VRLA stands for Valve Regulated Lead Acid, which means that the batteries are sealed. Gas will escape through the safety valves only in case of overcharging or cell failure. VRLA batteries are maintenance free for life.
Sealed (VRLA) AGM Batteries
AGM stands for Absorbent Glass Mat. In these batteries the electrolyte is absorbed into a glass-fibre mat between the plates by capillary action. As explained in our book ‘Energy Unlimited’, AGM batteries are more suitable for short-time delivery of high currents than gel batteries.
Sealed (VRLA) Gel Batteries
Here the electrolyte is immobilized as gel. Gel batteries in general have a longer service life and better cycle capacity than AGM batteries.
Because of the use of lead calcium grids and high purity materials, Victron VRLA batteries can be stored during long periods of time without recharge. The rate of self-discharge is less than 2% per month at 20°C. The self-discharge doubles for every increase in temperature by 10°C. Victron VRLA batteries can therefore be stored for up to a year without recharging, if kept under cool conditions.
Exceptional Deep Discharge Recovery
Victron VRLA batteries have exceptional discharge recovery, even after deep or prolonged discharge. Nevertheless repeatedly deep and prolonged discharge has a very negative effect on the service life of all lead acid batteries, Victron batteries are no exception.
Battery Discharging Characteristics
The rated capacity of Victron AGM and Gel Deep Cycle batteries refers to 20 hour discharge, in other words: a discharge current of 0,05 C. The rated capacity of Victron Tubular Plate Long Life batteries refers to 10 hours discharge. The effective capacity decreases with increasing discharge current (see table 1). Please note that the capacity reduction will be even faster in case of a constant power load, such as an inverter.
Table 1: Effective capacity as a function of discharge time (the lowest row gives the maximum allowable 5 seconds discharge current)
Our AGM deep cycle batteries have excellent high current performance and are therefore recommended for high current applications such as engine starting. Due to their construction, Gel batteries have a lower effective capacity at high discharge currents. On the other hand, Gel batteries have a longer service life, both under float and cycling conditions.
Effect of temperature on service life
High temperature has a very negative effect on service life. The service life of Victron batteries as a function of temperature is shown in table 2.
Table 2: Design service life of Victron batteries under float service
Effect of temperature on capacity
As is shown by the graph below, capacity reduces sharply at low temperatures.
Fig. 1: Effect of temperature on capacity
Cycle life of Victron batteries
Batteries age due to discharging and recharging. The number of cycles depends on the depth of discharge, as is shown in figure 2.
Fig. 2: Cycle life
Battery charging in case of cycle use: the 3-step charge curve
The most common charge curve used to charge VRLA batteries in case of cyclic use is the 3-step charge curve, whereby a constant current phase (the bulk phase) is followed by two constant voltage phases (absorption and float), see fig. 3.
Fig. 3: Three step charge curve
During the absorption phase the charge voltage is kept at a relatively high level in order to fully recharge the battery within reasonable time. The third and last phase is the float phase: the voltage is lowered to standby level, sufficient to compensate for self-discharge.
Disadvantages of the traditional 3-step charge curve:
- During the bulk phase the current is kept at a constant and often high level, even after the gassing voltage (14,34V for a 12V battery) has been exceeded. This can lead to excessive gas pressure in the battery. Some gas will escape through the safety valves, reducing service life.
- Thereafter the absorption voltage is applied during a fixed period of time, irrespective of how deep the battery has been discharged previously. A full absorption period after a shallow discharge will overcharge the battery, again reducing service life (a.o. due to accelerated corrosion of the positive plates).
- Research has shown that battery life can be increased by decreasing float voltage to an even lower level when the battery is not in use.
Battery charging: longer battery life with Victron 4-step adaptive charging
Victron developed the adaptive charge curve. The 4-step adaptive chare curve is the result of years of research and testing.
The Victron four-step adaptive charge curve solves the 3 main problems of the 3-step curve:
- Battery Safe Mode In order to prevent excessive gassing, Victron has invented the ‘Battery Safe Mode’. The Battery Safe Mode will limit the rate of voltage increase once the gassing voltage has been reached. Research has shown that this will reduce internal gassing to a safe level.
- Variable absorption time Based on the duration of the bulk stage, the charger calculates how long the absorption time should be in order to fully charge the battery. If the bulk time is short, this means the battery was already charged and the resulting absorption time will also be short, whereas a longer bulk time will also result in a longer absorption time.
- Storage mode After completion of the absorption period the battery should be fully charged, and the voltage is lowered to the float or standby level. If no discharge occurs during the next 24 hours, the voltage is reduced even further and the battery goes into storage mode. The lower storage voltage reduces corrosion of the positive plates. Once every week the charge voltage is increased to the absorption level for a short period to compensate for self discharge (Battery Refresh mode).
Battery charging in case of standby use: constant voltage float charging
When a battery is not frequently deeply discharged, a 2-step charge curve can be used. During the first phase the battery is charged with a limited current (the bulk phase). Once a pre-set voltage has been reached the battery is kept at that voltage (the float phase). This charge method is used for starter batteries in vehicles and in uninterruptible power supplies (UPS).
Fig. 4: Four-step adaptive charge curve
Optimum charge voltage of Victron VRLA batteries
The recommended charge voltage settings for a 12V battery are shown in table 3.
Table 3: Recommended charge voltage
Effect of temperature on charging voltage
The charge voltage should be reduced with increased temperature. Temperature compensation is required when the temperature of the battery is expected to be less than 10°C / 50°F or more than 30°C / 85°F during long periods of time. The recommended temperature compensation for Victron VRLA batteries is -4 mV / Cell (-24 mV /°C for a 12V battery). The centre point for temperature compensation is 25°C / 70°F.
The charge current should preferably not exceed 0,2C (20A for a 100Ah battery). The temperature of a battery will increase by more than 10°C if the charge current exceeds 0,2C. Therefore temperature compensation is required if the charge current exceeds 0,2C.
Victron Energy Limited Warranty Policy
Victron Energy warrants its products to be free from defects in workmanship and materials for a period of 5 years from the date of purchase by the end user, with a maximum of 66 months from the Victron Energy invoice date. Exceptions on this are: lead acid batteries; 2 years from date of purchase by the end user, with a maximum of 30 months from the Victron Energy invoice date, Lithium-ion batteries; 3 years from date of purchase by the end user. In addition to this proof of correct battery usage is required when making a battery warranty claim.
During this period, Victron Energy will, at its option, repair or replace the defective product free of charge. The warranty does not include performing or reimbursing de‐installation, transportation and re‐installation. This warranty will be considered void if the unit has suffered any physical damage or alteration, either internally or externally, and does not cover damages arising from improper use like:
• Reverse of battery polarity.
• Inadequate connection.
• Mechanical shock or deformation.
• Contact with liquid or oxidation by condensation.
• Use in inappropriate environment (dust, corrosive vapor, humidity, high temperature, biological infestation...).
• Breakage or damage due to lightning.
• Connection terminals and screws destroyed or other damages, like overheat, due to insufficient tightening.
• For any electronical breakage except due to lightning (reverse polarity, over‐voltage due to external cause), the state ofthe internal control diode and of the inputs/output X and Y capacitors determine the warranty.
This warranty will not apply where the product has been misused, neglected, improperly installed, or repaired by anyone else than Victron Energy or one of its authorized Qualified Service Partners. In order to qualify for the warranty, the product must not be disassembled or modified.
Repair or replacement are our sole remedies and Victron Energy shall not be liable for damages, whether direct, incidental,special, or consequential, even caused by negligence or fault.
Victron Energy owns all parts removed from repaired products. Victron Energy uses new or reconditioned parts made by various manufacturers in performing warranty repairs and building replacement products. If Victron Energy repairs or replaces a part of a product, its warranty term is not extended. In case of replacement the new component has a warranty of 6 months, without effect on the initial warranty period. All remedies and the measure for damages are limited to the above. Victron Energy shall in no event be liable for consequential, incidental, contingent orspecial damages, even if having been advised of the probability of such damages. Any and all other warranties expressed or implied arising by law, course of dealing, course of performance, usage of trade or otherwise, including but not limited to implied warranties of merchantability and fitness for a particular purpose, are limited in duration to a period of two (2) years from the date of purchase.
Life Support Policy
As a general policy, Victron Energy, does not recommend the use of any of its products in life support applications where failure or malfunction of the Victron Energy's product can be reasonably expected to cause failure of the life support device or to significantly affect its safety or effectiveness. Victron Energy does not recommend the use of any of its products in direct patient care. Victron Energy will not knowingly sell its products for use in such applications unless it receives in writing assurances satisfactory to Victron Energy that the risks of injury or damage have been minimized, the customer assumes all such risks, and the Liability of Victron Energy is adequately protected under the circumstances.
As a product requires service, it must be brought back to the place of purchase. In case no contact can be taken with the merchant, or if he is either unable or not allowed to provide service, direct contact should be taken with Victron Energy.
Warranty on Repairs
The warranty period on products or on printed circuits boards repaired by Victron Energy as well as on printed circuit boards for replacement is 6 months from delivery by Victron Energy.
It is the responsibility of the sender to sufficiently package these products. The transport must be organized in a way to avoid any damage, especially when a single unit or heavy unit is sent.
If a part of the terms and conditions set out above is held invalid, void or unenforceable due to any particular national or international legislation, it shall not affect other parts of the terms and conditions remaining.
For Australia only
Our goods come with guarantees that cannot be excluded under the Australian Consumer Law. You are entitled to a replacement or refund for a major failure and compensation for any other reasonably foreseeable loss or damage. You are also entitled to have the goods repaired or replaced if the goods fail to be of acceptable quality and the failure does not amount to a major failure.