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Flat battery vs Tubular battery

Updated: May 23, 2022

There was a time when only Flat plate lead-acid batteries are available for home power backup. However, due to constant changes in industrial development more and more types of advanced batteries are available for home power backup. And this lead to massive diversified types of batteries to choose from.


Here, every battery has two main parts electrolyte and electrode. Where electrolyte is a medium by which electrons flow between electrodes and electrodes are the metallic conductors that store the powers between them.


The difference between the types of batteries depends upon the type of electrodes and electrolytes they have. Some of the common types of electrolytes and electrodes are mentioned below.


Electrolytes could be:

  • Gel type

  • AGM type

  • Flooded type

And Electrodes could be:

  • Flat Plat

  • Tubular

  • Tall Tubular


Each type of battery has a different advantage over the other type of battery and in this blog, we will discuss the following:


Difference between flat plate battery & tubular battery:


Flat and tubular batteries both are members of the lead-acid battery family. However, in a flat plate battery both positive and negative electrodes of a Flat plate are in shape. But in a tubular battery, negative electrodes are flat plate type and positive electrodes use a frame structure consisting of a series of vertical spines connected to a common bus bar. Each spine is covered by non-conductive tubes filled with a paste of lead oxide active mass.


The below figure shows the structure of the pasted flat plates, uses as both electrodes of the flat plate battery and negative electrodes of the tubular battery. These plates are made by pasting the lead oxide active mass on a mesh grid.



Pasted Flat Plate Electrode
Pasted Flat Plate Electrode

Also, the below picture shows the frame structure used as a positive electrode of the tubular battery. This frame structure consists of a series of vertical spines connected to a common bus bar.

Tubular Plate Electrode
Tubular Plate Electrode

Each spine of the above frame structure is covered by below shown non-conductive tubes filled with a paste of lead oxide.


Flat Battery Vs Tubular battery


A tubular and flat battery could be a flooded or gel type battery. So for a fair comparison between Flat and tubular batteries, we will compare a flooded flat battery with a flooded tubular battery.


Charge Cycles [at 80% DOD]

One charge cycle is equal to discharging a fully charged battery up to 80% of its capacity and then fully charging it again. Here, the charge cycle of a flat battery discharge is 50-1000. Whereas for tubular battery same is 800-1400. However, a low DOD [depth of discharge] increase the charge cycles of a battery.


The actual charge cycles may differ from manufacturer to manufacturer



Self-discharge [also called charge retention]

An offloaded and off circuit battery loses energy over time, this phenomenon is called self-discharging or charge retention capacity of the battery. Here, the self-discharge rate of a flat plate battery is higher than a tubular battery.


Float current

Once the battery is fully charged it required low current charging at a rate equal to its self-discharge rate. This low current charging is called float charging or trickle charging. Since the self-discharging rate of a flat battery is higher than a tubular battery, it also required a high float charging current.


The method of both trickle and float charging is the same but in float charging the battery is prevented from overcharging. Whereas in trickle charging battery can be overcharged.

Maintenance

Low self-discharge rate and high charge cycle, reduce the maintenance of a tubular battery as compared to a flat battery.


However, there are other types of batteries that required no maintenance. Gel tubular battery is one of the batteries that required no maintenance. Read our blog on “Gel tubular battery Vs Tubular battery” to learn more.


Thermal management

The thermal management property of a battery means, how good its heat convection. The tubular plate electrode design of the tubular battery makes convective heat transport easier. Hence, increase the thermal property of the battery.


However, flat plate electrodes have poor thermal properties as compared to tubular batteries.


The thermal management of the battery is also, depends upon the quantity of the electrolyte it has. Furthermore, a tall tubular battery has higher electrolyte volume than a tubular or flat battery hence it has better thermal management properties than both flat plate and tubular battery.



Electrical resistance

A well-defined pore size permits easy movement of the electrolyte, hence reducing the internal electrical resistance of the battery. A tubular battery has low electrical resistance as compared to a flat battery.



Deep-Cycle Capability

The deep-cycle capability of a battery, it defined as how deep a battery can discharge multiple times without getting damaged. Good thermal management, low electrical resistance and high charge cycle make tubular batteries more suitable for deep discharge applications as compared to a flat battery.


However, it is not recommended to discharge the tubular battery as well as flat battery by more than 50-60% for better battery life.


Dimension

The dimension of both tubular and flat battery is almost identical. For example, the dimension of a Livguard, 150Ah tubular battery is [LxWxH] 520x275x308 mm which is almost identical to the dimension of a Livguard, 150Ah flat plate battery that is [LxWxH] 500x350x400 mm.



Weight

Tubular batteries are slightly heavier than flat batteries. For example, the weight of a Livguard, 150Ah tubular battery is 52 kg which is slightly higher than the weight of Livguard, 150Ah flat plate battery which is 47 kg.


Warranty

Due to the high charge cycle, tubular batteries have a higher warranty period than a flat plate battery. For example, the warranty of a Livguard, 150Ah tubular battery is 54 months which is higher than the 36 months warranty of a Livguard, 150Ah flat plate battery.


Cost

A tubular battery is 40% more expensive than a flat plate battery. However, tubular batteries have a higher life expectancy.


Life Expectancy

There are lots of conditions like ambient temperature, depth of discharge and number of charge cycles that affect the life expectancy of a battery. However, in identical conditions, tubular batteries have a higher life expectancy than flat batteries.


Tubular batteries have a life expectancy of 4.5-5 years, which is higher than the 2.5-3 years of life expectancy of flat plate batteries.



Which is better Flat or tubular battery?

Flat batteries are the most economical battery and ideal for regions where power cuts are low [1-2 times in a week] and light loads [non-AC and non-motor loads]. However, tubular batteries are more expensive than a flat battery but more suitable for off-grid solar power plants, regions with high numbers of power cuts [almost every day] and for heavy loads like AC and Motors.



Since tubular batteries can be charged faster than a flat battery, can be discharged deep without getting damaged and have a high charge cycle. Hence, these batteries are most suitable for a solar inverter. learn more


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