I'm over my head

[Sunking]

Sunking and Live2bFree thank you. Now we are getting somewhere. What batteries do I look at. I've never even heard of 2v batteries, other than the little discs for welding helmets and calculators.

That is because you are stuck inside a 12 volt box. Lead acid batteries are 2 volts, not 12 volts like a 6-cell car battery. A 12 volt lead acid battery is actually 6 batteries in a common case. The issue is capacity vs weight. In a 12 volt battery the largest AH you can find is around 200 AH. Any larger and they become to big and heavy to handle.

12 volt battery is just fine if your application requires 200 AH or less. But what if you need say 12 volts at 1000 AH? A 12 volt 200 AH battery weighs around 120 to 150 pounds or roughly 50 to 60 pounds per Kwh of capacity. that means a 12 volt 1000 AH battery would weigh in around 750 pounds. Is that a problem for you? It is for me and the battery using public

True Deep cycle batteries are even heavier. You typical 6 volt golf cart battery weighs twice as much. A 6 volt 200 AH battery weighs as much as a 12 volt 200 AH starter or hybrid battery. They have a lot more lead in them. OK I think you get the point. Lead acid batteries come in 2, 4, 6, 8, 12, 24, and 36 volt cases. 24 and 36 are used in marine and trucking. 12 volt is a car battery and the box you are stuck in. Time to get out of that box.

Good Deep Cycle batteries come in 2, 4, 6, 8, and 12 volts. At 48 volt battery with 8000 watts of panels requires a minimum 1250 AH's. That is roughly 3600 pounds. You want to avoid Parallel battery strings. at 1250 AH's demands you use 2-volt 1250 AH batteries. Or as close as you can get. In this class you are talking a commercial battery like Rolls, Crown, and Trojan.Example Rolls makes a few that would fit the bill. Models like S-1725, S-1400 EX, and even a 4-volt 4KS25P. It would take 24 units in the 2 volt cells and 12 in 4-volt batteries. If you think these are large batteries think again. I served with the Silent Service and we used a 2-volt 10,000 AH battery in strings of 220 cells in series. Each cell weighed 1200 pounds. Those were for propulsion, and there are more for
communications and life support.

Back to your application. You will go into sticker shock when you find out what a 48 volt 1250 AH battery cost. That is what it takes to handle 8000 watts of power at 48 volts. Just the way it works. So I hope you understand my urgency when I say your batteries are way undersized. They can only handle 4800 watts being the AGM's that they are. I sugges tin the future you get away from AGM because they cost twice as much as FLA and only last half as long as FLA.

[Live2BFree]

Howdy, love your enthusiasm but I dont think any battery is currently going to give you 20 years in a daily cycled off-grid solar setup, hopefully one day

I agree, but unless I miss my guess the OP isn't really looking for daily cycle on his batteries. I think his intention--conceived improperly, as it were, when the build was started--is to have a backup source of power charged/cycled on occasion but to be primarily grid-tied. Given less than daily cycling and some improvements to his system, I'd bet he'd get ten years out of quality batteries if he maintains them properly...

[Sunking]

They're specialty batteries for the most part, used pretty heavily in the telecom industry among others. You'd do best if you could find a local telecom getting rid of used ones because they're often taken out of service at a specified date rather than based on their condition, and they've been known to be good for years and years afterward (because they've only been used for backup the same as you intend, without a lot of cycling).

Not a good choice. Telecom batteries are made like car batteries. They are not made for cycle service. Telecom industry goes on the Calendar life of the battery, not cycles. Batteries have two life specs. 1 is cycles, and 2 is calendar life. Whichever comes first.Telecom batteries have 100 to 300 cycles and 5 to 10 year Calendar life.

When they sell them to the public is to turn a liability into an asset. It cost them thousands of dollars to dispose of them and a mountain of EPA red tape. Or they can sel them dirt cheap to the unsuspecting public. Most of that cash goes to the engineer and warehouse personnel pockets. They get rid of a huge problem and put the monkey on the buyers back.

I know, I have worked in the telecom sector for 35 years in DC plants. We always cycled starting in October to make Xmas cash. Once you sign the papers, you own the problem.

[Brush Ape]

So if I use something like the Rolls S-1400EX in series, then I'll only need 12v? But don't run them parallel to make multiples of 12v? Weight is not an issue, I built the shed for all the solar stuff to hold battery weight. Also can I set them directly on a wood floor or do they need a table or a shelf?

[Brush Ape]

I just reread your last post. So I need 24 2v batteries? Can I build this 12v at a time? Or is it bad to add new batteries to batteries already in service as the older ones will drag the new ones down?

[Live2BFree]

To do it right you should add them all at the same time. That's the "perfect world" rule...but I long since stopped believing in perfection and started going with what I could actually DO. I can't spend thousands and thousands and thousands of dollars on a proper battery bank all at once, so I'll have to spread it out while trying to take care of my existing batteries well enough that they don't have too detrimental effect on new ones as I'm able to add them. You may be in the same circumstance. If you can build a proper battery bank in one lump purchase, that's how to do it. If not, it may not be "perfect" but I wouldn't let the quest for absolute perfection stop me from doing what I can, when I can.

As for a shelf, there are advantages to that. Having an air gap between the shelf and the floor may allow air to circulate better around the batteries, which would help to keep them cooler. I'd go with some form of wire shelf if that was my intention, maybe a stainless steel or coated shelf like they use in commercial kitchens. Keeping them up off the floor would help if your shed floods--literally--since every inch higher means less chance of having the water reach the terminals. It's unlikely your shed floods, though, so that's less of a consideration--and a little moisture on the floor isn't going to hurt anything.

I suspect the gist of your question, though, is whether it's okay to leave batteries on a floor because of the tales we've been told all our lives about how that's bad for batteries. The truth is that a hundred years ago, it WAS bad to leave a battery on the floor. The cases were made of wood back then and the acid would leak out over time. On concrete floors this was bad because it corroded the concrete and could also cause the battery to ground. Today's batteries, though, are perfectly safe on ANY floor because the cases don't leak unless they crack. They can, of course, crack if they freeze, or overheat, or simply are abused. All of those things are low percentage risks, though, as long as you take basic precautions against them.

[SunEagle]

I agree, but unless I miss my guess the OP isn't really looking for daily cycle on his batteries. I think his intention--conceived improperly, as it were, when the build was started--is to have a backup source of power charged/cycled on occasion but to be primarily grid-tied. Given less than daily cycling and some improvements to his system, I'd bet he'd get ten years out of quality batteries if he maintains them properly...

Maintaining FLA batteries may extend their life somewhat but after 5 years they will never get back to delivering 100% of the name plate power. So all calculations on what they should deliver will be incorrect.

The idea of keeping the batteries in a state of "suspended animation" until they are needed is a "pipe dream" based on today's technology. If you have the money to burn then go purchase the batteries but do not expect to get 100% out of them after they have passed the manufacturers rated life span.

[sensij]

I just reread your last post. So I need 24 2v batteries? Can I build this 12v at a time? Or is it bad to add new batteries to batteries already in service as the older ones will drag the new ones down?

You still haven't said what you are trying to accomplish with this system. You are grid-tied, so we are guessing that you want this as some kind of backup in case power goes out. Conventionally, you would move the critical loads to their own sub-panel so that the batteries were not powering every circuit in the house (expensive), and instead were keeping power to whatever is most important to you. Once you've identified those critical loads, you can figure out how much power and energy it takes to run them, size the battery to support it, and size the array to support the battery.

With what you have, there are two reasonable ways forward... add more batteries to take the extra current you are capable of generating, or remove / reorient panels to drop the charge current down to a level that will not kill your batteries. Choosing between those options requires more information than you have shared. Your next step should not be to spend more money, but to really assess what you want to power and for how long. Until you have that, you will continue to get mixed messages and advice that may be good or bad, but impossible to trust.

[Live2BFree]

What Sensij just said is by far the most intelligent response you've gotten yet. Reasonable, authoritative, lacking snark and most importantly--actually attempting to help you in some reasonable way without giving specifics that he can't give without a better idea what you're attempting to accomplish. Sounds like you would benefit from a clear explanation of your intended goal, rather than the rest of us simply guessing as to what that might be and trying to "help" accordingly.

[Brush Ape]

I'm looking for the house to be powered during grid down. The most important thing would be the well. Second would be freezers, I guess. Hot water heater is a huge draw, so I wouldn't be opposed to shutting it down and heating water on a fire. Lights, igniter on the stove, to be used judiciously. Anything with standby power or a stupid glowing light for no purpose would be immediately unplugged. Heat can come from the woodstove. AC isn't a necessity. I'd rather prolong the battery use. I do know this; The water heater and the dryer running simultaneously are a little over 10kw

[Brush Ape]

Oh, and the point of it in the first place was to be just a little more self sufficient. If we can sell some back, that's a bonus.

[Logan005]

Kitchen range, water heater and dryer should be converted to gas, or do not use when on backup power. 12 volts is the wrong voltage, you will need a 48 volt battery bank and you will still need to be careful how you use power. no electric heaters. Make coffee on a gas stove. use stove instead of microwave. use a smaller TV and less lights when grid is down. the stereo in many homes entertainment system can use in excess of 300 watt's, no halogen light bulbs. Best to use the newer LED bulbs, although CFL bulbs are ok too. Best of luck with it.

[Sunking]

You are Grid Tied? WTF are you doing?

You do know any power you generate on batteries is 5 to 10 times more expensive than buying it right? Nothing you are doing make one bit of common sense. You have pissed away a ton of money to only pay even more.What are you thinking?

[Raj]

Brush Ape, Your only problem is that your battery bank is about half the size it needs to be for an AGM bank. The rest of the system will work fine. If I were you I would contact Vmax Battery and tell them that you bought the wrong size battery. See if you can send them back and get 8 of the 350AH 12 volt AGMs. The 350s are 769 bucks, 6160.00 total and the best price I could find by far. It won't hurt to ask, if they won't you can still sell them as new to someone as another poster said. The 350s would be set up like your 175s, 2 strings of 4 for a 700AH bank that will take up to a 200 amp charge. You just need to check the strings once in a while to make sure the voltage is about the same. By the way, the 350AH batteries weight 185 lbs, so 2 couple of guys and a good 2 wheel hand truck are needed. Anyway, that's what I would do. Good luck on the return if you decide to go that direction.

[Brush Ape]

You are Grid Tied? WTF are you doing?

You do know any power you generate on batteries is 5 to 10 times more expensive than buying it right? Nothing you are doing make one bit of common sense. You have pissed away a ton of money to only pay even more.What are you thinking?

Here's what I was thinking when I made the decision to set up.
1. Remove some of our dependence on the power company, and therefore have more of our money stay home. Yes, I know the initial investment has to be recouped first. But every penny I get to pay for the system makes it closer to ours.
2. Sunny days recoup a bit faster through the sell feature.
3. Have a battery bank for grid down. We have hurricanes here on the east coast.
4. Add the generator in '16 to further make it a stand alone when needed.

What is it about this that I constantly amaze you with my apparently amoeba like thought process?