Connecting the load or power strip
If you are connecting directly to a radio or other device, you will need to install Powerpoles on
their cords. Modern radios use RED wire for positive, and BLACK wire for negative (or com-
mon or ground). Double check this if you have non-standard equipment. Plug this wire into
the PWRgate terminal marked OUT.
If you are connecting the output to a RIGrunner power strip you may use a West Mountain
Radio 3 ft or 6 ft extension cables with #12 red and black insulated wire and pairs of
Powerpoles on both ends.
At this point, check the system operation with the power supply. Simply turn on the power sup-
ply, and turn on the equipment, the equipment should work normally.
Connecting the Battery
The battery wire should be as heavy and as short as possible. We suggest #10 wire less than
3 feet long. Batteries have less voltage than power supplies therefore voltage drop is more
important. WARNING: a fuse must be installed physically as close to the positive terminal of
the battery as possible. A short circuit in a battery wire, connected to a large battery, will
instantaneously cause the burn white hot.…avoid this situation! We did not put a fuse in the
PWRgate as it would NOT protect the wire itself against a short.
Batteries have side posts, top posts, studs or fin terminals. Deep cycle, marine, AGM, etc. usu-
ally have two different sized polarized 3/8 inch and 5/16 inch studs. West Mountain Radio car-
ries power supply cables and battery fuse kits. We also have lugs to convert top posts to
studs.
Batteries
Caution: Handle batteries with knowledge and extreme care! Automotive
and marine batteries have dangerous chemicals that can spill out. These
batteries emit hydrogen that will explode from a small spark sending
shrapnel and acid in all directions.
Batteries can get very hot when improperly charged or shorted, and
explode. Shorted battery wires can and will cause fires, use a fuse locat-
ed directly at the battery plus terminal.
Chose a 12 volt battery with an ampere-hour rating according to your power needs. Find a
battery with an true ampere hour rating, do not pay attention to “cranking amps”.
Automotive and marine batteries are not safe as they will spill acid and give out explosive
hydrogen fumes. They are much more dangerous than gell cell or absorbed glass matt (AGM)
batteries. Gell and AGM batteries will not spill, will not explode and last longer.
Automotive and marine batteries are normally only used in protected, well ventilated, loca-
tions.
Automotive and Marine lead-acid types offer the best price to power ratio but they are dan-
gerous. Marine batteries will tolerate deep discharges slightly better than auto batteries, but
the can easily be damaged by repeated deep discharge. Gell cells and absorbed glass mat
(AGM) batteries have many advantages and are usually worth the extra price. Select a battery
that offers both safety and performance. See our RIGrunner links page for links to web sites
with extensive battery information,
http://www.westmountainradio.com/linksrr.htm.
System checkout.
When the power supply and battery are connected, and the PWRgate is powering a load, a
quick checkout is as follows. Simply turn on your equipment, unplug the power supply; the
equipment should operate without interruption, now powered by the battery. Plug the power
supply back in, and the equipment will now be powered from the ac power supply. You may
notice a slight drop in the voltage, this is normal. A power supply is a nominal 13.8 volts and a
battery is 12 volts.
If you would like use an ammeter, or a Whattmeter (sold by West Mountain Radio) to verify
operation, follow this. Simply measure the current from the power supply when it is connected
and powering the equipment. Measure the battery current when the supply is switched off or
is disconnected. To measure the battery charging current, place the ammeter in the battery
lead, make sure the power supply is on and the output is disconnected.
Voltages
Radio manufacturers list the recommended dc supply voltage range for a specific radio model.
Some radios are listed as 13.8 Vdc +- 15%, and others as 13.8 Vdc +-10%. Note that they are
not rated for 12 volt operation but 13.8 volts.
12 volt power supplies should be adjusted to supply to provide 13.8 volts dc. The PWRgate
has a diode in series with a voltage drop of 0.4V regardless of current. Therefore, the
PWRgate output will be 13.4 volts.
Fully charged 12 volt batteries exhibit somewhat over 12 volts just after charge. But when they
are supplying current, the voltage is diminished by the battery's internal resistance, typically to
12 volts nominal. The PWRgate will give a drop of 0.4 volts, thereby providing 11.6 volts to the
radio.
Additional voltage drops can easily occur due to the high current and the resistance in the
wires, the fuses, and the connectors. Therefore it is imperative to keep all wires as heavy and
short as possible, as low an AWG number as practical, and as few connectors as possible.
Also use a large supply fuses, 30 or 40 A to keep the fuse voltage drop low.
PWRgate charging circuit
The charging circuit is a simple "float" charger in order to maintain a battery near full charge.
The circuit is provided so that any 13.8 volt power supply will function safely as charger. It can
supply about 1 ampere if the battery is heavily discharged. As the battery voltage rises, the
charging current decreases until it supplies only a current equal to the quiescent discharge rate
of the battery.
If a large battery were heavily discharged, it could take over a week to re-charge the battery
using this circuit. Nevertheless, in most applications, the battery is only called on when a
power failure occurs, hopefully infrequently. The charging circuit is useful to prevent self dis-
charge of a battery keeping it healthy and ready for use. Otherwise batteries left unattended
will go bad in a few months!
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