What is the difference between AGM and Gel batteries?

The question of whether AGM and gel batteries are the same thing didn't come in through the Ask OPTIMA mailbox, but we did receive it from one of our customers on the H.A.M.B board, so we thought we'd answer it here for everyone's benefit (and so we could just reply with a link the next time someone else asks, because we get that question a lot). A gel battery design is typically a modification of the standard lead-acid automotive or marine battery. A gelling agent is added to the electrolyte to reduce movement inside the battery case. Many gel batteries also use one-way valves in place of open vents, which help the normal internal gasses to recombine back into water in the battery, reducing gassing. AGM batteries, as their name suggests use a glass mat to absorb the electrolyte. That's how you get the name- Absorbed Glass Mat.

All of that tech talk really doesn't matter for the vast majority of folks who use lead-acid batteries, because they'll probably never see or use a gel battery in their car or boat. Generally, gel batteries are less tolerant of high heat and are charged at lower power than traditional or AGM batteries. The real problem most folks encounter involves the charger they use to charge their batteries.

Some chargers have "gel" or confusing "gel/AGM" settings, that people think are appropriate or even intended for AGM batteries. Did you even notice the "most" qualifier in this charger setting picture? Gel batteries tend to have very narrow charging profiles and can be damaged easily by charging them inappropriately, so a setting that is suitable for a gel battery may not be suitable for any non-gel battery.

As a result, using "gel" or even "AGM/gel" settings may not fully-charge non-gel batteries, including OPTIMA SPIRALCELL AGM batteries and could damage them. For that reason, we always recommend avoiding any charger settings that mention "gel" in them anywhere. Just about any other charger setting- regular, deep-cycle, AGM, etc... basically anything that doesn't mention gel, will usually work just fine on OPTIMA batteries. Just be sure not to exceed a charging rate of 10 amps and be sure to monitor the battery periodically during charging to make sure everything is going smoothly.

You don't need a special charger to charge OPTIMA batteries, but we make chargers & maintainers that do a great job of charging OPTIMA batteries or any other flooded lead-acid batteries. However, they don't have settings on them for "gel" batteries, because we know nearly all the folks using them don't have gel batteries, they have AGM batteries.