What is an unattended battery?

So far, the battery you used has usually been functional, but you want to replace it with something better, even if you have to pay a little more. You ask in the store, and there you are offered to consider a maintenance-free battery.

However, you are hesitant because you do not really understand the difference between a conventional and maintenance-free battery, and you do not know exactly what to choose.

Let's see if we can help you ...

What is a maintenance free battery?

By “unattended battery” is meant that the battery is factory sealed. Unlike a maintenance battery that you can open, check the electrolyte level, and if you need to add distilled water, this cannot happen here simply because maintenance-free batteries do not open.

How many types of maintenance free batteries are there?

It is important to remember that almost all types of batteries that are currently available (with the exception of lithium-ion batteries) operate with lead-acid electrolyte. Therefore, the difference between different types of batteries lies in the technology that is used, and not in the electrolyte.

Main types of maintenance free batteries:

Conventional Lead Acid Batteries maintenance-free type
These types of maintenance free batteries are the most common types you can find on the market. The technology they use is called SLI, and all elements found in a serviced lead-acid battery are also present in a non-serviced battery.

This means that both types of batteries have positively and negatively charged plates, and there is a liquid electrolyte between them to provide a good chemical reaction.

The difference between the two types of “wet” batteries is that batteries that can be serviced can be opened and refilled with electrolyte, and in the case of maintenance-free batteries, it is impossible to refill the electrolyte.

In addition, unlike a regular lead-acid battery, which must be placed very carefully, since the likelihood of a spill is quite high, a maintenance-free battery can be placed at any angle, as it is sealed and there is no risk of spills.

Maintenance-free batteries also have longer battery life and lower self-discharge rates.

Important! Sometimes stores offer SLI maintenance-free batteries that are incorrectly labeled “dry.” This is not true, since batteries of this type have a liquid electrolyte and are “wet”. The difference, as we have already mentioned several times, is only that they are sealed at the factory, and there is no danger of spilling and leakage of electrolyte from them.

GEL batteries
This type of maintenance-free battery is called gel / gel because the electrolyte in them is not liquid, but in the form of a gel. Gel batteries are virtually maintenance-free; they are extremely rugged and reliable and absolutely safe to install in places with limited ventilation. The only drawback of this type of battery, so to speak, is its higher price compared to maintenance-free batteries with liquid electrolyte.

Efb batteries
EFB batteries are optimized versions of regular SLI batteries. EFB stands for Enhanced Battery. In batteries of this type, the plates are isolated from each other by a microporous separator.

A polyester fiber is placed between the plate and the separator, which helps to stabilize the active material of the plates and extend the battery life. This type of maintenance-free battery has a large number of charge cycles and is capable of partial and deep discharge twice as much as conventional batteries.

AGM batteries
This type of maintenance-free battery has much higher performance than conventional batteries. Their structure is identical to the structure of batteries with liquid electrolyte, with the difference that their electrolyte is connected to a special separator with fiberglass.

In terms of battery life, AGMs have significant advantages over liquid electrolyte batteries. Unlike conventional batteries, an AGM rechargeable battery has up to three times longer battery life, can be placed in any position, and even if the case cracks, battery acid does not spill. However, this type of maintenance-free battery is much more expensive than other types.

It became clear what a maintenance-free battery is and what are its main types, but let's see what their advantages and disadvantages are.
One of the main advantages of maintenance-free batteries, regardless of the technology used, is the following:

• unlike ordinary batteries, unattended batteries do not require periodic checks;
• during their work you do not need to make any maintenance efforts, except to charge them if necessary;
• since they are hermetically sealed, there is no risk of electrolyte leakage;
• can work in any position without danger of leakage of fluid from the housing;

The disadvantages include:

• This will not affect the battery, but. Since it is sealed at the factory, it is not possible to check the electrolyte for leaks, pour water or check sulfation.
• There are myths and legends that there is still a way to open the battery, and we assume that if you search, you will find such “ideas” on the Internet, but we strongly recommend that you DO NOT experiment.

There is a reason these batteries are enclosed in a sealed enclosure, right?

• unlike conventional batteries, unattended batteries are more expensive.

How to find out if the battery you are planning to purchase is regular or maintenance free?
It is easy! You just have to pay attention to battery design. If the lid is clean and smooth, and you only see the indicator and a few small gas holes, then you are looking at a maintenance-free battery. If in addition to the above items on the cover there are plugs that can be unscrewed, then you have a regular battery.

What are the best-selling brands of maintenance-free batteries?
When it comes to ratings, opinions are always different, because everyone has their own views on both the brand and the battery’s expectations.

Therefore, the rating that we present to you is based on our personal tests and observations, and you can accept it or choose another popular brand of maintenance-free batteries. The choice is yours.

Maintenance-free liquid electrolyte batteries
When we talked about what a maintenance-free battery is, we told you that this type of lead-acid battery is the best-selling in our country, as they have better specifications than ordinary ones and their price is much more acceptable than others types of maintenance free batteries.

That's why we start our rating with this type, and at the top of the rating - Bosch Silver. German plate casting technology with the addition of silver provides a stable power source and long battery life.

Bosch SilverPlus - this is an even better model, which is characterized by an even lower level of electrolyte losses, since there are special channels in which the liquid is deposited in the form of condensate.

Varta Blue Dynamic also contains silver, but the composite layout is different. This brand and model of maintenance-free battery is characterized by minimal self-discharge and long service life.

Gel batteries
The undisputed leader among batteries of this type for several years in a row is Optima Yellow Top. This model provides unique starting current characteristics - 765 amperes at a power of 55A / h. The only drawback of the model is its rather high price, which makes it less sold than other brands.

Of the AGM batteries, our favorites are Bosch, Varta and Banner. All three brands offer AGM maintenance-free batteries with extremely good performance and a very long battery life.

We hope that we have been helpful to you and that we have made your choice of battery a little easier.

Questions and answers:

What is a Serviced Battery? This is a lead-acid battery with open cans (there is a plug above each of them, through which distillate is added or the density of the electrolyte is checked).

What's a better maintained battery or not? A serviceable battery is easier to manufacture and therefore less expensive. Maintenance-free is more expensive, but more stable with respect to electrolyte evaporation.

How to determine if the battery is out of service? Maintenance-free batteries do not have service windows that are closed with plugs. In such a battery there is no way to add water or measure the density of the electrolyte.