Calculate Hydrogen Gas Emissions 5n5o6q

Calculate Hydrogen Gas Emissions – Industrial Batteries When deg a battery room, ventilation requirements need to be taken into consideration. Lead acid motive power batteries give off hydrogen gas and other fumes when recharging and for a period after the charge is complete. Proper ventilation in the battery charging area is extremely important.

• Calculating Hydrogen Concentration

• Calculating Room Volume

A hydrogen-in-air mixture of 4% or greater substantially increases the risk of an explosion. The concentration of hydrogen should be kept below 1% to provide a safety factor. Hydrogen gas is colorless and odorless. It is also lighter than air and will disperse to the top of a building.

• Determining Ventilation Requirement

• Determining Fan Requirement

• Do You Need Forced Ventilation

• Hydrogen Gas Detector (HGD-1)

The information below is provided for reference only. State and local codes may apply that supersede these guidelines. The following is for general understanding only, and GB Industrial Battery takes no responsibility for these guidelines.

Step 1: Calculating Hydrogen Concentration

A typical lead acid motive power battery will develop approximately .01474 cubic feet of hydrogen per cell at standard temperature and pressure. H = (C x O x G x A) ÷ R 100 (H) = Volume of hydrogen produced during recharge. (C) = Number of cells in battery. (O) = Percentage of overcharge assumed during a recharge, use 20%. (G) = Volume of hydrogen produced by one ampere hour of charge. Use .01474 to get cubic feet. (A) = 6-hour rated capacity of the battery in ampere hours. (R) = Assume gas is released during the last (4) hours of an 8-hour charge. Example: Number cells per battery = 24 Ampere size of battery = 450 A.H. (H) = (24 x 20 x .01474 x 450) ÷ 4 100 H = 7.9596 cubic feet per battery per hour top

Step 2: Calculating Room Volume For a room with a flat roof volume is calculated W x L x H less the volume of chargers and other fixed objects in the battery room. W= Width L = Length H = Height Example: Room size 80 feet long, 60 feet wide and 30 feet tall. V = 60 x 80 x 30 V = 144,000 cu.ft. top

Step 3: Determining Ventilation Requirement Assume 75 batteries stored. 7.9596 x 75 = 596.97 cubic feet per hour (7.9596 calculated in Step 1) Battery room 144,000 cu. ft. from example in Step 2 V = R x P ÷ H x 60 minutes (V) = Ventilation required (R) = Room cu. ft. (P) = Maximum percentage of hydrogen gas allowed (H) = Total hydrogen produced per hour V = 144,000 x .01% ÷ 596.97 x 60 V = 144.73 or the air should be exchanged every 144.73 minutes (2 hours 24 minutes) top

Step 4: Determining Fan Requirement Fan Size = R x 60 minutes ÷ V (R) = Room cu. ft. (V) = Ventilation required 144,000 x 60 ÷ 144.73 = 59’ 697.36 cu. ft. per hour or 995 CFM. The ventilation system should be capable of extracting 59,697.36 cu.ft. per hour or 995 CFM. top

Step 5: Do You Need Forced Ventilation In theory the 596.97 cu. ft./hr. only represents .004% which is < 1%. Therefore forced ventilation would not be required for this example. However, the following should be considered before ruling out forced ventilation: Is the battery room closed in or open? If closed in no natural ventilation may be possible. Since hydrogen gas rises are there areas in the ceiling where gas may collect in greater concentrations. The above calculation represents worse case scenario assuming all batteries are gassing at the same time. This is highly improbable. If natural ventilation is sufficient in an open area forced ventilation should not be required. If your calculations determine a percentage <1% hydrogen concentration, we recommend a Hydrogen Gas Detector for safe measure, part number HGD-1.

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Hydrogen Gas Detector (HGD-1) Operation Should the concentration of hydrogen gas in the air surrounding the sensor reach 1% by volume, the "1% caution" yellow LED will light and the 1% internal relay will close. Should the hydrogen gas concentration reach 2% by volume, the "2% warning" red LED will flash and an 80 db alarm will sound; the 1% relay will remain closed and, if a Dual-Relay model, the 2% internal relay will close. Either relay can activate a remote exhaust fan and/or alarm. Location Hydrogen, colorless and odorless, is the lightest of all gases and thus rises. The detector, therefore, should be installed at the highest, draft-free location in the battery compartment or room where hydrogen gas would accumulate. The size of the area one detector will protect depends upon battery compartment room. The detector measures the hydrogen gas in the air immediately surrounding the sensor. If hydrogen gas might accumulate in several, unconnected areas in the compartment or room, individual detectors should be placed at each location. Optional Accessories: steel junction box mounting on wall or ceiling; modular jack (with duplicate LEDs; test button; and buzzer if needed) for remote placement; telephone-type cable for connecting the modular jack to the detector. Added Benefits In addition to protecting your employees and your property, the detector also may reduce the following costs:Electricity – Heating – Air Conditioning. Instead of continuously running an exhaust fan to prevent hydrogen gas accumulation, use the detector to activate the fan only if the concentration reaches 1%. Insurance. Installation of a detector in areas where batteries are charged may result in a reduction.

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[email protected] Hydrogen Concentration Worksheet

Compliments of: Industrial Battery and Charger, Inc. Charlotte, North Carolina During the recharging process, a lead battery releases hydrogen and oxygen through the electrolysis of sulfuric acid. The beginning of gassing is determined by the battery voltage, but the amount of gas depends on the current that isn't absorbed by the battery

and is used in the electrolysis. As the battery reaches its full state of charge, the acceptance of current becomes less and the liberation of hydrogen is more. Four percent (4%) concentration of hydrogen is dangerous and has a potential for an explosion. Generally, the maximum allowable concentration of hydrogen is 1.50% of the room's cubic footage. To keep the hydrogen concentration below 4%, adequate ventilation must be provided. Rate of Hydrogen Release 1 Ampere x 1 Hour x 1 Cell = 0.016 cubic feet / Ampere Hour / Cell Battery Hydrogen Calculation Ampere Hour x Finish Rate (percent) x Number of Cells x 0.016 Cubic Feet / Ampere Hour / Cell

Example: Quantity = 10 Batteries Type = 18-85-21 Ampere Hour = Ampere Hour per Positive x Number of Positive Plates Ampere Hour = 85 Ampere Hour Plate x 10 Positive Plates Ampere Hour = 850 Ampere Hour Battery Hydrogen Calculation 850 AH x 0.05 x 18 Cells x 0.016 Cubic Feet / Ampere Hour / Cell = 12.24 Cubic Feet / Hour / Battery x 10 Batteries = 122.40 Cubic Feet / Hour Room Calculation 40' Long x 30' Wide x 15' High = 18,000 Cubic Feet 18,000 Cubic Feet x 0.015 (Maximum Allowable Concentration) = 270 Cubic Feet (Maximum) Rate of Concentration Calculation

270 Cubic Feet (Maximum Allowable) ÷ 122.40 Cubic Feet / Hour = 2.2 Hours or 132 Minutes Rate of Air Volume Removal 18,000 Cubic Feet ÷ 132 Minutes = 136.40 Cubic Feet / Minute

BATTERY TUTORIAL

While there are many battery chemistries today, and new types becoming commercially viable over time, we deal with the lead acid types, flooded, AGM, and true Gel, as they are widely used in the applications we specialize in. Lead acid battery technology has been used commercially for over a century. Some archeological finds of the appropriate materials in a man made configuration suggest the principle has been known and used much longer than that. Their construction is of lead alloy plates, and an electrolyte of sulphuric acid and water. A battery is made up of a number of cells, and the lead acid chemistry dictates a fully charged voltage of about 2.12 volts per cell. Thus, a nominal 6 volt battery has three cells with a full charge voltage of 6.3 to 6.4 volts, and a 12 volt battery has six cells, and a full charge voltage of 12.7 volts. High quality, high performance lead acid batteries may may exhibit higher cell voltage. The cell has two plate types, one of lead and one of lead dioxide, both in with the sulfuric acid electrolyte as either a liquid, absorbed in a mat, or a gel. The lead dioxide (PbO2) plate reacts with the sulfuric acid (H2SO4) electrolyte resulting in hydrogen ions and oxygen ions (which make water) and lead sulfate (PbSO 4) on the plate. The lead plate reacts with the electrolyte (sulfuric acid) and leaves lead sulfate (PbSO4), and a free electron. Discharge of the battery (allowing electrons to leave the battery) results in the build up of lead sulfate on the plates and water dilution of the acid. More on sulfation and its problems later. The specific gravity of the electrolyte as measured with a hydrometer in flooded batteries, indicates its relative charge (strength), or level of dilution (discharge). The reversibility of this reaction gives us the usefulness of a lead acid battery. The sealed versions contain the water, hydrogen, etc. under normal use, for recombination, and eliminate the maintenance of checking water levels, and corrosion around the terminals.

Charging the battery is reversing the process above, and involves subjecting the battery to voltages higher than its existing voltage. The higher the voltage, the faster the charge rate, subject to some limitations. There is a gassing point to consider, and true gel batteries have a lower peak charge voltage, because bubbles can occur in the gel which don't dissipate, and result in battery damage. More on this in the charging tutorial. The electrolyte may be absorbed into a mat type material so there is no free electrolyte (AGM battery), or may be in a gel format which also stabilizes it (true Gel battery). Current lead-acid batteries are basically distinguished as deep cycle/storage (rated in amp hours), or automotive SLI type (Starting/Lighting/Ignition), rated in cranking amps. There are also combination types, rated for both duties, but these usually have a lower cranking amp rating than a starting battery of the same group size.

SLI Batteries SLI batteries are designed to release a high burst of amps for a short time (a starting sequence), and then be relatively quickly recharged from the equipment's charging system (alternator). Typically, a starting sequence discharges less than 3% of the battery capacity. SLI batteries are not designed for repeated deep discharge, and their life is considerably reduced when subjected to this. There are wet (flooded) and totally sealed, maintenance free batteries (AGM - absorbed glass mat) in this class. These generally have a high plate count, and the plates are relatively thin. They are rated in CA, cranking amps (at 32 degrees F), and CCA, cold cranking amps (at 0 degrees F).

Deep Cycle Batteries Deep cycle batteries are designed with thicker plates, to have a constant discharge rate, and to be deeply discharged and subsequently accept recharging. They are called RV, marine, deep cycle, storage, and sometimes golf cart batteries, as these are the typical markets they apply to, as well as others. There is no benefit to deeply discharging deep cycle batteries as a maintenance procedure, and they have no memory effect. They are typically rated in amp hours (ah), but may have a CA and CCA rating, if they are dual purpose, or occasionally used for starting purposes. Deep cycle lead acid batteries are available in two configurations - wet and sealed. A wet cell battery has a higher tolerance to overcharging, however, it will release hydrogen gas when charging that must be properly vented, and the water levels must be checked frequently. Sealed lead acid batteries can be of AGM (Absorbed Glass Mat) or Gel construction, and both are sometimes called VRLA (valve regulated lead acid) batteries.

Frequently the term "Gel" is used to refer to any truly sealed, maintenance free battery, and this practice causes confusion to battery consumers, as the AGM and true Gel have some different characteristics, particularly in the charging requirements of the true Gel. Both types are maintenance free, have no liquid to spill and gassing is minimal. Other names for the sealed types are starved electrolyte, maintenance-free, dry cell, and spill proof. Most of these are Department of Transportation (DOT) approved for air transport, and classified as non-hazardous. The Gel is the least affected by temperature extremes, storage at low state of charge and has a lower internal discharge rate, but has peak charge voltage requirements that are measurably lower than a flooded or AGM battery. An AGM battery will handle overcharging slightly better than the Gel Cell. Included in the AGM category are the Optima™ and the Odyssey™, as well as several other high performance sealed batteries. The smaller batteries you find in house alarm systems, computer UPS (uninterruptible power supply) boxes, etc., that say "sealed lead acid", "spill proof", or "maintenance free", are almost always AGM type batteries. If it doesn't say "gel" on it, or have a "G" in the part number, it's not a gel.

High Performance Batteries We mentioned the Optima™ and the Odyssey™ high performance batteries. There are others such as the Rock Racing™ as well. These batteries use materials and construction techniques and achieve excellent results, which the price tends to reflect. The Odyssey units exhibit extremely high burst amps for the first 5 seconds, a critical feature in starting high displacement or high compression engines. They also can be totally discharged and recharged many times (rated at 400 cycles at 80% depth of discharge). For dual purpose, starting and deep cycle, these are hard to beat. We keep an Odyssey PC1500 charged and ready in the shop for emergency jumps or other situations, and testing. Enough said.

Battery capacity Battery capacity is a measure of the energy the battery can store and deliver to a load. It is determined by how much current a battery can deliver over an industry standard period of time. The unit of measure is called "ampere hour" (ah). The battery industry standard is a 20 hour rate, i.e. how many amperes of current the battery can deliver over 20 hours at 80 degrees F until the voltage drops to 10.5 volts for a 12 V battery and 21 volts for a 24 V battery. For example, a 100 ah battery will deliver 5 amps for 20 hours.

Occasionally a company or marketer will use a 10 hour rate or some other rate, so be sure which rate you are given when comparing brands and group sizes. Battery capacity is also expressed as Reserve Capacity (RC) in minutes. Reserve capacity is the time in minutes a battery can deliver 25 amps at 80 degrees F until the voltage drops to 10.5 volts for a 12 V battery and 21 volts for a 24 V battery. A relationship between amp hours (ah) and reserve capacity (RC) can be approximated with this formula: ah = RC times 0.6

Typical battery sizes

BCI*Group

Battery Voltage, V

Battery AH

31

12

105

4D

12

200

8D

12

245

6

220

GC2

(Golf Cart)

* Battery Council International

High battery discharge rates As discharge rate is increased above the industry standard 20 hour rate, the usable capacity decreases, due to the "Peukert Effect". The decrease is not linear, and is shown in the chart below.

Battery Capacity/Rate of Discharge

Discharge Hours

Usable Capacity

20

100%

10

87%

8

83%

6

75%

5

70%

3

60%

2

50%

1

40%

This must be taken into consideration when sizing a battery for a particular application. If it is a high current draw, battery capacity must be increased over the simple calculated amp hour requirement.

Battery life and depth of discharge (DOD) Battery life is shortened the more deeply it is discharged in each cycle. Increasing a battery bank capacity over minimum requirements will increase the life of the bank. True Gel batteries tend to have a higher number of cycles than AGMs when cycled deeply, hence their frequent use in golf carts and wheelchairs/scooters when sealed batteries are used, and deeply discharged daily.

Average Life Cycle Chart

Depth of Discharge % of AH capacity

Cycle Life

Cycle Life

Cycle Life

Group 27/31

Group 8D

Group GC2

10

1000

1500

3800

50

320

480

1100

80

200

300

675

100

150

225

550

Temperature effects on batteries Lead acid batteries lose capacity in low temperatures. At 32 degrees F, a battery will deliver about 75% of its rated capacity at 80 degrees F. This needs to be considered when sizing a battery bank of required capacity for colder environments. A heated or insulated compartment is advisable for very cold climates. High temperature keeps battery chemistry more active, and measurably decreases battery life. A battery that may last 5 years in a 60 F to 80 F environment, may last only 2 years in a desert environment.

Internal discharge Batteries are subject to an internal discharge, also called self-discharge. This rate is determined by the battery type, and the metallurgy of the lead used in its construction. Wet cells, with the cavities inside for electrolyte, use a lead-antimony alloy to increase mechanical strength. The antimony also increases the internal discharge rate to between 8% and 40% per month. For this reason, wet cells should not be left unmaintained or uncharged for long periods. The lead used in Gel and AGM battery construction does not require high mechanical strength since it is stabilized by the gel or mat material. Usually calcium is alloyed with the lead to reduce gassing and the internal discharge rate, which is only 2% to 10% per month for the AGM and Gel batteries. Any battery discharge, including internal discharge, produces sulphation on the battery plates as part of the chemical cycle, and given enough time, this sulphation hardens, causing diminished battery capacity at best, or total loss of function. Routine charging after use, or use of a "floating" charger for long periods of storage (boat batteries, ATVs, etc.) prevents this diminished capacity and maximizes battery life. A large portion (approaching 50%) of lead acid batteries have diminished capacity or become unusable due to sulphation, and never reach their rated lifespan. There are electronic devices (chargers and stand alone devices) for dealing with sulphation, but the best practice is avoiding the situation in the first place with proper battery management, including use of quality 'smart' chargers.

Summation on attaining maximum battery life From the discussion above, it can be seen that there are several issues pertaining to battery life. Recharging in a timely fashion after use, avoiding total discharge if possible, routine maintenance charging or use of a "float" charger on batteries in storage or out of

season (jetski, snowmobile, ATV, etc.) are all things which contribute to good battery life. Avoiding extreme temperatures, especially heat, when possible, and checking water levels in flooded batteries are essential as well. There are some applications which are more likely to reach the end of the cycle life of a battery, and have diminishing capacity as a result. Wheelchairs and scooters used daily and heavily fall into this category. I have added a page dealing with battery prices and the reasons they are rising and probably will continue to do so for a while. This situation contributes to the reasons to seek maximum battery life.

Series and parallel connection of batteries When two or more batteries are connected in series (positive to negative in a string), their voltages add up but their AH capacity remains the same. So, two 12 V, 100 ah batteries connected in series result in a 24 V, 100 ah pack. The negative of one battery connects to the positive of a second battery, and the remaining terminals are the system connections. When two or more batteries are connected in parallel (positive to positive, negative to negative), their AH capacity (amperage) adds up but their voltage remains the same. So, two 12 V, 100 ah batteries connected in parallel result in a 12 V, 200 ah pack.

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