Although both are technologies that make the battery "maintenance-free" and hermetic, they differ in use and cost.
While AGM technology is ideal for both cyclic use (i.e. those requiring many charge/discharge cycles) and for buffer use (i.e. as an energy reserve that remains available unused for a long time ), GEL technology is mainly used for heavy cyclic use.
The AGM battery is an accumulator that does not contain liquid acid but has an absorbent microfibre glass felt inside. This material traps battery acid like a sponge, allowing you to use the limited space and volume of the battery more efficiently in order to obtain better performance for the same size.
AGM technology allows you to immobilize the acid while making it available for the plates and making the reactions between the acid and the plate material occur quickly. Since the plates of an AGM battery are very compact, the vibration resistance is better than standard batteries. Furthermore, the self-discharge of AGM batteries is very low (less than 3% per month), but above all, being built in such a way that it cannot be opened, the AGM battery is leak-proof and maintenance-free. Therefore, if properly charged, this type of battery does not require particular attention and/or precautions during its life (no need for additions of distilled or demineralized water).
GEL technology is designed for deep charge/discharge cycles in extreme environmental conditions.
Making use of resistant plates and gelatinous electrolyte, gel batteries are able to withstand 400 100% charge/discharge cycles.
GEL batteries, compared to AGM, offer greater resistance in deep discharges, better performance in adverse environmental conditions (even with high thermal excursion), stratification of acid practically absent and better cost/duration of life and cost/cycles.
On the other hand, GEL batteries cannot exceed certain parameters during charging. The maximum voltage must not exceed 14.4V (while for AGM batteries the limit is 14.7V) therefore they need special chargers to avoid the partial formation of the lead plate, thus causing the battery to lose capacity after a few charge cycles/download.
Often there is a lot of confusion about the use of the two terms and we commonly tend to call all hermetic batteries "GEL", but it is necessary to distinguish with precision the different construction technologies of these highly performing batteries.
First of all it should be underlined that the quality of both the construction technologies of these batteries is very high.
For buffer use, the problem does not arise as AGM technology is certainly better.
For cyclic use, we recommend:
- use of AGM batteries when there is limited absorption because this is less delicate in withstanding numerous charge/discharge cycles;
- use of GEL batteries, for heavy cyclic use, when there are high absorptions (electric vehicles, industrial cleaning machines, etc.).