Solar powered AC air conditioning, a bummer or a challenge?

[billvon]

Eh, I'm sure I could do it, but for a permanently installed, expensive unit (which I'm desperately trying to avoid), stuff should be left to professionals.

Well, so should solar. But it sounded like you wanted to try this on your own. Good rule of thumb - it is ALWAYS, ALWAYS cheaper to cut loads first (most efficient A/C, more insulation, LED lights etc) than keep the inefficient loads and add more solar/batteries. So if you are really aiming to reduce power usage, spending your effort on installing the mini-split will pay better dividends than installing battery backed solar.

I will revisit this if a cheaper solution can't be found, but that would mean admitting failure first.

Admitting failure? Sounds like it would be a win to me.

[PhillyTitan]

So do it yourself. If you can drill holes and pull coolant lines/wiring you can install one. Once you have it connected call an A/C guy and for $99 he will purge the lines and charge it.

Eh, I'm sure I could do it, but for a permanently installed, expensive unit (which I'm desperately trying to avoid), stuff should be left to professionals. I believe caution should be exercised when installing permenent air conditioning units without a permit and a HVAC certified installer.

I will revisit this if a cheaper solution can't be found, but that would mean admitting failure first.

[billvon]

Yep. A mini split is not viable. When I looked into those last year, I seem to remember astronomical charges for installation.

So do it yourself. If you can drill holes and pull coolant lines/wiring you can install one. Once you have it connected call an A/C guy and for $99 he will purge the lines and charge it.

[Sunking]

That is not the case for most battery banks for communication facilities where the primary power sources are grid and generator.

Not the case for any of them. Stationary Batteries for Telco are designed like a starting battery and discharged at C/4 and higher. They are used for emergency stand by only which is rare. When commercial power goes out, the generator starts and takes over within minutes. If the genny fails to start the site will crash in an hour or less from over heating even if it is -40 below zero outside. Built thousand of telephone office and cell site plants. Press those batteries into cycle service and you wil only get a couple hundred of cycles out of them

Some cell facilities do use off-grid solar power, in which case they would also use deep cycle

Yep built a few hundred of them. Most usually have 10 day reserve capacity and over sized panels plus generator. However they do not use batteries I speak of here on the forum. They are industrial grade. Not so sure if salvaged or replaced batteries would be a good idea as they will have already had 10 years of cycle service on them, or failed in service. They are only warranted for 10 years.

Here is a nasty secret folks should know. Utility batteries are large and require EPA permits to trace then from Cradle to Grave. It cost utilities a lot of money to remove them, store, and dispose of them. To make up from some of those losses, and more importantly relieve them of the EPA liability and fines, is they find a sucker to buy them. Once you sign those papers, it i snow your problem and liability. If there is a spill, fire, or accident with them, you wil be held responsible. Dump them illegally, they will trace them back to you and hold you accountable for the clean up and heavy fines plus any criminal charges locals will hit you with. .

[PhillyTitan]

for a small off-grid air conditioner, you need to look a what are called "Mini-Split" systems, some even have a vari-speed compressor and fans which will greatly reduce your power needs. But they are not cheap.

Yep. A mini split is not viable. When I looked into those last year, I seem to remember astronomical charges for installation.

[Shockah]

The article makes it clear that the used batteries in question were in cycle rather than float service and so can be presumed to have been designed for cycle rather than UPS use.
That is not the case for most battery banks for communication facilities where the primary power sources are grid and generator. Some cell facilities do use off-grid solar power, in which case they would also use deep cycle rather than UPS batteries.
The people who got those batteries cheap (less than salvage value?) were quite fortunate.

Yah,,, I inquired about the purchasing 276 batteries which were removed.
I got a "we'll look into it" from the DOT, but never any follow up.
Obviously some insider pulled of a good heist.

Then I later came across this guy who bought 7 "NEW" @ $20 each from the maintenance contractor...

[Mike90250]

for a small off-grid air conditioner, you need to look a what are called "Mini-Split" systems, some even have a vari-speed compressor and fans which will greatly reduce your power needs. But they are not cheap.

[inetdog]

The article makes it clear that the used batteries in question were in cycle rather than float service and so can be presumed to have been designed for cycle rather than UPS use.
That is not the case for most battery banks for communication facilities where the primary power sources are grid and generator. Some cell facilities do use off-grid solar power, in which case they would also use deep cycle rather than UPS batteries.
The people who got those batteries cheap (less than salvage value?) were quite fortunate.

[Shockah]

I am going to stick my neck out with an educated guess or bet. I bet those installations are at altitude?

Both are within 2 miles of shore line.

The 7x35ah AGM is on the east coast of the island. I believe his cycles are less than 20%, but it is used nightly, as he lives in an off-grid shack.
He acquired the batteries new, in 2006, from the vendor who was maintaining the emergency call boxes.
( That is a story in itself. )

The other is on the west coast of Oahu, the hotter side. It is an off-grid home that uses 2 FLA former fork-lift batteries.

[Sunking]

Although that is the rule, I personally know of 2 exceptions on Oahu where the off-grid batteries are 7 years and still going...
and one of those is a bank of 7x 35ah AGM batteries in parallel on a bus bar. Had me swallowing my words when I critiqued his system.

I am going to stick my neck out with an educated guess or bet. I bet those installations are at altitude?

[Sunking]

Hey Sunking, I really mean types of batteries not brands. I really have no knowledge at all about the subject, only that AGM is supposedly very good and low on maintenance.

That is a much deeper subject, but I will try to KISS it. (Keep It Simple Stupid)

Lead acid batteries fall into two groups of Flooded Lead Acid (FLA) and Valve Regulated Lead Acid (VRLA) In those two groups of FLA and VRLA are three sub categories of Starting Lighting & Ignition (SLI) Hybrid which are marketing names for Golf Cart, Floor Machine, RV, Marine, and Leisure.. Last in line are Deep Cycle batteries which is what you want.

SLI batteries are designed to crank engines and be recharged very quickly. They are made with very thin spongy plates to increase surface area which lowers internal resistance. That low resistance is what is needed to provide very high current required for starting engines, and then be recharged very quickly. If pressed into cycle service will fail only after a few cycles. Those thin plates will sulfate and dissolve quickly when deeply discharged and charge slowly. Bottom line do not use SLI batteries for cycle service. You can spot a SLI battery real fast if you see a spec called CCA or cold cranking amps. They will not have a Amp Hour Rating, only CCA.

Hybrid batteries are a cross between SLI and Deep Cycle batteries trying to be the best of both worlds but fall short in either applications. They have thicker plates than SLI batteries so they can be cycled and last longer than SLI, but not as thick and heavy of a plate as true Deep Cycle. They do have a place in RE applications. They can provide higher discharge and charge rates than deep cycle batteries because they have more but thinner plates than deep cycle. Thinner plates mean more surface area and lower resistance. So they can be used in places where you have to use high charge/discharge rates in excess of C/8 up to about 1C in some types like AGM. The trade off is cycle life is sacrificed. Another use for hybrid batteries is their various marketing names like Golf Cart, Floor Machine, RV, Marine Deep Cycle. A dead give away is they wil have a Spec called RC = Reserve Capacity meaning how many minute the battery can deliver 25 amps. MCA or Marine Cranking Amps, along with Amp Hours. They are available in both FLA and AGM models

Deep Cycle batteries are the long lasting types and they are not created equal. True Deep Cycle batteries have fewer but much heavier thicker plates thant can be cycled many times. The thicker plates reduce resistance and limits charge and discharge current to about C/8 where C = the battery 20 hour amp hour rating. So if you have a 100 AH battery they can only supply around 12 to 13 amps without significant voltage drop. But those thick heavy plates last a long time. Th eonly spec you will see published on a True Deep Cycle battery is AMP Hours usuall the 20 hour discharge rate. High end batteries will publish Amp Hours at 100 down to 1 hour discharge rates. A Deep Cycle Battery will never have a CCA, MCA or RC spec. Only Amp Hours.

Need some more discussion on FLA and VRLA. FLA is just what you think, a flooded battery that you have to add water too. They are the least expensive and last the longest period. In the VRLA family are Absorbed Glass Mat (AGM), and Gel Electrolyte. No need to discuss Gel batteries as they are not good candidates for RE applications. Gels are used for emergency standby applications and that is it so no more discussion. AGM are excellent batteries sort of. By design they have very low internal resistance and the plates can be made of pure lead which contributes to low resistance and small spaces. They can be charged/discharged at very high rates which has usefulness in RE applications. IMO they are niche application batteries. For example planes and mobile applications where spillage cannot be tolerated. Extreme cold of arctic and ant-arctic of 50 below zero, remote locations, or where very high charge and discharge rates are required. Th ereason they are niche application is cost. For a given capacity they cost twice as much as FLA and only last half as long. So in the end they cost 400% more than FLA and you had better have justification to spend that extra.

[PhillyTitan]

Then i would say, just quit now. Any neophyte trying a MAJOR project, is going to make mistakes. YOU open the fridge 3x a day. But the cat gets in there 7x a day and there goes your power budget, along the the primo brand batteries. If you leave the porch light on one night because you were sick and forgot.... Mistakes happen, and you need to design your system to be resilient enough to not die from the first one.

The experiments have already begun. I've already purchased solar lights for the shed and front porch. Flood lights will be replaced by a $50 system.... I have already decided to run the small appliances and interior lights and whatnot on a smaller, separate 12V solar system. And I'll do some experimenting with it, but I've already learned enough to know that the longevity for it is indeed possible.

The energy hog is what I'm hoping to find a solution for. If one can't be found then I may not even start building.

[russ]

The most important information to share about solar may be energy conservation, I don't remember seeing that here yet.
Abe

Read a small amount on the site and you will see that conservation is pushed very much.

[Mike90250]

...And that's a nugatory on the battery thing. That is the one component that I don't want to experiment with. Thus I'd like some more input on the battery.

Then i would say, just quit now. Any neophyte trying a MAJOR project, is going to make mistakes. YOU open the fridge 3x a day. But the cat gets in there 7x a day and there goes your power budget, along the the primo brand batteries. If you leave the porch light on one night because you were sick and forgot.... Mistakes happen, and you need to design your system to be resilient enough to not die from the first one.

[K7ABE]

Hey Sunking, I really mean types of batteries not brands. I really have no knowledge at all about the subject, only that AGM is supposedly very good and low on maintenance.




Abe I've said this before, but I don't mind saying one more time. It's the individual components that I'd like to keep down in cost. For instance, a 24VDC 12,000 BTU air conditioner would be at least $1700.00 (<-- the only one I found with a price tag on it). Or a solar array professionally installed for $10k. A few batteries for a couple hundred each is not an extreme cost. The first question on this thread was is it viable to have a sustainable working system that won't break the bank when one of the individual components fail.

Yes and a good high efficiency 24V refrigerator is about $2500. I use a lower cost, less efficient refrigerator and extra solar panel to cover that. Early I was advised to build the biggest system possible within my means, all with one charge controller & 1 and inverter. I found using smaller systems with interchangeable components works better for me, if a charge controller goes out I have one on the shelf. This also allows many other flexibilities within the systems. The batteries are the only part of my system that are individualized for specific task. The most important information to share about solar may be energy conservation, I don't remember seeing that here yet.
Abe