# Battery question for solar power system



## BACOG (May 17, 2012)

Need help in calculating proper capacity batteries for solar system. Right now at my house I am running about 262 KWH per month. So a new place would probably run that or up to 280 KWH per month. The property I am interested in has very little to block the sun. So that should not be a problem. 

I am planning on running a sinewave inverter and drawing 120 vac off of that. Hard to wean the family off 120.

Any ideas for the batteries? 

Looking to get totally off the grid. In my home state 2 things we have a lot of is sunlight & wind. First choice is solar panels. Second choice is wind/solar.


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## Harry Chickpea (Dec 19, 2008)

Those levels are _totally _impractical for solar. Please do some basic reading before investing a dime.


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## whistler (Apr 20, 2005)

Doing some rough, back of the envelope calculations, I bet you could get away with no fewer than 90 industrial size batteries at $1049 each.


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## Rick (May 10, 2002)

There is a whole bunch of out of the box thinking in your future. A 
generator will help you with you peak demand and also help charge those poor batteries.

Huge Refrigerator, air conditioner, clothes dryer, microwave, toaster, hair dryer, Television, Desktop Computer, circular saw.

Might be a couple of targets on a solar hit-list up there.

Our best friend is a wood cook-stove.

Best of luck on this journey!


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## TnAndy (Sep 15, 2005)

Harry Chickpea said:


> Those levels are _totally _impractical for solar. Please do some basic reading before investing a dime.



HUH ? *280kw/hrs* per MONTH is impractical ? 

That's only 10kw/hrs/day. 

I currently generating over 600/mo on average. 

He's well within practical. It's the folks using 2,000kw/hrs/month that have a financial lesson in store for them trying to go solar.

As for batteries, it depends on what you want to spend, what kind of quality to you want, how many days of no sun you'll have on average, and so on......but off the top of my head, I'd start with a 1000 to 1200 amp/hrs, (12 L-16's will get you there) and a generator so you don't ruin them IF the sun doesn't shine.


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## tarbe (Apr 7, 2007)

Harry Chickpea said:


> Those levels are _totally _impractical for solar. Please do some basic reading before investing a dime.


One of us is reading the OP's question incorrectly.


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## Jim-mi (May 15, 2002)

. ."Ideas for batteries" . . .

Lots

Generally "first timers" need to start out with a "lower end" set of batteries . . . because of lack of experience people tend to blow through their first set . . . . .the bats get abused / over used and die sooner than they should............

Once you learn how to really pare down you use of electric, things will go easier. . . .

You want to be sitting down when you see the price tag for the super premium batteries.
The HuP Solar-One and Absolyte are very pricey..........

Start learning electrical conservation --now--
That will be a huge help when you do go off grid.....................






























































Solar One and Absolyth


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## BACOG (May 17, 2012)

Rick said:


> Huge Refrigerator, air conditioner, clothes dryer, microwave, toaster, hair dryer, Television, Desktop Computer, circular saw.


The first thing on the hit list is the electric cook stove. Been looking at wood cookstoves and found a couple I like.

Fridge & microwave can be deleted for smaller models. Only need so much refrigeration. A smaller microwave would fill my needs perfectly. Toaster can go down the road & don't have a hair dryer. Don't like TV. The computer & power tools are a must though. 

I do believe I will have to get rid of some items & downsize to make this happen.


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## Jim-mi (May 15, 2002)

Now your talking / thinking......................

Also consider Propane...............




Electric stoves do not even make good boat anchors . . . . . lol.


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## wy_white_wolf (Oct 14, 2004)

280 KWH per month

280Kwh / 30days = 9.33Kwh average per day

9.33Kwh * 5 days atonomy = 46.65Kwh battery bank

46.65Kwh / 48 volts = 971.875AH battery bank at 48volts

Closest that Rolls-Surrette puts out would be 1104AH at 4 volts so you would need a dozen of them at $1009 each plus shipping

http://www.wholesalesolar.com/products.folder/battery-folder/Surretterolls.html

WWW


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## BACOG (May 17, 2012)

Thanks wy white wolf. PM sent.


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## Lilith (Dec 29, 2012)

not sure about the batteries you will need but, we (the construction company I am taking over from my dad) recently built a 100% off grid Cabin in a remote area. We had the solar system installed first, and built the house off of it 90% (we had 6 days in a row of no sun and had to run our largest tools off a generator). There were 6 deep cycle solar batteries (I will assume top of the line), 6 huge solar panels, (200+ W ea?), and a complete outback power systems inverter and regulator system .... total cost was just under $20,000.

The household appliances that were on the chopping block were #1 the coffee pot, #2 the fridge (propane fridge was installed), #3 the dish washer, #4 the hot water heater (propane was installed) and #5 the cook stove (propane was installed). The electrician also wired in all LED lights, denied the ceiling fans, and told them that space heaters, hair dryers, and curling Iron, use in the house voided ANY liability or guarantee. Poor Doctor's wife has to use a percolating coffee pot, wash her dishes by hand, and let her hair dry naturally while they are vacationing there.

We had very few problems running compressors, saws, and other tools on the job site as long as we did not use more than one at the same time (ie: don't make a cut while the compressor was running if the lights were on.) When we did use multiple tools at the same time, we often tripped the system's protective breakers. I'll ask the electrician we used for exact info on the system next time I see him. All and all, it was a good system to use, and sounds like it would only need minor beefing up for your uses.


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## wy_white_wolf (Oct 14, 2004)

Lilith said:


> ...6 huge solar panels, (200+ W ea...


He's going to need a lot more than that.

6 200watt panels = 1200 watt array

insolation for Laramie Wy is a low of 1.68 hours in December 

http://www.gaisma.com/en/location/laramie-wyoming.html

1200w * 1.68 * 30 days ~ 60.5Kwh

Far cry from the 280Kwh he's looking at and that's without figuring any system losses.

WWW


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## Jim-mi (May 15, 2002)

That 'system' that Lilith posted about is a reasonable 'small' system.
But it has ordinary L16 type batteries.......

The 'premium' batteries I posted about would chew up most of that $20,000...........

I just posted that as an example that there is a very wide range in battery prices....
As in; . . Good . . . Better. . . .Best.......

A very good point that Lilith mentioned is that they had to revert to using a generator because the work needed to be done **now** . . .But the sun was Not shining (threw the clouds).


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## BACOG (May 17, 2012)

wy_white_wolf said:


> He's going to need a lot more than that.
> 
> 6 200watt panels = 1200 watt array
> 
> ...


Very true. 

When I was an EMT one of the first things we had to do before treating someone was stop the hemoraging before further treatment. 

Same concept here. Stop the usage as much as possible. Actually my goal is to get my usage down to 200 -225 Kwh or even less. There are some things that will have to go i.e. cookstove, large fridge, etc. and somethings that will have to be downsized i.e. any appliance is in this category. The only thing that are pretty well exempt from downsizing or elimination is the computer & power tools.


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## BACOG (May 17, 2012)

Jim-mi said:


> The 'premium' batteries I posted about would chew up most of that $20,000............


The batteries I am looking at are these. http://www.batterygiant.com/Product/US2200 

To get 48v I would have to put 8 of them in a string & to hit a minimum of 1600ah I would have to have 7 strings. Total cost of the batteries would be about $7657 not including shipping.


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## Jim-mi (May 15, 2002)

Sorry to pour cold water on your thoughts......................

Those batteries are really bottom of the line . . . . . .

And paralleling "7" strings together is a very BAD idea............

Even using copper bus bars and 0000 inter connectors not all the bats will be charged properly. Very soon problems will develop.

A battery bank configured like that will have a short life.




sorry about that . . .more often than not the truth hurts.


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## 12vman (Feb 17, 2004)

Ever consider a total 12 v.d.c. system? I get by with 512 watts and 4 golf cart batteries. Appliances are propane (2 fridges and a cook stove) but 100# cylinder lasts me ~5-6 weeks. I get 3 months worth of hot water for showers and whatever from a 20# cylinder. I even have a 74" projection TV-DVD system with surround sound..  (No Inverters Involved)


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## Lilith (Dec 29, 2012)

Quick question ... if you have more panel generation than you can store, can you use the power directly without going through the batteries? Idk about others, but I mostly use my power tools during daylight hours, along with most of my other power consuming things, and it seems to be that an extra panel may be cheaper than an extra high quality battery.


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## TnAndy (Sep 15, 2005)

If you have a battery system, it all "goes thru the battery" sorta, in that the system takes care of the battery first, and if other demand is nothing, then there is no generation by the panels.

Technically, you wouldn't know if it was coming from the panels, or the battery.....say one cloud blew over while you were consuming.....the battery would supply your needs....then the cloud moved on, the panels would top off the battery, and then pass the extra on to what you were using....

But the short answer is, yes, you could use that extra power elsewhere. 
It can't hurt to have extra generating capacity.


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## JohnP (Sep 1, 2010)

12vman said:


> Ever consider a total 12 v.d.c. system? I get by with 512 watts and 4 golf cart batteries. Appliances are propane (2 fridges and a cook stove) but 100# cylinder lasts me ~5-6 weeks. I get 3 months worth of hot water for showers and whatever from a 20# cylinder. I even have a 74" projection TV-DVD system with surround sound..  (No Inverters Involved)


I just recently went from 170 to 305 watts. Gettin there. Aside from charging other batts like laptops and running a tv/dvd off inverter, we're 12 volt. Could you tell me more about your surround sound system? PM would be good as not to further thread jack. Thanks


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## wy_white_wolf (Oct 14, 2004)

Lilith said:


> Quick question ... if you have more panel generation than you can store, can you use the power directly without going through the batteries? Idk about others, but I mostly use my power tools during daylight hours, along with most of my other power consuming things, and it seems to be that an extra panel may be cheaper than an extra high quality battery.


There's a limit on how big one can go on the array compared to the battery bank. Lead acid batteries don't like to be charged above C/8 (AH capacity divided by 8) with the ideal rate being C/10 to C/12 range. 

If you built an array that say put out C/6 of your bank as soon as you quit using the extra power all of it would go into the bank and likely damage the batteries.

WWW


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## wy_white_wolf (Oct 14, 2004)

BACOG said:


> The batteries I am looking at are these. http://www.batterygiant.com/Product/US2200
> 
> To get 48v I would have to put 8 of them in a string & to hit a minimum of 1600ah I would have to have 7 strings. Total cost of the batteries would be about $7657 not including shipping.


Very bad idea to have 7 strings of batteries. First you have to add breakers on every string so that if 1 battery shorts out all the other strings aren't grounding out through it. Without them it could blow the batteries up.

You will end up with differential charging problems as you can not build it without slight differences in resistance on each string. When not charging then they all try to equalize out to lowest charged string. The same happens when you put a load on them. The strings with the least resistance will have more amperage pulled from them. When the load is removed the other strings will equalize down to the level of discharge of the lowest string. That's why multiple string system are short lived compared to a single string system. 

When it comes tom for maintenance do you really want that many connections to clean? How about taking hydrometer readings and topping off all those cells? That's 168 cells to maintain. A single string will have 24 cells for a 48V bank.

WWW


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## Jim-mi (May 15, 2002)

Also with a PV panel heavy system you would need a mighty good controller to keep from blowing up the batteries.

What comes to mind to be able to handle that would be a 'Midnight Classic' . . . . which comes in at over $ 700 bucks per . . . . . .


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## Rick (May 10, 2002)

wy_white_wolf said:


> There's a limit on how big one can go on the array compared to the battery bank. Lead acid batteries don't like to be charged above C/8 (AH capacity divided by 8) with the ideal rate being C/10 to C/12 range.
> 
> If you built an array that say put out C/6 of your bank as soon as you quit using the extra power all of it would go into the bank and likely damage the batteries.
> 
> WWW





Jim-mi said:


> Also with a PV panel heavy system you would need a mighty good controller to keep from blowing up the batteries.
> 
> What comes to mind to be able to handle that would be a 'Midnight Classic' . . . . which comes in at over $ 700 bucks per . . . . . .


I don't get these comments.... I have a 500 watt array, with 4 L16 RE 6Volt Trojans, wired as 12 volts. If I read this correctly, if I had just 2 of those batts my xantrex 35 watt controller might have issues keeping the batteries from blowing up?


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## Jim-mi (May 15, 2002)

Rick you must have missed the posts about adding 'more' PV panels.
When -not- using the extra currant (as a home load) the batteries could / would get into overcharging issues.
So if the charge controller is not a "good" one nasty issues would soon develop.

The equipment you list is just fine for a small system. . . .And the C35 controller is not over taxed 
But if you were to add another 100 watt panel you controller would be getting pretty hot . . .meaning shorter life before it goes Poof............


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## Rick (May 10, 2002)

Thanks Jim-mi.

Some here warned me of peak cloud effect, but the C-35 has stood the test as you say.

Along the lines of what another poster asked, I'd like to have another 100 to 200 Watts of panels (with a larger controller of course) with the idea I would use enough watts daytime that the extra panel would be just to maintain my float cycle until dusk. Is this feasible?

It is really only a winter thing, and I'm crazy enough to move the spare panel to the pond in summertime to blow bubbles.

Does this seem feasible?


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## Jim-mi (May 15, 2002)

I have analog meters on my different PV arrays so I have often watched the "edge cloud" effect of the out put.
For the most part it is a short enough phenomenon that most reasonable--like your C35--equipment can handle the "short" overload.....
Next time you get a "popcorn" cloud condition go put your hand on the controller.......
How warm / hot is it . . . ???
If it is too hot to touch, it is time for you to get a larger capacity controller.......


who is it Don Hoo (sp) . . . ."Tiny bubbles" . . . . . . . .never mind . . . .


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## Rick (May 10, 2002)

Jim-mi said:


> I have analog meters on my different PV arrays so I have often watched the "edge cloud" effect of the out put.
> For the most part it is a short enough phenomenon that most reasonable--like your C35--equipment can handle the "short" overload.....
> Next time you get a "popcorn" cloud condition go put your hand on the controller.......
> How warm / hot is it . . . ???
> ...


I checked for overheating on the c35 in the past and it checked out good.


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## wy_white_wolf (Oct 14, 2004)

Rick said:


> I don't get these comments.... I have a 500 watt array, with 4 L16 RE 6Volt Trojans, wired as 12 volts. If I read this correctly, if I had just 2 of those batts my xantrex 35 watt controller might have issues keeping the batteries from blowing up?


.

Are those the 370n AH ones?

No because even if you had only 1 string your battery bank would be @370AH. 35 amps of charging would be under C/10. If anything with 2 strings you do not have enough to properly charge them.

WWW


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