketplace, 2 24v 100ah lithium batteries, Renogy 40a MPPT Charge Controller and Giandel 24v 2000w PSW inverter.  It wasn't cheap but I can run my home network equipment that draws 2700 watts/day unless I run into several cloudy days.  For reference, that was in late fall/early winter.  I only run it when I'm not on travel so I haven't checked it lately.  I'm going to order an ATS so I can run it when I'm not here.  (Wife can't or won't baby sit it when I'm gone)

If you plan to DIY it, make sure you understand current requirements on your wires very well and make good crimps.  You can catch things on fire.

I have ordered a Kill O Watt meter and will get a 24 hour run wattage report. I understand batteries will be purchased last and will be pricey. Looking at Renology and BattleBorn batteries. Thanks for the input, will be trying to learn and research more.

Look at building your own batteries. It will cost 1/2 or less than ready made batteries and you can use a much better bms than they use. I much prefer to use an active balancer bms like the jk bms. I built 2 280 ah 12v batteries for my 12v system which runs my chest freezers and a 304 ah 48v battery which is paralleled to 3 100 ah 48v eg4 batteries that run my house inverter.

So I have 37 kilowatt hours of battery storage along with 8.2 kws of solar which allows us to run about 97% or so off grid.

Using a chest type freezer will lower your energy consumption.

Energy-efficiency
Chest freezers are more energy-efficient than upright freezers. Generally, they cost a little more than $4 a month to run when divided. Upright freezers cost around $14 a month to run. Both options come in energy-efficient models, which can further your cost savings.

Chest  vs  Upright Freezer

You can also by chest refrigerators which would also be more efficient.

16 Cu. Ft. Convertible Chest Freezer with 3 Storage Levels

I think I will do something similar, and add panels later.

@zoe17

I would not go with that inverter.  I would go with the EG4 inverter https://signaturesolar.com/eg4-6000xp-off-grid-inverter-split-phase/
as it has circuit breakers and fuses built into the inverter.  It costs more, but you get a lot more for the money plus the ability to expand to 240v if needed with another inverter.

If it's too much money, I would look at this inverter instead https://signaturesolar.com/eg4-3kw-off-grid-inverter-3000ehv-48/.  It has a higher max voltage than the growatt inverters do.

I will use the EG4 one. Same as the Will Prowse video, and from signature. Thanks for the mention. I just showed that one as the dolly mount showed first on YouTube.

Keep in mind calcs above are average energy consumption for calculating battery size.  

For calculating inverter size you need to go off MAX concurrent draw.  Not average.  With 3 fridge freezers they won’t run all day long. They will turn off and on.  Probably at different times.  Make sure you track peak draw and give your inverter some headroom over that.

I have 10 200ah lifepo with 5 40a mppt chargers in parallel, 44 100w panels wired to ( 4 in series) using 14ga wire.
I run 4 freezers 2 5cu' and 2 7cu'+ 58' tv, powertools, fridge, tools, mower' chainsaw ect.
I need to run generator from mid oct to feb, last gen run was mid feb.
I am considering getting a heat pump pool heater to hydronic heat my floor and domestic hot water.
I figure I can heat my water to 100 deg and my floor to 80 in three hours a day, in winter my genset will blow waste heat at the heat pump.
I will only run the heat pump during the hottest part of the day.



eta 20 year old trace sw2512 with charger that I run at 13amps on propane 3500 watt.

eta I just ordered 24 100w panels today $.50/watt

I would factor 20-30% more when sizing inverter for losses and non coincidental loading. But I would manually cycle the loads if needed.

Probably late to the show here. But while battleborn is a good premium choice, you can go far cheaper and its still ok. Depends on your budget and your reliability tolernace. Seems like you are already familiar with Will Prowse.

Go on Craigslist and buy one or two used 250w solar panels for $50-100 each. Then look at the Apollo or Sol charge controllers on DIYSOLARFORU.com. $169-249ea, and they run 20% off sales on holidays. Then go to Harbor Freight and get a PureSine 2000/4000 inverter. $300.

This will power a small cabin and is scaleable. I’m currently running 4 panels at my cabin this way and it meets all my needs. I will be scaling up to 26 panels eventually so cloudy winter days are transparent to me as the panels drop 75% of their production on overcast days.

Watch all of Will Prowse's videos. You'll learn all you ever wanted to know about solar "generators" batteries, cells. He is thorough without being boring or including a bunch of useless info.