If you’re interested in the internals of the Mazda supplied Panasonic battery then here’s a photo of one with a section of the top cut off.
Described, even by Mazda in their own workshop manual as a Gel type battery, it would appear that the battery is in fact an AGM battery.
Easiest way of telling (and give yourself a workout while doing it 
) is shake it about. If it makes sloshing noises, it’s lead acid, if it’s silent, it’s AGM.
Dont understand the difference between a Gel and an AGM, but I’d prefer to know is it looks like I’ve a new AGM…
Gel are good but AGM are even better.
They are so reliably leak proof that my Ducati 999 had one fitted on its side as standard.
They also have very high CCA figures, so are very good at spinning your engine over for instant starting.
Yes, I used to think this was a gel battery. It’s sealed and no discernable movement of fluid. It can be inverted without spillage or other issue(not recommended). Someone used an inverted panasonic placed on top of his car panasonic to start a car; must have been a MK2.
Without doubt by far the best battery for the MK1-MK2.5 MX5, particularly where seasonally used.
Maintenance free, long lasting, safe, small, and most important of all resistant to abuse, regular charging, etc.
Nothing else comes close and reassuringly expensive
Just buy when they have one of their regular 10% off bank holiday specials.
I checked with MX5 Parts and they think the Panasonic is a gel battery although the Westco is AGM.
A quick google for the Panasonic reveals Gel is almost unfailingly in the decription, but a quick look on a miata.net page sees the Panasonic described as AGM, looks like someone somewhere in Mazda / Panasonic marketing did/does not know what they are talking about :- Panasonic OEM battery availability? - MX-5 Miata Forum
