If you use a parallel configuration, the two batteries must be identical: same rating
and same manufacturer and ideally new batteries, or at least operated as a pair for
their entire service life. Each battery must be charged separately before installing to
ensure they start at the same charge level. Batteries which are dissimilar in any way
may not charge and discharge equally, leaving one battery undercharged.
To connect two batteries in parallel, prepare two shunt cables of the same gauge
used to connect the batteries to the motor controller. Connect the positive post of
one battery to the positive post of the other and the negative post of one battery to
the negative post of the other.
One post will share two compression terminals: the shunt and the cable to the motor
controller.
24 VOLT BATTERIES
24 volt batteries are less common than 12 volt batteries. You may find it more
convenient and less expensive to use two 12V batteries in series.
Figure 2: Two 12 V batteries in series, providing 24 V
To connect two batteries in series, connect the negative post of one battery to the
positive post of another using a short piece of battery cable of the same gauge used
to connect the batteries to the motor controller. The two remaining posts are each
connected to the motor controller using two battery cables, supplying 24V.
WINDLASS BATTERIES
It is possible to share an existing battery bank with a windlass, providing it has
sufficient capacity to meet both windlass and thruster usage, and is close enough to
the bow to supply the bow thruster. It is not recommended to power the stern
thruster from the windlass batteries due to the need for longer cable runs. Supplying
both bow and stern thrusters from a single battery is not recommended. The more
deeply discharged a battery becomes before it is recharged, the fewer charge cycles
it can provide in its lifetime, so if both thruster and windlass are used to a point
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