AGM batteries and GEL batteries are sealed lead-acid VRLA batteries requiring no maintenance, suitable for solar storage, backup power and off-grid sites. AGM (Absorbed Glass Mat) excels in low self-discharge and shock resistance — ideal for irregular use (motorhome, boat, occasional backup). GEL offers better deep discharge tolerance and heat resistance for regular daily cycling. Important: both technologies should not be discharged beyond 50% of nominal capacity — beyond that, lifespan drops sharply. For more cycles and usable kWh, see our LiFePO4 lithium batteries. Available from Ultracell, Victron and Banner.
AGM or GEL:AGM = low self-discharge, shock/vibration resistant, ideal for irregular use (motorhome, boat, occasional backup). GEL = better deep discharge tolerance and heat resistance, suited to regular daily cycling and off-grid sites.
Depth of discharge: never exceed 50% of nominal capacity — a 100 Ah battery gives you 50 Ah usable. Beyond 50%, lifespan drops sharply.
Capacity (Ah): calculate your daily consumption in Wh, divide by voltage (12V or 24V), multiply by 2 (to respect the 50% rule), then by required days of autonomy.
Budget vs lifespan: cheaper to buy than lithium, but 3 to 5 times more expensive per usable kWh over lifetime. Compare with our battery comparison guide.
Need more cycles: for intensive daily use, LiFePO4 lithium batteries are 5 to 10 times cheaper per usable kWh over their lifetime.
