A Xiluopu scooter Li-ion pack sat for over two years without charging; on the charger the green light stays on and it won’t charge; after two years unused the chance of waking it is very small, most likely dead; label says 48V 21Ah; opening the epoxy board releases a strong sour electrolyte smell, many cells are corroded through by leaked electrolyte, 100% not worth repairing. The customer decides on a rebuild: the scooter is only for getting around and doesn’t need that much capacity, 10Ah is cheaper; new EVE 18650 cells at 2.5Ah each, 13 series × 4 parallel = 48V 10Ah. The cells, with fish paper on, are laid into the jig in 13S4P order, one row positive-up, the next negative-up; the scooter case has no room for holders, so it is a holder-less design with an epoxy board between each series group for insulation; 0.2 thick nickel-plated steel strip spot-welded, the welder set to a suitable current, every cell welded, watch for missed or loose welds, weld both faces, leave the main + and − out. After welding, wrap several turns of strapping tape so it becomes a solid block that won’t come apart under vibration. Fish paper where the harness runs and where the BMS sits; the BMS harness is soldered in order to each group’s tab; the BMS is fitted and the + / − power leads connected; assembly done, only a charge / discharge test to pass and it’s finished. Comments: with alternating rows do the + and − have to be on the two sides; the positive lead is too long, should be thicker (2); how much for a pack (many); how much for 48V20A; do you sell batteries; address.