Ranger Communications RCI-5054DX Product Review page 7

recharge these packs with the PLUS.
Although the MH-C777PLUS can be
directly powered from 12 V dc (a ciga-
rette lighter cord is provided with both
models), the packs that can be charged
are then limited to those that contain at
most four NiCd or NiMH cells, or two
Li-ion cells. One workaround for this
would be to set up a system that powers
the unit's included ac supply through a
12 V dc to 115 V ac inverter.
Operating the MH-C777
When a battery pack is initially con-
nected to this model, the charger's micro-
processor quickly measures the pack volt-
age and flashes a red front panel LED. The
number of flashes corresponds to the num-
ber of cells that it has detected inside the
pack. Note that if one or more of the cells
are fully discharged, the microprocessor
may be fooled into thinking that the num-
ber of cells in the pack is fewer than the
actual number. If this occurs the pack will
not be properly recharged.
The more deluxe model avoids this by
immediately starting the charging pro-
cess, and then stopping and determining
the cell count a few minutes later. You
can manually duplicate this action on the
more basic model by briefly disconnect-
ing the pack from the charger after the
first minute or so and then reconnecting
it. This will to force the microprocessor
in the MH-C777 to make a second assess-
ment of the number of cells in the pack.
On this basic model, the charge state of
the attached pack is indicated by a set of
three LEDs. These light up to show when
the pack is in the low, medium or full charge
states. When a full charge is attained, the
charger automatically switches to a low
current trickle charge mode.
Conditioning of a battery pack can be
done at any time by simply pressing the
button. The MH-C777 will
DISCHARGE
then slowly discharge the battery to what
it considers a low state-of-charge and then
automatically perform the charging pro-
cedure.
Operating the MH-C777PLUS
When a battery pack is initially con-
nected to this model, the charger applies
a "surface charge" to the battery for a pe-
riod of three minutes. This allows any
depleted or reverse-charged cells to come
up within their normal voltage range. At
the end of this stage, the microprocessor
determines the voltage of the pack. Charg-
ing then begins at a constant current of
800 mA (400 mA for lithium batteries).
During the charging process, the dis-
play shows the mAh of charge accepted,
the battery voltage, the elapsed charging
time and the operating status ("Quick
Charge" or "Full").
76 March 2002
Quick charging will cease when the
microprocessor detects either a slight re-
duction in the battery voltage, that a spe-
cific period of time has elapsed without
an increase in battery voltage or that
the pack has reached a temperature of
123° F. When the Quick charge cycle is
completed, the unit automatically enters
a low-rate trickle charge mode.
Lithium-ion batteries are charged under
a different routine. The initial charge cur-
rent is tapered rapidly with increasing bat-
tery voltage. Maha states that it can take as
long as 10 hours for a Li-ion battery to
reach full charge. They illustrate this by
saying that when charging a fully depleted
1200 mAh Li-ion battery pack, the accu-
mulated charging capacity will likely be
300 mAh at the end of the first hour, 550
mAh at the end of the second hour and
1150 mAh at the end of the fourth hour.
However, the remaining 50 mAh of charge
can take up as much as 3 to 5 additional
hours. This is because the Li-ion cell is
highly intolerant of overcharging. Of
course, the final 50 mAh adds little to the
overall capacity of the battery, and for all
practical purposes charging can be manu-
ally terminated after the first four or five
hours, even though the charger will not be
indicating that the battery has reached full
charge.
The user must be reminded, however,
that the charger cannot automatically iden-
tify which type of battery has been con-
nected to its terminals. The NiCd NiMH/
Li-ion selector switch must be set in the
correct position before the battery is con-
STRAYS
THE PENN-OHIO DX SOCIETY
DIGITAL PREFIX AWARDS
PROGRAM
The Penn-Ohio DX Society (PODXS)
recognizes the achievements of Amateur
Radio operators worldwide by offering its
new Digital Prefix Awards Program.
To qualify for the mixed basic award the
applicant must have a minimum of 400 dif-
ferent prefixes confirmed by either hard
copy QSL or eQSL. There are many more
specific digital awards being offered—PSK
DPX, RTTY DPX—with a minimum con-
firmed requirement of 300 each. Endorse-
ments to the basic awards are in increments
of 50. Continent and Band endorsements
are also available.
All applicants must use the PODXS
DPX application—PODXS form 3-36, and
the endorsement list, PODXS form 3-37—
or a computer printout. If you use the lat-
ter option for the endorsement list, please
maintain a similarity to the PODXS form
3-37.
nected. Failure to do this will likely result
in damage to lithium batteries.
Conditioning of a battery pack is per-
formed by depressing the
button within 30 seconds of attaching
the battery to the charger. The
MH-C777PLUS will first surface charge
the battery to determine its nominal volt-
age and then discharge the pack at a rate
of about 300 mAh to what it considers a
low state-of-charge. A series of beeps will
then be emitted. At this point the charger
will pause for about 15 minutes before it
begins the main charging cycle.
Summary
Either the MH-C777PLUS or the
MH-C777 chargers are capable of doing
a fine job of keeping your collection of
rechargeable battery packs in tiptop con-
dition. Charging them with either of these
units is fast and safe, and the connection
alternatives offered on the units are flex-
ible enough to work with almost any bat-
tery pack. With the MH-C777PLUS,
though, you'll enjoy the added benefits
of having a continuous readout of
voltage, battery capacity and elapsed
charging time, as well as an excellent in-
dication of remaining battery life.
Manufacturer: Maha Energy Corp,
545-C W Lambert Rd, Brea, CA 92821;
714-990-4557, fax 714-990-1325; sales@
mahaenergy.com; www.mahaenergy.
com. Manufacturer's suggested list price,
MH-C777PLUS, $89.95; MH-C777,
$49.95; MHS-CW4 clip-lead accessory for
the MH-C777, $4.
Go to www.qsl.net/wm2u/podxs_dpx.
html or hometown.aol.com/n3dqu/
podxs_dpx.htm for detailed information
and instructions. You can download the re-
quired forms in either PDF or zipped
Microsoft Word format.—Ernie Mills,
WM2U, wm2u@arrl.net.
DISCHARGE