An older 240VAC Makita DC1850 Battery Charger is failing to charge Makita 12VDC 1.3Ahr batteries, even though these batteries can be charged with another charger (different brand). This DC1850 charger produces a potential of 38VDC across the output terminals. When a Makita 12V battery is inserted into into the charger, there is a strong spark when the contacts first touch and then....nothing else happens.