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What is the Difference between a SLA, VLRA and AGM batteries?
SLA (Sealed Lead Acid) and VRLA (Valve Regulated Lead Acid) are different acronyms for the same battery. This battery type has the following characteristics: Maintenance-free, leak-proof, position insensitive. Batteries of this kind have a safety vent to release gas in case of excessive internal pressure build up. AGM (Absorbed Glass Mat) refers to a specific type of SLA/VRLA where the electrolyte is absorbed into separators between the plates consisting of sponge like fine glass fiber mats. SLA batteries are divided up into specific subsets of batteries:
What are the differences between AGM sealed lead acid batteries and Gel Cell Batteries?
Both types of batteries are sealed, valve regulated batteries allowing them to be used in any position. The difference lies in the way the electrolyte is immobilized. In case of AGM (absorbed glass mat), the newer of the two technologies, the electrolyte is absorbed by the glass fiber separator who acts like a sponge. In a gel-type battery the liquid electrolyte turns into a gel right after the battery is filled. Gel batteries use a different type of separators which are not absorbent. Because of the design, gel cell batteries don't offer the same power capacity as do the same physical size AGM battery. For example, an AGM battery that is 12V 100AH, whereas, for example, a gel cell battery in the same size case would only be rated at 84AH.However, the Gel Cell excels in slow discharge rates and slightly higher operating temperatures. The internal design is otherwise similar.
What is the Hour Rate of a SLA Battery?
HR (Hour Rate) - All SLA type batteries have their capacity rated depending on the amount of Amps they can discharge over a certain period of time. General SLA Batteries are usually rated at 20HR, meaning their current over a period of 20 hours. If a battery is rated at 20Ah capacity at 20HR, it means that the battery can discharge 1 Amp per hour over that 20 hour period. A High Rate Battery will typically be rated at 10HR or less. So if a High Rate Battery that is 20Ah capacity at a 10HR, it would be able to discharge 2 Amps per hour over a 10 hour period.
Generally, a battery will have more effective capacity if it is discharged slowly and conversely, the battery will have less effective capacity if it is discharged quickly. For example, if a 20Ah (10HR) rated battery is discharged over a 20 hour period (20HR), the effective capacity could be 23Ah. If the same 20Ah (20HR) battery is discharged over a 5 hour period, then the effective capacity maybe only be just 15Ah, a loss of 25%.
High Rate Batteries however are manufactured in a way to maximize quick discharge at the expense of deep cycling and cyclic life. They can discharge high Amps at very short periods of time. For example, a 20Ah (10HR)
High Rate Battery can discharge 70 Amps over a 5 minute period, while a General SLA Battery may only be able to do just 45 Amps.