Thanks for responding so quickly Nicknorman. The batteries have been on charge for three days, the yellow light is flashing indicating in the float phase, the charge current is down to less than 1 amp so I infer that they're as fully charged as this unit can get them (12/800/35 on five 105ah sealed cells) . I cannot work out from the manual which light actually is the "bulk" light. What happens after the five "all three led flashes" is that the green and yellow light come on together for maybe two or three seconds then it goes to yellow only. At which point should I flip the rocker switch to "on" ? Thank you for you patience.