Hi there, Carl. I know that all the 12V stuff is fixed. But doesn't the PLC operate up to 24Vdc input? Remember, the only thing the output from the 3 diodes feeds is the PLC supply rail. Also keep in mind that the supply that feeds the PLC doesn't have to be regulated. It simply needs to be higher than the float voltage on the batteries - that ensures that the charge is not being removed from the batteries while AC power is available. I guess that I may not be seeing the whole picture. dwayne At 05:43 PM 4/10/2007, Carl Denk wrote: >I wish I could do that, but The battery voltages are fixed at what they >are, and the maximum voltages of the other parts is fixed too. Looks >like the next higher voltage supply is 15 volts, that's a little higher >than I would like to operate, plus the batteries float at 13.8 volts. >That relay is quite beefy, with 10 amp contacts, and if the move maybe a >dozen times a year, that would be a lot, plus it could be put on >maintenance schedule to replace every few years. The whole system is >based on the Kohler engine electrical which is 12 volts (nominal), then >all the sensors (pressure, voltages, temperatures) are selected and >calibrated based on the 12 volts. -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 22 years of Engineering Innovation (1984 - 2006) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist