Differences between AGM and GEL Battery, to Help in Your Choice

If you have a trolling motor, a fishing boat, a 4 × 4 or a solar installation, for example in an isolated site, you have already asked yourself: should I choose a gel battery or an AGM battery? What is the differences between agm and gel battery? How do I choose?

First of all, what is the GEL / AGM battery?


The GEL battery is a technology that relies on electrolyte frozen by the addition of silica gel. In some batteries, phosphoric acid is added to improve the life cycle in deep cycling. In contrast, the AGM “Absorbed Glass Mat” battery technology is based on an assembly of fiberglass blotters that are compressed between electrodes and impregnated with electrolyte (70% water & 30% acid). The assembly being sealed and totally sealed in both gel and AGM cases.


But then what are the notable differences between these two types of batteries?


There are several differences between these two types of technologies. The first difference easily visible but not negligible is the price. Indeed the AGM battery is more competitive price than the GEL battery because of its less expensive technology.

But we must not stop at this first point even if it is important. This difference in price has a reason indeed GEL batteries have a discharge rate of 100%, you can fully discharge the battery, even with a long-lasting discharge, you will keep the initial performance of They retain their properties in time. The AGM batteries have a discharge rate of 80%. It is also a very acceptable discharge rate but this means that a gel battery can be completely emptied before being recharged, which is not desirable on an AGM battery which must be recharged at 80% of its discharge. The consequence of this is that the duration of a gel battery will be slightly higher than that of an AGM of the higher number of cycles.


The GEL battery is ideal for repetitive cycles, so for daily use with slow and deep discharges. The AGM battery is ideal as a service battery as marine battery and camper battery but can also be used as a starter battery if necessary.


In terms of temperature range the GEL battery can withstand temperature ranges from -15 ° to 50 ° while the AGM battery is resistant to temperature ranges from 0 ° to 40 °.


The gel and AGM batteries also called VRLA have three common points, they are waterproof, they do not need maintenance and are resistant to shocks and vibrations. This is a real plus for mobile uses on land or sea. In addition to this the gel batteries can be used in upside down position.




To complete this guide is to help you in your choice it is necessary to know that there are different types of capacities, dimensions and terminals. These are important elements to take into account especially when installing them in small spaces but also when the question arises: should I take two batteries of 100 Ah or a single one of 200 Ah. The dimensions and average weight according to the capacities are the following (they are given as indicative because they can vary from one mark to the other):

75A / h = 242mm X 175mm X 190mm. 22 Kg

105 A / h = 330mm X 175mm X 240mm. 30 Kg

200 A / h = 520mm X 230mm X 240mm. 66 Kg

Finally there are 4 types of Terminals:


  1. SAE stem terminals: conical rods manufactured to SAE standards so that all battery cable clamps can be connected.
  1. Side terminals: molded in the wall, near the upper edge; The battery cables attach to it with a bolt that is screwed into the terminal.
  1. L-shaped terminals: mainly used on special application batteries for lawn and garden equipment, snowmobiles and light vehicles.
  1. Stud Terminals: Threaded terminals typically used on heavy duty batteries.


In conclusion:


The difference between a gel battery and AGM will be rather perceptible over the long term. Indeed over the duration of the gel batteries will be more efficient due to the number of possible cycles and will in theory have a longer life. However, AGM batteries have very interesting characteristics, they are suitable for use in service batteries, they are more powerful than conventional batteries (starting battery) and are more profitable in use. They therefore have an interesting price / performance ratio.

So for those who want to keep their batteries as long as possible and who have an intensive use the gel battery is a good choice. For those who have a “normal” use and want a competitive price / performance ratio then the AGM battery will be a good choice.


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