diy solar

diy solar

More Batteries or More panels? What is the tactical approch for expansion?

S

Solar Scott

New Member
Joined
Nov 10, 2023
Messages
51
Location
Misssouri
After purchasing the 6000XP and 4000 watts of panels (10) in a single string with one LL_S battery, I have since bought another two LL_S batteries. I have a 300 to 500 watt load on the system that drops the (3) LL_S batteries to about 50-60% SOC every morning and reaches 100% charge by 11:00 ish. I purchased a transfer switch to utilize the afternoon power, have not completed the install. I have also purchased the EG4 mini split that draws 600 watts and have installed it yet either. (Building a 300 square foot addition keeping me busy)
Should I be looking at batteries, or a second string of panels?
What is the best use of the SOC in a 24 hour period? Attempt to pull it down to 20% as the sun rises?
With the additon of the Mini Split, will (3) LL-S batteries carry it overnight in summer/winter?

What are the common stategies among veteran users of solar? I am 6 months into the process and will install the minisplit and transfer switch to analize the affects before my next expansion purchase.

Thank you all for any opinions!
 
Panels are cheap. 10 more into MPPT 2 would give you a rough average of 32kwh per day.(both strings)
Enough to charge 6 rack batteries, or maybe 2-4 with daily usage included.
Imo, would do 10 panels and 1-2 more batteries as funds allow
You could probably do one more battery now with 4000w of panels. 5:1 battery to panel would allow 4 batteries but may not charge them to 100 if completely depleted without generator or grid assistance
 
It depends on what you want.
If you want more autonomy. (Running time without sunshine) get more battery.
If you aren't getting enough power when you have sunshine, get more solar.
Probably best to wait until you add more loads. As it seems to be going well, at the moment.
 
timselectric said:
It depends on what you want.
If you want more autonomy. (Running time without sunshine) get more battery.
If you aren't getting enough power when you have sunshine, get more solar.
Probably best to wait until you add more loads. As it seems to be going well, at the moment.
Click to expand...
Well put! That makes so much sense. Things are going very well and its been fun so far. Plenty of solar (summer) and enough batttery, I need to load thing down. November and December in Missouri will be a differnt story im sure.
 
timselectric said:
Probably best to wait until you add more loads. As it seems to be going well, at the moment
Click to expand...
I agree loads should be the driver. My loads vary inversely to production, meaning that I have more winter loads. I could not afford enough batteries but I have added more solar but not enough to erase the winter deficit. Fortunately my Net Metering agreement allows me to use the grid as a seasonal battery and I pay $230 per year for that. My deficit from September to March is 1500 kWhs. I zero out by True Up in September.
My issue is that my utility has a limit of 1 kW additional solar and I have added over 2 kW so I have to limit some of that excess in summer so as not to have the daily peak go above the limit. One tactic is the additional panels are west facing so their production peaks later and lasts longer into early evening in summer. I have two EVs which I often charge from excess solar during the day so my annual export is within a reasonable amount for my "stated" capacity.
 
Last edited:
My approach was to first get a real-life working system powering some circuits in the home. Then I went back and forth - incrementally more panels and incrementally more battery.

My goal expanded over time till I maxed out my property with panels and was able to achieve power for critical loads 24/7 for 8 months of the year. Then I expanded the battery to lower the 80% DOD to 40% DOD for longer life + bonus of 24-48hrs of extra battery for low PV days.

For me, the 'end' is physical space for panels and.... practical limits for the Powerwall (space, safety). Ultimately would like to cover the 4 months of winter but would take some combination of 250 more panels OR 4000kwh battery bank....
 
Last edited:
Solar Scott said:
After purchasing the 6000XP and 4000 watts of panels (10) in a single string with one LL_S battery, I have since bought another two LL_S batteries. I have a 300 to 500 watt load on the system that drops the (3) LL_S batteries to about 50-60% SOC every morning and reaches 100% charge by 11:00 ish. I purchased a transfer switch to utilize the afternoon power, have not completed the install. I have also purchased the EG4 mini split that draws 600 watts and have installed it yet either. (Building a 300 square foot addition keeping me busy)
Should I be looking at batteries, or a second string of panels?
What is the best use of the SOC in a 24 hour period? Attempt to pull it down to 20% as the sun rises?
With the additon of the Mini Split, will (3) LL-S batteries carry it overnight in summer/winter?

What are the common stategies among veteran users of solar? I am 6 months into the process and will install the minisplit and transfer switch to analize the affects before my next expansion purchase.

Thank you all for any opinions!
Click to expand...
More of both it is like can you have too much Money.
 
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