CANBusInterface

After choosing the right cable cross section, it is very important to use the
same cross section for the negative cable. The right location of the mass
connection is an important basis for an installation free from unwanted
signals. For this reason we advise you to choose a highly conductive point
of bare metal on the body of the car. But be careful, the sheets of the trunk
are often just glued, which sometimes is unrecognizable due to an excellent
paint job. Alternatively the mass conductor can be led back to the
negative pole of the battery. If you are looking for a good central mass
connection, you should consider big solid screws, which generally have
excellent contact with the chassis.
The charging current delivered by the generator can also cause unpleasant
interferences. This charging current mainly consists of direct current
that is superposed with alternating voltage. Depending on the frequency,
these alternating voltages sometimes have very strong glitches. If additional
consumer units are connected e.g. the heating, the ventilation etc. the
proportion of the alternating voltage is rising. These interfering alternating
voltages can stray into the signal path of the car-hifi-system. For this reason
you should try to separate the power supply from the signal cabling.
Furthermore, the electric circuitry of the car and the original cable trunks
should be avoided when installing the car-hifi cables. These highly capacitive
and induced fields sometimes appear in neighbouring conductors and
disturb the sound quality extremely. The glitches can be evened by the use
of an anti-interference capacitor (article 530 by Dietz) installed directly in
the charging cable of the generator. If there is more than one mass
connection for the car-hifi system, the result will be mass loops, so called
potential differences. They can be avoided, as mentioned before, by using
one central mass connection for all components of the car-hifi system. If
there are still interferences, it is possible to pull in bonding conductors. For
example, the generator mass can be connected with the negative pole of
the battery. Another bonding conductor can be drawn between the mass
connection of the radio and the antenna mass. In some cases, a connection
between the RCA mass and the antenna mass may be successful. If
none of these measures is successful the only solution is an interference
suppressor. It is available for the RCA cable as well as for the power
supply.
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b) Second battery
fA frequently asked question in this context is: Is my generator able to
Acharge two batteries or my high-current battery? The answer is: yes, it
is possible, but it takes longer until it is completely charged. Short distance
drivers ought to think about buying a generator delivering a higher charging
current. In case two or more high current batteries are used, it is really
necessary to buy a bigger generator. If it is handled correctly and if it is
charged from time to time, the battery’s life can be extended. When charging
a high current battery it is important that the voltage applied to the terminals
never passes 15V. So, when is it necessary to buy a high current
battery? In general: from 500-Watts Sinus on it makes sense buying a high
current battery. From 1000-Watts Sinus on the original battery normally
has the function of a starter battery and supplies the car electric. The only
task of a later installed high current battery is to supply the car-hifi components.
Presumed that the charging power is sufficient, you can add an
unlimited number of consumer units. Cars equipped with a great number
of consumer units as board computer, air conditioning, several window
defrosters, independent vehicle heater, heated seats etc. and a powerful
car-hifi system, should always have a second battery, if possible a high
current battery. A high current battery has two decisive advantages compared
with an originally installed battery. First, the internal resistance is
lower; second, the cold test current is higher. These two factors influence
the quality of the music enormously. An excellent sound presentation as
well as perfect impulse fidelity are only guaranteed, if the internal resistance
is as low as possible (less than 3,0mOhm) and if the cold test current
is much higher (at least 700Ampere) than in a usual battery. The indication
ampere-hour (Ah) is more relevant for the permanent use of a heater.
But it does not matter at all if 50Ah or more are indicated. It is often
very difficult to find a place to install the second battery in the car. In most
cars there is no space left in the engine compartment, so the only possibility
to install the battery remains the trunk. Concerning the cable length,
this location offers an important advantage: the loss of power on the way
to the output stage is much lower. You should pay attention to a stable and
secure installation. Good air circulation is important in case of gas leakage.
For the installation of the second battery a high-current relay is necessary
(HCR 180); it is installed in the charging conductor between the first
and the second battery. The cable up to the input of the relay must be
equipped with an adequate fuse. The relay is opened and closed by the
ignition. That means if the second battery is discharged, it is still possible
to start the car. Compared to insulation blocks working with diodes, a relay,
due to its construction, does not cause a power loss. In spite of the advantage
of making it possible to start the car, harmful discharges should be
avoided.
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