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Quizzes > Science

Are lithium-ion batteries wet-cell? True or false

Quick, free lithium ion wet-cell quiz. Instant results.

Editorial: Review CompletedCreated By: The Frizzy Atom BombsUpdated Aug 28, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art battery quiz on golden yellow background tests true or false statements about recombinant batteries IQ challenge.

Use this quiz to see whether lithium-ion batteries are wet-cell or dry-cell and clear up common myths fast. You will review basics like anode, cathode, and electrolyte in minutes. For more practice, try our battery quiz, explore electrolytes and fluid balance, or tackle science true or false questions.

Which term is commonly used for recombinant lead-acid batteries?
Lithium-ion
Nickel-metal hydride
Valve-regulated lead-acid
Flooded lead-acid
Recombinant batteries are sealed lead-acid designs that internally recombine gases and are commonly known as valve-regulated lead-acid (VRLA) batteries. They utilize a pressure relief valve to maintain optimal internal pressure and prevent gas escape under normal conditions. The name distinguishes them from flooded designs that vent gases freely.
What is the primary recombination reaction in VRLA batteries?
Sulfuric acid decomposes directly into water and sulfur dioxide
Oxygen from the positive plate recombines with hydrogen at the negative plate
Oxygen reacts with carbon to form carbon dioxide
Hydrogen oxidizes the positive plate material
In VRLA batteries, oxygen generated at the positive plate diffuses through the separator and reacts with hydrogen at the negative plate to form water. This internal recombination reduces gas emission and maintains electrolyte levels. The process allows the battery to remain sealed and maintenance-free under normal conditions.
Why do VRLA batteries generally not require water top-ups?
They are not sealed and can vent freely
They recombine oxygen and hydrogen internally to regenerate water
They have removable vent caps for manual refilling
The electrolyte is stored in an external reservoir
VRLA batteries are sealed designs that internally recombine gases to form water, which minimizes electrolyte loss. Because of this recombination, there is no need to add water under normal operating conditions. This feature contributes to their maintenance-free reputation.
What design feature allows AGM batteries to prevent acid stratification?
They use absorbent glass mat to hold electrolyte
They rely on external circulation pumps
They incorporate silica gel additive
They have open vent caps for equalization
Absorbent Glass Mat (AGM) batteries use a fiberglass mat separator that absorbs and retains the electrolyte. This design holds the acid uniformly around the plates, preventing stratification over time. The mat structure also enhances recombination efficiency and reduces gas release.
Gel lead-acid batteries use which substance to immobilize the electrolyte?
Synthetic polymer membranes
Absorbent glass mats
Porous rubber separators
Silica fume to form a gel
Gel batteries incorporate silica fume that reacts with sulfuric acid to form a gel-like substance, immobilizing the electrolyte. This gel prevents acid stratification and reduces the risk of spills. It also allows the battery to operate in any orientation without leakage.
Under normal float charging, VRLA batteries emit:
Continuous oxygen venting
No gas at all
Minimal gassing to relieve overpressure
Large amounts of hydrogen gas
When properly float charged, VRLA batteries operate below the gassing threshold most of the time, leading to minimal gas production. Occasional gassing may occur to relieve internal pressure, which is controlled by the valve. This limited gassing helps maintain a sealed environment.
Sealed VRLA batteries can be mounted in any orientation without leakage because:
They contain an internal liquid pump
They use a freely flowing liquid electrolyte
The electrolyte is immobilized in gel or AGM
Their vents are always open
VRLA batteries use either absorbent glass mat (AGM) or gelled electrolyte to immobilize the acid, which prevents spills. This design allows the battery to be positioned in various orientations without leakage. The sealed construction and pressure relief valve further ensure safe operation.
A distinguishing feature of recombinant batteries is:
They use a one-way valve to control internal pressure
They require weekly watering
They have external acid reservoirs
They operate without a pressure relief valve
Recombinant (VRLA) batteries are equipped with a one-way pressure relief valve that opens only if internal pressure exceeds safe limits. This replaces removable vent caps found in flooded batteries and allows a sealed construction. The valve helps maintain proper recombination and prevents excessive gas release.
The term 'maintenance-free' in VRLA batteries implies:
No need for electrolyte top-up under normal conditions
No need to monitor state of charge
They self-discharge completely
Unlimited cycle life
In the context of VRLA batteries, 'maintenance-free' means the battery does not require periodic water addition because of its internal recombination process. However, it does not mean the battery has an unlimited lifespan or that its state of charge doesn't need monitoring. Proper charging and temperature control remain important.
What is the typical float charge voltage per cell for VRLA batteries at 25°C?
2.60 V
2.25 V
2.45 V
2.15 V
The recommended float charge voltage for VRLA batteries at 25°C is about 2.25 V per cell. This voltage maintains full charge while minimizing gassing and water loss. Deviating significantly can lead to undercharge or overcharge.
Which factor most significantly accelerates VRLA battery aging?
Short circuit events
Frequent equalization charging
Low discharge rates
High operating temperature
Elevated temperatures accelerate the chemical reactions inside VRLA batteries, leading to faster degradation of active materials and water loss. A general rule is that battery life halves for every 10°C increase above optimal temperature. Managing operating temperature is critical for longevity.
What is the approximate recombination efficiency of a well-designed VRLA battery?
Less than 10%
Above 95%
70-80%
50%
High-quality VRLA batteries achieve recombination efficiencies above 95%, meaning most internally generated gases recombine to form water. This high efficiency minimizes electrolyte loss and extends service life. Efficiency depends on design features like separator porosity and catalyst presence.
In VRLA batteries, gassing typically starts when charge voltage exceeds approximately:
2.6 V per cell
2.3 V per cell
1.9 V per cell
2.1 V per cell
Gassing in VRLA batteries typically begins when voltage per cell exceeds around 2.3 V during charging. Below this threshold, the recombination reactions dominate and water loss is minimal. Exceeding it leads to gas evolution, which vents through the safety valve if prolonged.
Which maintenance practice is unnecessary for VRLA but essential for flooded lead-acid batteries?
Load testing
Temperature monitoring
Regular voltage checks
Periodic electrolyte top-up
Flooded lead-acid batteries require periodic electrolyte top-up to replace water lost through gassing. VRLA batteries recombine gases internally and are sealed, eliminating the need for top-ups. Nevertheless, VRLA still requires proper charging and monitoring.
VRLA batteries can suffer from thermal runaway if:
Battery is deeply discharged
Charging current generates excessive heat at high rates
Float voltage is set too low
Ambient temperature drops below freezing
Thermal runaway occurs when charging current and internal resistance generate heat faster than it can dissipate. In VRLA batteries, overcharging at high current raises internal temperature, reducing recombination efficiency and accelerating reactions. This positive feedback can damage the battery.
What happens to VRLA battery capacity at very low temperatures (e.g., -20°C)?
Battery overcharges
Capacity increases slightly
Capacity remains unchanged
Capacity decreases significantly
At low temperatures, the kinetics of the electrochemical reactions in VRLA batteries slow down, leading to a significant drop in usable capacity. Ice formation in the electrolyte may also occur if deeply discharged. Cold environments require compensation or insulation to maintain performance.
What is a common indicator that a VRLA battery has reached end of life?
Increased internal resistance
Visible electrolyte stratification
Smooth constant voltage response
Decreased specific gravity reading
As VRLA batteries age, internal resistance rises due to factors like sulfation and grid corrosion. This results in reduced charge acceptance and voltage sag under load. High resistance is a reliable indicator that the battery is nearing end of life.
Which standard specifically covers valve-regulated lead-acid batteries?
IEC 60896-21/22
UL 810
IEEE 1188
ISO 9001
IEC 60896-21 and IEC 60896-22 are the international standards for stationary valve-regulated lead-acid batteries, outlining performance, testing, and safety requirements. These documents specify design and operational criteria for VRLA cells and batteries. Adherence ensures reliability and compliance in critical applications.
Which component inside a VRLA battery catalyzes the recombination of oxygen and hydrogen?
Copper connecting straps
Lead dioxide positive plates
Carbon paste on the negative plate
Fiberglass separators
The carbon additive or paste on the negative plate serves as a catalyst for the oxygen reduction reaction, recombining oxygen and hydrogen to form water. This feature is critical to internal recombination efficiency. Without it, gas generation would exceed recombination capacity, leading to venting.
During overcharge, what gas is primarily evolved if recombination is exceeded?
Hydrogen
Nitrogen
Carbon dioxide
Oxygen
If overcharging continues beyond recombination capacity, the negative plate cannot consume all oxygen, and water electrolysis produces hydrogen gas. This hydrogen must vent through the overpressure valve to prevent excessive pressure buildup. Continuous overcharge leads to water loss.
The pressure relief valve in VRLA batteries typically opens at around:
10-12 psi
0.5 psi
2-3 psi
20-25 psi
VRLA batteries use a one-way pressure relief valve set to open at approximately 2-3 psi (14-21 kPa) to release excess gas and prevent case rupture. The valve then reseals when pressure returns to safe levels. This mechanism maintains a sealed environment while protecting against overpressure.
In a VRLA battery, what is the role of microporous separators?
Store excess electrolyte for high discharge rates
Facilitate gas flow to the exterior
Serve as catalysts for recombination
Prevent electrode shorting while allowing ionic conductivity
Microporous separators in VRLA batteries maintain physical separation between positive and negative plates to prevent short circuits. Their fine pore structure allows electrolyte ions to pass through while minimizing gas transport, aiding recombination. Proper separator design is vital for performance and longevity.
What mechanism leads to positive grid corrosion in VRLA batteries?
Oxygen evolution reaction at the negative plate
Acid stratification
Oxidation of the lead grid at high float voltage
Water condensation on the plates
Positive grid corrosion in VRLA batteries is primarily driven by oxidation of the lead grid metal under float charging conditions. High float voltages accelerate this corrosion, thinning the grid and increasing internal resistance. Over time, this process reduces battery capacity and life.
How does high-rate partial-state-of-charge cycling affect VRLA batteries?
Causes acid stratification and increases sulfation
Enhances recombination efficiency
Has no significant effect on performance
Improves overall battery life
High-rate cycling at partial states of charge prevents full recharge, leading to acid stratification and crystal formation of lead sulfate (sulfation). This impedes charge acceptance and reduces capacity over time. Proper charging regimens are necessary to avoid this degradation.
Sulfation in VRLA batteries primarily results in:
Lower internal resistance
Increased electrolyte volume
Reduced available capacity due to lead sulfate crystallization
Improved conductivity of plates
Sulfation occurs when lead sulfate crystals form on the electrode surfaces and harden, reducing the active surface area. This crystallization cannot be reversed easily under normal charging and leads to permanent capacity loss. Prevention requires full recharge and proper maintenance.
What is a typical recommended equalization charge interval for VRLA batteries?
After each discharge cycle
Never
Weekly
Every 3-6 months
Although VRLA batteries are sealed, an occasional equalization charge every 3 - 6 months can help balance cells and reduce stratification. Equalization involves a slightly higher voltage charge that encourages gassing and mixing of the electrolyte. It should be done carefully to avoid excessive water loss.
What is the effect of deep discharge below 1.75 V per cell on VRLA battery plates?
Plate shedding and irreversible capacity loss
Enhanced grid structure
Plate densification and increased capacity
No effect if recharged promptly
Discharging VRLA batteries below about 1.75 V per cell can damage the active material, causing it to shed from the plates and leading to permanent capacity loss. This deep discharge stress accelerates aging and reduces service life. Avoiding excessive depth of discharge extends battery longevity.
The recombination reaction in VRLA batteries occurs primarily at which interface?
Electrolyte-separator interface
Negative plate-electrolyte interface
Positive plate-grid interface
Separator-case interface
Recombination of oxygen and hydrogen in VRLA batteries takes place at the surface of the negative plate where the carbon catalyst is located in the electrolyte. This interface provides the site for the oxygen reduction reaction. Efficient recombination depends on proper contact and catalyst presence at this boundary.
What is the main factor determining recombination efficiency in VRLA batteries?
Catalyst surface area on negative plates
Specific gravity of electrolyte
Case material composition
Separator thickness
Recombination efficiency in VRLA batteries is largely driven by the catalyst surface area present on the negative plate, which facilitates the oxygen reduction reaction. Larger and more uniformly distributed catalyst sites improve gas recombination. Separator structure and electrolyte properties also influence but are secondary.
According to IEC standards, the maximum allowable water loss for VRLA batteries during float service is approximately:
10% per month
5% per year
1% per day
0.1% of electrolyte per month
IEC standards specify that VRLA batteries should lose no more than about 0.1% of their electrolyte volume per month during float service. This stringent limit ensures long-term sealed operation without maintenance. Excessive water loss indicates overcharging or design issues.
Which analytic technique can be used to assess the state of health of VRLA batteries by measuring internal resistance?
Thermogravimetric analysis
Electrochemical impedance spectroscopy
X-ray diffraction
Gas chromatography
Electrochemical impedance spectroscopy (EIS) measures frequency-dependent impedance characteristics and can accurately assess internal resistance and state of health in VRLA batteries. It differentiates resistive and capacitive elements and tracks degradation. Other techniques do not directly quantify internal resistance in situ.
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Study Outcomes

  1. Identify Battery Cell Components -

    Understand the roles of the anode, cathode, and electrolyte in various battery types for accurate quiz responses.

  2. Analyze Recombinant Battery Statements -

    Evaluate which of the following statements is true of recombinant batteries to bolster your technical battery knowledge.

  3. Differentiate Battery Types -

    Distinguish lithium-ion batteries from other wet-cell systems, assessing true or false claims effectively.

  4. Evaluate Battery Chemistry Statements -

    Apply critical thinking to technical quiz challenges, improving accuracy when judging battery chemistry true or false statements.

  5. Apply Battery Facts -

    Leverage key battery facts and technology concepts to boost your score on true/false quizzes and reinforce learning.

  6. Enhance Battery IQ -

    Track and improve your expertise through scored battery technology quiz challenges, ensuring comprehensive mastery of battery facts.

Cheat Sheet

  1. Recombination Mechanism in VRLA (Recombinant Batteries) -

    Recombinant batteries, also known as VRLA batteries, leverage an internal oxygen recombination process: oxygen generated at the positive plate diffuses to the negative plate and recombines to form water, eliminating the need for water top-ups. This true characteristic answers "which of the following statements is true of recombinant batteries" by highlighting their sealed, maintenance-free design (Source: US DOE Battery Consortium; IEEE Transactions on Industry Applications).

  2. Sealed, Maintenance-Free Design -

    By using a pressure-regulated valve and gel or AGM separators, recombinant batteries maintain internal water balance and prevent electrolyte leakage, making them fully sealed and maintenance-free (Source: IEEE Spectrum; Journal of Power Sources). This design also enhances safety by limiting gas escape and reducing acid spillage risk.

  3. Anode and Cathode Roles -

    The anode undergoes oxidation (loss of electrons) while the cathode undergoes reduction (gain of electrons), driving current through the external circuit: for example, in a lead-acid cell, Pb at the anode oxidizes to PbSO₄ and at the cathode PbO₂ reduces to PbSO₄ (Source: Electrochemical Society). A handy mnemonic is "An Ox, Red Cat" (Anode Oxidation, Reduction at Cathode) to remember electron flow direction.

  4. Wet-Cell vs. Dry-Cell Classification -

    Although often quizzed with "lithium-ion batteries are considered wet-cell batteries true false," the correct answer is false: lithium-ion batteries use non-aqueous electrolytes and fall under dry-cell classification (Source: Battery University). Lead-acid batteries with flooded cells remain classic examples of wet-cell designs.

  5. Electrolyte and Separator Functionality -

    The electrolyte facilitates ion transport between electrodes, while separators prevent physical contact and short circuits; in AGM (absorbed glass mat) separators, the acid is immobilized in fibreglass mats for improved recombination efficiency (Source: Journal of Power Sources). Understanding how electrolyte composition and separator porosity affect conductivity and self-discharge rates is key for optimizing battery performance.

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