Difference Between High Tech Batteries – Gel And AGM
Gel Sealed Batteries
The production technology of gel batteries is called GEL. They use a gel-like electrolyte instead of a liquid electrolyte. Silica gel (silicon dioxide SiO2), allumogel, and other substances are used as an electrolyte thickener. When wetted with sulfuric acid, these substances form a thixotropic gel.
Gel batteries have slightly worse load characteristics compared to classic batteries: it is more difficult to remove large currents from them due to the higher internal resistance. Batteries with liquid electrolyte work better at high load currents in short modes. However, in a gel-like electrolyte, gases have time to return to the electrolyte and, thus, the maintenance-free problem is solved.
To recharge GEL batteries, it is necessary to use chargers that provide charge voltage instability of no more than ±1%. Since in case of exceeding the value of the charging voltage recommended by the manufacturer by 0.05V, the recombination mechanism does not have time to work, the temperature inside the battery increases, the rate of gas evolution increases, which leads to a violation of the contact of the active mass of the electrodes with the electrolyte, loss of water, drying out of the battery, in causing the battery to fail.
Gel batteries are also critical to ambient temperature and discharge the battery with more than possible currents.
Under normal operating conditions, gel batteries do not require maintenance during their entire service life and must not be opened. But if they are violated, the battery will quickly age.
Batteries With Absorbed Electrolyte (AGM)
AGM (Absorbent in Glass Mat technology) technology is a technology in which a liquid electrolyte is absorbed into porous glass fiber separators placed between the electrodes.
The process of gas recombination is provided by special separators AGM. The material for the manufacture of AGM Battery are glass mats made of ultra-fine fibers in combination with paper fibers. Such a separator is a porous system that, like a sponge, absorbs and retains electrolyte due to the action of capillary forces. At the same time, it provides electrolyte access to the electrodes. The porosity of such a material is more than 90%, which allows gas molecules to freely move between the plates. The small pores are then filled with electrolyte but the larger ones remain free to circulate evolved gases.
The AGM separator, wrapping plates or made in the form of an envelope, has increased elasticity and elasticity. Therefore, when assembling the block of electrodes, the separators and plates are closely pressed against each other. It ensures the retention of the active mass in the cells of the current collectors and eliminates the risk of a short circuit due to swelling of the electrodes and accumulation of sediment at the bottom of the cells and at the same time it also ensures the interaction between electrolyte and active material. The porous structure of the separator provides minimal resistance to electrolyte flow during filling.
The increased assembly density of the block, the increase in the area of the active surface of the plates and the retention of the active mass on the plates provide a reduced internal resistance of sealed-type batteries and determine the main advantages of AGM batteries:
- Resistant to deep discharges;
- High charge rate;
- Charge tolerance in fast mode;
- Durability due to better retention of the active mass on the plates;
- The ability to give off an electric current of great strength in a short period of time;
- Almost complete tightness allows you to place AGM-type batteries in any position and increases the safety of vehicle operation;
- Increase the capacity of AGM batteries compared to gel batteries of the same volume and weight. AGM batteries are even more gassy than gel batteries and are less affected by ambient temperature.
Both positive and negative sealed batteries electrodes are made up of lead calcium tin alloys. It greatly reduces grid corrosion and swelling. The active material used is made from 99.9999% pure lead. The purity helps to eliminate the negative effects of contaminants. If it is made of impure material it can cause electrodes corrosion and can increase battery self-discharge.
As with gel batteries, AGMs require chargers with charge voltage fluctuations of ±1%. The maximum charging voltage for GEL and AGM car batteries is indicated by the manufacturer (approximately for gel-like 14.35V, and for adsorbed 14.4 – 15V).
GEL and AGM batteries do not require maintenance during their entire life, except for the correct choice of charger and monitoring the condition and operation of the generator.