Page 297 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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280 Automobile mechanical and electrical systems

Figure 3.49 Round battery posts

The bench charger should be situated in a well-ventilated area of the workshop.
Smoking should also be prohibited, if it is not already. Bench chargers with
voltage control have high initial current outputs, which fall as the battery charges.
Chargers with current control can be adjusted to suit individual batteries.
The usual rule for battery charging is that the charge current should be set to
Key fact
about one-tenth of the ampere-hour (Ah) rating of the battery. Alternatively,
Ideal charge rates: one-tenth of about one-sixteenth of the reserve capacity, or one-fortieth of the CCA fi gure
the ampere-hour rating of the gives a good guide. A fully discharged battery will take about 12 hours to fully
battery, one-sixteenth of the reserve recharge. When recharging partially charged batteries, it is recommended that
capacity, or one-fortieth of the cold
cranking amp rating. they should be checked at regular intervals. Always switch off the charger before
disconnecting the leads and carrying out any tests.
Fast chargers are portable items of equipment that will charge a battery in a short
space of time at several times the normal rate. They can also be used for engine

starting, depending on design. There is a risk of overcharging and overheating
a battery with fast chargers, so frequent checks should be made to check for
gassing and battery temperature. Charging should be stopped when heavy
gassing is evident or if the battery feels more than just warm to the touch.

The external features of a battery are the type and size of the terminal posts, the
dimensions of the battery and the method of fi xing to the vehicle. The terminal
posts are clearly identifi able as positive or negative, by the positive sign ( ) and/
or red colour, and the negative sign ( ) and/or black colour. The positive and
negative posts, on tapered round terminals, are different sizes. The larger post is
the positive one and the smaller is negative. The difference in the sizes is used
to minimize the risk of incorrect fi tting. There are two size ranges, with a smaller
version used by some manufacturers, generally in the Far Eastern geographical
zone, and a larger size used by Western European and American manufacturers.
These round post terminals use a clamp-type cable terminal ( Fig. 3.49 ).
Some manufacturers use batteries with a fl at, or ‘L’ terminal on the battery, a fl at
Key fact
terminal on the cable, and a nut and bolt to complete the connection ( Fig. 3.50 ).
Battery cables must have suffi cient Some US vehicles use a side terminal, which has an internal thread, and the
cross-sectional area to carry the connection is made with a bolt through a fl at terminal on the cable.
starter motor and electrical systems
current. Battery cables must have suffi cient cross-sectional area to carry the starter
motor and electrical systems current. The feed to the starter motor is a heavy-
duty insulated cable, and the earth or ground cable is of similar construction.