AGM or Gel? Whats the difference?
Gel Cell Batteries vs. Absorbed Glass Mat (AGM): What’s the Difference?
So your buddy is telling you to get a gel battery. He says they last longer, can’t spill acid all over your ride and have more cranking power when you need it. His opinions can all be considered fact except for one; he doesn’t know the difference between gel and AGM batteries. Common mistake but now you can set him straight after this quick read.
In recent years, an alternative to conventional, flooded (spillable) lead-acid powersports starting batteries has been introduced: the valve regulated lead acid (VRLA) battery. These types of batteries offer many advantages over conventional flooded lead-acid batteries, including:
– can be mounted and used in almost any position (versus conventional batteries, which must remain upright)
– are sealed and non-spillable
– no fume emissions
– more resistant to vibration
There are, however, two distinctly different types of VRLA batteries: gel batteries and absorbed glass mat (AGM) batteries. AGM batteries are often mistaken for gel batteries, due to their similarities, but if you’re looking to understand more about how your powersports battery works and how to find the best battery for your particular ride, it’s important to understand the key similarities and differences between gel and AGM batteries.
How Gel & AGM batteries are similar
Both AGM and Gel batteries are “recombinant” batteries – this means that the oxygen which is normally produced on the positive plates of all lead acid batteries (technically, both Gel and AGM batteries are classified as lead acid batteries) is absorbed by the negative plates. This prevents the negative plates from producing hydrogen, and instead produces water – which is retained within the battery. The result of this chemical process is that the battery is self-replenishing, and never needs to have water added to the electrolyte.
This is why both AGM and Gel batteries are “valve regulated” – because they don’t need to be replenished, they are sealed, and they are instead regulated by safety valves. These special pressure valves in both these battery types ensures that if the battery floods, dangerous gases can escape safely.
As a result, both AGM and Gel batteries are completely maintenance free and can be installed and operated in virtually any position (except upside down). They are also more rugged, being more resistant to vibration virtually spill-proof.
Absorbed Glass Mat & Gel: what’s the difference?
Gel batteries contain a gelled electrolyte which is “Thixotropic”. This Thixotropic gelled electrolyte contains sulfuric acid, fumed silica, pure demineralized and deionized water, and a phosphoric acid. The electrolyte in Gel batteries does not flow like a normal liquid; it has the consistency and look of petroleum jelly.
Absorbed Glass Mat Batteries
In AGM batteries, the liquid electrolyte contains high purity sulfuric acid and totally demineralized, deionized water (no phosphoric acid). This electrolyte is trapped in sponge-like glass mat separators.
AGM and Gel compared
Because of the physical properties of the Thixotropic gelled electrolyte in Gel batteries, Gel batteries tend to lose power faster than AGM batteries in temperatures below 32°F. AGM batteries, on the other hand, excel in high current and high power applications as well as extremely cold environments, making them ideal for cold weather riding or snowmobiling and also for running juice-drawing aftermarket accessories.
Another key difference between AGM and Gel batteries is depth of discharge. Gel batteries are more acid starved than AGM batteries, which better protects Gel batteries’ plates, making these types of batteries best suited for deep discharge applications.
Deep discharge is rarely necessary in powersports riding, however, and Gel batteries have drawbacks for powersports starting applications. Gel batteries typically have a higher price point, shorter life span and less size compatibility than their AGM counterparts.