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Author Topic: PWRgate PG40S & AGM batteries  (Read 21514 times)
K4IDK
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Posts: 38




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« on: July 04, 2013, 05:43:45 PM »

I'm using a PWRgate PG40S with AGM marine batteries.  The PWRgate manual says to install a jumper at J1 and to adjust the power supply to provide 14.5 volts.  I already installed the jumper.  I have 2 different power supply set-ups.  One uses an Astron RS-35M and the other uses a SEC 1235M. 

I'm assuming that I need to adjust both of the power supplies in order to provide 14.5 volts to the PWRgate, but I have no idea how to do so on either of these power supplies.  Any help would be greatly appreciated. 

If it makes any difference, the current voltage from either power supply is 13.8 volts.  The reason that I'm using AGM marine batteries is that I have a friend that competes in bass fishing tournaments and he changes out his batteries every year.  I managed to get both of my batteries just by offering to get rid of them for him!  Smiley

Thanks in advance,
Robert
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K4IDK
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« Reply #1 on: July 04, 2013, 06:13:09 PM »

Disregard the question about the SEC power supply.  I found the manual and figured it out.

But the Astron is still a mystery to me, so if anyone know about how to adjust the output on one I'd greatly appreciate it.
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LA9XSA
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« Reply #2 on: July 05, 2013, 04:31:17 PM »

There's supposed to be a trimpot inside the Astron that lets you adjust the voltage.

It's R5 in this schematic:
http://www.repeater-builder.com/astron/pdf/astron-rs35m-annotated.pdf

Some people install a dial on the outside so they can adjust it without opening it up.
« Last Edit: July 05, 2013, 04:36:05 PM by LA9XSA » Logged
K4IDK
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Posts: 38




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« Reply #3 on: July 06, 2013, 10:29:04 AM »

There's supposed to be a trimpot inside the Astron that lets you adjust the voltage.

It's R5 in this schematic:
http://www.repeater-builder.com/astron/pdf/astron-rs35m-annotated.pdf

Some people install a dial on the outside so they can adjust it without opening it up.


Thanks for the information.  Does adjusting the R5 pot effect anything else besides voltage? 
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W9IQ
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« Reply #4 on: July 07, 2013, 03:47:32 AM »

Robert,

I have the same set-up and it has been working great in my shack for many years.

The R5 adjustment only affects the output voltage.

My Astron is dedicated to the PWRgate so I just added a label to my Astron to remind me that the output is dialed up a bit in case I ever re-purpose it.
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W6EM
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« Reply #5 on: August 31, 2013, 09:00:00 AM »

I'm not professing to be a PWRGate expert, but it sounds like it uses a series diode in the charger path to the battery.  Be careful in "cranking up" regulated supplies that end up as a float source for lead acid batteries.  13.8V, the ideal float voltage won't gas or boil off the electrolyte over a long time.  However, the forward drop of most diodes is a function of current.  The higher the current, the greater the drop.  So, if PWRGate is assuming about a 0.7V forward drop for a series diode, it may NOT be that much when only floating the battery.

You could, unless the PWRGate somehow disconnects the regulated supply during no-load float conditions, end up floating the battery at about 14.2V, as the turn-on voltage of a Si junction is only about 0.3V and that's the diode drop you'd have during a float situation instead of 0.6 to 0.7V.

There are devices out there that will very precisely switch at set voltage points (low and high).  Perhaps PWRGate uses them and my thesis is incorrect.  I hope it is.
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K1CJS
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« Reply #6 on: August 31, 2013, 04:01:15 PM »

13.8 to 14.2 volts is about the required voltage to keep lead acid batteries topped off.  In an automobile, the alternator usually puts out more, but the usual car battery is not an AGM (absorbent glass mat) type battery either--unless it's an Ultima.

Like everything else, regular maintenance is the key to long lasting battery performance.  Exercising the batteries doesn't hurt either, it helps.  Pull the AC and run your station off batteries for a while.  Depending on if you're transmitting a lot, one to three hours will usually draw the batteries down, but not that much.  Reconnect the AC and let the charger bring them back up to nominal.  Do this every four to six months and your batteries will last quite a while.  73!
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W6EM
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« Reply #7 on: August 31, 2013, 07:35:47 PM »

AGM batteries are sealed with "burp" vents.  If the amount of gassing from high charging voltage cannot all be absorbed by the glass matting, the burping will result in loss of electrolyte and shortened lifetime.

In other words, unlike automotive batteries, you can't replace lost water.

You will generate gas at voltages above 13.8 or so.  Short term excursions, as in automotive charging, where cells can vent, isn't a problem.
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W6EM
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« Reply #8 on: September 01, 2013, 05:35:54 AM »

After finding and reading the PWRGate PG40S operating manual, it is not just a simple switching device.  It contains a charger, probably based on the UC3906 chip, according to its description of operation.

So, the caution concerns about setting the power supply input voltage too high are nil, since the chip and its series FET do control float voltage carefully.

I would only question the choice of Schottky diodes as an "or" gate instead of P-Channel Power MOS devices to switch DC sources.  Perhaps a few milliseconds of interruption as a trade off for the heat dissipated via the series diodes.
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NA4IT
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« Reply #9 on: September 02, 2013, 01:32:37 PM »

The PWRgate PG40S is $139.95. Plus you supply a supply...

The APS30 supply / charger is $162.90. No extra adjustments, no extra wires, connect it to the battery, and battery to the shack and you are done....

http://cascadeaudio.com/power_converters/power_converters.htm

Mine in use...

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W6EM
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« Reply #10 on: September 02, 2013, 02:09:11 PM »

Nice supply, but doesn't appear to contain a battery charger and conditioner as the PWRGate Super-duper model does.

Based on the few clues in the PG manual, it looks like the PG Supermodel uses only two of three UC3906 battery charger chip features.  Then again, having a 0.5-0.7V margin between recommended float voltage and power source voltage setting is pretty thin for full-featured charger function at greater than 1 A charging capability.....
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W9GB
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« Reply #11 on: September 10, 2013, 04:21:01 PM »

TI U3906 - Sealed Lead-Acid Battery Charger: Datasheet
http://www.ti.com/lit/ds/slus186c/slus186c.pdf

UNITRODE Products from TI : Application Notes

Simple Switchmode Lead-Acid Battery Charger
by John A. O’Connor
http://www.ti.com/lit/an/slua055/slua055.pdf

Improved Charging Methods for Lead-Acid Batteries using the TI UC3906
http://www.ti.com/lit/an/slua115/slua115.pdf

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W6EM
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« Reply #12 on: September 10, 2013, 05:48:15 PM »

TI U3906 - Sealed Lead-Acid Battery Charger: Datasheet
http://www.ti.com/lit/ds/slus186c/slus186c.pdf

UNITRODE Products from TI : Application Notes

Simple Switchmode Lead-Acid Battery Charger
by John A. O’Connor
http://www.ti.com/lit/an/slua055/slua055.pdf

Improved Charging Methods for Lead-Acid Batteries using the TI UC3906
http://www.ti.com/lit/an/slua115/slua115.pdf


There's a 1-Amp 3906 charger project in older ARRL Handbooks.  Chapter 27, Figure 66.  Far-Circuits sells the PC boards and chips.  Easily modded for higher charger currents.

I'm led to believe that the PWRGate deluxe has an internal UC3906 to go along with two lossy big "or" diodes..

 
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