Monitoring Bank With Analog Volt Meters

[ChrisOlson]

Or, do that.  It's easier to buy a few bags of ice

Dude, you could not even buy a bag of ice anywhere around here.  Kwik Trip, the other convience store in town - no place had it and they were all out.  They all got these ice chests sitting outside that get filled up when a truck comes around - well the truck never showed up and they were all empty for better than two weeks.
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Chris

[dnix71]

Battery charging monitors exist for off grid applications and electric vehicles.

http://www.linear.com/product/LTC6802-1 I don't know the cost, but this one has the usual mosfet dump switch to force equalize a string as individual cells get "full."

The newer lithium ion battery packs for cordless tools have BMC chips on each cell and a dump wire to bleed off excess charge during recharge. The better BMC's also monitor discharge and cut off that cell when it's voltage get's too low.

That way you get the maximum use of a series string of cells.

If one of you electrical wise guys here wants to make a very very useful product, then design a cheap battery monitor for the common lead acid batteries that people use for offgrid backup.

The telcos may have a similar product minding their stacks. Given the high cost of backup power, even a fairly expensive BMC would pay for itself soon enough.

[Watt]

Or, do that.  It's easier to buy a few bags of ice

Dude, you could not even buy a bag of ice anywhere around here.  Kwik Trip, the other convience store in town - no place had it and they were all out.  They all got these ice chests sitting outside that get filled up when a truck comes around - well the truck never showed up and they were all empty for better than two weeks.
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Chris

Chris

You are being literal with that suggestion yet you pass over the real ones.  Even water from a well would be cooler than ambient air.

It sounds as if during the month of July that generator would have been the best bet.  When money is no object, those batteries could have been kept cool.   

[ChrisOlson]

far better to have to worry about too cold, no damage can occur provide you have enough charging capacity to stir the electrolyte

That's the deal for us.  I have a fan that blows house air into the battery cases in the winter to keep them around 60 degrees or so.  But the real problem for us is 40 below zero, not 100 degrees above.  That was the most unusual July ever in history.

So coming up with all these battery cooling theories is pretty much fruitless.  The main thing is that my gauges showed me when one got low on water before its time, and I caught it before it got wrecked.
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Chris

[Volvo farmer]

I got Rolls batteries and they do not do well with low charging voltages.  So they tend to gas more than a Trojan I think.  In the really hot weather the battery temperature got well up over 110 degrees and I don't think they got below 100 degrees for most of July.  Add to that that we had day after day of bright sunny weather and they got bulk/absorbed every single day.  The temperature compensation had the absorb down to around 28.2 or so, but they still went thru a LOT of water.

Let me put it this way - my batteries are not going to die from being sulfated, and they got the plates in em to handle being bubbled all the time.  Just have to keep water in em.   
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Chris

I just replaced my Rolls/Surrette bank of S530s after a little more than six years because I had two cells drop below 1100SG on two separate batteries within a three month time span. I subscribed to the same mantra as you do, that my batteries were not going to die of sulfation, and I was going to cook them long and hard at every opportunity. 

I think I noticed the same thing as you while trying to equalize. Battery temperature would get up over 110F and I could just keep dumping current in and the current requirement kept rising with the battery temperature at 32V. In the second hour of a two hour equalize, I could put over 60A into the 800 Ahr bank and still not maintain the 32V recommended for equalize.

Looking back, I think it was a mistake to let my batteries get that hot. I thought I was going to get ten years out of my bank because I was smarter than the average guy yet I only got six. I'll never know why they didn't last longer either.

Just be aware on that seven year pro-rated warranty, that it's almost useless in the last couple of years. When my first cell died, I was eligible for about $50 in credit, but because the internal resistance of new and old batteries is so different, it would be foolish to replace only one battery in a six year old bank, and the problem of mixing new and old batteries is compounded if the strings are in parallel.

[Watt]

far better to have to worry about too cold, no damage can occur provide you have enough charging capacity to stir the electrolyte

So coming up with all these battery cooling theories is pretty much fruitless.  The main thing is that my gauges showed me when one got low on water before its time, and I caught it before it got wrecked.
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Chris

True Chris, glad you had your meters.   

For the record, the cooling only came after you commented on your battery environment for July.  My calendar shows August.

As usual, any suggestion to your err must not be the case.  Hope you and your batteries the best. 

[ChrisOlson]

I think I noticed the same thing as you while trying to equalize. Battery temperature would get up over 110F and I could just keep dumping current in and the current requirement kept rising with the battery temperature at 32V

VF - I didn't understand that either.  The hot weather, for whatever reason, made them pull a lot of amps.

I remember that you had that battery that went south before its time - that's too bad.  Nobody that lives off-grid likes that to happen because it's usually pretty expensive.
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Chris

[ChrisOlson]

You are being literal with that suggestion yet you pass over the real ones.  Even water from a well would be cooler than ambient air.

It sounds as if during the month of July that generator would have been the best bet.  When money is no object, those batteries could have been kept cool.   

I think it would take someone who lives off-grid to understand this - but I'm not about to unhook and drag 2 tons worth of batteries outside in 100+ degree heat to hose them down.  Nor am I going to cool them with water in my utility room and flood it, and have water running into the house.  We have only two things that managed to stay cool in that weather, and that was the inside of the 'fridge and the freezer.  We couldn't get it below 90 degrees in our house even.

We live OFF-GRID.  We do not have conveniences like central air conditioning.

Secondly, we tried running the generator when we started up the AC unit, because the AC unit pulls 12 amps 24 hours a day, which is almost 35 kWh per day.  Unless the wind is blowing good, that's more power than we can usually generate in a day just to run that window AC unit.  But the generator got hot too - it burned a quart of crankcase oil in only 18 hours in the heat because I only had 15W-40 in it and I couldn't buy any SAE 40 oil around here anyplace to save my a$$.  Nobody carries it anymore.  And the inverters constantly kept spitting it off because it was down on power in the heat and kept lugging down under load so the frequency dropped below spec.

So I backed down the amps that the inverters could draw, and that didn't fix it either.  The windings and AVR got so hot the voltage would drift down, and when it got to 219 the inverters didn't like it - generator spit off again.

For somebody who lives with grid power they really don't understand what it's like to be the power company.  There's all sorts of "solutions" from the sidelines I suppose.  But when you're on the front lines fighting the battle it's a little different perspective.
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Chris

[bob g]

Chris, i think everyone is trying to help you get the 10 years out of your bank, however at this rate i would be surprised if you make another hot summer with this set if you don't take measures to rectify the heating issues..

maybe it might take a different generator and more fuel burned in july next year and let the batteries just sit idle during the extreme heat if you can't cool them?  maybe not?

remember the old adage, "big batteries come with big responsibilities"

it used to be the separators would carbonize when the batteries were subjected to 115 degree F or more, this caused permanent damage to the cells causing higher than normal charging current and higher self discharge,,, more heat and the longer it took place the worse it got.

now i would expect the separator to be of a different material today, however the temp range guidelines have not changed, last i recall rolls/surrette does not want them on operation over 115 degree's F, so clearly something gets damaged from  higher temperature use?  or so it would seem to me?  high heat is hard on something inside those cases.

like i said we are just trying to help

bob g

[ChrisOlson]

like i said we are just trying to help

Understood.  We don't live in a hot climate here - at least not before all these records started getting set.  A really hot day for us is 90 degrees - and a really hot stretch of weather is 90 degrees for 3 days in a row.

This was the first time in my life I have seen temperatures at that extreme here.  So my system is not designed for Arizona.  We live in the Wisconsin North Woods.  And I'm not going to re-design it for Arizona because of one record month that happens once in a lifetime.

Here we are - middle of August and our batteries are at a nice comfy 75 degrees:



This is the normal for us.  In the winter I have to fight to keep them at 60 degrees so they got some decent storage capacity because the days are short and we use twice the power in the winter.

This is NOT about elaborate battery cooling schemes.  It's about a way to keep batteries balanced long term because I believe that the death knell for many off-grid batteries is sounded because of balance problems.

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Chris

[Watt]

You are being literal with that suggestion yet you pass over the real ones.  Even water from a well would be cooler than ambient air.

It sounds as if during the month of July that generator would have been the best bet.  When money is no object, those batteries could have been kept cool.   

I think it would take someone who lives off-grid to understand this - but I'm not about to unhook and drag 2 tons worth of batteries outside in 100+ degree heat to hose them down.  Nor am I going to cool them with water in my utility room and flood it, and have water running into the house.  We have only two things that managed to stay cool in that weather, and that was the inside of the 'fridge and the freezer.  We couldn't get it below 90 degrees in our house even.

We live OFF-GRID.  We do not have conveniences like central air conditioning.

Secondly, we tried running the generator when we started up the AC unit, because the AC unit pulls 12 amps 24 hours a day, which is almost 35 kWh per day.  Unless the wind is blowing good, that's more power than we can usually generate in a day just to run that window AC unit.  But the generator got hot too - it burned a quart of crankcase oil in only 18 hours in the heat because I only had 15W-40 in it and I couldn't buy any SAE 40 oil around here anyplace to save my a$$.  Nobody carries it anymore.  And the inverters constantly kept spitting it off because it was down on power in the heat and kept lugging down under load so the frequency dropped below spec.

So I backed down the amps that the inverters could draw, and that didn't fix it either.  The windings and AVR got so hot the voltage would drift down, and when it got to 219 the inverters didn't like it - generator spit off again.

For somebody who lives with grid power they really don't understand what it's like to be the power company.  There's all sorts of "solutions" from the sidelines I suppose.  But when you're on the front lines fighting the battle it's a little different perspective.
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Chris

Hate me because I have Air conditioning....  Hate me because I spent $27,000 on electrical poles ( 5k each installed ) and a transformer to have grid power?  Sure, go ahead but, I don't refuse to have grid power.  Sure, I would have spent more for the comfort of having grid if something happens to me and my wife decides to turn the switch off on all this stuff.  Could I have gone strictly OFF GRID, YOU BET, but I do not flame you for being so unfortunate not to have the option.

I'm currently building a solution for my RE components to stay cool, which does include Air conditioning, and I have wasted more money than it can return.  So what, money is an object but I know why cool batteries are important.  My " July " is from April to October. I just bought more solar to cover the a/c....

Have I blamed you for being OFF GRID? Nope.  I made a simple suggestion your batteries are being cooked and you go all crooked over a simple observation.  That was not the brunt of the comments to you.  You picked ONE which was a past tense. 

My main concern * WAS * the charge voltage and battery connections. You have changed part of this since early spring, I * ASSUME *.

So, what happened to your unlimited funds or those 500kw diesel generators?  Oh, I bet you never thought you would need one and never implemented that into your contingency plan.  Has that hot July influenced your battery longevity?  I bet so, but since they are yours, I'm guessing you are ok. 

All my concerns and observations came from your comments in various posts.  You can be king of the hill all you want, but even you make mistakes and should not be afraid to get help or be criticized.  Hell, you've given plenty to others who now appreciate your persistence.   

[ChrisOlson]

All my concerns and observations came from your comments in various posts.  You can be king of the hill all you want, but even you make mistakes and should not be afraid to get help or be criticized.

King of the hill?  ROTFLMFAO!  JFC.

I posted on how my battery monitoring system works and how I got my bank wired, and why, and it gets twisted into a battery cooling thread.  LOL!

Actually, where I live I have a solution for my RE components to stay WARM because it gets colder'n a witch's tit in a cast iron bra here in the winter.  For us that's five months out of the year and the rest of the year is (normally) mild.

It's easy to come up with all these "solutions" to a problem that's not really a problem on a forum.  Generators?  Yeah - we got a 250 kW Cummins genset for running our grain handling system.  Am I going to run it to keep batteries cool because of a record hot month?  No.  The thing burns 450 gallons of fuel per day.

Am I going to buy a bigger standby gen because of one record hot month that happened once in 117 years?  No.  I sized our generator to our system for peak efficiency and getting the most kWh/gallon of fuel burned - not for the extremes.

Again - this not a battery cooling thread.  It's about balance between batteries in a bank.  Next thing you know somebody will come up with something really off the wall, like liquid hydrogen cooled batteries.  So before we get carried away with battery cooling schemes, I would like folks to know that my balance meters were worth the effort to install them - they're a useful tool.  And no matter what you do, keeping very large battery banks balanced is a challenge.  It's worth the effort to make sure, if you have a large and expensive bank, that they are indeed running balanced at all times.
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Chris

[Watt]

All my concerns and observations came from your comments in various posts.  You can be king of the hill all you want, but even you make mistakes and should not be afraid to get help or be criticized.

King of the hill?  ROTFLMFAO!  JFC.

I posted on how my battery monitoring system works and how I got my bank wired, and why, and it gets twisted into a battery cooling thread.  LOL!

Actually, where I live I have a solution for my RE components to stay WARM because it gets colder'n a witch's tit in a cast iron bra here in the winter.  For us that's five months out of the year and the rest of the year is (normally) mild.

It's easy to come up with all these "solutions" to a problem that's not really a problem on a forum.  Generators?  Yeah - we got a 250 kW Cummins genset for running our grain handling system.  Am I going to run it to keep batteries cool because of a record hot month?  No.  The thing burns 450 gallons of fuel per day.

Am I going to buy a bigger standby gen because of one record hot month that happened once in 117 years?  No.  I sized our generator to our system for peak efficiency and getting the most kWh/gallon of fuel burned - not for the extremes.

Again - this not a battery cooling thread.  It's about balance between batteries in a bank.  Next thing you know somebody will come up with something really off the wall, like liquid hydrogen cooled batteries.  So before we get carried away with battery cooling schemes, I would like folks to know that my balance meters were worth the effort to install them - they're a useful tool.  And no matter what you do, keeping very large battery banks balanced is a challenge.  It's worth the effort to make sure, if you have a large and expensive bank, that they are indeed running balanced at all times.
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Chris

And as I figured, you missed the mark and are again off on a tangent AGAIN.  For the Third time, this has nothing to do with keeping your batteries cool for last month.  Just a passing, throw some ice on them - comment.  Really this is a - your charging scheme is flawed response - which affects your batteries and JULY was the month which proved the flaw.

And<<<<<<  if you have another JULY, you will further cook your batteries further decreasing their longevity. 

You commented about your normal generator not big enough and could not stay cool with the load, not me.  Well, as you have commented before, with those unlimited funds, you could easily run that 250kw generator. 

450 gallons a day?  Wow, we run 425Kw 3406 powered generators day in and day out with two 3412c powered pumps, two 3408c floor motors on a couple of our triples and whole lot doesn't use that amount of fuel in a 24 hour period.  What size A/C do you have? Flat out, ya those generators use the fuel but fuel consumption is load dependent.

I guess there is a limit to what you will do to save those Rolls batteries.

[Watt]

"So even though some folks told me the analog meters won't work and I should have digital, I'm still pretty happy about a couple things.  The meters do work.
1. They told me that I had a battery low on water and I caught it and corrected it before it got wrecked.
2. Arranging big 12 volt batteries in large parallel strings with only one series connection works. "

This is more than a " Look at my gadgets and see how they work ".  There is argument in the very statements above. 

The truth of the matter: Observing those meters, how long did it take to tell you had a battery problem?  And, with only two meters and 24 batteries, all those two meters did was tell you which bank to check first Yet, you still checked both banks.
1: Long enough the battery had already been subjected to high temps and low level.
2: Not instant enough that a normal 3 month battery condition/service interval would not have picked up the same issue.

And another couple of personal truths:
1:  I have my doubts as to what you really have and how it is connected as you have had so many changes to date.  Do I matter, heck no.
2: I never read where " they wouldn't work", only the digital meter would give a near exact state and not have to rely on the analog meter and it's scale.  Does that matter, heck no.

However, there is more to the story.

So, I'm done now.   

[ChrisOlson]

I just replaced my Rolls/Surrette bank of S530s after a little more than six years because I had two cells drop below 1100SG on two separate batteries within a three month time span

Volvo Farmer - I was going to comment on this before the thread got hijacked into battery cooling schemes and generators.

I don't think a person has to have the same setup as we have for a set of bank balance meters to be useful.  You mentioned that you now have twelve 2V cells for your 24 volt system.  Well, try an experiment:

Take two batteries - it doesn't matter what the voltage is as long as they are matched.  For giggles, let's say we have two sixes.  Hook them in series and hook up a regulated charging source that holds them at a constant voltage - let's say it's 14.0 volts.  Check the voltage on each battery and they should both be at 7.0 volts.  Now, apply a load to one of those batteries, like a 6 volt tractor light bulb, or whatever - enough of a load to cause a voltage drop on that battery.  Verify that your regulated voltage source is still at 14.0 and check the voltage of each battery again.  The one with the load will be lower - let's say the load dropped it to 6.0 volts.  The other one will be at 8.0 volts.

Hook the same two batteries in parallel and hook up a regulated charging source - say it's 7.0 volts.  Apply your same load to one of them and now measure the voltage of both.  They will both still be at 7.0 volts.

When a battery goes bad it's voltage is going to be either high or low, depending on what happened to it, and the charging state.  Placing that load on one battery simulates this and shows how it will affect the other batteries it's connected with if you have one that is running at different voltage than it should.

Even with your new string of twelve 2V cells, you can tap the bank at midway and put a 12 volt voltmeter on each end to the midway point and monitor the halves.  If one of those cells has a problem, based on what I've seen it will show up immediately by the voltmeters not agreeing with one another.  It don't matter if the meters are digital or analog, as long as they can be calibrated to read what a known good test meter says for each half when you hook them up.

Maybe the meters will never show any difference, and if they don't that's good.  But if there ever comes a time when they don't agree, there is no doubt you have a problem with that battery bank - and it's an economical at-a-glance monitoring tool that is really very simple.
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Chris

[ChrisOlson]

So, I'm done now.   

Don't let the door hit you in the a$$ on the way out, OK?  If you don't find the information in the thread useful without throwing your battery cooling twist on it, then go someplace else.  I didn't post it for you.
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Chris

[bob g]

Chris
you put more faith in two chinese 2 buck analog meters than i would with a 10k set of batteries... might be ok for an experiment but i would want something a bit more reliable myself.

your point as it relates to series connected batteries and differential voltages is valid, however parallel connections are not without issues of their own.



bob g

[Watt]

So, I'm done now.   

Don't let the door hit you in the a$$ on the way out, OK?  If you don't find the information in the thread useful without throwing your battery cooling twist on it, then go someplace else.  I didn't post it for you.
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Chris

Well, I was done.  Nope, that door didn't hit me, I was open minded enough to take advice and watch for it and hold on to it as I passed through.  It has closed easily behind me.

You really are blind aren't you. 

Wow, only you would see these posts as " battery cooling ideas", get some rest and re-read tomorrow. 

I'm happy you didn't post this for me, I don't need these meters so far.  I have my batteries connected properly and can depend on 3 months no problems even with the junk I have.

This is where I am nice to you, admins and mods. 

You are the man Chris. 

[ChrisOlson]

your point as it relates to series connected batteries and differential voltages is valid, however parallel connections are not without issues of their own.

Yes, parallel connections have their own issues.

Say you have four 6V batteries connected series/parallel for a 12 volt system.  Take two batteries and connect them parallel.  Then connect the other two parallel.  Then make a single series connection between them.  This would be similar to my setup.

If you have a bad battery in that bank, the bad one will have less amp-hour capacity than the three good ones.  But if you apply a 12V load to the bank the bad one is going to pull the good one that it's hooked to down with it (if it's hooked parallel).  If you're monitoring the halves of the bank the side with the bad battery is going to show lower voltage than the other side that has two healthy batteries.

And that's why I think hooking up a couple simple volt meters to monitor that is worthwhile.

Yes, the meters I used are cheap $15 Radio Shack meters.  But they're pretty sensitive and I can easily see a needle's width difference on them, which is .05 volts.  Because they monitor the halves of a series bank, if one half goes down on voltage by only .05 volts, the other half has to go up on voltage by the same .05, which is a full .1 volts difference between the two halves.  That's extremely easy to detect with those cheap meters.

It was only .1 volts difference that made me pull my batteries back in July and check the water because I had never seen them be anything but dead on up that point.

If you want to buy $100 apiece digital meters, it don't matter as long as what you have is sensitive enough to alert you that the the two halves of the bank aren't the same.
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Chris

[birdhouse]

i'm not here to say that series is better than parallel, or that digital is better than analog. 

granted, i have a much smaller system, but i have 8 (6v) batteries wired in series/parallel.  480Ah @ 24v.  the thing i like about my battery system, is none of the batteries are directly wired in parallel.  i can stick a VOM on any given battery at any point and get a decent idea of how that battery is doing compared to the others.  in chris's system, a specific battery cannot be tested unless the interconnects are removed.  the whole parallel string will read the same voltage despite the fact that a single battery, or even single cell is weak. 

i like put a VOM on each battery after the end of a night of decent draw from the bank because i believe that is where they will show their differences.  a simple 5 minute procedure will prove any culprits! 

if i find a culprit, i run the air compressor for a while to get the bank lowish, then shoot for equalize the next day after absorb has been reached. 

then i equalize again.  that has seemed to sort any imbalances i've had.  i never center tap for 12v!  that the devils work! 

adam

[DamonHD]

That courtesy thing, can we try it again please everyone?

If Chris wants to keep this to the narrow original topic that seems fair enough.

The battery life at high temperatures issue is also interesting, but clearly contains quite a lot of 'heat' of its own and there's a load of interesting stuff there: maybe a new thread should be started for that.

Chris, I could lock this thread if you liked.  I think your point is clear that you are happy with the two simple analog[ue] meters and believe that they saved the day.  'Nuff said.

Rgds

Damon

[ChrisOlson]

in chris's system, a specific battery cannot be tested unless the interconnects are removed.

Adam, this is true.  I had to go thru all 24 batteries with just a gut feeling that they were low on water to find the one that had the problem because there is no way to tell by voltage checking to find which one is pulling the others down without disconnecting them all in a parallel string.

Damon - no sense locking it as some folks have some interesting points like the one Adam just brought up.  The way I see it, monitoring battery banks and keeping them balanced is a very real issue, regardless of whether you use primarily series connections or parallel.  I really think a lot of folks just hook them up and just check water now and then - and that's it.

I remember reading about one setup (don't remember if it was here or someplace else) with series sixes where a connection in a battery cable end went bad and destroyed the entire string due to a wide variation in voltages on the string.  I think it was a 24 volt system with Trojan batteries.

So that's why I posted it.  My way is not the only way, but it's one way that works for the type of batteries we got.  And I think it is unwise for anybody to just hook them up, think they got them hooked up "the right way" and assume it's good to go and you have to do is check water.  A battery can fail at any time in a bank, and without a way to catch it before further damage occurs it can get quite expensive.

Monitoring with simple permanently installed voltmeters at bank midpoint taps is one way to monitor a bank, and I'm satisfied that it works.  That's what the thread is all about - to show people that fact, and that it's not an expensive thing.

Whether or not the meters are digital or analog I don't think matters as long as they can be calibrated to a known accurate meter and use the same meter to calibrate each monitoring meter.  From what I've seen with most of the cheap digitals is that you can hook up two different digital meters to the same battery and they will typically read a few hundreths of a volt difference.  I got two Doc Wattsons that don't agree hooked to the same battery.  And that's why I selected the meters I got - I can calibrate them easily with a screwdriver and a digital meter.
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Chris

[DanG]

I wonder of a 'plus/minus'  swing-from-center  swept needle indicator would be possible with a little circuit wizardry, reporting just the first 2/10th volt difference...

[bob g]

DanG

i think you are on to something there!  perhaps instead of meters
some sort of comparator circuit that can be adjusted to maintain
a green light if the two banks are within some tight parameter and
alternatively set a red light directing attention to the bank that is lagging?

that would be cool and useful,

bob g

[ChrisOlson]

That would be sort of like one of those ammeters that shows discharge or charge, and when the needle is in the middle it's in balance.  It would take a special design meter but I see no reason why that couldn't be done.

All you need, if you are measuring at one midpoint tap, is three wires to the dual voltmeter setup like I have.  Next thing we know, one of the RE outfits like MidNite Solar, will come out with one   
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Chris

[Frank S]

I have been thinking while following this thread and that is always dangerous.
 First off I for one like analog meters they are simple and for the most part more than sensitive enough But what I was thinking about along the lines of Dan and Bob's previous posts . would be  the addition of a pair of LEDs maybe duel colored ones. like red green the circuit would probably only need a couple of resisters. that way both banks in balance both LEDs would be green out of balance the higher or lower depending on how the resister were wired would show red.
 A piezo alarm could even be wired across the banks that would sound if one bank were lower than the other.
 
For connecting a large bank or multiple banks in series parallel I like bus bars for the parallel with individual cables connecting the batteries to them with disconnects this way any single cell or battery can be dropped out of circuit
 just a thought

[bob g]

Frank

my thinking as it relates to buss bars

what i am planning on doing, when it comes time to install the set of batteries i plan on using, instead of the ones i have been using in testing is this

the buss is 48volts, however the theory of operation is independent of voltage.

the buss would be a gang of anderson plugs, so that i can plug in the 8 batteries and have them series connected via the buss gang.  in this manner i can switch positions of a battery or switch out a battery for the spare on plan on having on hand.

there would be a second plug for the spare to be connected to, it would be maintained in float there until needed, as a weaker battery takes the spare position i can then work with it by careful charging, equalization, watering etc. and then set it to float until the time comes it is needed.

by using this method i can use anyone of the batteries as a pilot battery for purposes  of monitoring temperatures, voltage, and water levels via a purpose built autowatering system, perhaps.

my concern with any bank is getting down the road a bit and having a battery go boobs up and then not having a battery of similar age/condition to replace it with... simply replacing it with a new battery is likely to cause all sorts of other problems i wouldn't have to address had i had the spare.

having the spare allows me the ability to take better care quicker than i might without it, without the spare i might be pressed to continue to use a stuggling battery while trying to figure a way around it, causing more problems for that battery and perhaps others in the string.

so yes, i like your idea of cables from the individual batteries up to a buss connection of some sort, i particularly like the anderson plug because it is somewhat self cleaning each time it is extracted and inserted, at least those connections would see more frequent attention

at least i think

bob g

[ChrisOlson]

First off I for one like analog meters they are simple and for the most part more than sensitive enough But what I was thinking about along the lines of Dan and Bob's previous posts . would be  the addition of a pair of LEDs maybe duel colored ones

LED's would actually be better than meters to my way of thinking.  With the analog meters I do have to get up to them and look at the position of the needles to make sure they're even.  LED's would be really simple - if it's green its good - if it's red it's not good.

I have no clue how to build a voltage comparison circuit to turn on LED's, but I'm betting it's really simple.
--
Chris

[JW]

Simple LED Voltmeter Circuit
http://www.ecelab.com/circuit-simple-led-voltmeter.htm
search
led bargraph voltmeter



JW

[WindriderNM]

How qbout an underground battery shed.
-

[dloefffler]

Really dumb question.

If the issue is individual battery voltage, 24 meters would be less that $300, why not just buy 24 meters, place one across each battery and eliminate guesswork?

Dennis

[ChrisOlson]

Because if I did that, despite the fact that it would be really cool, my wife would look at it and go, "What the hell is this?"   
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Chris

[DamonHD]

Don't you need a little mystery in your marriage?  %^P

Rgds

Damon