Victron 12V Solar GEL Battery

VRLA technology of GEL and AGM solar batteries

VRLA is an abbreviation for Valve Regulated Lead Acid, which means that the battery is waterproof. Gas will escape through safety valves only in case of overload or failure of elements.
VRLA batteries have exceptional leak resistance and can be used in any position.
GEL and AGM batteries are maintenance-free for life.

Waterproof GEL batteries (VRLA)

In this type of battery, the electrolyte is immobilized in gel form. GEL batteries generally have a longer life and better cycling capacity than AGM batteries.
Low self-discharge Thanks to the use of lead-calcium grids and high purity materials, Victron VRLA batteries can be stored for a long time without recharging.
 The self-discharge rate is less than 2% per month at 20ºC.
Self-discharge doubles for every 10ºC of temperature increase. In a cool environment, Victron's VRLA batteries can be stored for up to a year without recharging.
Exceptional deep discharge recovery Victron VRLA batteries have outstanding recovery capability even after deep or prolonged discharge.  It should be noted, however, that frequent deep or extended discharges have a detrimental impact on the lifespan of any lead / acid battery, and that Victron batteries are no exception.

Battery discharge characteristics

The nominal capacities of Victron batteries are given for a discharge in 10 hours, for a discharge current of 0.1C. Effective effective capacity for faster discharges at high intensities (see Table 1). The reduction of  capacity will be even faster with consumers with constant power such as converters.
Because of their design, Gel batteries have less effective capacity at high intensity. On the other hand, Gel batteries have a better life in use in floating and cycling.
High temperatures have a very negative influence on the service life. The expected life of GEL batteries can vary by 30% depending on whether the average temperature of the environment is 20 ° or 30 °.
Batteries age due to discharges and refills. The number of cycles depends on the depth of discharge  as shown in Figure 2.

Longer life thanks to Victron's 4-stage adaptive load

Victron Energy has developed the 4-step adaptive load. This innovative technology is the result of years of research and testing.
 Victron's adaptive load method eliminates the 3 major drawbacks of the traditional 3-step load:
BatterySafe Function : To avoid excessive gassing, Victron invented the BatterySafe function. The BatterySafe function slows the rise of the charging voltage when the gassing voltage is reached. Studies reveal that this process reduces internal gassing to a safe level.
Variable absorption time : The Victron charger calculates the optimum duration of the absorption phase according to the duration of the initial charge phase (Bulk).
  If the Bulk phase was short, the battery was low and the absorption time will be shortened automatically.
   A longer initial charging phase will give a longer absorption time.
Standby function :
Once the absorption phase is over, the battery is in principle fully charged and the voltage is reduced to the maintenance level (Float).
  Then, if the battery is not used for 24 hours, the voltage is reduced further and the battery charger goes into "sleep" mode.
   This "standby" voltage minimizes corrosion of positive plates.
    The voltage will then be raised to the level of absorption once a week for a short time to compensate for the self-discharge (Battery Refresh function).  

Effects of temperature on charging voltage and optimal charging current

The charging voltage should be reduced as the temperature increases. Temperature compensation is required when the battery temperature can drop below 10 ° C / 50 ° F or exceed 30 ° C / 85 ° F for a prolonged period of time. The recommended temperature compensation for Victron VRLA batteries is -4 mV / cell (-24 mV / ° C for a 12V battery). The median temperature compensation point is at 20 ° C / 70 ° F.
The charging current should preferably not exceed 0.2 C (20 A for a 100 Ah battery). The temperature of a battery will increase by more than 10 ° C if the charging current is higher than 0.2 C. The temperature compensation is therefore essential for charging currents greater than 0.2 C.