Battery Leaks

[dlaing]

Hmmm....I suspect you should have just left it after reaching 15V. According to the charts, at one amp charging rate you needed over 3 hours to charge it completely.

I suspect tomorrow morning the battery will read a little above 12.6.

This is fine for now, but you could probably run it up to 15V or even a little higher.

Gary Cheeks advice should be appropriate for your situation:

You can take a healthy battery up to the 15.0>15.5 volt range for a couple of hours.(No longer and no higher voltage, In other words two hours above 15 volts MAX and less if the battery hits 15.5 in less than 2 hours ) This will bring the lazy cells closer to the level of the stronger ones.

[docc]

It was at 12.79 this morning. It's probably 50 F in the garage. I probably shouldn't worry but usually the AGM batteries don't drop voltage while sitting and this one is only a year old.

 

I put the 1 amp charger back on and it started charging at 15v, went to 15.5 in one minute. I unplugged it when it showed 16v at 5 minutes.

 

Maybe all is well, but it sure is reassuring to put the VOM on and see that "12.84."

[dlaing]

It was at 12.79 this morning. It's probably 50 F in the garage. I probably shouldn't worry but usually the AGM batteries don't drop voltage while sitting and this one is only a year old.

 

I put the 1 amp charger back on and it started charging at 15v, went to 15.5 in one minute. I unplugged it when it showed 16v at 5 minutes.

 

Maybe all is well, but it sure is reassuring to put the VOM on and see that "12.84."

Yah, but 12.79 is fine, too. Better than i expected, so you probably did the right thing draining it down and recharging.

I would not have taken it up to 16V, but at 50F and only five minutes above 15V while on a 1A charger, I find it hard to imagine it did any harm and now you may be at 99%!!!!

I am too paranoid to even run it above 15V, but that is with a 2A charger, so I bought the special charger.

If you have 7 batteries similar in size to Spark500 or Hawker PC545 I would recommend investing in the 6A Odyssey Ultimizer.

OMAX-6A-1B 6A, single bank with

quick disconnect 310, 535, 545, 625, 680

 

But if you have bigger batteries, you might want the more powerful and expensive chargers:

 

OMAX-12A-1B 12A, single bank 310, 535, 545, 625, 680, 925

 

OMAX-25A-1B 25A, single bank 310, 535, 545, 625, 680, 925, 1200,

1500/34, 1500/34M, 1500/34-78, 1700/65

 

OMAX-40AS-3B 40A, triple bank

sequential charger

310, 535, 545, 625, 680, 925, 1200,

1500/34, 1500/34M, 1500/34-78, 1700/65,

2150/31

 

OMAX-50A-1B 50A, single bank

310, 535, 545, 625, 680, 925, 1200,

1500/34, 1500/34M, 1500/34-78, 1700/65,

2150/31, 2250

 

OMAX-50AS-3B 50A, triple bank

sequential charger

310, 535, 545, 625, 680, 925, 1200,

1500/34, 1500/34M, 1500/34-78, 1700/65,

2150/31, 2250

 

But it is your money and you seem to be getting by with your 1A charger.

 

One way to get by with a charger that goes up to 16V, to allow a fuller charge without exceeding 15.5V, is to use jumper cables to wire a couple of batteries together, positive to positive/negative to negative, but be sure they don't differ in voltage by more than maybe 0.2V. So bring each of them up to 15.0V before hooking them up together.

Heck, you may be able to wire all seven of your batteries together!!!!

But if you do that, I would not take the charge up for too long.

[Guest Gary Cheek]

Deep discharging a lead acid battery should be avoided.

 

The whole "memory" thing with Ni-Cads has now infected lead-acid battery "thinking" I am afraid. "Memory" as originally described by General Electric Corp in the 1960s is NOT a factor in modern Ni-cads and it never was a factor with lead-acid cells. One of those wive's tales gone urban legend.

Lead acid batteries have their lives materially shortend by each and every deep discharge. Try to avoid deep discharging.

You can spend a few more $$ to charge your batteries. I use a mixture of cheapo and exotic chargers at work. Here at home I stick with the cheapos. It is far from rocket science but the people who peddle batteries and chargers may lead one to believe otherwise.

 

Docc, the temperature is a factor in battery voltage that is all too often overlooked. A reading of 12.5 at 50F may be 12.7 at 70F. It is also a factor that needs to be considered when charging. If you have a fancy high $$ charger and do not know for sure if it has temperature compensation it is best to use it at room temps only NOT in cold weather conditions. The temp compensation should read the BATTERY temperature for the best results.

 

The automatic chargers are a lot like automatic cameras. With a little practice you can get more accurate results with a hand held meter than programmed auto-exposure. Ask Ansel Adams!

[Ryland3210]

According to the "Battery University", for charging lead acid batteries:

 

"General guidelines suggest a compensation of approximately 3mV per cell per degree Celsius. The voltage adjustment has a negative coefficient, meaning that the voltage threshold drops as the temperature increases."

 

For example, with a 12 volt lead acid battery having 6 cells, if the battery's temperature is 5 degrees C above the 20 degree C standard measurement temperature, ( 77 F instead of 68 F), the equivalent voltage would be

 

- 3mv X 6 cells X 5 degrees C = - 90mv (lower)

 

or said another way: 1/10 volt lower for each 10 degrees F higher than 68 degrees

[dlaing]

Interesting stuff about temperature....now I have to redo the chart with temperature compensation

I could not find any thing about temperature compensation for the Odyssey Ultimizer, but the Odyssey Optimizer said operating temperature:

-20 to 50 ºC (-4 to 122 ºF)

I don't understand why Docc got a better final voltage when charging from discharged to 14.8 than he did from partially discharged to 15V. Strange.

[Guest Gary Cheek]

He may have generated more internal heat.

[docc]

According to the "Battery University", for charging lead acid batteries:

 

"General guidelines suggest a compensation of approximately 3mV per cell per degree Celsius. The voltage adjustment has a negative coefficient, meaning that the voltage threshold drops as the temperature increases."

 

For example, with a 12 volt lead acid battery having 6 cells, if the battery's temperature is 5 degrees C above the 20 degree C standard measurement temperature, ( 77 F instead of 68 F), the equivalent voltage would be

 

- 3mv X 6 cells X 5 degrees C = - 90mv (lower)

 

or said another way: 1/10 volt lower for each 10 degrees F higher than 68 degrees

 

 

Thanks for the good input. Looks like there won't be a 0.25 volt difference in charging target voltage within 40 degrees F of the optimum temperatre.

 

And, Gary, is 'deeply discharged' 50% or lower? From what I recall 12.3 is about 50% and 12.05 is 25%.

 

Or would you go with readings after a 3 minute load?

[Ryland3210]

Thanks for the good input. Looks like there won't be a 0.25 volt difference in charging target voltage within 40 degrees F of the optimum temperatre.

 

And, Gary, is 'deeply discharged' 50% or lower? From what I recall 12.3 is about 50% and 12.05 is 25%.

 

Or would you go with readings after a 3 minute load?

 

A clarificaton:

 

20 degrees C is not an "optimum" temperature, just used as the benchmark for most physical specifications because it is a typical room temperature.

 

A 40 degrees F difference would correspond to 0.4 volts.

 

BTW, I agree with Gary on avoiding deep discharge of lead acid batteries. One of the differences between deep cycle batteries is a larger distance from the bottom of the plates to the bottom of the case. This is to allow more space for material sloughed off the plates caused by deep discharging/charging cycles-not something you want to do on purpose.

[dlaing]

Gary seems to suggest Voltage rises with battery temperature

"A reading of 12.5 at 50F may be 12.7 at 70F."

and Ryland seems to suggest the opposite.

"1/10 volt lower for each 10 degrees F higher than 68 degrees"

I would think that Gary is correct, in this case.

But I was going by my interpretation of Ryland's math when I was perplexed by DOCC's results.

Gary's numbers make more sense, presuming the longer charge session after a complete discharge will result in a warmer battery.

[Guest Gary Cheek]

I was just making a quick guesstimate without digging up references. The difference varies from type to type but the battery capacity rises with temperature.

[dlaing]

I was just making a quick guesstimate without digging up references. The difference varies from type to type but the battery capacity rises with temperature.

So, the capacity rises with temperature, atleast going from freezing point to room temperature, but the potential drops.

 

So a battery going from 32F to 72F might have voltage reading of 13V at 32F and the engine may not start because of a lack of capacity, but when the temperature goes to 72F the voltage might read 12.6V, but the capacity has gone up so, the engine should start.

I think I now sort of understand

[Guest Gary Cheek]

http://www.homepower.com/files/battvoltandsoc.pdf

[Ryland3210]

So, the capacity rises with temperature, atleast going from freezing point to room temperature, but the potential drops.

 

So a battery going from 32F to 72F might have voltage reading of 13V at 32F and the engine may not start because of a lack of capacity, but when the temperature goes to 72F the voltage might read 12.6V, but the capacity has gone up so, the engine should start.

I think I now sort of understand

 

Yes, but note that my reference is speaking of the voltage to which a battery should be charged to obtain a given percentage of charge as a function of temperature. i.e. a cold battery must be charged to a higher voltage to reach 100% of capacity. And as you say, its capacity will be higher at higher temperatures.

[Guest Gary Cheek]

THE FOLLOWING IS LIFTED FROM THE SITE:http://www.windsun.com/Batteries/Battery_FAQ.htm#Temperature%20Effects%20on%20Batteries

 

Gelled electrolyte

Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.

 

Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th's less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. In hot climates, water loss can be enough over 2-4 years to cause premature battery death. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages.

 

AGM, or Absorbed Glass Mat Batteries

A newer type of sealed battery uses "Absorbed Glass Mats", or AGM between the plates. This is a very fine fiber Boron-Silicate glass mat. These type of batteries have all the advantages of gelled, but can take much more abuse. We sell the Concorde (and Lifeline, made by Concorde) AGM batteries. These are also called "starved electrolyte", as the mat is about 95% saturated rather than fully soaked. That also means that they will not leak acid even if broken.

 

AGM batteries have several advantages over both gelled and flooded, at about the same cost as gelled:

Since all the electrolyte (acid) is contained in the glass mats, they cannot spill, even if broken. This also means that since they are non-hazardous, the shipping costs are lower. In addition, since there is no liquid to freeze and expand, they are practically immune from freezing damage.

 

Nearly all AGM batteries are "recombinant" - what that means is that the Oxygen and Hydrogen recombine INSIDE the battery. These use gas phase transfer of oxygen to the negative plates to recombine them back into water while charging and prevent the loss of water through electrolysis. The recombining is typically 99+% efficient, so almost no water is lost.

 

The charging voltages are the same as for any standard battery - no need for any special adjustments or problems with incompatible chargers or charge controls. And, since the internal resistance is extremely low, there is almost no heating of the battery even under heavy charge and discharge currents. The Concorde (and most AGM) batteries have no charge or discharge current limits.

 

AGM's have a very low self-discharge - from 1% to 3% per month is usual. This means that they can sit in storage for much longer periods without charging than standard batteries. The Concorde batteries can be almost fully recharged (95% or better) even after 30 days of being totally discharged.

 

AGM's do not have any liquid to spill, and even under severe overcharge conditions hydrogen emission is far below the 4% max specified for aircraft and enclosed spaces. The plates in AGM's are tightly packed and rigidly mounted, and will withstand shock and vibration better than any standard battery.

 

Even with all the advantages listed above, there is still a place for the standard flooded deep cycle battery. AGM's will cost 2 to 3 times as much as flooded batteries of the same capacity. In many installations, where the batteries are set in an area where you don't have to worry about fumes or leakage, a standard or industrial deep cycle is a better economic choice. AGM batteries main advantages are no maintenance, completely sealed against fumes, Hydrogen, or leakage, non-spilling even if they are broken, and can survive most freezes. Not everyone needs these features.

 

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Temperature Effects on Batteries

Battery capacity (how many amp-hours it can hold) is reduced as temperature goes down, and increased as temperature goes up. This is why your car battery dies on a cold winter morning, even though it worked fine the previous afternoon. If your batteries spend part of the year shivering in the cold, the reduced capacity has to be taken into account when sizing the system batteries. The standard rating for batteries is at room temperature - 25 degrees C (about 77 F). At approximately -22 degrees F (-27 C), battery AH capacity drops to 50%. At freezing, capacity is reduced by 20%. Capacity is increased at higher temperatures - at 122 degrees F, battery capacity would be about 12% higher.

 

Battery charging voltage also changes with temperature. It will vary from about 2.74 volts per cell (16.4 volts) at -40 C to 2.3 volts per cell (13.8 volts) at 50 C. This is why you should have temperature compensation on your charger or charge control if your batteries are outside and/or subject to wide temperature variations. Some charge controls have temperature compensation built in (such as Morningstar) - this works fine if the controller is subject to the same temperatures as the batteries. However, if your batteries are outside, and the controller is inside, it does not work that well. Adding another complication is that large battery banks make up a large thermal mass.

 

Thermal mass means that because they have so much mass, they will change internal temperature much slower than the surrounding air temperature. A large insulated battery bank may vary as little as 10 degrees over 24 hours internally, even though the air temperature varies from 20 to 70 degrees. For this reason, external (add-on) temperature sensors should be attached to one of the POSITIVE plate terminals, and bundled up a little with some type of insulation on the terminal. The sensor will then read very close to the actual internal battery temperature.

 

Even though battery capacity at high temperatures is higher, battery life is shortened. Battery capacity is reduced by 50% at -22 degrees F - but battery LIFE increases by about 60%. Battery life is reduced at higher temperatures - for every 15 degrees F over 77, battery life is cut in half. This holds true for ANY type of Lead-Acid battery, whether sealed, gelled, AGM, industrial or whatever. This is actually not as bad as it seems, as the battery will tend to average out the good and bad times. Click on the small graph to see a full size chart of temperature vs capacity.

 

One last note on temperatures - in some places that have extremely cold or hot conditions, batteries may be sold locally that are NOT standard electrolyte (acid) strengths. The electrolyte may be stronger (for cold) or weaker (for very hot) climates. In such cases, the specific gravity and the voltages may vary from what we show.