West Mountain Radio claims that their "Super PwrGate" has a voltage drop
of only 0.3V to 0.4V, so they can charge a Gel-Cell battery from a 13.8V
P/S or can handle an AGM battery simply by raising the P/S voltage to
14.1V. Any idea what they use for a pass transistor?
The "Micro M+" solar battery charger described in some recent editions
of the ARRL Handbook uses the STP80PF55 P-Channel MOSFET
(80 Amp, R[DSon] = 0.016 Ohm) as the control device. Could this be used
in conjunction with the UC3906 without too much difficulty?
> I used to charge a deep cycle flooded marine battery with the TI
> data sheet here: http://focus.ti.com/lit/ds/symlink/uc3906.pdf
> all you need is a few precision pots and the low resistance resistor
> you need to set the max charge current.
> I had a 115AH deep cycle flooded marine battery that with a straight
> no frills charge took 4 days to charge fully, tested by hydrometer
> With 1 foot of 14 gauge wire for the max charge resistor and precision
> 10 turn pots to set the other settings, and a 30 amp PNP pass
> transistor on a fan cooled heat sink I was able to charge that battery
> in 8 hours full charge, then it goes to a maintain charge, not a
> trickle charge.
> Basically I was charging at 23 amps after the UC3906 checked that no
> cells were bad, then once it gets to a predetermined voltage it scales
> back the charge, all the levels for this are set by multiple precision
> pots and you can take it thru 4 levels of charge. I had the max
> setting for 15.5 volts when the battery was fully charged to roll back
> to maintain charge.
> You will need a unregulated 18 volt supply, because the PNP drops 4
> volts in VSAT. and once it gets the battery up there in voltage, the
> PNP doesn't need to be full on in VSAT
> After using auto chargers and straight charges I found the UC3906 the
> best choice over all.
> There is a switch mode TI chip also but you don't want that one
> Mouser stocks these last time I bought them it was like $4 each.
>> I'm looking for charger/maintainer -- either an off-the-shelf unit or a
>> schematic so I can build my own -- suitable for a flooded deep-cycle
>> battery, either a pair of 6V "golf cart" batteries in series or a Group 31.
>> I don't want an RFI generator: I already have one.
>> I already have a few 13.8V 25A power supplies, one of which I would be
>> quite willing to "crank up" to a higher voltage to compensate for the
>> voltage drop in the control circuitry.
>> Something like the West Mountain Radio "Super PwrGate" (PG40S) would
>> work, although the automatic switch-over feature is not essential. That
>> device is intended for Gel-Cell and AGM batteries and not recommended
>> for flooded batteries -- absorption-charge voltage too low and
>> float-charge voltage too high, their tech support people tell me.