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What is the Difference Between Sealed and Unsealed Battery?

Unlike unsealed batteries, sealed batteries have a fixed amount of fluid or electrolytes. The difference in fluid movement is significant and determines maintenance, shelf-life due to utility, and power bursts. 

Before buying a new car battery, you must decide between sealed and unsealed options. Conventional car batteries are unsealed – that was the most suitable method before the advent of sealed options. Both are still in use today, but one fast dominates the other. The apparent difference in design and engineering makes most drivers wonder which would be better for their vehicle. 

This blog post will analyze the differences between sealed and unsealed batteries. 

What are sealed batteries?  

If you have spent some time at the auto shop, you would probably have heard the phrase “sealed batteries.” People who drive old cars will likely be confused about this battery type because it is a modern invention. 

It has been designed to prevent leakage and loss of electrolytes. Unlike unsealed batteries, you get minimum access to the fluid in sealed batteries. The internal chemical reaction will not be disturbed by anything. 

That is done to prevent the electrolyte from spilling, a common occurrence with its rival. Essentially, we can call them a modification of unsealed batteries. 

AGM lead-acid batteries and gel-filled batteries are two major sealed battery types. The former option is filled with acid-saturated fiberglass mats. At the same time, the latter contains gel electrolytes that have been engineered to mix with fumed silica and sulfuric acid, creating a putty-like substance. 

AGM batteries are cheaper and more powerful, but gel-filled units last longer. However, both are excellent and popular choices because they require less maintenance. The batteries run on a limited amount of electrolytes throughout their lifespan. You do not need to replenish them like unsealed batteries. 

What are the pros of sealed batteries? 

  • Excellent performance during extreme weather. The temperature barely affects AGM and gel-filled batteries. 
  • They require less maintenance because the internal fluid is sealed, protecting and preserving the electrolyte produced. 
  • They do not require ventilation systems. 
  • Adding water is unnecessary and impossible. It does not need to be topped off because the manufacturer has decided a constant quantity. It will complete its shelf life based on the current internal fluid supply. 
  • You can use sealed batteries for a long time. They can last up to five years with little maintenance.
  • They are sealed at the top to prevent acid or gas from leaking in any circumstance. 
  • Sealed batteries also charge faster than unsealed ones.

How to tell if your battery is sealed

The most obvious way to tell if your car battery is sealed is by checking the labels. It concisely states the type, whether it is “gel-filled” or AGM lead-acid. You can also check the model number for more information. 

When you shake it, the internal content immediately settles when you set down the battery. It is another telling sign that your battery is sealed because this model has been designed to restrict the movement of battery fluid. 

Finally, you can use the following steps if the options above are unavailable. 

  • Get a voltmeter.
  • Remove the terminal cover and connect the positive lead to the positive terminal.
  • Follow suit by attaching the negative lead to the negative terminal. 
  • Read the voltage result – an approximate readout of 12.8 or 12.9 volts means your car battery is sealed.
a single car battery

What are unsealed batteries?

Unsealed batteries are also called flooded rechargeable batteries. They also contain a fluid, usually a combination of water and sulfuric acid. It flows freely, hence the name “flooded batteries.”

If it is a liquid lead-acid battery, you will find a cap on it. Avoid opening it. 

There is no seal on this option, which allows the water to flow freely inside the cell. Since there is sufficient space for movement, unsealed batteries can provide more powerful bursts of energy. 

What are the pros of unsealed batteries? 

  • They are strong enough to power your engine. 
  • Unsealed batteries are also great for harsh weather, but this is subject to some conditions.
  • They last a long time, with an average lifespan of three years. 
  • Servicing and maintenance of unsealed batteries are relatively affordable. 
  • Unsealed batteries are excellent backup options.
  • They last longer than sealed batteries, making them excellent backup options.  

What are the cons of unsealed batteries? 

There are a few downsides to using unsealed batteries. They include: 

  • Although unsealed batteries are great even during bad weather, it is not uncommon for the fluid in them to freeze during the winter. 
  • Unsealed batteries also need proper ventilation when the weather is hot. Otherwise, the liquid evaporates. 
  • This is a no-brainer. Unsealed batteries are not protected from leakage. They have been designed to be opened now and then, which can also be a disadvantage. 
  • When you shake an unsealed battery excessively, you can damage it. 

How to tell if your battery is unsealed?

When you shake the battery lightly, if the liquid inside keeps moving when you finally stabilize it, this is a telling sign that it is an unsealed battery. 

What is the difference between sealed and unsealed batteries? 

The difference between sealed and unsealed batteries is significantly physical – the former has removable caps that can be opened when the water needs replenishing. On the other hand, sealed batteries have no outlets for this feat. As such, the water in them cannot be topped-up. 

Both have various advantages. They also have their downsides. You can permit your personal preferences to determine which option to purchase for your vehicle. You have ample information to decide which is better for your vehicle, so make informed decisions.

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