what to do

[Broocel]

Good day everyone,

We have a solar powered off grid home. 8 x 365w LG panels. 4400w Magnum inverter. outback flexmax60 charge controller. and 8 x 6v batteries wired in series. (stark energy 533aH.)
We have a propane generator for backup.. Propane also runs our on demand hot water, dryer, and oven.

The home is woodstove heat only; but is A-frame.. and the south facing wall is all windows, so heat is not an issue and we actually only used 2 cord of wood all winter.

So we purchased this home in October of last year. All winter, if we had two consecutive cloudy days, on the third day we would have to run the generator.
Now that the sunny times have returned, the generator runs less frequently. But maybe this depends on whether the kids run their fan all night or not. After a couple of consecutive cloudy/rainy days, the power goes out at 7am when we turn on the coffee maker. Running the generator for 4 hours would fully charge the system. .

My questions are.. can I add two 6v batteries to the bank, so that it's a 60v system versus 48v? or can I split 10 batteries into two banks of 5 (30v each) in series and parallel? or do I need to add 8 batteries, parallel to the current set. (do the banks need to be 48v?)

Or do I instead add 4 more panels to max out the inverter, and increase charging capacity in sun & cloud?

thank you for your time. I appreciate your time.

take care

 

[WindWizard]

My questions are.. can I add two 6v batteries to the bank, so that it's a 60v system versus 48v? or can I split 10 batteries into two banks of 5 (30v each) in series and parallel? or do I need to add 8 batteries, parallel to the current set. (do the banks need to be 48v?)

First question No. The inverter has a 68 Volt maximum limit and two more batteries would push it over the limit and also your generator is setup for a 48 volt battery.

Second question No. The inverter has a 50 volt minium limit and your generator is setup for a 48 volt battery.

You are running a 48 volt system so in order to increase your battery bank, then you will need to add another 8 x 6 volt batteries
in series and then parallel the two banks.

It will take the generator twice as long to charge your batteries but it will provide twice the amount of time you are on batteries.

The batteries are $782 each so it is a bit expensive. I am using LFP 280 amp hour cells. I have 128 of them but they should (knock on wood) last longer than AGM batteries.

Others may give you some advice on how to keep your AGM's balanced.

 

[Broocel]

First question No. The inverter has a 68 Volt maximum limit and two more batteries would push it over the limit and also your generator is setup for a 48 volt battery.

Second question No. The inverter has a 50 volt minium limit and your generator is setup for a 48 volt battery.

You are running a 48 volt system so in order to increase your battery bank, then you will need to add another 8 x 6 volt batteries
in series and then parallel the two banks.

It will take the generator twice as long to charge your batteries but it will provide twice the amount of time you are on batteries.

The batteries are $782 each so it is a bit expensive. I am using LFP 280 amp hour cells. I have 128 of them but they should (knock on wood) last longer than AGM batteries.

Others may give you some advice on how to keep your AGM's balanced.

thank you.

 

[ksmithaz1]

How old are the AGM's? I'd move to /LifePO4, but it's gonna set you back a bit and you can't mix. I'd get the extra panels, cheap by comparison

 

[Broocel]

How old are the AGM's? I'd move to /LifePO4, but it's gonna set you back a bit and you can't mix. I'd get the extra panels, cheap by comparison

the AGM's were new Spring 2023 from the previous owner. thank you

 

[MichaelK]

Are these your batteries? When measured at the 20hr rate, they are only 424Ah.


That being said, the charge rate you are going them might be a little on the low side. Most AGMs like a charge rate of 0.2C, which in your case should be 424Ah X 0.2C = 85A. They are really not matched well with a controller that can only handle 60A.

Assuming you de-rate output to 85% like I usually do, what you are actually feeding them is likely to be....
[(8 panels X 365W)/50V charging] X 85% = 49.6A. Call it 50A.

You will need to make a decision here. Either replace the 60A controller with a higher amperage model, or buy a second flexmax 60. For either choice, you really need to be adding more panels to boost the charge rate up. This system I'd say would be more optimal with almost double the amount of solar, or about 5000W. Do NOT add more batteries until after adding more solar capacity. Adding additional batteries without additional solar is a guaranty for failure!

How are the panels wired now? Are they 4S2P, or 2S4P? Adding four more panels could be problematic in the sense that you might exceed the amp limit of your controller. That's why you need a larger/second controller. One option is virtual tracking. You could add eight more panels in two additional strings, but have one string facing East to Southeast, and the second West to Southwest. This will extend the hours in the day when the controller is receiving full power, and it will help a LOT in cloudy/rainy weather when output is only 10% of normal.

 

[seneysolar]

Right now panels are cheap, id add more panels and a 2nd parallel charge controller. This would speed up recovery and help in low light conditions.

Have you verified the charge controller settings and determined that you are reaching full charge when you do have a sunny day? Adding storage without adequate charging will make matters worse. Battery storage is still the most expensive form of energy.

Living off grid requires some adjustments in lifestyle. Cutting energy usage saves tons of money in an off grid setup. Besides, perk pot coffee tastes better and wont drain your batteries!

 

[50ShadesOfDirt]

I, too, would apply new design principles to your "existing" (built by someone else) situation:

1. reduce, and the good news here is that much reduction has been done for you (propane, wood heat, solar gain, etc ... all good stuff); only thing left to discover is what your family can do, lifestyle wise for now. investigate the loads, rerun the numbers (redo all calcs), see where you are, and where you could be

2. review the design. buying someone else's system, in lieu of excellent documentation and design notes, could mean you are buying someone else's problems. figure out the design intent of everything, especially the battery-bank (AGM?, was this a "winter" env decision?). Your magnum I feel good about, as my 4024 has been running over 5+ years, and I think it'll hit 10 pretty easily. But, review each and every component:
- inverter (again, this is a good strong selection)
- mppt (afterthought?, or are there better choices, as who knows where previous owner ran out of money?)
- battery-bank (this could very well be a problem, even though agm)
- solar panels (afterthought, ditto on money)
- wiring, fuses, etc. (do a safety review, here)

3. sell the agm's, replace with LiFePO4 battery-bank, sized per your family (not just watts & load types, but by family size & type, the power-hungry little buggers). I'm efficient, and power-considerate ... my wife and two daughters to this day find new ways to deplete the battery bank (which I've now doubled) in the blink of an eye. You could spend days of your life figuring out the exact AGM issues, or, just convert to LiFePO4 ... it is life-changing!

4. with battery-bank converting to LiFePO4, a review of the solar panels, as others suggested, might be next, and depends on #1

5. overall system: The good news here is that your system design does have a backup (propane) gen; depending on it's size, it'll recharge the battery-bank (even new LiFePO4, thru magnum inverter/charger) in short order.

In short, start from the beginning in terms of designing the system (and if you don't want to do this, have someone do it for you), and identify the weak spots in the current design. My guess is that the AGMs (which in theory & best practice can only give you half-rated-capacity) are the heart of the problem.

This forum has tons of posts to lead you through all of the above ...

Hope this helps ...