Total life of batteries

[ChrisOlson]

When I put in my bank balance monitoring system, that eliminated having to do a full service (including load testing each battery) on the bank every 90 days - I'm going to stretch that out to a year unless the gauges indicate there's a problem.  But like Adam I still check water every month even though I know they don't use any in the winter.  I got a hard lesson on that this past summer when it was hot and I ran one battery down on water to where the plates were exposed, and the others were only a hair behind.

Our bank got increased to 2900 amp-hours today because I put our RV batteries and boat batteries on the bank to help out in the winter months and keep them working instead of sitting around all winter.  Those boat and RV batteries tend to be a bit "lazy" until the controller does an auto-equalize and gets them stirred up good, or whatever it does.  They tend to spend most of the year in a discharged state instead of being charged every day.  After a full winter of being worked on the bank they go back into the boat and RV in tip-top shape.  That's my anecdotal evidence that deep cycle batteries need to be worked to keep them healthy.
--
Chris

[gww]

Bob g
Thanks,  I just needed to know how to start on the right foot.  I believe you covered this well.

Chris and Adam
Again,  all real exsperiance related to me helps,  some I have heard from others but I seem to be kind of dence.  I either forget part or remember wrong so I keep trying to feed myself a steady diet of info till I can actually put it into practice in a little over a year.  If I repeat my questions please bare with me I think I'm getting senile.

Bill
I have read in other places that a three hour absorb cycle is almost a minimum and you have confirmed this.

It seems overwhelming,  about like owning lots of stuff with motors and trying to keep up with oil changes.  I'm not good at doing that but If I can start out properly maby I will get some good habits that will exstend my battery life before I backslide.
Thank you all
gww

PS
It will be nice to have something like this that I can refer back to that fits my spicific situation.

[ChrisOlson]

I have read in other places that a three hour absorb cycle is almost a minimum and you have confirmed this.

I'm afraid I have to disagree with this.  End of absorb should be determined by either specific gravity, or when the total charge amps drops to less than 2% of the ah capacity of the bank at absorb voltage.  Going by time only will boil the snot out of them in hot weather and deficit charge them in cold conditions.
--
Chris

[BillBlake]

Bob g
Thanks,  I just needed to know how to start on the right foot.  I believe you covered this well.

Chris and Adam
Again,  all real exsperiance related to me helps,  some I have heard from others but I seem to be kind of dence.  I either forget part or remember wrong so I keep trying to feed myself a steady diet of info till I can actually put it into practice in a little over a year.  If I repeat my questions please bare with me I think I'm getting senile.

Bill
I have read in other places that a three hour absorb cycle is almost a minimum and you have confirmed this.

It seems overwhelming,  about like owning lots of stuff with motors and trying to keep up with oil changes.  I'm not good at doing that but If I can start out properly maby I will get some good habits that will exstend my battery life before I backslide.
Thank you all
gww

PS
It will be nice to have something like this that I can refer back to that fits my spicific situation.

Some experts claim that your not going to get into as much Internal Resistance dropping down
to 50% DOD with Lead Acid as you will with Ni-Fe.

Yes avoiding that last +20% of the charge cycle is nice in Lip and on paper but demands a
heavy payment
with both technologies.
Less with Ni-Fe but in both cases a 'Finish Charge' or a 'Boost Charge'
is going to be necessary every X number of days to avoid big problems including Capacity Loss.

Capacity Loss is the 800 pound Gorilla that doesn't seem to get factored in enough when
dollar figures start getting thrown around out there.

Then with Lead Acid we get into a number of other concerns like sulfation.

We may have not seen the end of what the Government and Industry has to say about
Sulphation Prevention.

So some Off-grid people may not want to fight City Hall and may decide to just go ahead and automate

'The Storage Battery Pamper Process according to Old Bill'

without much (if any) dependence on fuel and generators.

We need to take a long cool Look at that last +20% and then deals with it
cool and slow.


Bill Blake

[ChrisOlson]

Yes avoiding that last +20% of the charge cycle is nice in Lip and on paper but demands a
heavy payment
with both technologies.
Less with Ni-Fe but in both cases a 'Finish Charge' or a 'Boost Charge'
is going to be necessary every X number of days to avoid big problems including Capacity Loss.

Bill, I find it hard to understand what you're saying.  But in my experience cycling lead acid batteries between 50 and 80% SOC doesn't hurt them at all as long as they get fully charged at least once a week.  The less frequent a full absorb cycle takes place, the more frequent equalization charges will be required, since deficit charging to only 80% SOC does cause some sulfation on the plates that the next full absorb cycle won't remove.

But in the end the battery still spends roughly the same amount of time gassing and bubbling during its life, whether it gets fully charged every day, or short cycled regularly and equalized more often.
--
Chris

[gww]

Chris
So on a 416 ah battery, When it gets to a 8.3 amp charge rate at absorb voltage, it can be stoped or planned for?  Will the outback or doc wattson show the charge rate?  Can individual batteries be voltage checked while still hooked to the bank?  In a working system do you always have to have a rest for spicific gravity to mean anything?  The three hour was mentioned as a starting place on the outback system as the default time is one hour and all users posting seem to advise this is not long enough.  It might take 5 hours.

adam
I do have a morningstar 60.  I may not have to use it but am glad you pointed out what to watch for if I do.

Bill
If I am reading correctly, I believe Chris has acknowledged and adressed your points.

Thank you
gww

[bob g]

if it were me, i would err on the side of a slightly longer absorption charge "at first" , followed by knocking off the surface charge, and i would definitely let the battery rest overnight,  then check the specific gravity to determine if the battery is fully charged,,,, if it was then i might decrease a bit of absorption time on the next cycle and recheck, or increase if it was indicated that the battery was not quite topped off.

your going to do about 2 dozen breakin cycles anyway, what a perfect time to get a handle on what the absorption time ought to be under average usage and charging conditions... remember the times will get shorter as the battery breaks in.

by the time you have done the breakin cycles, you should have the charge regime sorted out to a fairly accurate degree.

if you are afraid of getting lax or lazy, please don't get lazy during the breakin cycles, this is where you will learn exactly what the charging requirements are for you batteries,,, then later should you get a little lax at least you will have documentation of what the batteries are supposed to be when in tip/top shape.

without having a benchmark (from your experience and data in the log book)  you really have no clue what the batteries needs are down the road, and will definitely be a busy man if you get lax later one and let them get out of whack... hard to get them back into shape if you don't know what the shape is supposed to be.

does that make sense?

bob g

[ChrisOlson]

So on a 416 ah battery, When it gets to a 8.3 amp charge rate at absorb voltage, it can be stoped or planned for?

That's correct.  8 amps charge rate after being held at absorb voltage for whatever time it takes indicates that absorb is done.  At that point your battery is 95% charged and dropping into float and holding it at float voltage will finish the job.

A good charge controller should have an ending amps setting for absorb, and not just a timer.  You only use the timer to set the minimum time and maximum time, but ending amps should be the deciding factor.  Different types of batteries may be different.  So the the first few times you charge your battery keep checking it with a hydrometer during absorb.  When it gets to the right SG for your battery type note the charge rate at that point.  There's a 99% chance it will be right around 2% of the AH capacity of the battery, and that's what you use for ending amps for absorb.

I don't like any type of charge controller that only uses a timer because that required time changes considerably with temperature of the battery.

Absorbing too long only excessively heats the battery and uses a bunch of water.
--
Chris

[gww]

Bob g
Yes it makes sense.  I will be getting my first expereince when I put this together.  In a different post you had pointed out needing to know the load to size the charging and battery bank. 

I did it a little backwards and got the panels.  I have decided on 16 sams club batteries and I figure the next step will be figuring what loads will be added to posibly macth the charge use regiment.

 So, I am trying to get my testing proceedure in my head so I can check what the loads do in real life to the batteries so I know when I get it right.  Thats the purpose for needing to know how to get good readings, after use, for 50% dod 80%dod and 100% full charge. 

I don't Know my inverter charging capabilities very well either.  I know I can set the absorb voltage and time. I can set the float voltage.  I can set the low voltage. 

What I am using you info for is to try and figure how to get the regiment as seamless as posible with a 50/80 charging regiment and still get full charge once a week.  That I don't know is not from not reading everything I get my hands on ie; manuls, forums etc etc.  I may not get it completely strait untill install, use and mistakes. 

I am bugging you guys to cut down on the mistakes.  I believe I could get 100% charge daily with little intervention and with my current knowladge.  Going only 80% with 100% weekly may be harder.

Getting the discharge percentage might be hard also.  I might be able to put a known discharge base on math and when it gets to where I think 50% is I could shut it off and check the voltage in a couple hours and see if it is right. 

That is why the question on spicific gravity and whether it can be checked on the fly.  On the fly would make it easier to get 24 hour results with the actual loads I want to use.  Also would it be better to try for full charge every day rather then 80% daily with full charge once a week if the once a week required me manually doing something that might be forgotten?

I also keep getting the pull to buy more panels. I have enough to fill one mx 60 charge controller now for a 48volt system.  The panel shipping is only $100 here in indiana through an ebay dealer in indiana.  When I get to missouri if I want more I may get them just as cheep but the shipping may kill me.  I got 1400 watts delivered for .94 cents a watt.  I don't want to buy more till I try out my system because then I need anouther $500-$600 charge controller.  I can't use any of it for a year till I can move back home.

Mostly I am trying to figure out how to do what ever I end up with before I have to do it.
Thank you for your help
gww

[gww]

Chris
As I explained to you in a different post, it takes me so long to type a response that I just cant bare not to post it when I get it done. Even if some of my questions have been answered by the new poster.  I seem to get the total post kind of mixed up doing this and for that I apoligize.  It seems that you have indicated that I can check spicific gravity on the fly.  If I have this wrong please correct me.
Thanks
gww

[JW]

Gww,

If you preview your post you will be able to see any aditional posts, before you reply. So hit preview when your ready to post and you should get the warning in red letters at the top of the page, this also happens when you dont preview, the forum will force you to hit post again to post. At that point you can see if theres been a new post(and read it) "before" you commit and reply.

All, Im working on some addition enhancements for the forum, so that the forum will be easyier to use and surf...

JW

[gww]

JW
I actually have saw the red post has been made.  I just still want to post what I have writen as It was hard for me to write.  Some times this makes me look dumb.  These guys have been really cool about it. 
Thanks
gww

[JW]

I do the samething   I will scan over the most recent post and say, well it took me this long to get this reply together, im posting it.

JW

[birdhouse]

gww-
 i think you're overthinking things some.  i believe you have outback inverters capable of charging the bank from a 110V (genset) source.  i would only use this function if the batteries are getting fairly low and still need to be drawn from...  even then i would only burn gen fuel to get them up to 80% SOC...   a good charge controller like the Ts-60 from morningstar (like you have) will do the trick during the next solar day to get the bank to float without burning excess gasoline during the minimal draw of the end of the charge cycles. 

i understand that you want to know every detail before you own an offgrid system, but much of the knowledge and understanding does come from maintaining your own off grid system.  solid charge controllers do much of the work for you.  they can even be programmed to do automatic equalization for you. 

it basically "boils" down to equalizing, adding distilled water, and not drawing too much from the bank, and if you do, fire up a genset to get them back up a bit.  it's not rocket science!   

adam

[gww]

Adam
Are you sure its not rocket sience?  It seems like it is if you haven't done it yet.  I think that comes from the amount of money spent.  Some of that money already on mistakes.  The other thing is that I can't actually try it now due to location and I am trying not to waste this time and also trying to keep my enthusiasm high so I don't get sidetracked.  I bought the morningstar cause I was going to have my turbines hooked strait to the batteries and use it as a dump controller.  I now have a sceem to just preheat hot water using a relay and the inverter through the outback mx 60 charge controller.  I may not have to use the morningstar at this time.  If I buy more panels I may have to find a way to intigrate it into the system as the mx60 is full.  I may be overthinking but as long as everybody doesn't throw their hands up and quit responding I have really learned a lot here. Lots of misconceptions I had have been corrected.
Thanks
gww

[DamonHD]

Just remember that there are no perfect solutions, no two usage or charging days exactly the same, habits and understanding will change, etc, etc.

So as long as you get things broadly right (so as not to start a fire or let magic smoke out) and you add (say) 25% to your budget for errors and tinkering, then you're doing at least as well as me.

Rgds

Damon

[BillBlake]

Yes avoiding that last +20% of the charge cycle is nice in Lip and on paper but demands a
heavy payment
with both technologies.
Less with Ni-Fe but in both cases a 'Finish Charge' or a 'Boost Charge'
is going to be necessary every X number of days to avoid big problems including Capacity Loss.

Bill, I find it hard to understand what you're saying.  But in my experience cycling lead acid batteries between 50 and 80% SOC doesn't hurt them at all as long as they get fully charged at least once a week.  The less frequent a full absorb cycle takes place, the more frequent equalization charges will be required, since deficit charging to only 80% SOC does cause some sulfation on the plates that the next full absorb cycle won't remove.

But in the end the battery still spends roughly the same amount of time gassing and bubbling during its life, whether it gets fully charged every day, or short cycled regularly and equalized more often.
--
Chris

Chris, This thread is probably better off staying geared with older conventional methods.
I do have to wonder if people understand the difference between 'Absorb' and 'Finish'
Charging as was mentioned in that Sandia National Labs <snip>.

Then for Lack of a better term I have chargers that 'Feather Charge' where not only is the little
computer brain always calculating Voltage and Amperage but it 'Feathers' the Charge
(back and forth, like an accordion)

HOW IT LIKES IT - as well.

"You are about to enter 'The Battery Zone' where for the next X number of minutes

WE Control the Horizontal.

WE Control the Vertical.

Do not attempt to touch any Dials".

Not to be confused with 'Pulse Charging' (which is cunnin in it's own right).

Until we all get on the same page with what people are actually talking about I agree that
it's going to be hard to understand.

They don't always try to take a drug addicts dope away but many times will replace it
with something else less harmful.


Bill Blake

[BillBlake]

The 'Accordion Finish Charge' battery charger is a fairly cheap deal from Schumacher.

It has a glitch once a year (or so) that has been written about on the Intenet
but I put it in the Legendary Class (for what it is) anyway.

The boys at Amazon seem to
Loves it :-)

http://www.amazon.com/gp/product/B000H961YI/ref=as_li_ss_tl?ie=UTF8&tag=schumacher0a-20&linkCode=as2&camp=217145&creative=399349&creativeASIN=B000H961YI

For 24 Volts moving up to the Yacht Class in price this may be the most efficient battery
charger that I ever found which may also put it in the Legendary column after enough years.

Sterling-Power also has a European Division that HAS TO follow the Standards over there.
That makes a huge difference. Quite the sleeper to Many in the forums.

http://sterling-power-usa.com/sterlingpowerusaprocharge-24volt30ampbatterycharger.aspx

For DC to DC Battery Chargers I'm still looking.

Many are called but so far None are chosen for the Old Bill Seal.

The efficiency of 48 Volt battery chargers can't seem to begin to touch the Sterling-Power
24 Volt Standards so I'm still looking. It will be a good while because of a new research project.

Bill Blake

[bob g]

Bill

what do you plan to plug the sterling charger into?  mains/utility or generator, or ??

just curious

thanks for the links on the sterling chargers, i was aware of their offerings of alternator controller/regulators, but really never looked into their chargers.  i am liking their alternator controllers/regulators, they are much better priced than the balmar regulators, even though they lack a couple functions that can be worked around.  i have about a half dozen other multistep regulators from various manufactures, and have tested them all.  i have not picked up a sterling regulator yet, but plan to for testing.

bob g

[BillBlake]

Do you remember how Clarence the Angel told George Bailey that he really did have a
wonderful life in the movie 'It's a Wonderful Life.'

The movie was considered a failure when it first came out. Today, needless to say,
it's in the Legendary Column watched by millions. 
Some people every possible Christmas season of their lives.

http://en.wikipedia.org/wiki/It%27s_a_Wonderful_Life

Your batteries could also have a Wonderful Life.

Your answer is that the high efficiency battery charger gets plugged into a

high efficiency inverter. That last 15% to 20% is taken care of cool and slow,

2 to 3 times per week, automatically by a smaller battery bank that only gets a fraction of the

total discharge cycles. 'Blivet Charging' was schemed away. :-)

Cost wise it's about the same as generators over the years but with many
Wonderful Life advantages.


Bill Blake

[bob g]

ok Bill,

let circle the wagons and focus on the question

what do you plan on plugging this high efficiency charger into?

do you plan on recharging with mains power? or from a generator?

for whatever reason you don't want to answer? so lets move on

no one has ever said that a battery bank can't have a long and wonderful life, i know i haven't!  however ...

a long and wonderful life might not be the most effective use of the battery or the best return on investment!

yes you can extend the life of the battery by fully recharging it very slowly and carefully vs. just slamming it full as fast as possible, maybe... maybe

maybe because we cannot recharge a battery (flooded cell) too slowly or we end up with stratified electrolyte and the bottom of the plates eaten away prematurely,, you got to heat them up with some regularity to get the electrolyte mixed up.... babying them along generally does not mix things very well.

then there is this,
if you are relying on a battery bank for power, when the hell are you going to have the lengthy time to carefully and slowly recharge them fully 3 times a week?   can't very well do all this babying and pampering and use them at the same time now can we?

then there is the efficiency thing,

flooded lead acid batteries while being charged average about 90% efficient from 50-80% state of charge, (actually up to about 85%)
the last 15-20% ranges in efficiency from about 85 down to as low as 50% efficient near the top of the charging cycle.

that last 20% is not only hard to do, very time consuming but also very inefficient.  so planning a system that requires 3 full recharges a week is probably going to be twice as costly as it needs to be, or is going to burn significantly more fuel than it needs to, and it is still debatable whether the end result is really going to extend the life of the battery  bank and provide any real gain in our return on investment.

what good does it do to save X amount of money on our batteries by extending their lives if it takes 2X amount of money in fuel burned or 2X the amount of panels?  and we still have to go without using these batteries during these pampering sessions 3times a week?

there is just a hell of a lot more to consider than simply focusing on getting the maximum lifespan out of a battery bank.

i know i can get 20 years out of a set of batteries if i simply keep them on float most of the time, cycle them very shallowly once a month, recharge them immediately afterward, and keep the electrolyte mixed, however when it is all said and done what have i gotten out of them for all the effort??  not very much power!  yes i had some power available if i needed it, but what good is a battery bank to an offgrid installation if it sits there being pampered and not used?

the only way such use of a battery bank makes sense in an offgrid installation is "if" one has ample enough alternative energy coming in such as solar,wind, hydro or whatever. and he manages his loads to where they are less than and also concurrent with the power being supplied,, and the batteries are only used if all else fails. under this condition it might make sense, however how many folks can qualify this type of use?  probably less than 1% can

most folks are not going to sit in the dark at night when the sun isn't shining or not do anything on days that are cloudy and the wind is not blowing.  they are going to want to do things that require the power that they are either making or have made and stored in the battery bank.

i guess i don't agree with your philosophy as it relates to batteries, their use, and their care.

bob g


bob g

[BillBlake]

ok Bill,

let circle the wagons and focus on the question

what do you plan on plugging this high efficiency charger into?

do you plan on recharging with mains power? or from a generator?


bob g

Your mains power has been Eliminated by the scheme.

Your generators (except for far-out circumstances) have been Eliminated by the scheme.

Old thinking and old news ways have been replaced by new ideas in the scheme.

Another smaller battery bank and another smaller pool of Solar Panels takes the place

of ANYTHING ELSE while the panel price is low.

Your 'Finish Charge' price is controlled for many years.

If Iran went off and fuel doubled your sunshine price remains the same.

Your high efficiency charger plugs into a high efficiency timer which plugs into ....

well your starting to get it :-)  .....  a high efficiency inverter.

Batteries charging Batteries.

Got it ??


Bill Blake

[bob g]

Bill

are you serious?

batteries charging batteries?  via a high efficiency inverter and a high efficiency charger?

have you done any real homework on this scheme? seriously?

the flooded lead acid battery is well under 80% efficient above about 85% state of charge, decending down to 50% efficient nearing full charge.

the best inverters are about 93% efficient, and only within a narrow window of operation generally

your efficient charger is advertized at being about 90% efficient

so lets add it up
\
80% battery efficiency charging X 93 % inverter efficiency X 90% charger effiiciency = about 67% overall efficiency and this does not factor in the efficiencies of the battery you are using to charge this battery with, or the fact that the batteries efficiency is headed down to 50% near full charge.

by the time everything is factored in, you will be doing good to get 20% efficiency? 

i don't see this as a viable scheme under any conditions.

please expand on your theory of operation, perhaps i am missing something?

bob g

[Frank S]

I for sure don't need to jump in here but I'm confused as to why you would want to try to charge a battery from a battery.
 OK I can see a large bank of batteries being used through what ever means to charge up a small or a single battery for a vehicle or a power tool but under most conditions that I can think of it would be more like a battery discharging a battery.
 The only thing I can think of would be say if I had a 24 or 48v bank that was maintained by my array or a standby generator and I had a vehicle that I needed started or a power tool to be charged up then a DC to DC charger would make sense I don't see where an inverter would come into play unless I were going from DC to mains then back to DC other than that I admit I'm at a loss But I treat mechanical like English I can read it and understand it in 147 dialects, and possibly write it and speak it in maybe 4 dialects.
Electrical I treat like German Lived in Germany for 3 years so I can read it or understand it a little and speak it a little very slowly when needed
 Electronics I treat like Arabic even though I've been immersed in it for 9 years  I cant read it I can't understand much of it and I sure can't speak it
 So for those few of us like me who are sadly lacking in electronic schemes  would it be possible to expand on what you are trying to portray please

[BillBlake]

Since the Sun doesn't charge you per gallon often it's TIME not efficiency that becomes
the 800 pound gorilla.

To keep the cost down some people will run a smaller SUPPORT BANK of batteries and since
they may plan on 104 Discharge Cycles per year vs. the everyday 365 in Cycles from the
MAIN BANK
it becomes possible to run them down to 50% DOD (or so) and still get a similar amount
of years out of the batteries from BOTH banks.

66% or more of your support battery Solar Charging will be at a very high efficiency rate.

The other percentage (normally) has 2 or 3 days (cool and slow) to get charged up -

not (IF LUCKY) 2 or 3 hours.

Then we also have PLENTY of time to Finish Charge the Main Bank twice per week

how YOU LIKES IT using the support charging bank of batteries and an advanced charger

like a Gentleman or Gentle-lady.

The only way to get to the bottom of a good scheme is to question it  :-)


Bill Blake

[ChrisOlson]

Cripes.  This has gone totally off the wall.

When you live off-grid the generator is not the Evil Enemy.  It's your friend.  When Mother Nature either goes on a rampage, or on vacation, the generator is the most reliable source of power you got, that you can count on every single time.  Going to extremes that involve spending ten dollars to save a dime on battery finish charge inefficiency is pretty pointless, to my way of thinking.  For pete's sake, why are you going to charge one bank with solar panels, then run it thru an inverter and "high efficiency" timer(?), then a "high efficiency" charger back to another bank?  Why not just use the solar power to charge the batteries and be done with it?

This scheme is sort of like buying a car and you want to get 10,000 miles/gallon with it.  So you buy another one and push the first one with the second one so the first one gets good gas mileage, and you don't have to fill it up as much.

Just buy the right equipment to do the job, and get the job done without fartin' around with elaborate BS that entails a full time job to keep it all working.  That's my principle.
--
Chris

[BillBlake]

Generator.

Something that normally also needs a DC CHARGER and always has it's noisy, position telling, smelly hand in my pocket.
It's not my friend.

The scheme is to kill it - real good and real smart.

You can't 'Hitler' a topic like this into reason. Viewpoints need to be considered along with a
little 'sinking in' time.

Remember it's no money in my pocket and no skin off my nose irregardless of what anyone does.

If I'm asked a serious question I will try to give a serious answer but that's about it.

We are talking about a 'Sun Power Time Bank' that GETS OFF the $4 per gallon (and rising) fuel.

Regularly and automatically.


Bill Blake

[ChrisOlson]

Generator.

Something that normally also needs a DC CHARGER and always has it's noisy, position telling, smelly hand in my pocket.
It's not my friend.

Yeah well, where I live when when the sun don't shine and the wind don't blow for a week, and everything is encased in snow and ice at 30 below zero, I don't care how big your Sun Power Time Bank is.  You'd better go make friends with the generator real darn quick or you'll be burning smelly candles and oil lanterns to stay out of the dark.
--
Chris

[BillBlake]

Provisions for dire circumstances and exclusions for 'The Great Northwest' were made a good while back.
What most people are talking about (I think) would be more ordinary conditions
where one day of Sun may be a tad weak.

Not ENOUGH TIME no matter how many Solar Panels. (The younger guys should get it.)

However 2, 3 or 4 days of Sun may be real 'Ducky' to get the 'Support Bank' charged up to snuff.
Keep in mind that as part of the scheme we Do Not 'suck' ANY power out of the smaller
support battery bank while it is getting ready to do it's

'Solar Charging Time Displacement' trick.

If it gets TOO TOUGH we just Fly In Equipment and

'The KW Kid'

to start barking orders with a big cigar (that smells funny) hanging from his Lips . 

Bill Blake

[dnix71]

If your support bank was NiMH or NiFe, not lead acid, then you could run down the support bank completely without doing them harm. But I wouldn't use them to boost the other bank. Your support bank would be smaller but more expensive per kw-hr.

Get the 100% DOD kind of batteries when they are cheap and available and use them when you have to to spare the lead acid from staying run down so long they sulfate.

You don't have to live in the frozen north to not have sun or wind for a week. It happens here in south Florida, too. We have a front stalled for a week now. Some sun between the rain, but not enough to float.

[bob g]

Bill

all i can say is this about you scheme

i am sure glad you didn't propose charging the first bank off the second bank, having just charged the second of the first

maybe i am in the minority here, but like Chris i see the generator as my friend, and unlike you and maybe others i see a battery as a consumable.

a generator as a friend means, sizing and then using it in the most efficient manner economically feasible.

a battery as a consumable means, getting the most kw/hrs out of it over its lifespan.  i don't see any other metric that we can use to determine the return on investment.

good luck with your plan

i think i will stick with the direction i am headed.

bob g

[Frank S]

I can understand someone's  line of thinking about a second bank but what I fail to see would be why? I don't live anywhere near a place where there is cold temps or snow but solar will not work when it is covered with dust either. there is a guy here who is running a test case solar PV & 3  small 2KW turbines he has 10 square meters of PV the turbines have a 6 meter diameter swept area
 one would think that when the dust is thick enough to render PV useless that the wind would also be blowing hard enough to more than compensate. 3 times in the month of may alone his bank ( don't know how large it is) was so far down that he experienced total shut down and stayed that way for another 2 days each time. so that means in May alone he was effectively without power in his test lab for a total of 6 days in 1 month
 Generators are the only way to go for back up. if you are so inclined as to be total off of fossil fuel or money out of pocket. then develop an alternative like growing algae. Palm oil or some other non food stuff organic
 batteries will last only so long no matter how they are cared for.
 IF you have enough PV to run your establishment completely and fully charge your bank in a short solar activity day then so much the better.
 having 2 banks only makes sense if one of them needs to be mobile.
 the bank can rest when you turn off the television and the lights and go to sleep hoping you have enough wind to top them off before morning.
 A battery is like a cloth baby diaper no matter how many times you wash it eventually it is going to change colors and rot away.   

[bob g]

maybe the reason i am not generator averse is based on my being able to fuel it in so many different ways, everything from diesel, to waste motor oil, veggie oil, alcohol, wood gas, propane, natgas, and any number of fuels i can retrieve with my grain press.

might be i would not be so much in favor of one, if pump diesel was my only source of fuel? and i lived way the hell out in the boondocks where resupply would be very costly?

i guess i just accepted the fact that a generator is a reality for offgrid existence for 99% of installations, and long ago got my head around that idea and worked out how to use one efficiently and effectively for battery charging.

bob g