Oops! I was writing from memory and got it wrong: West Mountain Radio
specify cranking the P/S up to 14.1V for Gel-Cells and to 14.5V for AGM
batteries -- to allow absorption-charge voltages of 13.8V and 14.2V,
respectively.
And the voltage drop is 0.25V to 0.5V, depending on current.
"Perce"
On 02/14/11 03:39 pm, I wrote:
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?
"Perce"
On 02/13/11 03:35 pm, raypsi wrote:
I used to charge a deep cycle flooded marine battery with the TI
UC3906
data sheet he 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.
On Feb 12, 6:42 pm, "Percival P. wrote:
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.
"Perce"