Batteries Exposed

[SamoaPower]

I would like to present a few thoughts and opinions concerning batteries and battery charging to perhaps stir the thinking and creative juices which might even lead to an answer or two or, at least, some provocative discussion. As we inch our way up the learning curve with the intent of keeping our alternative energy lights burning brightly, we soon discover among the myths, opinions, facts and so-called facts that the topic is not as easy or simple as first thought.

To get the ball rolling, I offer a few observations and opinions:

     1.  Battery manufacturers want to sell more batteries.

     2.  Flooded cell batteries are the only practical type to use, Gel and AGM notwithstanding.

     3.  Trojan T-105's offer the most bang for the buck.

     4.  Chronic undercharge is more ruinous to batteries than recurrent modest overcharge.

     5.  Most alternative energy source battery banks are probably chronically undercharged.

     6.  No one makes a charge controller that does it right.

     7.  Many in warm climates probably have the wrong density electrolyte in their batteries.

     8.  Most installations are under-instrumented to maintain batteries correctly.

     9.  Batteries are part of a system and system design is all-important.

    10.  The compromises made in an evolving energy system often lead to a devolved system.

Discussion on the above:

1. Battery manufacturers seem reluctant to provide hard information to help us with our problems. Sure, they offer basic tips and caveats but try to find out exactly how a battery works and you meet a stone wall. They're not interested in trying to help us in achieving maximum longevity; they just want to sell you more new ones.
   
2. Flooded cell batteries are pretty forgiving as long as you pay attention to two critical factors - battery (not just ambient) temperature during charging and electrolyte level. Let either one of these get out of hand and you're in trouble. I got a couple of years out of a pair of very expensive AGMs but found them too touchy to charge conditions with a variable charge source (solar, wind) to be practical. See No. 6.
   
3. I've read with interest the comments about Sam's Club batteries. Unfortunately, no Sam's Club here in American Samoa. Having searched for and tried a number of different batteries, I keep coming back to the 105s. At about $70 each they're hard to beat IF YOU TREAT THEM RIGHT! (it goes for ANY battery)
   
4. Most users and charge controller manufacturers seem to put preventing overcharge as their priority when they should really be paying attention to the other end of the scale. Chronic undercharging with its attendant hard sulphate build-up is the main cause for less than optimum longevity and loss of capacity. A routine, controlled modest overcharge can actually be beneficial - like a mini equalization charge. The only, real limit to this is the battery temperature and water loss. The importance of temperature was really brought home to me when I read (from a manufacturer) that for each 15^F increase in battery (not ambient) temperature above 80F, for an extended period, will reduce battery life by HALF! Shows why car batteries don't last long - it gets HOT under the hood. Did you ever get 8-10 years out of a car battery in a car?
   
5. In the belief that most users probably use a commercial charge controller and my opinion that current charge controllers don't do the job right (see next item), I can't help but conclude that most have chronically undercharged batteries with a loss of capacity and longevity. 90-95% charge is NOT full charge.
   
6. I'm sure I'll get a lot of static on this one. Charge controller design has evolved quite a bit from the days of the simple bang-bang, on-off controllers of the past. The typical three phase (bulk, absorption and float) approach is a definite improvement over the early ones. They can work reasonably well, if not accurately, with a fixed (mains) charge source. Now, what really exacerbates the problem is that we have to deal with a charge source(s) that varies considerably in current availability vs. time - all the way from zero to many amps. To the best of my knowledge, they (the manufacturers) still don't successfully address the primary issue of how do we determine the battery's state-of-charge (SOG).  If we don't know the SOG, how can we determine when to terminate charging? Many simply use battery terminal voltage as the controlling parameter to switch charge phases but, as these representative curves show, terminal voltage varies considerably with charge current and battery actual (not necessarily rated) capacity in Amp/hours for a given SOG. E.G., 2.4 volts/cell at C/100 to 2.77 volts at C/6 for 100% returned charge. (C=battery capacity) Do you know your actual capacity?  It's obvious that you can't use terminal voltage alone to determine SOG.
   
   

Some use the charge current decreasing to some preset value (usually based on guesstimated capacity) during the absorption phase and call it 100% SOG and switch to float phase. But what happens when the current availability - clouds or wind dies - decreases below that set point? It erroneously thinks the battery is full and switches to float leaving the battery undercharged. So, what to do? If you have one of these controllers, you could increase the bulk voltage set point to say 14.8 volts to try to guarantee an overcharge but it's only a halfway measure. I'd be happy to learn that someone has finally come out with one that does it right - I'd probably buy it tomorrow. I have designed one but other current projects are in the way to finish the prototype.

7. If you live in a temperate climate, the usual supplied acid of S.G. 1.280 is fine. However, those in a warm climate like the southern states or in the tropics, as I am, can improve battery life by using a less "hot" acid of S.G. 1.265. The problem is that many southern battery dealers don't appear to know this and still use 1.280 acid. There will be some loss in capacity but is more than made up for by increased longevity. The best approach is to buy your batteries dry and add your own acid. If you can't find 1.265 acid, simply dilute 1.280 to 1.265. Got your hydrometer handy?
   
8. I'm sure there are some out there who set up a system using a simple controller with a couple of LED indicators and depend on the controller to do the job right and remain blissfully unaware of what's really going on. If you can afford to replace your battery bank every couple of years, please continue on. For those of us not so deep in the pockets, a different approach is advisable. The minimum instrumentation I consider necessary is a digital voltmeter, a digital ammeter and shunt that measures net current into or out of the battery and a digital amphour meter that measures net energy in and out of the battery. I tend to go overboard and measure EVERYTHING in sight with separate permanent meters (digital panel meters are cheap these days), not a multimeter. It's the only way I know to get a handle on what's going on dynamically. Next step is data loggers.
   
9. The battery bank is one component of a system consisting of charge source(s), battery and loads. The design of such a system needs to be done in a logical fashion with components matched to each other, to the resources at hand (sun, wind) and to the system task requirements (loads). It's similar to the wind generator problem of matching the turbine blades to the wind and the alternator to the combination. The name of the game here is efficiency for minimum dollars. Battery banks are often sized according to the carry-over time for the designated load. This is only part of the issue. Batteries also need to be sized to the capability of the charging source. A battery bank that's too large for the charge source(s) will spend too much of its time undercharged and those that are too small will waste a lot of the available energy.
   
10. The urge or need for system expansion inevitably happens. You run across that super deal on a bunch of used batteries and you jump on it. Now, what do you do with them? Do you simply hook them up in parallel with your main bank and hope for the best? You could actually lose in the long term by doing so. Unequal charge sharing could result in your "good" bank being undercharged. Batteries within a bank should be matched to each other. Ideally, a bank should be purchased at the same time and maintained in the same way. If you have batteries of a different size, type or age, the best thing to do, is set them up as a separate bank and switch them alternately with the main bank for charging. Take a systems view to changes and determine how well balanced the resultant system will be.
    
    

Of course, there are more issues but this post is already too long. Another time perhaps.

[Flux]

This will stir up a hornets nest, but I agree with a lot of what you say.

There is unlimited information on charging a battery with proper algorithms from a properly designed charger, discharging it to a certain percentage and then repeating the process. May be useful for some applications, but most of us have to grab charge as and when we can and may be discharging at the same time. Information on this seems rather limited.

I haven't found modern batteries to be any better than ones we had 50 years ago, they are more convenient and need less maintenance but most of them sit on stand by systems and never do anything in anger and when the crunch comes they don't always do it.

Efficiency may be a bit better with the clever things and self discharge is less, but the good old Plante cells in glass jars lasted about 20 years in many set ups and they were actually being used.

At least wet cells can be equalised and if you do it regularly then I think the charge controllers are good enough. It would be better if they included a low volt cut off but most people watch the volts.

I haven't found voltage to be useful as a means of determining state of charge, some will be half charged when standing for 12 hrs and showing 12.4v and others I have tried have been nearly flat, although they both show about 12.8v when full charged and left to stand.

If you are charging and discharging then volts are meaningless.

Flux

[SamoaPower]

I appreciate your input Flux.

Exactly! Battery manufacturers don't seem to want to address the issues concerning variable charging sources and simultaneous discharging. It's probably because they don't have the answers to a problem that's not simple.

Yes, the technological "improvement" in batteries seems to be a mixed blessing. If you are willing to baby-sit the so-called "advanced batteries", they offer advantages. Neglect them for a little while or provide them with a less than optimum diet, they turn around and bite you.

I have to take exception to your comment that charge controllers are good enough if you equalize. Yes, equalization is necessary and best performed regularly (for flooded cells), but is not enough in itself. If the battery is left chronically undercharged between equalization charges, the damage has been done. I view undercharging as a cumulative effect that, to a certain degree, is irreversible. The greater the accumulated undercharge, the greater the loss in longevity. Do you know of a controller that prevents this? I don't.

How do we define "good enough"?

Battery terminal voltage is the easiest for anyone to measure and is probably why controller manufacturers emphasize that parameter to demonstrate the effectiveness of their product. Ha! Such is far from reality. When someone wants to talk about real state-of-charge, I'll be happy to listen.

Thanks again Flux.

[wpowokal]

Flux your second last paragraph, I agree but could we concider (as a way of explaining)a battery as an expandable tank with a pressure gauge as a level indicator (volt metre).

Lets say the tank is 2 metres tall so our pressure gauge says 2m when the tank is full assuming the pressure gauge is located at the bottom of the tank.

But there is full and there is full, now we pump a bit more water into this tank. As its already at 2M it will expand (remember this is an expandable tank), and in that way hold more.

The  pressure gauge still reads 2m because its showing relative height/voltage not girth.

The voltage on a battery is like this pressure gauge, it does not lie but only tells part of the story.

Oh and age of battery has an effect on this storage capacity, many reasons, but once again volts are deceiving.

For what it's worth I do not beleive battery manufacturers deliberatly misslead. We mortals miss use them on occasions.

My batteries came from the last power station I worked at, the replacement set lasted some 12 months. Some mortal carrying out the monthly test, place charger on boost for 6 hours (equalise charge), forgot to put the charger back to float (now this is 25+ year old technology)

Result the batteries boiled dry, now did the manufacturers fail to tell the electrical section how to care for batteries?

What gets up my left nostral is my State of Australia says I can not buy these batteries because I am not a licenced toxic waste dealer.

anyway good thread, and later, cause its late here.

allan down under.

[Phil Timmons]

Well, sure.  And good thing this is in the "Rants" section.

I tend to agree with all that and a whole lot more.

Seems the real question is what is the best energy storage method/medium and batteries chronolically come up as a default answer without much thought -- almost like an old habit.

I suppose I should be biased towards batteries as well -- electrical/electronic background -- but by what seems like good design goals they just do not make it.  What is the expected life cycle you all experience?  Typical is 1000 (or less) full cycles?  Yeah, I know, keep them floating and they last longer . . . but what was the point of the exercise to start with?  To store and withdraw energy, right?  Not create a slow bleed and small return?

And then the biggie-sized waste problem?  Was this ever the object of Renewable Energy?  Just not sensible to me.

I am not promoting one energy storage system over another, but this a pack of fairly smart guys (and gals) -- We have to be able to think up something better than this.

[ghurd]

For #10, we switch 2 battery banks between 1 solar charger, because of bigger new and smaller used batteries. It works great. More people should try it. A spare charged pair of used T-105s can be quite a bit of power at crunch time.

For #6,I think Morningstar has done a fine job with their controllers. Their website has some specifics. I believe their PWM algorithm compares battery voltage change to duty cycle with all available amps, maybe not. Also reduces the need or frequency of equalization.

For #8,we hardwired in $3 HF multimeters. It helps as long as you understand what you see.

For #1, 99.999% of the population wouldn't understand it, or be able to do anything about it. The people who do make charge controllers.

Why wind first got my attention.

A tangent of #4, hardly ideal, both banks of our main batteries spend 4 to 5 continuous months undercharged, very rarely reaching 13V while charging during those months. So far it has not been as damaging as I expected. The old bank is 6~8 years old, the new bank is 2~3, the last retired battery (12v 100ah) recieved a lot more abuse than these lasted 12(?) years.  These get used down to 10V sometimes at crunch time, even though I would not recommend doing it!

Complicated power requirements, but we need more when we have less. Complicated economics too, income vs new batteries, but the battery cost isn't that relative even if they only last a week.  (No grid)

The current batteries 'seem' none the worse for wear, so no complaints about longevity under the circumstances.

More would be better, but doesn't make economic sense for us. Except for an inexpensive windmill, that was recently added (No fear of overcharging with that one, but it helps).

Allen, add a very tiny hole between 2 halves of your water tank and you have surface charge too!

Most people can't do anything if the charging system is not keeping up anyway. Or the batteries wouldn't be low. Should they sit in the dark if the battery is low? My wife wouldn't do it.

Naturally everyone would like twice as many PVs, more bigger wind gens, and a lot more battery. We are still in the framework of what we have to work with.

G-

[Gary D]

There is a chart from Trojan on a link provided by our hosts. The interesting thing is how discharged the battery is even with a high voltage... Am just starting the jurney into deep cycle batteries myself.

Got to use a good specific gravity hydrometer to determine true state of charge? Even works during charge/discharge... Link below or click otherpower link at top of page and click the links section on batteries...  Gary D.

www://otherpower.com/otherpower_battery_metering.html

[Gary D]

Stupid me, I'll try the link again...helps if you type it correctly

http://www.otherpower.com/otherpower_battery_metering.html

[windstuffnow]

  Very interesting subject!   I haven't researched the battery end as much as I probably should but have learned a lot just from experience working with my battery bank.  Some learning mistakes and some expensive... learning none the less.  I used to monitor my bank by the volt meter using a chart similar to that of the otherpower page listed below.   This is very decieving and doesn't really give you a reasonable "state of charge".  You'll see voltages in the range of charged but your bank can actually be considerably discharged even with reasonable voltages.   Unless you have a very accurate way of counting amp hours used and put back you'll never really know the state of your batteries.

  I purchased a Trimetric meter just for that reason... it counts what goes in and what comes out in amp/hours.   I don't think its a perfect system but it certainly helps in giving you a real "fuel level".   Considerably more accurate than a simple voltage check.  Some of the things I'm a real stickler about is keeping them full, never taking them down below 80% ( although difficult not to do at times) and equalizing them at least every 30 days.   I have a set of T105's that are going into their 7th year now, so far, have done a really nice job.   I strongly believe if you follow the above 3 rules as well as monitor them closely you will get the most from your bank.   Their not a "maintenance free" part of your system and do require alot of attention in my opinion.  

  There are other monitors out there similar to the Trimetric and all have a reasonable investment cost, I believe its a wise investment.  I'm not trying to sell these things but I have to say I've learned the most about my batteries and usage/charging from using it.

.

[John II]

Thanks for bring this subject up again SamonaPower

Batteries are definitely the "weak link" of the alternative energy systems. I wish Hydrogen storage and fuel cells were more available at much lower prices.. but such is not the case. Other storage systems such as compressed air is horrendously lossy. New revolutionary battery designs are always promised just around the corner, but never show up on the market place for one of two reasons. (1) The have problems that ultimately can not be ironed out. (2) They function so well, that manufactures can't sell new batteries often enough and it cuts into the over all profit strategies. After all if you did have something that lasted twice as long, but cost the same amount to make.. which would you rather sell over the long term ?

Over the years, I have seen several different battery companies provide a specific gravity viewing gauge right in the corner of their deep cycle batteries. At a glance you can see the exact level of charge of each battery that way. As far as I know... this is absolutely the best and perhaps only way of knowing a batteries true state of charge.

Also while possibly too pricy for home owners, there are companies that provide specific gravity gauges that will install on batteries and provide telemetry information to multi channel data loggers. This would seem ideal to me. Take a look at this URL.

http://www.serveron.com/products/BM-main.asp

I wonder if a good low cost one could be engineered for people with less than a corporative budget ?

You'd have to have your little glass bulb that would float at X height in the battery acid depending on it's specific gravity. Then you'd need a very low cost low tech way of accurately measuring it's height.

One method might be to have an translucent opaque piece of plastic for the top of your floating bulb. The surface would be rough sanded. Then fire a very directional narrow beamed current regulated LED onto it's surface. Then have a photo cell pickup located next to the LED to pickup the reflectivity of the opaque plastic.

The closer the bulb rises towards the LED and the photo cell... the brighter the reflection, and the further away from the LED and the photo cell the dimmer the reflection. The photo cell would reflect this variance in light to a sequencally switched A/D converter or in other words a low cost multi channel data logger.

Even if each homemade gauge registered a different reading do to in-accuracies of home production. One could use a pressure chamber to alter the density of liquid to change the density of the fluid via pressure and map the curve of each home built gauge independently. This individual curve could be applied to that cell on your computer, and you'd have accurate readings on all of your electronic gauges.

A small cheep low energy palmtop or laptop computer could crunch the math and show you the health of each battery as well as exactly what percentage of charge each battery is at. It could red flag trouble and sound an alarm when you need to take corrective actions.

There might be better ways of measuring the specific gravity of a battery electronically. Any ideas out there ?

John II

[Propwash]

Don't feel bad because you can't get Sam's Club batteries. I just purchased some and they are not worth the gas money I spent hauling them home. I started using my mill with an old set of Caterpillar starting batteries. After hooking up four of the new Sam's batteries I had less usage than with the old Cat batteries. I bought a hydrometer and started checking them. In every battery each cell had a different reading. One battery showed a flat reading when the others were showing a full reading. I returned that one and got a new one. I connected all of the six volt batteries together to equalize them before reconnection to the windmill. They would not equalize. Each battery had a different reading after being connected together for two days. I didn't think this could be possible. I have set them back up for 12 volt use and hooked them to my mill but at this point I think I will go back to the old Cat batteries.

  I am a greenhorn at this stuff for sure, but what is nagging me is how you can charge a bank of batteries when using a charge controller that diverts the charge when it senses a 13.8 voltage . My batteries can be so flat that my inverter kicks out but yet a good gust of wind will push my volt guage up to 14v. Once my batteries get up to 11 or 12 volts a wind gust will create a surface voltage far above 14v. I guess what I am asking is if your controller senses the high voltage surface charge and diverts it ,is light wind the only time you can get a charge in your batteries with out it being diverted. Is my problem that I don't have enough batteries to absorb the charge I am putting into them?

                                Kevin

[Clifford]

At the moment, I'm running on 4 big yellow Walmart Specials...  

I managed to get a short in the system somewhere and deep cycle them down to 6V...   Man is it a major hassle to recharge them with solar in the middle of the winter.

I know the idea of chronic undercharging....   The bat voltages seem to jump around too much to be of any high value to determine battery state..   I can only seem to get a general state if I look at voltages like:

< 10, 10-10.5, 10.5 - 11, 11-11.5, 11.5-12, and > 12.  And as I'm recharging my banks, it is not uncommon for the votage on the bank to drop by 1/2 volt overnight due to absorbtion or something (opposite is true when the bank is fully charged).

I haven't done any cell to cell comparisons, but so far the bank of 4 bats seems to run well as a single unit.

As far as cut-offs...

I thought part of the idea of the cut-off was an increase in resistance as one nears capacity.  Thus, rather than cutting off at 13 or 14V, one should cut off when the resistance increases (or, maybe this is reflected by the slope of the voltage curve increase (with constant input)).

[Flux]

We don't have Sam's Club here but I agree that some of the cheap so called leisure batteries are not as good as a top quality starter battery, but I suppose you get what you pay for.

Those Cat batteries don't come cheap but they are good value if you can drop on some at a reasonable price. At the cheap end I don't think starter batteries are worth buying, but the top end ones will serve quite well despite the continual warning not to use starter batteries.

Set your charge controller voltage higher, 13.8 is float volts. If you can set 2 levels I would charge from low to about 14.8v then let the volts  float at 13.8.

If you only have one setting then about 14.4 may be a good compromise if it doesn't float at that voltage for more than a day or two at a time, if so try 14.2

Flux

[SamoaPower]

Ed, I certainly agree that a "fuel gauge" provides significantly more information than simple instrumentation. However, this still requires more personal attention than many are willing to give. I think what most of us want is a controller that can be trusted to do the job right, with a check, now and then, to see all is well.

Unfortunately, batteries remain a high maintenance item if you want them to last a reasonable time. By the way, congrats on seven years from your T-105's. Have you checked their actual remaining capacity lately? It's a tedious job, but I'd be interested in knowing the results.

[SamoaPower]

Wow, John II, you start off with a "low tech" idea, which got high tech pretty quickly. All kidding aside, you're absolutely right that specific gravity is the definitive way to get a good handle on state-of-charge (SOG). I've also played around, in my head, with a few ideas on how this might be done, but haven't found one yet to be reasonable.

Your optical solution has merit, although it would be nonlinear due to r^2. Also, there may be some second-order nonlinear effects in S.G. vs. SOG itself. Like you point out, custom calibration may be needed.

Let's keep working on it.

[Propwash]

Hi Flux, thanks for your input. The Sams batteries that I purchased were 6volt deep cycle golf cart batteries. The Cat batteries are 12volt starting batteries. I currently am not using a charge controller. I am not sure if a c60 will be large enough for me. I saw 150 amp readings in the last heavy wind that we had. This was during heavy gusts but 60-100amp readings are very common so I don't know if a 60amp controller will be enough. I currently use a 1500watt electric heater to make use of the amps in heavy wind. It has a 850 watt setting which I use as well depending on voltage readings. I shut my mill down when I am not around to watch it in heavy winds.

                           Kevin

[SamoaPower]

Don't give up on your Sam's batteries yet. It sounds like they are badly in need of equalization and the technique you used of simply connecting them all in parallel won't do it if you're not also charging at a high enough voltage. Connecting them in parallel alone, without charging, doesn't work. Leave them connected for 12 volts and supply a charge (if your wind won't do it, use a mains charger) that will get the voltage up to at least 14.8 (more is okay). It may take a while. Once they get there, see that they are bubbling freely and leave them there for another two hours. Don't let the electrolyte level get below the level of the plate tops and check the case temperature. If they get uncomfortably warm, terminate the process. I don't like to see them over 110F.

Let them cool and check the specific gravity - don't forget the temperature compensation. They should be better equalized, but may require repeating the process one or more times. This is okay as long as the water is maintained and you don't allow them to get too hot.

I agree with Flux that if your controller cuts off at 13.8, you're going to be undercharged. Set it higher if you can. If you can adjust the float voltage as well, I suggest setting it to 13.2 to 13.5, depending on ambient temperature. Higher temp - lower voltage. A float of 13.8 will have you adding water every week or so.

The main problem is the controllers. They're simply not up to the job.

[ghurd]

Clifford,

How much solar and what controller are you using?

The 1/2 V overnight drop seems small, like the solar is undersized.

Just curious.

G-

[Bruce S]

Ed;

A little off topic:

   I was going to make mention about the similar meter that we are testing for our companies e-trike battery banks.

I would be very interested in know more about the trimetric.

The one we use maxes out at 60Ahr bi-directional.

I will say that our little banks of 40Vdc and 20Ah banks aren't in a league with the T105s and such, but will say that by using this, little meter we can easily tell what the SOC is of the bank and have even gone so far as not trusting any of the chargers.

Could you send me a link the the Trimetric so I can check it's number against what we use?  

Thanks

Bruce S

[windstuffnow]

  Hi Bruce,

    The trimetric meter can be found here... http://www.bogartengineering.com/  .  I thought it was a bit pricey when I purchased it but I'm really glad I did.   I've learned a lot from using it.

.

[windstuffnow]

  I think any RE system is going to have a considerable amount of maintenance especially on the battery end.( unfortunately ).  

  I have no idea of their remaining capacity, they'll still go 3 days without any input which brings me down to the 80% mark.   How do you test for this?  If its to timely I doubt I'll do it, way to busy now, but it would be nice to know how?

.  

[Clifford]

Ok...

I am somewhat undersized....  for economic purposes, and because I consider it a temporary install.

My System:

6 x Siemens 48W panels.

- 4 of them flat on the roof (at the normal roof slope).

- 2 not mounted (& DIODE Connected)

- The four on the roof feed about 10 ft of 10 GA stranded and 30 ft 10GA solid wire to a Manson SBC-7120 controller.

- All feed into 4 Walmart Special Deep Cycle Batts (12V, parallel).

Most of the winter I was averaging about 2 to 3 AH(12V)/panel/day.  I think I am now getting up to about 5 AH/Panel max and hoping for more soon.

My house wasn't designed for solar, and I'm not planning on it being a long-term install.  I also lack the space or wind for a good windmill.  Thus, I'm trying to limit my initial investment.

I can do ok with the house lights.

However, I managed to get a Bosch Aquastar 240FX.  It works very nicely with a grid-tied system.  But, it is an unexpected power hog.  And, of course, central heat is another power hog that I've been trying to limit the use of.

Why is my power generation low?

- Angle (flat on roof, no tracking)...  as I've been reading, it is much more than pure geometry, but also determines reflection which is bad.

- Cloudy days are a killer

- At low sun angles, I can get some shade (somewhat better now that most of the leaves are gone.

- Maybe the panels are just "old".

- WINTER

[joshua]

What type of deep cycle batteries do you have?  What group size, reserve capacity?

Josh

http://www.BohannonBattery.com

[Buck L]

Large Batteries are rated in amp hrs. The best way to test them is to set up a load say 10 amp. and let them drain down. (note the time it takes)  Then recharge the Bat. with a good auto cut back Charger. do the test again. this will give you the usage of the Bat. If you have a bank of Batteries, then you need to seperate them and test each of them by there self. L Buck

[bj]

     Samoa--don't disagree with anything, just an observation.  As

I have a small homebuilt genny, used a D-8-D battery as load.(cat battery)  Just

for evaluation.  I assumed that when manufacturers do not recommend

discharging to below 80, or in some cases 85%, they meant voltage.

     As a result of testing, lots of it, I think this means capacity.

Which I think has almost nothing to do with voltage.  On the big

battery, the volts stay up (11.5) until 10 minutes before dead.  This

is with a 250 Watt resistive load.  Charging with the genny takes time,

depending on the wind of course, But, I have noticed voltages at the

battery, of in the neighborhood of 17 volts.  Not much bubbling, until

the amps have dropped off.  Then bubbling starts without abandon.  That

is when I disconnect.  Going by volts, I only got a couple of hours

with the load.  Ignoring volts, and only going by amps, and bubbling,

I get most of a day.  

    Does this make any sense?  If not, sorry.  If it does, then

hoefully it has helped.

    BTB I trust the amp meter more than the volt.

    bj

[jim622]

I want to thank each and every one of you that added to this post. I have learned a lot of useful information, that will save me big bucks in the long run.

Thanks again

Jim622