Hi all, I had this quandary when using older VP Oncores that I bought at an auction. The on board rechargable batteries were defunct and the receivers did not have a connection to pin 1 of the header. I solved the problem by connecting a schottky diode between the battery terminal on the board and pin 1 so that I could put a 3 V Li cell on the mother board. That works very nicely. The diode avoids damage to the Li cell from the charging circuit. Rechargeable Li cells are very hard to find down here. Morris ------------------------------ > Date: Wed, 06 Apr 2011 13:53:40 -0700 > From: WB6BNQ <wb6bnq@cox.net> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Oncore battery backup (answer to question) > > > First, which Oncore receiver is he using ? If it is the older series such as a GT+ or UT+ they are designed to have a > Lithium 3 volt cell soldered onto the board. The memory draws 5 micro amps at 3 volts and 100 micro amps at 5 volts. There > is an external connection available to provide the battery back-up off board with a caution of NOT exceeding 5 volts. > > The non rechargeable Lithium COIN battery has a discharge function that holds its voltage fairly constant right up until the > end. They will last a very long time with just 5 micro amps of discharge. >