Some of the Consolette type power supplies found in the MSR-2000 40 watt Canadian Repeaters have a simple TO-3 type (2N3771) transistor & one resistor set up to act as a battery interface circuit. Works great and it's simple. If someone was really interested, I might be able to draw up or dig out the circuit diagram for it.
skipp > Lee Williams <[EMAIL PROTECTED]> wrote: > > Well,what I came up with is since the Micor supplies arent > adjustable,was two silicon diodes in the charging circuit. Drops it to > 13.5v then added a contactor,normally closed,with a 125vac coil to > connect direct to the batteries during an outage. I will post the > results once implemented. 73,Lee > > Eric Lemmon wrote: > > There is a simple way to have a reliable backup battery system without a relay. Try this: > > > > Connect your fused repeater power cable directly to the battery terminals, without any intervening devices. Connect your power supply to the battery through a single Schottky diode. Adjust the power supply voltage so that the battery is floated at its optimum voltage, to account for the small forward voltage drop across the Schottky diode. I use a Schottky diode because its forward voltage drop under load is much smaller than that of a silicon diode and is stable. > > > > The diode is needed because some power supplies have a tendency to go into a "crowbar shutdown" mode if the AC input goes away (as during a power failure) while a DC voltage is maintained at its output by a battery. Such an event will blow fuses and will almost certainly shut down the repeater. > > > > Unless the repeater operates almost continuously, the power supply does not need to match the current draw of the radio during transmit. I have a 50 watt base station set up this way that has a 26 Ah VRSLA battery floated by an Astron RS-10 power supply, and it has been 100% reliable through many power outages. > > > > I used an International Rectifier #122NQ030R diode, simply because it was easy to mount on a copper bar that is bolted to the positive terminal of the power supply. The "R" in the part number indicates reverse polarity, meaning that the diode terminal screw is the cathode, which is convenient for attaching the load wire. Here's the datasheet: > > http://www.irf.com/product-info/datasheets/data/122nq030.pdf > > > > 73, Eric Lemmon WB6FLY > > > > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
