Battery shed?

[jvnn]

I am looking into putting up some PV for my house.
One of the possibilities is to put the array on the ground about 100' away from the house.

It would solve a few problems to have the batteries and electronics in a shed right by the array and pipe the AC to the house.
My question is what temperatures can these components tolerate?

Thanks!   - Joel

[Wolvenar]

I'm not sure of their upper temperature limits.
I do know that even if they tolerate that upper limit, it shortens the lifespan considerably the longer exposure it has.

The lower temps..
Well until recently I had mine in a shed as you plan for over 6 years, and the winters here are known to get as low as -40.
Not only did it perform well in the cold, it seemed to like it.
The shed in the summer was very well vented, and did not get much over the outdoor temp.

[Rover]

Depends on where you live, My winters are usually mild, typically above freezing, my summers are hot. Opposite of Wolvenar

I have mine in  shed that can reach 110F , some active fan cooling helps though. It is still not the optimum place to put the batteries. I did not have a choice.

Other factors to consider is the price of copper to run to a battery bank in the house, the safety or danger of having a battery bank in the house.

What size bank? Number of panels?

Rover

[jvnn]

What size bank? Number of panels?
Rover

I'm still sorting out those details, but I'd like to put out around 2000 to 3000W of panels.
And a battery bank around 10kWH give or take.
I live near Fort Collins, CO so my temps are between you and Wolvenar, max highs maybe 100, min low maybe -10.

Right now there are still a lot of unknowns to be sorted so the final system could look a good bit different from what I'd like.

What I do know is I want batteries and an inverter that can switch on the grid when my SOC drops.
I'd like to be able to use the grid rarely, but my main goal is to have a viable backup for when the grid goes down.
I'm ok with cutting down my load in a blackout scenario and I'll choose that over the cost of a bigger bank.

[Rover]

I'm really hoping you are not doing this as a cost saving measure. If you have grid it is not, when you consider the purchase price of what you intend.

Personally, I think 10KW/hr of battery bank is low considering a possible 3KW panel array and guestimated power usage. I'm hoping some others will chime in.

My bank is roughly 10KW/hr (8 gc2 6 volt batteries @ 230 a/hr each, bank @ 12V = ~11 KW/hr) and 900W of panels, I use it solely for offgrid stuff, not attached to my house which is on grid

We now enter the realm of having to know what your power needs are (in W/hr/day or month)

Rover


(note I edited this post as my fogged brain forgot the bats were 230 A/hr @ 6V)

[jvnn]

No I'm definitely not trying to save cash.
Considering my electric bill averages $55/month and my usage around 11kWH/day, there's no way.
I have a neighbor who is grid tied with 2700W of panel and she estimates her payback around 30+ years.
With battery costs I'll never hit payback.

Really what I'm trying for is a backup system that will make enough to get by when the grid is down.
I'm willing to shed load and schedule load in backup mode.

So yeah, 10kWH of battery is probably a bit light.
That will save some cost on the part that has a limited service life, and who knows maybe down the road I put  in a bigger bank.
That's my thinking now, but hopefully you folks out there will steer me away from a major gotcha.

Thanks - Joel

[Wolvenar]

Once you start, you will always be wanting that little bit more
:-)

A little clarification on my last post.
The electronics like the cold, the batteries didn't so much.
But as far as I can tell they only lost capacity during the time they *are* that cold

[ksouers]

I'm in a similar situation as Rover. 12KWh battery bank with 1400W PV residing in a detached garage without heat or cooling.
Daily usage is about 4KWh. I have computer equipment running 24/7 and use it to power my machine shop and some appliances in the house (TV, satellite, lights, internet). The system was also built primarily as a backup system for power outages.
So far the system has been quite tolerant of cloudy days, usually getting a decent charge on all but the worst rainy days. It would take a couple days of almost no charging to take the bank down dangerously low with normal load.

Daytime summer temperature runs 105+, the garage temps are close to a little warmer. Winter lows run about 10-20 but can and do drop below 0.


I too think your bank is too small for the PV you plan, so either cut back a bit on the PV or add some batteries, though you can never really have too much of either. You'll be glad for every bit of it when the excrement hits the turbine.


Kevin

[jvnn]

Lots of good responses so far, thanks everyone!

It sounds like an outdoor shed is a workable option for my climate etc.
Now to get the rest of the bugs worked out and get the $ put together.
Still lots of things to think about in terms of system size, components...

I'll keep you all posted if/when I move forward.

-Joel

[RichHagen]

Charged batteries can tolerate quite a bit of cold, although the performance suffers in that you will get more of a voltage drop for a given amp draw, and the maximum amps the bank can put out will be reduced.  I have an electric car, and when I got it, the lead acid batteries in it were all busted from freezing.  Dead batteries are less acidic and the freezing point of the electrolyte is higher although I don't have the specific info on that.  In a working system you will probably never let you batteries get that flat though so it should not be that much of an issue for you I would think.  Conversely I recall that batteries in the tropics don't last as long because of the higher temperatures.  Typically as a rule of thumb for most chemical reactions, the rates about double for each time the temperature is increased by about 10 degrees Celsius, so I would reckon that a battery stored and used at an average temperature which is about 10 degrees Celsius, or 18 degrees Fahrenheit warmer would last only about half as long, but that's just an approximation of course.   Rich

[Watt]

Charged batteries can tolerate quite a bit of cold, although the performance suffers in that you will get more of a voltage drop for a given amp draw, and the maximum amps the bank can put out will be reduced.  I have an electric car, and when I got it, the lead acid batteries in it were all busted from freezing.  Dead batteries are less acidic and the freezing point of the electrolyte is higher although I don't have the specific info on that.  In a working system you will probably never let you batteries get that flat though so it should not be that much of an issue for you I would think.  Conversely I recall that batteries in the tropics don't last as long because of the higher temperatures.  Typically as a rule of thumb for most chemical reactions, the rates about double for each time the temperature is increased by about 10 degrees Celsius, so I would reckon that a battery stored and used at an average temperature which is about 10 degrees Celsius, or 18 degrees Fahrenheit warmer would last only about half as long, but that's just an approximation of course.   Rich

Rich

One of the traction batteries I have came used from a coffee company with a date on it nearly half the age of another battery which came used from a cold beer distributing company.  That battery from the coffee company is in far worse shape as the positive terminals have expanded way faster than that of the one which was left in a colder environment.  I have no idea of the care the two had.  Just offering a bit of observation. 

[Rover]

Hi Joel,

I just got back in town, so I had to scroll back..

but ...
"Really what I'm trying for is a backup system that will make enough to get by when the grid is down.
I'm willing to shed load and schedule load in backup mode"

That is your watt hour target.... what is it? Is it everything? or parts thereof... freezers, fridges... etc

Get that number and build to it. You can overdo a battery bank if you can keep it maintained when needs are low. Based on your needs... a large battery bank is better than a large array.

In my use, in hurricane/Nor Easter region.... when the grid goes down, there is little useable sun.

But everyones situation is different.

Rover.

[jvnn]

Well Rover, that's a pretty good way to look at it, so here's my "back of the napkin" calculations

Fridge 2.2kWH/day   (or furnace in winter - one or the other but not both)
Lighting 0.6kWH/day  (I'll try to run a bunch of LED lighting at 24VDC)
Fudge factor 1kWH/day

ok 3.8 kWH/day in backup mode
Now around here we very rarely go more than 3 days without some sun, so I'd like to be able to draw 3 days without killing the bank.
So that's 11.4kWH and I'd like the bank to get no lower than 60% state of charge so that's a 28.5kWH battery bank - OMG!


Now to back down a little from that;
Winter is when the lack of sun is most likely, so I would be running the furnace at 1kWH/day.
That reduces my daily need to 2.6kWH and gives a battery bank of 19.5kWH - still a big expensive bank.

How does that rough calculation look to you?
And how is 60% SOC for a bottom limit on rare occasions in terms of not killing the batteries?

[Rover]

Welcome to the fun part...

Knocking off what you "need" vs what you "must" have.

I did not take the time to run numbers... but .. it does seem in line. Look at as what you would size a generator for (portable)


Rover

PS.. also decide.. if the generator is a lower cost solution