Allow the battery to charge for at least 24 hours before using it again. If the battery remains below this critical level for several days, it begins to sulphate, which causes irreparable damage to the battery. Try recharging it with a trickle charger. If that fails, you'll have to replace the battery. Tip: to prevent this from happening, it is best to charge the battery regularly (24 hours every 2 weeks), this will improve the life of the battery.