The Group 4D Lithium Iron Phosphate Deep Cycle Battery (36V, 105Ah, ABYC certified) uses LiFePO₄ (Lithium Iron Phosphate) cells. Depending on the specific brand, the cells are either A‑grade prismatic LiFePO₄ cells or certified cylindrical LiFePO₄ cells. The most common suppliers for this battery type are Abyss Battery (USA) and West Marine, both of which source UL‑listed, IEC‑certified cells from large OEM lithium manufacturers.