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Help DIY solar generator
#1
Greetings all. If someone doesn't mind could you help me design a generator or complete smallish solar system big enough to run a deep freezer, big refrigerator, ceiling fan and a few lights along with moden, router, PC, TV and DVD player...... off grid. The bare necessities lol.

I've watched some you tube videos but haven't run across what I'm looking for. Everyone wants to use  100s of small batteries welded together. I want something easy to build, quick to build, and powerful enough for the above. Portable would be nice but not a have to have item.

Could I use 1 or 2 electric car batteries and a few Canadian Solar panels?  How many? Should I use another brand? How many watts do I need to keep my batteries charged. What kind of battery should I get. Best other components like inverter, charge controller ect?

The panels will be ground mounted and cables ran 50' or so to the house.

Sorry to be so green but I figure you guys know alot more than I do.

thanks,
swampf0x
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#2
10kWh of battery
BMS
some fuses/breakers

An 2kW inverter preferable with built in MPPT solar charger
and a couple of solar panels.

This with cables, fuses and all other


Now the tricky question is that there are 100s of factors..: For instance money,, and what you can get hold of.

You can use Car batteries but its just not worth it since they wont last you long at all and you wont be able to run much of them more than for an hour or so before degrading them....


100% off grid? What type of weather or where do you live? So many questions
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#3
>10kWh of battery
Following up on @Daromer's post - you could achieve a 10kWh lithium based battery with 16 x 120ah LifePo4 cells in series (e.g. 48v nominal)  OR  8 x 240ah LifePo4 cells in series (e.g 24v nominal) - which would take care of the 'many small batteries' issue.    For solar charging - which is quite variable by season / area - a 1,000w-1,500w worth of panels for sunny summer/spring/fall may get you in the ballpark.    Of course - dead winter (low-sun/clouds all day) you need 5 times that in solar panels.  

I would characterize your ask as on the larger side of solar generator and verging on a smaller home system Smile
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#4
You could also use EV batteries. This would be a huge jump forward in time needed to assemble everything. Again, you'd need to drop a lot of $$ to get them, though. You could easily drop $2k on an EV battery, depending on capacity size and SOH.
If you go this route, check your local salvage yards first. Then go to shipping, or driving long distances, to get them.
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#5
This started out as a way to stay comfortable and not loose food during a extended power outage. Then I got to thinking......Maybe I could build a small off grid system to power part of my home and still keep the power company for the big jobs. (I'm still in thinking stage/planning stage.)

I'm disappointed about the 6 Kwh solar panels needed for rainy/snowy wintery weather. As far as needing a lot of solar panels for winter............maybe. I'm in SW VA. I do have a 6000w generator to charge the batteries with, once in a while when needed. Maybe run it an hour or so a day??? I have no clue how this all works.

I like the idea of using 8 x 240ah LifePo4 cells in series (e.g 24v nominal) 8 is much better to hook up than 100s. How much will 8 cost me? I'm not pinching pennies but I don't want to waste money either.

Can you guys recommend a BWS and inverter?


Thanks everyone for the kind help.
swampf0x
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#6
Check out Batteryhookup and batteryclearinghouse they both have byd LiFePo4 batteries 24v think batteryclearinghouse is closer to sw VA but batteryhookup has what appear to be better batteries. The BYD batteries are ex commercial solar farm ESS/grid leveler systems. both offer free local pickup of batteries.

later floyd

2.5-3.5 kwh per 24v BYD LiFePo4 battery
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#7
The panels are meassured in kW not kWh.

Yes its not cheap and no you dont save any money of you plan for it to work year around. Just slightedt Cloud or Winter Monty degrades output alot. For instance the worst Winter Month i only get around 5% of the capacity of the panels. This just covers the losses in the system.....
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#8
(10-01-2020, 04:20 AM)swampf0x Wrote: This started out as a way to stay comfortable and not loose food during a extended power outage. Then I got to thinking......Maybe I could build a small off grid system to power part of my home and still keep the power company for the big jobs. (I'm still in thinking stage/planning stage.)

I'm disappointed about the 6 Kwh solar panels needed for rainy/snowy wintery  weather. As far as needing a lot of solar panels for winter............maybe. I'm in SW VA. I do have a 6000w generator to charge the batteries with, once in a while when needed. Maybe run it an hour or so a day??? I have no clue how this all works.

I like the idea of using  8 x 240ah LifePo4 cells in series (e.g 24v nominal) 8 is much better to hook up than 100s. How much will 8 cost me? I'm not pinching pennies but I don't want to waste money either.

Can you guys recommend a BWS and inverter?


Thanks everyone for the kind help.
swampf0x

Hey there! One thing you could try is setting up some automation routines to minimize electricity usage and maximize storage+production. We use a weather API on top of homeassistant for that. I'm originally from your neck of the woods and based on my experiences in the flat lands, should work just as well there!

(10-01-2020, 05:14 AM)daromer Wrote: The panels are meassured in kW not kWh.

Yes its not cheap and no you dont save any money of you plan for it to work year around. Just slightedt Cloud or Winter Monty degrades output alot. For instance the worst Winter Month i only get around 5% of the capacity of the panels. This just covers the losses in the system.....
The OP is in SW VA, they get far more daylight during the winter months than folks in Sweden. I'm not sure if OP is a totally lost cause for solar Smile As I've mentioned, we use weather + home automation to help adjust.

Edit: Removed product recommendation as it's a bit out of the spirit of the forum
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#9
>I'm disappointed about the 6 Kwh solar panels needed for rainy/snowy wintery weather. As far as needing a lot of solar panels for winter............maybe. I'm in SW VA. I do have a 6000w generator to charge the batteries with, once in a while when needed. Maybe run it an hour or so a day??? I have no clue how this all works.

Once you have a solar system with batteries...  then yes, using a generator to charge the batteries works great.    Say you create that 10kwh battery bank and target a 60% DOD each day - that's 6kwh/day.  You'll need 120v (or 240v) -> DC 48v charging....   

One option -  several inverters (medium to higher price) include charging as a feature.    For example, my AIMs 48v@2000w supports 20a of charging.  But if we do the math - 20a * 48v (battery) = 960w.   The generator would have to run 6hrs/day to get 6kwh of charge into the batteries.   6hrs/day, day after day is not trivial between oil changes, gasoline/propane etc.    You can buy inverters with 'heftier' charging amps to reduce hours of generator run time - but I'm just saying you need to pay attention the charging amps and 'do the math'.    Here's the chart showing charging amps for each AIMS model to give you an idea of 'pretty mainstream' amp capabilities:



Another option -  You can buy (and hook in parallel) as many 120v -> 48vdc chargers the batteries can accept amps.   I have 3 in parallel that can produce 2250w of charge - which I run from my 3000w Honda generator.    You could buy as many as your generator can handle and reduce generator run time. 

Panel option - IF you have room, extra panels actually make sense in the long term $ wise.  Generators are expensive machines that wear, use fuel, are noisy, and require maintenance Smile    

Maybe start with generator / winter backup and then gradually expand panels?
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#10
Hey a local. LOL Pleased to meet you.

One of the places above has BYD 24v 8s Lifepo4 3kWh batteries listed. Could I use 4 of those? Start out as like a power wall for backup and use a few solar panels and a 6000w generator to charge a little each day using 4 chargers? Then add additional solar as I can.

Description says :

"If you get a module that tests 4 kWh that's a bonus. But we are pricing these as if every module was 50% of original capacity."

"Large lifepo4 modules are hard to keep in balance blow 3v per cell and above 3.4v per cell. Set your charge to 27v, discharge cutoff to 24v, and you will be very happy with the performance. Ride that discharge curve line and get very extended cycle life out of these. We check to make sure every cell has voltage and guaranteeing every cell has voltage and is still usable. We are not guaranteeing capacity but we tested a lot of these and realistic expectations are between 2.75-3.75 kWh out of the original 5.2kWh. We've priced these WAY BELOW the $100/kWh mark so worse case scenario its still an amazing deal."

"It is possible you will need to balance these. The ones we tested were stored discharged to around 2.8v and they would be a little out of balance but simply charging them up to 3.3v would balance them. We recommend the ISDT Q8 balance charger, its cheap and works amazing for this pack. Also you can easily add a Daly 8s lifepo4 BMS to this. The battery does not come with a BMS but the wiring is there and the sides pop out for easy access. The main positive and negative posts are easily accessible. You can always cut the posts, drill a hole in the main busbar leads, and simply add a nut and bolt. These are super easy to work on. No soldering needed to add a BMS. They are rack mountable. They can supply a crazy amount of amps so no worries about lack of power. Yes they are a little degraded but they have a ton of life left and at this price you can't go wrong. Maybe even add an active balancer but definitely use the batteries in the range of the discharge curve as shown. Large lifepo4 cells when fully charged typically drop in voltage. When we tested these they have been sitting for a while and still had good voltage so self discharging is not a concern although you will see self discharging when fully charged. They'll drop to 3.4-3.5v which is where they should be anyway as you can see with the discharge chart. You will lose some capacity but ultimately you want a setup that lasts many more cycles and stays balanced. Get them while they last!

Fully Charged voltage: 29.2v
Recommended fully charged operating voltage: 27v
Fully Discharge voltage: 20v
Recommended fully discharged operating voltage: 24v
Recommended max continuous discharge: 300a
Recommended max continuous charge: 150a
Weight: 125 lbs.
Dimensions: 20" deep x 17.5" wide x 6" tall"


Thanks guys you are a huge help for me.
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