Moved from the sticks into the suburban sticks

mikeo · December 2016

Ok, haven't been around for a few years, I am older but not necessarily wiser. I sold my farm with my original solar setup and have moved to the suburbs on two acres. I live in a tornado zone so I would like to install a hybrid grid tie system for net metering with battery backup. I want to keep the price down. A few years ago I bought two pallets of the 205w Evergreen solar panels. I have 10 left and just bought two more from a fellow I originally sold a pallet to. That gives me 2400 watts of solar panels. I would like to keep my battery costs low so I am considering a 24V battery bank. I have used fork lift batteries in the past but they sure do use a lot of water but the price is good for reconditioned batteries. The only 24V grid tie/Hybrid inverter that I can find are the now discontinued XW4024 which I can purchase on Ebay for around $3200. Add to that a 80A or 90A charge controller at about $600 and with the surplus 200A breakers, battery cables and other wiring I have around and by building a 3 string combiner box, plus $2000 dollars worth of refurbished batteries, I would have a 2400w grid interactive system for less then $6000 dollars. Oh yeah, I also need to add a Honda 3000 watt inverter generator for another $2000. Then I think in 2017 I could get a Tesla battery with integrated charger for about the same price. Oh what should I do. Any alternative ideas to this concept will be appreciated. Yes I still live in the country where I need power to run the well to flush toilets and to have water. Natural gas is not available, nor is DSL internet, cable TV or landline phone service.

mike95490 · December 2016

24V is not really going to save battery $$
a 24V 400ah system has the same storage that a 48V 200ah bank has. And then you can get by with a single 60A MPPT controller.

mikeo · December 2016

Thanks Mike, I not sure of the scale-ability of quality solar batteries. The price of a quality charge controller is less than $100 between 60A and 80A. L16's at around 400AH run at least $250 ea, so 4 batteries in a 24V system which I would say would be my minimum AH capacity for this system. What quality batteries would you recommend at 200AH that would be at least the same cost for a 48V system? By the way, I think L16's are marginal quality for standby solar backup. My previous bank was two banks of 12V fork lift batteries weighting almost 700lbs each at 900ah for a 24 volt system and cost me $1200.00

westbranch · December 2016

Mikeo, have you done your loads assessment yet?
I know you know the routine.... critical vs optional... days of autonomy....etc... that should determine just how big to make the battery... have fun...

Estragon · December 2016

Seems to me 8 golf carts for a 48v system is likely to compare well with your L16 price.

As Westbranch says, start with the loads.

mike95490 · December 2016

Estragon said:

Seems to me 8 golf carts for a 48v system is likely to compare well with your L16 price.

beat me to it. Pointless to over size the bank, if you don't kill them from usage, they fail of old age. Size it for 3-5 days of usage, so you don't have to start the genset every foggy morning.
My daily loads run about 7Kwh, so my optimal bank would be 20Kwh - 35Kwh Ouch !

bill von novak · December 2016

mikeo said:

Ok, haven't been around for a few years, I am older but not necessarily wiser. I sold my farm with my original solar setup and have moved to the suburbs on two acres. I live in a tornado zone so I would like to install a hybrid grid tie system for net metering with battery backup.

Is there a specific reason you want batteries? They're expensive and somewhat dangerous, and require maintenance and fussing.

If you want backup, a generator is a much better deal (especially with propane as fuel; fuel and generator will last longer.) If you want some solar backup you can get an SMA grid tie inverter with their "secure power" feature and run up to 2000 watts while the sun is out; when it's not out, run the generator. If you want some backup power for critical loads (i.e. computers, lights, radio) then computer UPSes are cheap, can be recharged from either source above and are easily replaced every 5-10 years.

Personally I wouldn't try to go with a battery bank unless you were losing power every week for a day or so at a time.

Dave Angelini · December 2016

The case for 24V becomes much better when you use 2V 1,100 amp hour cells. You should do that math also with 48V.
For grid-tie it really is up to you but for offgrid, golf carts just are not anywhere near what you need for a home with more than one person.
If you use an XW your generator choice should really be 240vac.

I also never understand why one with a decent grid would want batteries unless there is a medical or utility issue like Hawaii.
Good to see you again Mike. ! If you need a 24V XW I have 2 spares and a 4548 and a 600V 80A controller gathering dust.

mike95490 · December 2016

Dave Angelini said:

The case for 24V becomes much better when you use 2V 1,100 amp hour cells. You should do that math also with 48V. ....

But with 48V, you only need 550AH, half the lead. Anyway, we are all guessing because the OP never stated his daily load

edit:
(argh, my bad, same lead per BB below)

BB. · December 2016

Remember that 550 AH @ 48 volts will weight about the same as 1,100 AH @ 24 volts... The only difference is that you have 24 cells in series (at 1/2 the AH rating) vs 12 cells in series.

-Bill

Dave Angelini · December 2016

Well........ the math sounds good but in the real world you can't get a 550 AH battery off the shelf anywhere. Certainly not an L16 or a battery that is reasonably priced. I have no idea either what the OP wants or needs.

I do know that alot of my clients (in the real world) know that a 24V 1,100 AH bank is about the capacity they need to live in a home with 3 or 4 people. There are of course people who need more storage and the jump to a 48V 1,100 AH bank is a very nice solution but expensive when they need replacement. I can get L16's shipped most anywhere in the world and so I do not even look at othere sizes.
I know there are other ways to do this but I really like it simple and the Surrette, US, and even the rediculous Trojan 2V cells are all I look at for an offgrid home.

The OP needs to know a number and with his experience he probably does. The difference in the 1,100 ah batteries I use is $3,600 @ 24V and $7,200 for a 48V lead acid bank. Quite a bit more for AGM lead acid.

Nice that the days a getting longer again!

Estragon · December 2016

I wonder why someone doesn't make a mid-sized 2v? I would definately have considered something around 600ah. 350ish at 48v is a bit small, 700 means parallel strings, 1100 is too big for needs and available charging sources. Going 24v means more charge controllers and inverters.

softdown · December 2016

Estragon said:

I wonder why someone doesn't make a mid-sized 2v? I would definately have considered something around 600ah. 350ish at 48v is a bit small, 700 means parallel strings, 1100 is too big for needs and available charging sources. Going 24v means more charge controllers and inverters.

I would imagine the lack of demand for a mid sized 2 volt drives the lack of supply. While 2 volt batteries are often the best solar solution, I do not believe that a large percentage buy them. Angelini does but others on the board do not readily come to mind.

2 volt is often best because one bad cell is easily replaced without tossing a group of good cells. I have a small batch of old 8Ds with five good cells and one bad cell. Nothing but scrap. I doubt that 12 volt batteries are the way to go unless their quality is very high.

mcgivor · December 2016

Estragon said:

I wonder why someone doesn't make a mid-sized 2v? I would definately have considered something around 600ah. 350ish at 48v is a bit small, 700 means parallel strings, 1100 is too big for needs and available charging sources. Going 24v means more charge controllers and inverter

Someone dose
http://www.hoppecke-us.com/home_usa.html

Dave Angelini · December 2016

Try pricing and availability on Hoppecke

My comments often do not apply to many here because my market is for people in large homes who do not have fun with this stuff but expect flawless results!

Estragon · December 2016

I didn't know they had NA distribution. Will have to check them out when replacing the bank. Thanks

mcgivor · December 2016

Dave Angelini said:

Try pricing and availability on Hoppecke

My comments often do not apply to many here because my market is for people in large homes who do not have fun with this stuff but expect flawless results!

As an electrican, I began explaining how a particular installation worked to client, was cut short with the statement
" I don't care how it works, I just want it to work when I need it to". Hope your clients are a little more understanding and interested in your efforts.

Dave Angelini · December 2016

Image: https://us.v-cdn.net/6024911/uploads/editor/70/td5g2jaa1vj5.jpg

Some are interested and they do have to get up to speed with my guidance or send more checks

Not many of them would accept going outdoors to dry their hair when they have to be at xyz in 45 minutes. Maybe one of them....
Merry Christmas! Some Spicey Thai lime sauce and shrimp with a cold one later

new2PV · December 2016

Back to the original poster, cost for cost kw I would say the forklift battery is still the cheapest, but you will have to do the work to maintain it. Dont bother with a 120 volt gen it must be 240 or your going to have issues, even if you use a transformer to bump the voltage.

Dave Angelini · December 2016

If the OP comes back we always try to help, until then it is prime time for side tracking! A solar tracking joke....

Moved from the sticks into the suburban sticks

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