Conflicting GB Indstrial Battery information ...

[WindyOne]

I was looking for battery information when I came across this conflicting information on the GB Industrial Battery - FAQ web page ...

http://gbbattery.com/FAQ.html


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2.       Over Charging and Opportunity Charging
·          Industrial batteries are typically designed to last at least 1,500 charge cycles, over a five to fifteen year period. Each time you charge a battery, regardless of how long, it constitutes one cycle.

·          Consistently charging a battery twice per day, during lunch breaks for example, is known as Opportunity Charging, and reduces the useful life of a battery by 50%.

·          The additional heat generated by opportunity charging a battery usually reduces the run time equal or greater in proportion to the amount of charge it actually received, making the practice completely ineffective and costly.

·          Routinely charging the battery before it is 80% discharged is another common form of over charging. For example, if you only use the battery a few hours a day, it's best to use it until it is truly in need of charging before actually plugging it in. Remember, each charge constitutes one cycle, so try not to charge unnecessarily.

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So does this mean the battery should be routinely discharged 80% before recharging?


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OVERDISCHARGING is a problem which originates from insufficient battery capacity causing the batteries to be overworked. Discharges deeper than 50% (in reality well below 12.0 Volts or 1.200 Specific Gravity) significantly shorten the Cycle Life of a battery without increasing the usable depth of cycle. Infrequent or inadequate complete recharging can also cause over discharging symptoms called SULFATION. Despite that charging equipment is regulating back properly, over discharging symptoms are displayed as loss of battery capacity and lower than normal specific gravity. Sulfation occurs when sulfur from the electrolyte combines with the lead on the plates and forms lead-sulfate.

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So, does this mean the battery should not be routinely discharged below 50% ?


Does anybody really know what GB Industrial battery recommends for the regular discharge cycle?

[WindyOne]

Also, I just noticed this statement ...

Industrial batteries are typically designed to last at least 1,500 charge cycles, over a five to fifteen year period. Each time you charge a battery, regardless of how long, it constitutes one cycle.

How can that be true when companies like Rolls and Trojan post graphs that show a huge increase in the number of cycles when the battery is only discharged 10% vs. 80% ?

[SparWeb]

Hi Wind1,
Welcome to the forum.
There are a couple of messages coming from GB on their FAQ page, so if we split hairs a little I think it will become clear what the lessons are.

One place to start is the definition of a "cycle" that they want to show you.  A cycle is a discharge and a recharge.  Whether the discharge is deep or not, or whether the recharge is complete or not, doesn't matter in the context of the first FAQ question.  All they want to show you is that if you operate a forklift during a morning shift, charge it during the lunch hour, run it all afternoon, then charge it overnight, then every day there will be 2 cycles on the battery set.  Compared to running the forklift all day, and accepting the deeper discharge of the battery, until it can be recharged once overnight, then you have saved one cycle, and hopefully improved the life of the battery.

What isn't explained or considered there is how deeply the battery would be discharged by doing that.  It may not be a bad thing!  Just sticking to the number of cycles, if you keep going back for a recharged you keep increasing the cycle count and that risks a premature end to the battery life.

Why don't I invent an example to illustrate: What if that forklift used 20% of its charge during a typical AM shift?  Well you can probably run for the afternoon and take out another 20% more of the charge, resulting in a battery with 60% charge left.  Recharge overnight and it sounds like a good system.  One cycle per day, no extra recharge cycles.  If you went to recharge that forklift every lunch hour, you would be wasting your time and money because you are adding an extra cycle every day. 

Depth of discharge also affects the life of the battery.  Sucking it down to 80% can be harmful to batteries.  Some types are more vulnerable than others, particularly Gel types I believe.  Some flooded lead-acids may be more tolerant, but in the case of a car starting battery, definitely not.  The GB's are deep-cycle FLA batteries, so the rules that apply to them should be followed.  A good rule of thumb is that a FLA battery should not be discharged more than 50% of its capacity, except in unusual circumstances.  That's what you should do, too.

Back to the example I made up, to show you the trade-off.  That forklift was using less than half of a full charge during a day's work, so it was probably OK to charge only once per day.  Now what if the forklift is used much more during the day?  Maybe it uses 35% charge in the AM shift, and another 35% in the PM.  Now the battery would go down to holding only 30% charge before the overnight recharge.  This will have a terrible effect on the battery life, and the way to address the problem is to charge it twice a day: once overnight and once during lunch hour.  This way the battery can always stay mostly charged, while still having a convenience recharge cycle, and not degrading its cycle life too much.

You can apply the same concepts to sizing up the battery bank you need, if you are considering a battery-back up or off-grid power system. 

[bob g]

here is a possible explanation for the opportunity charging effectively being an additional cycle on the battery

if you use the forklift and consume the top 25% during the morning shift and then recharge during lunch, you will be trying to stuff a lot of power into a battery that cannot accept it without heating and a lot of gassing.

if you use another 25% on the afternoon shift and then recharge overnight, if the charger is a good one, then maybe you could avoid trying to recharge in such a short amount of time, in doing so limit gassing and heating to a larger extent than at noon, however

i could see the effect being the same as two cycles on the battery, due mainly to increased heating and gassing. heating is a problem with forklift batteries because the cells are tightly packed in a steel enclosure making them harder to dissipate the heat especially from the inner cells. gassing can cause some erosion on the plates, so i would expect the manufacture would not want to excessively put the cells under any conditions that make for a lot of heating and gassing if it can be avoided.

this makes sense to me as a possible explanation, or a partial explanation which might also include other factors.

as for the difference in recommendation for 80% discharge vs 50% discharge, i have seen this before and have no idea why they would report both for their batteries.

in my research most, if not all fla literature and testing has returned the fact that fla batteries are more efficient both in charging and in returning more kw/hrs over their lifetimes if they are only discharged to 50%. 

then there is the 50/80 charge regime, which in testing has show to be the best at providing the absolute most kw/hr returned from an fla battery and is the most efficient charging regime.  the  regime calls for sizing the system so that in everyday use the battery is discharged to 50% state of charge, followed by a recharge to 80%.... this allows for the most efficient charge without undue heating or gassing, however you will then have to provide for a full charge to 100% every week to 10 days, in order to convert the normal sulfation and not allow it time to crystallize.  more frequent equalization charging is probably also part of the regime with some batteries. 

for a forklift battery the 50/80 regime might/ought to improve lifespan as well, in that the battery is for the most part infrequently charged to the point of heating and gassing. it would appear this would be easier on the batteries plates and separators. \

the 50/80 regime might not be applicable for you, in that you might need more capacity than what is available from the battery you are using on a daily basis.

fwiw

bob g

[dnix71]

If you read the fine print on sla's used in backup power supplies, they list 2 voltage ranges for the battery. One is float/standby and the other hard cycling. On standby you don't go above 13.8v usually. For hard deep discharge, you go quite a bit higher to equalize the battery.

http://www.tempestbatteries.com/html/tr7.2-12.html
http://evbatterymonitoring.com/WebHelp/Section_3.htm

Many US commercial forklift battery chargers for flooded batteries are ferroresonant. Those have constant voltage applied to the battery and the current tapers off as the battery charge rises. A tall 2 volt cell in a forklift has to be gassed and heated for a proper recharge. That's the only way to churn the electrolyte. In a car, gasoline/NG forklift, or boat if you charge the starting battery underway, the motion (bouncing and turning) stirs the electrolyte so it isn't necessary to force gassing to prevent the electrolyte from stratifying.

One of the things that shortens battery life in off-grid use if the stratification of the electrolyte. At least with a electric forklift, even though the battery isn't moving when it's charging, it does when the lift is operated. The batteries I have for backup sit on the floor from the first day until they are replaced.

[bob g]

i would buy into the concept of needing to stir up the electrolyte, i am just not sure whether the manufacture has concerns with doing it on a opportunity charge basis for its intended use powering a forklift.

it would definitely be a subject to discuss with the manufactures engineering dept to get clarification as to what their concern is with opportunity charging and each charge relating to a cycle, no matter how shallow the discharge.

when i related the 50/80 charge regime, the weekly full charge with its attendant gassing ought to be ample to keep stratification at bay.

bob g

[zap]

Here's some interesting info from East Penn/Deka on Opportunity Charging:
www.dekabatteries.com/assets/base/0810.pdf

[bob g]

Zap

thanks for the east penn link

when i think of east penn, i don't generally relate to them as a top tier battery manufacture, however i am beginning to rethink that position.

what i found most interesting in their article, was the charging rates they find acceptable for their batteries for opportunity or fast charging.

the second thing i found interesting was their concern with opportunity charging was having a battery that was never fully recharged.

the latter explains a lot as it relates to other manufactures worry about opportunity charging as it generally relates to forklift/material handling equipment used in environments by folks the for a significant part could really give a rats butt if the unit is recharged fully with some regularity.   that makes sense to me.

on the other hand, i wonder if the manufactures would be as concerned with opportunity and/or fast charging schemes by offgrid folks that are generally much more motivated to do things right, using high grade equipment, monitoring temps/compensation and doing regular equalization, along with monitoring specific gravity and keeping a log book.

the discussion on amp/hr throughput was not lost on me either, although there likely will be much discussion on this topic as the operational philosophy of any group is likely to be split between getting maximum cycles out of a battery vs. getting maximum amp/hrs out of a battery at the highest charging efficiency.  that difference is likely to hinge on what one has to recharge with, what the fuel costs are, and how reliable the charging source is.

bottom line, just like any question, there generally is no "one" perfect way of doing the battery/charge thing that will fit everyones use, equipment, or ability.  and there would appear to be just as many "wrong" ways of doing things too.

bob g

[ghurd]

the operational philosophy of any group is likely to be split between getting maximum cycles out of a battery vs. getting maximum amp/hrs out of a battery

Agreed.

And a 3rd group split, longest number of years.
Like a back-up sump pump?  I don't care if it only lasts 5 cycles, but I want it to make at least 1 cycle 10 years from now?  If you know what I mean.
G-

[dnix71]

The idiots guide to our walk behind powered lifts actually have a section on battery charging. These are Crown lifts with 4 six-volt GB Industrial sla's. These lifts have regular Anderson connectors but are designed to be recharged by a common extension cord plugged into a common 120vac outlet.

"Maintenance Free batteries are designed for deep discharged cycling, but are capable of being charged at convenient times ('opportunity charging') to extend battery capacity to complete a shift or task. When the practice of 'opportunity charging' is used, observe the following guidelines to achieve maximum battery life:

* Battery Pack should be between 30% - 60% depth of discharge.
* A minimum charge cycle of 30 minutes is recommended.
* For every minute of charge, an equal time period is required for 'cool down.'
* Allow for a full charge once a week.
* Every 2 weeks allow for an equalizing charge cycle of 10 to 12 hours following by an equal time period for 'cool down'
* Do not allow discharged batteries to sit idle for periods greater than 48 hours.
A fully discharged battery pack (2 flashing red lights) will require approximately 8 hours to recharge, plus 8 hours cool down.
If a battery charging cycle is interrupted, the Meter may indicate a fully charged battery when the truck is powered up. However the Meter will eventually (1 hour) adjust itself to indicate the correct battery state of charge."

The italicized words are actual misspellings in the manual. An equalizing charge may or may not be possible with the built-in charger, or it may be a feature of the charger. If you allow the battery to be fully charged, the internal charger will shut off and float the battery at 26 point something. I can't remember the value, but it won't harm the battery to leave the charger on all weekend, although I don't like leaving anything of value plugged in over the weekend if we aren't working Saturday.

One set of these batteries was replaced after 7 years. The battery gauge would show full until you used the lift a little, then it would drop off quickly. Some batteries in the string were way over voltage and others under, but the string voltage would be within range until you used the lift.