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4. Battery size depends upon your requirements. For
starter motor batteries the battery size should be based
upon the starter motor requirements - table below, and
never be of less capacity than the battery
manufacturers recommendation. If in doubt - ask!
5. If you require a domestic battery bank you will need to
calculate your power requirements, and then multiply
that by the number of hours you will need this power
(before you are able to re-charge the batteries). To
keep the installation simple and reliable we would
recommend a second alternator for a domestic battery
bank.
6. Battery charging alternators must be suitable for the
battery bank size. With ‘Lead Acid’ batteries it is
recommended that if you wish to achieve a long
battery life of 5 years and more - your alternator
should be charging in Amperes at about 10 to 20
percent of the battery bank in ‘Ampere Hours’.
Generally it is very easy to recharge to about 80
percent of battery capacity, but the last 20 percent is
important if you wish to achieve a long battery life,
and this can require an overnight charge. Battery life
and recharging tends to be a compromise and it is
generally not recommended that the alternator
develops in amperes more than 25 percent of the
battery bank rated in ‘Ampere Hours’. The battery
charging system must be a balanced solution; you
must have enough battery capacity but bear in mind
the recharge capability.
Generally it will take as long to recharge a battery as it
does to discharge a battery. I know that this is an
obvious statement but you can only recharge your
batteries when the engines is running, so if you only
use the engine for entering and leaving a marina you
may need an alternative solution for recharging your
batteries. Solar panels can be a good solution for
keeping batteries ‘topped up’.
7. Batteries must be in good condition and must hold
voltage. An idle standing battery would be expected to
be at least 12.6 volts and we would like to see at least
12v on the starter motor terminals. (After a full charge
the terminal voltage drops quickly to 13.2 V and then
slowly to 12.6 Volts).
8. The maximum charging voltage for a Lead Acid battery
is about 14.8 volts, above this voltage damage will
occur. We would expect a maximum output voltage
from our battery charging alternators of something like
14.8 volts at no load. At 50 percent load the voltage
drops to 14.3 to 14.4 volts and at full output the
voltage is 13.5.
9. Battery terminals and connections must always be
kept clean, in good condition and tight. Faulty
connections can lead to poor performance and even
(in extreme conditions) explosion.
Typical starter motor ratings with Kubota engines
Suggested Minimum Battery Size
Typical AH Typical CCA
Starter Capacity (kW) Engines @ 20 hour rate (Cold Cranking Amperage)
Less than 700cc 0.8 - 1.0 Beta 10 to 20 35 to 50 AH 350 to 400
700 to 1,500cc 1.0 - 1.4 Beta 25 to 43 65 to 75 AH 450 to 540
1,500 to 3,000cc 1.4 - 2.0 Beta 50 to 60 100 to 120 AH 580 to 670
Over 3,000cc 2.0 - 3.0 Beta 75 to 105 150 to 180 AH 1050 to 1200
1640_Aug_2013.qxd:beta 1660 manual 18/11/13 10:48 Page 21
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