DerekU

These links may be helpful https://www.rbbattery.com/efb-vs-agm-batteries-whats-the-difference/#:~:text=Even in low-voltage situations,were using an AGM battery. https://www.interstatebatteries.com/blog/how-to-charge-an-agm-battery#:~:text=What's an AGM battery charger,less than 14-15 volts. The charging differences began to be highlighted where motohome deep-cycle 'leisure' batteries (rather than starter batteries) were concerned, when motorhome manufacturers were switching from deep-cycle gel batteries to AGM batteries but retaining the same battery chargers. The problem was that, although most of the battery chargers used had a 'gel' setting and that setting could be used to charge other battery types, none at that stage had a dedicated AGM setting, with the result that the AGM batteries were unable to attain their 100%-full state of charge. Eventually chargers gained a specific AGM setting, but, by then, many motorhome owners had become wary of AGM technology. Advice is that - if a vehicle starts life with an 'ordinary' wet-acid starter-battery - there should be no problems replacing that battery with an EFB equivalent. But, - if a the vehicle starts life with an AGM starter-battery - only an AGM battery should be fitted as a replacement. However, it's to be expected (hoped) that any vehicle that has as OE an AGM starter-battery, will also have been provided with suitable electrical equipment to charge it properly. (Thanks for the offering to check which battery my Fabia has. I'll Message you with the VIN later.)

I recently bought a new Fabia SE L DSG (built in October 2023). Rough measurements suggest that its starter-battery is 063 size (Length/Width/Height in mm of 207x175x190) and the battery-tray's fixing points indicate that two different-size longer batteries could be fitted. My car's battery has no visible markings to indicate its manufacturer or its type (traditional wet-acid, EFB or AGM) or its capacity (though I'd guess at around 50Ah for a 063 size) and I'm reluctant to start removing stuff above the battery's top surface or to completely remove the battery in the hope that my idle curiosity would be satisfied. My car, unsurprisingly, has Stop/Start (S/S) - that I turn off each time I start the vehicle together with the loathsome lane-keeping assist feature - and, although 'received wisdom' is that cars with S/S should/must have an EFB or AGM starter-battery, that's definitely not always the case. My previous car was a 2021 Hyundai i20 mild-hybrid with a small lithium battery in its spare-wheel well and a dinky little 40Ah wet-acid starter-battery and, before anyone says "That's because it was a hybrid", the Hyundai i20N hot-hatch non-hybrid and with S/S has an ordinary 60Ah wet-acid starter-battery. I'd guess from on-line comments that my car's battery is EFB type as - unlike AGM batteries - the optimum charging regimen for EFB is the same as for a wet-acid battery's (and EFB tends to be cheaper than AGM) but I'd be interested if anyone KNOWS if that's the case (and perhaps who the OEM manufacturer is too). Obviously I could ask the technicians at the Skoda dealership I got the car from, but - as the Australians are fond of saying - that would be "Too Easy!"