The Diode has to be able to handle the max
current and reverse piv. The easy done high
current diode is a properly connected TO-3
transistor (2N3771 maybe) in parallel with
the trickle charging resistor. The transistor
is mounted on a small heat sink, which is
bolted to the supply case.
The Motorola Method sizes the paralleled
resistor to supply a modest trickle charge
to a lead acid battery when the battery is
at normal charge.
>From memory, the resistor value is about 60
ohms at 20 to 50 watts or something like that.
If the radio reverts to the battery, the diode
connected transistor provides the voltage.
As the battery drains, the radio will operate.
There is no provision for a low voltage disconnect,
so you might have problems within a low voltage
condition. One hopes the site generator kicks
on. Else you might provide fail safe controls
for a low voltage condition.
Running a battery into the ground (full discharge)
will greatly reduce it's life span.
Upon return of the AC Mains and DC supply voltage,
the battery will recharge at a modest high current
until it arrives back up toward the normal supply
voltage.
I like to replace the charging resistor with a small
3 terminal regulator circuit, which is set up to
vary the charge current based on the battery state
voltage. Once the battery is back up, the charger
trims back to a float mode.
skipp
> "Rick & Charlotte" <[EMAIL PROTECTED]> wrote:
> We use a bridge rec and an resistor for bat back up ..
> as skipp notes the resistor is for current limitting ..
> so the PS does not take a jolt if the battas are low
>
> I will see if I can find the drawing and post ot the
> group .. if not I will do another and post
> nice thing is you can put this inside the PS and
> bolt it the the frame .. and bring out 2 connectors
> for the batt .. I allways over rate the
> bridge
>
> I hope this helps ..
>
> On 8 Jun 2005 at 15:45, skipp025 wrote:
>
> > Motorola did the same thing... except they added a
> > resistor in parallel with the diode (which was a
> > TO-3 case transistor wired as a diode) for a battery
> > trickle charge.
> >
> > I took it one step further and made my own style
> > reverse charge circuit. Only takes a few parts...
> >
> > skipp
> >
> > > Eric Lemmon <[EMAIL PROTECTED]> wrote:
> > > Dave,
> > >
> > > The GE Mastr II and Mastr Executive II stations were
> > > both available with optional battery standby kits
> > > that were nothing more than some wire, a fuse holder,
> > > and a diode. Almost every LBI for a station combination
> > > has the information about connecting it into the
> > > power supply.
> > >
> > > Be aware that the above hookup does not provide a
> > > trickle charge for the battery- the customer
> > > must provide a separate charger. A bit cumbersome,
> > > but it works.
> > > 73, Eric Lemmon WB6FLY
> > >
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> > --
> > No virus found in this incoming message.
> > Checked by AVG Anti-Virus.
> > Version: 7.0.323 / Virus Database: 267.6.5 - Release Date:
6/7/2005
> >
>
>
> ========================
>
> Rick Szajkowski VA3 RZS
> Charlotte Darby VA3 CMR
> Node Owners of IRLP Node 2120
> 147.300 + VA3 OME
> 224.420 - VA3 OME
> Part of The Omeme Amateur Radio Club
> Peterborough Ont. Canada
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