Ranger Communications RCI-5054DX Product Review page 6

Maha MH-C777 and MH-C777PLUS Battery Chargers
Reviewed by Kenneth Stuart, W3VVN
ARRL Technical Advisor
It's probably safe to say that most of
us own a transceiver—or at the very least
a portable consumer electronics device—
that relies on a rechargable battery pack
for its power source. Perhaps that's why
rechargable battery choices and their
proper care and feeding always seems to
be a popular topic. 1
Maha Energy Corp provides a wide se-
lection of battery-related products to both
the communications and consumer elec-
tronics markets. Among these are replace-
ment and higher-performance battery
packs—of a variety of compositions—and
charging devices that can be used to replen-
ish them. Let's take a look at a couple of
the charging systems that Maha is currently
marketing to both consumers, and amateur
and land-mobile transceiver users.
Maha's product offerings include a few
different tabletop charging devices, but the
two that would seem to be of most inter-
est to radio operators are the MH-C777
universal charger/conditioner and the
more recently developed—and somewhat
more expensive—MH-C777PLUS univer-
sal charger/conditioner/analyzer. Both are
designed to rapidly recharge and condi-
tion nickel-cadmium (NiCd) and nickel-
metal-hydride (NiMH) batteries. The
MH-C777PLUS can also handle lithium-
ion (Li-ion) recharging duties.
The units employ microprocessor con-
trol. The devices begin the charging pro-
cess with a determination of the voltage
of the connected battery pack. The charg-
ing stage is then initiated. The systems
use any one of four parameters to sense
when to terminate the charging process:
1) The battery voltage begins to drop
2) The voltage of the pack rises above
its rated value
3) The pack reaches a certain tempera-
ture
4) The maximum time for the charg-
ing cycle elapses
Once the main charging cycle is com-
pleted, the units automatically switch to
a lower charging current stage in order
to balance the charge in the individual
cells, thereby "topping off" any that
might not have reached a fully-charged
state during the main cycle.
1
For additional information regarding recharg-
able battery types and their associated
characteristics, please refer to my Dec 2001
QST article, "Honey, They've Shrunk the
Batteries!"
2 A cup that can be adapted for this application
is available from W&W Maufacturing Co.
(See "Index of Advertisers," p 174.)
Consider the Choices
The MH-C777 is the more basic of the
two and will charge packs that are 4.8 to
12 V. The MH-C777PLUS offers some ad-
vanced features and is intended for packs
of 1.2 to 14.4 V (3.6 to 14.4 V for Li-ion
packs). The most obvious difference be-
tween the two chargers is the display ar-
rangement. The basic unit employs LED
indicators to show the charge state, while
the deluxe unit contains a much more so-
phisticated LCD readout. The display on
the MH-C777PLUS provides a wide range
of information, and this allows the user to
more fully monitor the charging or recon-
ditioning process. The mAh rate of charge,
or discharge, is continuously shown.
Elapsed time—in minutes—is also
displayed, as is the battery pack terminal
voltage.
The PLUS has a two-position switch
that must be set to correspond with the
type of battery pack. One of the positions
is for nickel cadmium and nickel metal
hydride, and the other is for lithium-ion
packs. When charging Li-ion packs, the
charger employs a "taper charging" pro-
cedure. As the battery approaches the
fully charged state, the charging current
is greatly reduced. Li-ion packs can take
as long as 12 hours to charge.
Those who frequently travel abroad
will be happy to hear that the inline trans-
former-type power supply that's provided
Bottom Line
The Maha 'C777-series micropro-
cessor-controlled chargers can help
you get maximum performance out of
a wide variety of rechargeable bat-
tery pack types.
with the PLUS will operate on any volt-
age between 80 and 240 V ac. The in-
cluded ac line cord fits standard US con-
venience outlets, but the transformer end
of the cord is terminated in the conven-
tional three-pin plug that's commonly
used on computer equipment. Locating a
suitable substitute cord to use in other
countries should be easy. The MH-C777
comes with a wall transformer supply
designed for 120 V ac use only.
Pack and Power Particulars
The physical design of the two units
is significantly different. The end of the
case of the 'C777 can be swung open and
the battery contact pin blocks reversed,
allowing it to work on physically larger
packs—such as those that fit the
RadioShack HTX-202/404 and some of
the older ICOM handheld units. (These
radios use the hefty BP-7 and BP-8 type
packs). The PLUS doesn't offer this fea-
ture. These larger battery packs cannot
be directly accommodated without the
use of some type of external drop-in
charger cup, and this accessory is not
2
available from Maha. A set of alligator
clip terminated jumpers is supplied with
the PLUS, but in order to use them on
the BP-series batteries you'll have to
slightly back out the contact screws on
the bottom of the packs. Though you
won't need it for these packs, the jumper
set is also available as an optional acces-
sory for the 'C777.
The two units employ entirely differ-
ent ac power supplies. The charging cur-
rent that's supplied by the one that comes
with the PLUS is somewhat greater—on
the order of 800 mA—so battery packs that
contain cells rated at less than 400 mAh
can quickly overheat during the charging
process. Maha recommends that you don't
March 2002 75