the very cold oil being more viscous. And
the freezing cold bites again because that
critical reaction between plate and acid is
also temperature-dependent, working much
more enthusiastically at higher temperatures.
So how do modern
chargers help?
Well, modern batteries, though excellent
in many ways, are very intolerant of abuse.
If left in a state of low charge for even
relatively short periods of time, sulphation
sets in on the plates and it’s difficult to
reverse. And thanks to stereo and ECU
memories, keyless entry systems and
security concerns, modern cars put a draw
on batteries like never before – even when
the car’s just sitting motionless on the drive.
So if a car isn’t used that frequently, or it’s
left parked up during the summer holidays,
attaching a smart charger and making
use of its maintenance charge mode is a
great way of preventing serious sulphation
from starting. Many smart chargers also
have desulphation cycles, which do a very
effective job of reversing damage.
No battery will last forever and eventually
corrosion will damage the plates excessively.
But it’s also true that overcharging, as a
result of using an old-fashioned charger
that boils the electrolyte until switched off,
CTEK MXS 7.0
Although renamed and
slightly updated, this is
essentially the same
unit that won our last
charger test. It’s pretty
expensive, but CTEK
have created a charger
that’s a perfect trade
off between price,
performance and features. The maximum
current output of 7 amps takes all batteries
up to 150 AH in its stride, and charge speed is
further boosted by an initial voltage spike to clear the plates, plus dedicated
modes for cold weather and AGM batteries. On the practical front, it’s a
genuine bonus that the charger is safe to use even when the car’s battery
is still connected. And moderate weatherproofing means sheltered outdoor
usage – such as under a closed bonnet – is also possible.
battery charger test in the
September issue? In the daft
timing stakes, surely that ranks
alongside Christmas carols blaring
out in shops in late August. We beg to differ.
You see, while battery failure is definitely
a mid-winter issue, it’s actually during
summer and autumn that the problems
leading up those failures start to manifest
themselves. That means, in theory at least,
that it is possible to take preventive action
now to avoid trouble later on.
As we all know, batteries are simple
chemical devices. The lead plates inside
them convert electrical current, from the
alternator or mains charger, into chemical
energy within the acid. The plates
work just as well the other way round,
converting the chemical energy back into
electrical current when needed.
Or, rather, the plates work well if they’re
in good condition. Over time, corrosion and
sulphation combine to make increasingly
large sections of the plates’ surfaces
inactive. Effectively, it’s as if the plate area
has shrunk, which obviously reduces a
battery’s ability to convert chemical energy
into electrical current and vice versa.
When the temperature drops in winter,
the ailing battery is hit with a double
whammy. Engines and transmissions
become heavier to crank over, thanks to
PRODUCT TEST
JAMES STANBURY
tests 10 battery
chargers and explains
why now is the time
to give your battery
some TLC.
Battery
Chargers
Car Mechanics September 2013 www.greatmagazines.co.uk/carmechanics
26
PRACTICALITY
The first two points only went to chargers
with the longest leads, with an extra
point being awarded to any unit supplied
with permanently-attached easy-connect
leads. Another point went to all units that
were sufficiently well-sealed to allow safe
outside usage.
SPEED We watched the early
stages of each charger’s cycle on an
oscilloscope to check the smoothness of
output and to see if the charger began with
a plate-clearing pulsed blast. Two points –
one for smoothness, one for plate-clearing
– were up for grabs. Up to two further
points were available for chargers with
the highest current outputs, and an extra
point was awarded to units with manually
selectable boost modes.
FEATURES Modes for AGM,
reconditioning and maintenance charging,
plus the ability to work as a power supply,
all earned a charger an extra point each.
ACCURACY This final point
only went to chargers with an output so
accurate that they were safe to be used on
batteries still connected to a vehicle.
THE TESTS
greatly increases the formation of corrosion.
By contrast, smart chargers automatically
switch to a safe conditioning cycle when
they detect a battery is close to full charge.
Most also have automatic diagnostic modes
that can warn you if a battery is suffering
from excessive self-discharge or from a
reluctance to accept decent charge levels.
Both problems are surefire warnings of
trouble just around the corner.
PRICE £99.99
CONTACT 01353 789800
PRICE from www.halfords.com
WEB www.ctek.com
PERFORMANCE 10/14
IS IT WORTH THE MONEY? 6/6
OVERALL SCORE 16/20
(1 pages)
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