Batteries & Cables - Beta Marine Beta 50 Operator's Maintenance Manual

BATTERY INSTALLATIONS
Starter batteries and battery cables are a major consideration for engine starting systems. Incorrect selection of both
battery and cables is a major cause of starting failure.
BATTERIES
1. Battery sizes: For starter battery capacity
recommendation please refer to 'Technical
Specifications' on page 6.
2. In extreme conditions, low temperatures, battery
capacity needs to be increased as performance will
decrease. This needs to be allowed for during selection
of a battery.
3. Battery terminals and connections must always be kept
clean, in good condition and tight. Faulty connections
can lead to poor performance and/or in extreme
conditions explosion.
BATTERY CABLES
1. Battery cables are sized on the motoring or rolling
current of the starter motor and the length of battery
cable run. This length is the total distance of both the
positive and negative cables added together. Under
normal circumstances the voltage drop in the starter
battery cable circuit should not exceed 0.8 volt and in
any circuit should not exceed 1.2 volts.
2. Starter batteries should be as close to the engine as
practically possible. The reason for this is to ensure that
the maximum voltage from the battery is available to
the starter motor. The longer the cable run the more
the voltage drop will be, due to resistance within the
cables.
3. For smaller engines we recommend battery cables
of 25mm 2 (4 AWG) conductor cross sectional area
with length up to 1.5m per cable. This equals a cable
run of 3m total which would have a voltage drop of
0.8 volts if the starter motor was using 160 amps
when motoring. Battery cables that are too small will
overheat and their insulation could catch fire.
4. Batteries must be in good condition and must hold
voltage. When measured, an idle standing battery
would be expected to be read a minimum of 12.6
volts and 12 volts on the starter motor terminals.
5. Charging circuits must be sufficient for the battery
system used. Ensure you have enough battery capacity
whilst considering the recharge capability. Depending
upon the battery type the recharge voltage will be in
the region of 14.7 volts.
4. When the supply is switched on to the starter motor
there will be a massive inrush of power in the region
of 5 times the motoring current. The battery will
be expected to supply this inrush and then recover
sufficiently to give the motoring current (often refered
to the 'rolling' or 'cranking' current). If the correct
battery is selected but the engine will not crank
at sufficient speed after the inrush then (assuming
battery cables are the correct size) the battery is either
discharged or faulty.
5. If the voltage at the starter motor terminals after the
inrush is not at least 10.5 volts it is likely that the
motor will either crawl at insufficient speed or not turn
at all. Battery cables could overheat.
6. Please note that cranking time should be no longer
than 10 seconds with at least a 10 second rest
between attempts.
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