walmart & sams club batteries

[sunbelt57]

Has anyone priced Walmart or Samsclub batteries lately? The only posts I could find are from 2005 ($59 for ~100ah). I saw on this forum someone saying that deep cycle batteries from these stores are fairly good to use for solar/wind applications. I looked on the Walmart website and they only had 2 - an agm and a gel cell. The sams club don't give you prices unless you have a membership card and sign up.

[zap]

The sams club don't give you prices unless you have a membership card and sign up.

Sam's Club showed me a price after I typed in a zip code and chose a store... no card... no sign up.
Energizer 6v G2C- $81.83

[theshadownose]

Omaha also 81.83  Energizer Brand 

6 volt
Minutes at 75 AMPS: 107
20 AMP Hour Capacity: 208
Reliable Cycling Ability
Deep Cycle
Gang Vent Design
Polypropylene Ribbed Cas

[sunbelt57]

I still couldn't find any batteries using the website so I called 'em. Yep, they got plenty in stock. 220AH 6v for ~85 bucks. I have to drive a ways to buy 'em because I am using my friend's account and there's no store near here.

[gww]

I have to buy them too.  What is the core charge? Does anybody have better sugestions? 
Thanks
gww

PS
Does sams club ever have sales and are they worth waiting for?

[phil b]

The core charge at Sam's was $9.00.

Look on top of the batteries. They have a dime sized sticker with the month and year they were made.
Even a few months difference in mfg. date, IMHO, tend to charge and discharge a little differently on the same system. (On mine that is)

Also, look at the manufacturer's name. Mine have all been made by Johnson Controls, then relabeled Energizer.

I want my batteries to be as close to identical quadruplets as I can get them, especially at almost $100 per battery out the door.

[bob g]

you definitely want as close to the same build dates, and the freshest batteries you can get..

i can't tell you how many times i have had to refuse batteries that have one or two that have been on the shelf for a year or more, not having been properly rotated.. those batteries always fail first in parallel strings and cause damage to the newer batteries in series strings... i got to where i would not accept them for use in hd trucks because the failure rates were almost always one battery in a group of four within 60 days.  worse in the winter months.

bob g

[sunbelt57]

OK let's say I found (4) brand new 6v batteries, bought them and used them for 6 months. Then I went back and bought (4) more new ones and put them in parallel with my other 4 in series for my 24v system. Would that be OK? If so, what about adding 4 more in a year?

[DamonHD]

I don't think you'll get complete consensus, but my understanding is that having different ages in parallel is far less bad then having them in series, but also I think that you should keep the basic format the same, eg flooded with flooded, gel with gel.

I have an old 100Ah 12V gel SLA in parallel with 400Ah of new SLA gel for example.  I have tweaked the wiring a little to try to be kind to old and new.

Rgds

Damon

[Mary B]

I am adding 4 more 6 volt 232AH bats in parallel tomorrow with my 3 month old string.

[gww]

Does sams ever have sales and if so how do you find out about them?  I need to buy 16 or 24 of them.  I haven't decided yet.  Also is the 20 hour rate to 50%?  I hear of poeple with 50kw system and am trying to figure what this means in useable power 20% or 30% etc. discharge rate.  To figure that do you times the 208 amp hours by the voltage?  I hope this fits with this post subject.
Thank you
gww

[bob g]

20 hour rate is till dead!

as for usable capacity is all depends on what you ascribe to when it comes to proper and efficient use of the batteries.

there are those that just need maximum amp/hrs output, and will trade off lifespan to get it,

there are those that want to maximize lifespan and are willing to go with less amp/hrs to get there, or they will put in massive amounts of battery capacity to start with.

and somewhere in the middle are those that weigh all factors against the cost of the energy needed and will arrive at a charging regime that maximizes efficiencies overall.

so the correct answer is?   tada... there is no one correct answer that will fit every application.

going off on a tangent now...

the biggest mistake folks make is starting at the wrong end of the equation.  they start out building a windgen for instance that is either too small to be useful, or too large to fully utilize, rarely correctly sized for the load and the  wind resource... unless they do a lot of homework to start with.

same goes with solar panels, generator sets, hydro installations, and buying a battery bank.

taking a breath and a swig of my coke...

far better to first, before you plan anything, and certainly before buying  batteries, is to get an intimate knowledge of your loads, all of them, can you economize? can you schedule? can you reduce with upgraded appliances? etc etc... then lay out a 24 hour load chart to see what your average loads are, when they are below average, above, and what the peaks are?  for how long and all that you can learn..

once you know that, the next step ought to be, taking a realistic look at the power sources available to you. if it is wind, you will need to accurately measure and determine what the wind resource really is? not what you think it is!  you will probably want to have a years wind charted in some manner to determine just what you might be able to harvest,, then you can size a windgen to optimize recovery of that resource... and from that have an idea how much  charging ability you have..
same for generator sets, hydro or solar

once you have the loads figured out, and the charging capability figured out, it is then very easy to determine the battery capacity needed.

the last thing you want to do is pay a small fortune for a large battery bank and then be faced with finding out you don't have enough charge capability to maintain them properly... undercharging is a killer of batteries.

probably more than you wanted answered?  i wrote this more for my own benefit, in an effort to get my head around why there are so many issues with battery banks with so many people...

i include myself in that group, however i have not spent my wad on batteries yet...

bob g

[ChrisOlson]

I hear of poeple with 50kw system and am trying to figure what this means in useable power 20% or 30% etc. discharge rate.

I like to use kW or kWh to measure the size of a battery bank because it provides a measure of energy storage independent of voltage.  Take a 200 ah @ 20hr rate 12V battery, for instance - I call that battery a 2.4 kW battery and roughly 40% of that is usable power.  So it would be able to store 960 watt-hours, or .96 kWh in a battery bank.

Amp-hours is a little more confusing because it doesn't mean much without a voltage stipulation.  A 1,000 ah 12 volt bank is only half the capacity of a 1,000 ah 24 volt bank, and so on.
--
Chris

[gww]

BoIb G
I have no ideal what I am doing.  I did it backwords.  I was bored so I built 2000 watts panels.  Then I bought a used 3648 dual outback inverters and all the bells and whistles.  Then I built 2 hugh p. 8' 500 watt turbines.  Then I bought a morningstar 60 charge controller.  Then I thought thats alot of inverter and I aught to atleast try to fill the outback mx 60 charge controller so I bought 6 mx 235 watt panels for anouther 1400 watts.

I am now trying to work out dump load for the turbine morningstar combo and the proper battery amount for my charging cappasity.

I was originally going to buy the bare minimum battery amount to run the inverter and then feed to the grid and just run the batts in float and just live with any outages with no power.  I read my power companies aplication prosess and they require all componants of the system to be bought, no homemade.  Thus I change my plan.

I would now like to use what my system provides with heathy batteries to supliment my wastefull power use.  Then if I add more I will worry about that then.  It might be so monumental bringing this all on line that I never get bored again.  Towers, solar racks, wiring, ect ect.

As you can tell I have no ideal what I need to do this.  How many batteries for my charging capabilities with the intention of using daily say down to 20% discharge.  I also believe that my homemade solar won't last that long but panels seem to be as cheap as I can build them for as I have used every bit of free glass I had and with cell breakage and no frames it still cost me 50 bucks for 60 watts and I paid $0.92  per watt for the mx panels.  they will cost more due to not having cords on them. As my panels go bad I will probly replace with new.

What amount of batts do I need so that my previous work can be used?

Thanks for any help you give me.
gww

[gww]

Chris
It was actually your responce in a thread that made me want to understand what a 50 kw bank ment and what it would do.  Help me with mine If you can.
Thanks
gww

[ChrisOlson]

Well, I'll try to explain.  But sometimes I'm not too good at it, and I have no experience with grid hybrid systems.  Only off-grid.  So here goes.

The batteries have a voltage and an amp-hour rating.  Multiply those two and you get a kWh rating.  But that's pulling the battery completely dead, and it doesn't maintain nominal voltage during discharge.  So I use 40% of what the kWh rating is to determine approximate usable power that you will get out of the inverter to run your house.  With my inverters and batteries this comes out really, really close to what I actually get in actual AC power out of the inverters.

The next step is figure out what your usage is in your home.  Let's say it's 10 kWh/day.  You have to put 15-20% more into a battery than you get out of it.  Figure 20% so you got a little room to play with  - your system needs to generate 12 kWh/day to supply the 10 kWh your house uses.

Going back to my previous post mentioning the 200ah x 12 volt battery - it stores about .96 kWh so you will need 10 of those to store one day's worth of power for your home.

Does that make sense?
--
Chris

[birdhouse]

gww-
being a 48v system, you'll need to buy those sams batteries in groups of eight.  so your stuck with buying 8, 16, 24, 32 ect... 

judging purely from your input devices (wind and solar), you could have a max of ~3.4Kw of solar coming in, and ~1kw of wind coming in.  i think i'd be looking at buying 32 of those batteries,  just to keep a fairly rounded system.  32 batteries @ 220 ah in a 48v system is a 42.2 Kwh bank.  using only 40% of the capacity gives you ~16.8Kwh of usable juice.  that's nothing to shake a stick at! 

above is just an example of what i would want from a system of the size of input you've got going on.  @ ~$85 a piece, thats $2700 plus core charges.  that sounds like a lot, but when you factor how much you've already got into your inverters, charge controllers, panels and turbines, it really is a smallish percentage. 

adam

[bob g]

if you have 10kw/hrs worth of loads to service per day
and accepting Chris' 20% more needed to charge the batteries
your need is now 12kw/hr per day as Chris stated

now in order to provide that load and the charging efficiency, you will need 12 of he .97kw/hr batteries, and then only if you plan on using them up each day...  which is probably not what you would want to do.

again using Chris' suggestion of using only 40% of the banks capacity
you would then take the load or 12kw/hr per day and divide by 40%
which come out to 30kw/hr battery bank or about 30 of the example batteries... now lets proof that to make sure.

a 30 kw/hr battery bank, and we only want to use 40% of its capacity per day, so 30 x 40%= 12kwatts,  so we have proven our math.

so what this means is this, if we use the batteries to provide for our load for the day and have no source of charging coming in, then we will need a 30kw/hr bank to cover the load for that day, and not deplete it under 60% state of charge, this should make for a decent lifespan.

now we can reduce this battery bank size if we have other sources of power coming in, if we have a 2kwatt pv capability and have 5 good hours of sun, then in theory we are making 10kw/hrs of power per day. if it is used to support the load, then obviously our battery bank only needs to be about 2kw/hrs if we have another way to charge it? 

this is a basic example, obviously we have other considerations, such as how many days do we expect to have no sun with a pv system, do we have alternate power sources, like wind?  etc.

if all you have is solar, and you are offgrid, then you probably ought to have a large bank, maybe 3days worth or more in cloudy area's, 3 days worth of power might mean a 90kw/hr battery bank if you want to keep to the 60% depth of charge limit.

we need more info to get a more definitive answer

bob g

[ChrisOlson]

Having too much battery capacity for your charging capacity is just as bad as not having enough battery capacity - it's going to put hours on the generator.  I think it was mentioned that this is actually a grid hybrid system, and that's where I get a little lost because now you have start justifying cost.  And there probably is no generator, so having a bank that's not sized right does not carry the consequences that it does for off-grid.

So that's where it gets really confusing for me when we're dealing with a system that can use grid power - how much money can you justify spending on a battery bank?  Really, all you need is enough for backup in the event of a power outage.  And just set up the Outback to flip back and forth from RE power to grid power, depending on the availability of RE power.  You don't have to put it into "sell" mode.
--
Chris

[gww]

Chris, adam and Bob G
I tried to answer last night but I got kicked off the board and couldn't reconnect.  Let me see if I got it close.  If I bought 24 200 amp hour batts. I would have about 50 kw bank.  If I make 10 or 11 kwhs per day I would have a good charge rate during the day.  This production might be low or high counting ineficiencys but probly close enough.  If I only go 20% discharge I have 10 kwhs to play with.  If I use my inverters as chris says, carrying the load and suplimenting with grid power.  Therefor once charged in the morning I could carry most loads up to charging rate from my panels and turbines during the day with night time discharge only going to 20%.  During cloudy and gridless days If I live without power It would not stess the batteries.  Does this seem like I got it right?  Secondly if I get smart enough to set my charge rate a little lower I could run low loads and charge during the day and maby not produce more then I can use at one time Therefor keeping all my power in the batts rather then shuting down the panels output.  Have I got this right?  If I got this right could I go with say 16 batts for 38kw bank and between charging and loads use all my power without stressing the batts?  I have more loads then I will ever cover and the hard part would be setting the charge rate to garrantee full charge of batts every day. The outback will want to do a complete charge from the grid but I believe has numerous settings for controlling this.   I really apretiate all your help.
Thanks
gww

[ChrisOlson]

If I use my inverters as chris says, carrying the load and suplimenting with grid power.  Therefor once charged in the morning I could carry most loads up to charging rate from my panels and turbines during the day with night time discharge only going to 20%.  During cloudy and gridless days If I live without power It would not stess the batteries.

gww, like I said I don't know a lot about grid interactive systems because I've never worked with one.

The important thing to remember is that roughly 20% off the power you generate with your panels and wind turbines is wasted in battery charging and inverter losses.  For every 1 kWh you put in, you will get roughly .8 kWh of energy to run your house.

It seems to me that the Outback inverter has a grid interactive battery backup mode in it.  The Outback will power what loads it can off of RE power until the batteries fall to a voltage level that you feel is getting too low, then it will automatically switch the loads from battery power to grid power (as long as the grid power is hooked to its AC input).  When the RE system brings the voltage back up to a point that you like, it will automatically switch back to battery power.  This does not require it to "sell" to the grid so you don't have to deal with your utility and all their requirements.

I think the question is, how long do you want to be able to run on battery power with a fully charged bank, and no incoming RE power (say, in the event of a power outage)?  Maybe somebody who is familiar with how to size a grid interactive battery backup system will chime on how to do that.

The above scenario just makes more sense to me than buying a large battery bank like somebody who lives off-grid has to have.  Batteries are very expensive, and for somebody who lives off-grid end up being the highest cost item over the years to maintain.  I think as long as you have grid power that you could use your RE capability to offset your grid power costs, have a backup for when the power goes out, and spend less money on batteries than those of us who live off-grid have to spend to keep our lights on.

As an example, I expect that our batteries alone will cost us roughly $1,000/year and many folks that have grid power and an energy efficient home will not spend much more than that in a year's time for their power bill.  So it seems to me that keeping your investment in batteries to a minimum will give you a higher return on your investment in RE equipment.
--
Chris

[madlabs]

I think Chris is spot on, to me batteries are the ball and chain of RE. My neighbor just screwed up and discharged his to dead, dead, dead. We hadda haul 'em to my place (since he can't equalize) and charge the crap out of them. Lucky it was only 4 batts. And the price of batts keeps going up.

Jonathan

[bob g]

gww

correct me if i am wrong, but have you not abandoned the grid tie scheme because of all the flaming hoops they utility wants you to jump through?

knowing if this is the case or note really makes a difference.

regarding batteries, i guess i look at them differently than some folks
while they can be seen as the ball and chain of a system, i choose to see them as an integral part of the system, and part of the consumables, much as i would view diesel fuel for a generator.

when you look at it that way then you are free to wrap your head around getting the best use of them, and that does not always mean getting the most years out of them...

just like diesel fuel you want to get the most btu's of useful work out of every gallon, you want to get as many kw/hrs out of the batteries as you can... that might well mean that they last 7 years instead of 10 years or somesuch.

again just like diesel fuel sizing is important, it does no good to buy twice as many gallons of diesel than you can effectively use if you can't store it properly or treat it properly.  the same goes for batteries, we don't want to buy twice the bank that we can manage and maintain properly.

i have long been a strong proponent of the 50/80 charge regime, this will give you a working 30% of the capacity of the battery bank for you to use. this regime has been proven (at least for flooded cells) to return the highest charge efficiencies, and the most kw/hr's output of a battery bank over their lifespan..  adopting this strategy does two things.  it clearly provides the info needed to size the bank for your load, tells you what you need to do the charging, and will give you a realistic idea as to both lifespan of your batteries and most importantly the real cost per kw/hr.

without narrowing down all but one variable, i see no way to accurately answer the question... trying to answer a multivariable question with more than one unknown variable is going to give you an answer that if correct is more based on luck than any thing else, and likely the answer you get will lead you far astray and cost you money in the long run,, if not the short.   so....

#1 variable :offgrid or ongrid?  a real biggie here!
#2 what is your average loads in kwatts per day?
#3 what is your peak load during the day?
#4 what loads can be scheduled?
#5 what is your average charging capability ?
#6 what is your peak charging capability?
#7 what are you using to recharge with, if solar how many hours per day?  how many days of sunshine per week? etc

and there are more ...

the more of these that you can accurately answer, the more information you can plug into established equations, which will then give you a group of answers, like

1.what size bank you will need
2. what will that banks first cost be
3. what will the cost per kw/hr be as related to the battery
4. what will i get in useful kw/hrs per day out of the batteries
5. what will i have to provide to the battery bank each day, and where
will it be coming from.
6. how long should i expect them to last?

and more questions will come up and you will have the information to answer them fairly accurately.

otherwise it is a crap shoot!  and just as gambling you can step up to the table and loose your lunch money.

bob g

[ChrisOlson]

BoIb G
I have no ideal what I am doing.  I did it backwords.  I was bored so I built 2000 watts panels.  Then I bought a used 3648 dual outback inverters and all the bells and whistles.  Then I built 2 hugh p. 8' 500 watt turbines.  Then I bought a morningstar 60 charge controller.  Then I thought thats alot of inverter and I aught to atleast try to fill the outback mx 60 charge controller so I bought 6 mx 235 watt panels for anouther 1400 watts.

I think it's prudent to go back to this because it provides much of the information needed.

In our area, we get average 3.2 kWh/kW of installed solar capacity with solar May to September.  From September to October and March to April that drops to 2 kWh/kW of installed capacity.  From November to February we get basically nothing from solar - average is around 1 kWh/day/kW of installed capacity.

This can vary by location and local weather conditions - it should be easy to figure this out based on solar insolation maps and/or others around you that already have solar arrays so they can tell you how they perform.

Wind power is a huge unknown.  Most people over-estimate how good their site is for wind power and it ends up being a total disappointment.  So basically, I would consider that the two wind turbines will hopefully just fill in a few gaps when the sun doesn't shine to provide some extra boost.  But don't count on it until you run those turbines for a full year to see how they perform on your site and your tower.

I think what I would do is figure out how many average kWh/day that you should get from your solar during the best time of the year.  And size the battery bank in usable storage capacity (measured in kWh) to 80% of what those panels can make in one day.  In theory, this will cycle your batteries down to 50% SOC on an average day, which should not hurt them at all, and with the Sam's Club 6 volts should give you at least 900 cycles before they start to show their age.

On a less than average day, hopefully the wind will kick in and keep everything humming along until the next nice solar day.  On a really good day dump power into water heating or something equally useful.  You have dual inverters so you can stack them for 120/240 - we have the same setup and 240 volt AC water heating is VERY efficient (close to 95% efficient).

On several bad days in a row, the inverter will revert back to grid power.
--
Chris

[bob g]

I was originally going to buy the bare minimum battery amount to run the inverter and then feed to the grid and just run the batts in float and just live with any outages with no power.  I read my power companies aplication prosess and they require all componants of the system to be bought, no homemade.  Thus I change my plan.




gww

this part of gww posting gave me reason to ask more questions, the answer he gave to those questions probably ought to be viewed under a different lens given he has changed his mind about grid tie/sell back.

so that is why i think it prudent to start back from square one, first determine what the real need is, grid tie or off grid?  to me this is like a fork in the road, while many of the questions might be the same, (down each fork) and the answers to many of the questions might also be the same, the equations used down each fork have some differences.

bob g

[ChrisOlson]

this part of gww posting gave me reason to ask more questions, the answer he gave to those questions probably ought to be viewed under a different lens given he has changed his mind about grid tie/sell back.

That's where it gets confusing for me.  There's differences between grid-tie/grid interactive with battery backup, and off-grid.

The Outback inverters can do all of them.  But I think the battery needs are different for each one.  It would be nice if someone with a grid interactive system that doesn't sell back, but provides battery backup in the event of a power outage would chime in with their experience on it, and what works and what doesn't.

If this was off-grid I could tell you what you need to make it work without putting a lot of hours on the generator unnecessarily.  For grid interactive I'm a little in the dark (pardun the pun).
--
Chris

[gww]

guys
I love you for the time you give trying to help.  I would have gotten back sooner but my laptop that is a week old took a crap on me and I've been working on it all day with no luck.  Not that you need to care but I'm on a laptop due to not being at home due to my first grandbaby being born at 4:47 am.  8 lb girl.  back to the subject at hand. 

Bob G
I thought I had answered a couple of you questions above.  I am not smart enough on computers to move text like you guys do so I'll have to recap

I wont be grid tied but will be grid interactive.  I use 25 to 33 kwhs per day.  Cris hit my charging capabilities and I'm willing to go with his sunlight hours also.  Im in mo. and mine might be alittle more but I don't trust my homemade to last.  I'm willing to compleetly discount the wind tubines at this time.  I have read alot on the outback forum and believ my inverter capabilities are interactive with the grid as chris describes it.  I also should be able to adjust my charging rate if it helps me to run loads rather then shuting down the panels.

although it might be nice to have power when the grid is down, I have always survived with none now.  Ive always had generators and have never, not once, fired it up during an outage (to lazy) and If we were out a week or so I would have to use the gen anyway.  So cloudy days I will just use the grid.  I get urges to build even bigger turbines before I've even flew the ones I have. (not going to do it though) I'm about to be retired and my income will go down so insted of saving now I am playing.  In the prossess of playing I would like to get something out of it.  I guess I want to use as much power as I can make to supliment what I'm using from the grid but don't plan on having to relie on it.

I would like to get the most use as cheaply as possible.  When I know what things work like someday I might exspand.

Johnathan
thanks for the veiw point.

Bob G I can't really anwer alot of you usage questions as I am in indiana and can't move home till nov. 2013. I don't have acess to measure so I'm using my charging abilitie and componants to figure where to start on my bank.

16=19968 20%=4000w batts or 24=29952 kw 20%=6000w or more?  I won't think you are trying to hurt me if it works out badly,  I gotto start someplace and your best is good enough for me.  Now I'm going to reread your post ten more times and see what I can learn.
Thank you
gww

[ChrisOlson]

Im in mo. and mine might be alittle more but I don't trust my homemade to last.

gww - in Missouri you'll definitely get more from your solar in the winter time than we do up here in the overcast (most of the time) north.  I would think that 1 kW of installed solar capacity is going to do at least 60 kWh/month during November/December/January for you, where we're lucky if we get 35-40.
--
Chris

[gww]

Chris
I don't mind derating and hoping to be plesantly suprised.  I used some of my homemade though a cheap grid tie inverter in iniana but only got about 30% of unloaded power.  I was getting 248 watts before the inverter and only 120 watts out of it.  350 watts worth of panels.  I only checked one or twice though.  Just a test,  I don't know how the outback works yet. unloaded most of the panels seem to hit the mark.  we'll see.
Thanks
gww

PS how many batts do you think in a wild guess sort of way?

[ChrisOlson]

The panels were running at 70%, which is not too bad.  On a nice day they might hit 85%.  On a perfect day (which doesn't happen very often) they'll probably hit rated power.  On the other hand, 248 in and 120 out is pretty dismal.  I'm assuming that inverter had to run quite hot.  The Outback, pulling from batteries, should deliver roughly 80% of what you put into the batteries.

Rough guess with 3.4 kW solar?  I'd say a conservative estimate would be 15 kWh/day on average in the summer (that's just a guess based on what ours do).  You need to calculate the equivalent hours of sunlight per day that your area gets to have that estimate closer.

But assuming 15 kWh/day, that comes out to 22 of those Sam's Club 225 ah 6 volters.  Since you got 48 volt you have to buy them in quantities of eight, which means 24 batteries.  That is using my method of how I figure it out - and that assumes discharging the batteries to 50% SOC every night - and you'll get 12 kWh out of the inverter for the 15 kWh into the batteries.
--
Chris

[gww]

Chris
I was hoping you would say 16 as $1600 isn't as hard to swallow but 24 it is.
I don't like the 50% dicharge.  Anouther thought,  I wouldn't mind running the batts in float all the time.  Say set the inverter to float at 54 volts or what ever the batt maker says and just using the re that is made when its made.  I guess my question would be that when the panels produce at times more then my loads are drawing the panels shut down.  I wonder if battery life would add more value then lost watts from the panels?  The only reason I can see discharging the batts at all is to use watts I can't use middle of the day.  I should have plenty of latitude with 24 batts.
Thanks
gww

PS
I always used 3.6 hours sunlight and then derated by 30% for year round production as a general rule of thumb when I play with numbers.  = 8568 watts  I have no practical experiance.

[ChrisOlson]

3.6 hours of sunlight would give you 3.6 kWh/day/kW of installed capacity, which wouldn't be all that different from our location in mid-summer.

16 batteries would also work fine.  I think you have more charging capacity than 16 batteries can take - but if you come up with a "dump" scheme (like heating water with 240 volt power from the inverters), you can do it with 8 batteries.  Just that with 8 batteries, or 16, you won't have the reserve to make it thru a couple cloudy days without the inverter switching back to grid power because the voltage got too low.

24 is the maximum for your charging capacity, the way I see it, during the best solar periods of the year.  In winter you don't have enough charging capacity for 24 so the inverter would switch to grid power more.  That is basically what happens with off-grid too - with the exception that the "grid" is the generator.  And we accept that it's normal to run the generator more in the winter.

So 16 batteries - I see that as working fine, except that due to being a little short on storage capacity you may be forced to switch the loads back to grid during the summer, when if you had the storage to match your generating capacity you could probably almost eliminate having to switch those loads to grid during the best energy producing periods of the year.

Does that make sense?
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Chris

[gww]

I am going to have to go back to the out back site and or manul and refreash on the outback inverter.  I was under the assumption that I really didn't have to match the loads in the sub-panel to have an all or nothing situation.  I thought if you were making 100 watts above charge rate, that it would seemlessly feed you 100 watts and grid 400 watts to a 500 watt load and still be charging your batts at the charge rate you set.

I am nowhere near being able to come up wit a trigger to start a hot water divertion as it would have to trigger independent of the inverter but work through the inverter I think?

You are the windturbine guru.  Will I get anything in a zone 2 wind area in the winter?  two eight footers.
Thanks
gww

16 batts and if i lose solar i'm still safe,  24 safe to add solar-turbine, hummmm...