Power source
Review how the Balmar MC-618 Alternator Regulator connects, how it operates and which installation requirements apply to this model.
Open this example as a new project. Use your own parts and cable lengths to make the plan yours.
The regulator needs separate power, ignition, field and sensing connections matched to the alternator and batteries. The field-output rating is not a continuous supply-load measurement. Use Balmar's complete harness diagram.
The regulator needs separate power, ignition, field and sensing connections matched to the alternator and batteries. The field-output rating is not a continuous supply-load measurement. Use Balmar's complete harness diagram.
Wiring diagram
Open this example in Crimp to use your own parts and cable lengths. Review the assumptions and installation notes as you adapt the circuit.
Installation notes
Guidance for this model, with sources linked beside the relevant advice.
Verified against the manufacturer's documentation (rev. SUP-0283 Rev F, MC-618 installation and operation manual), checked 2026-10-01. Manufacturer documentation →
The MC-618 controls the field of a 12 V P-type externally regulated alternator. The manufacturer’s regulator comparison specifies 15 A maximum field current. The alternator’s main charging output goes directly to the charging system, not through the regulator. No fixed quiescent draw is asserted by the catalog.
Manual pages 5–7 distinguish black ground, red power, brown ignition, blue field and the separately fused positive battery-sense lead. Sense the bank actually being regulated and provide a sound negative reference. Follow the supplied harness’s 15 A power fuse and 1 A sense fuse arrangement. Ignition enables regulation; it is not an alternator-output connection. Optional stator/tachometer, temperature, SmartLink and alarm wires are omitted from the simplified symbol.
Select the battery profile and verify its voltages against the battery maker’s limits. Install battery and alternator temperature sensors where specified. Belt Load Manager changes maximum field drive; it is not a precise, closed-loop battery-current limit. A 50% field setting must not be assumed to guarantee half the alternator’s nameplate current.
A lithium BMS needs an arrangement that stops alternator field production before disconnecting the charging bank. Follow the LFP recommendations, including appropriate ignition shutdown behavior and temperature protection. During commissioning, check sensing accuracy, alternator temperature and bank current at realistic engine speeds. Diagnose a no-charge condition from power, ignition, ground and sense measurements before replacing the alternator or regulator.
Build it out
Add MC-618 to your diagram, then connect your batteries, chargers and loads. Crimp calculates cable sizes and checks the connections as you draw.
Every cable you draw there is sized against ABYC E-11, from the same tables as the reference on this page.
Technical reference
Check the model, ratings and connection points against your own unit before choosing installation hardware.
Check stud sizes, fuse type, run length and how warm the space gets against the gear you actually have before you order.
Catalog connection points, current direction and planning limits. Check the manufacturer's pinout and connector ratings before installation.
POWER RED
power
positive · input
GROUND BLACK
neg
negative · input
IGN BROWN
ignition
signal · input
FIELD BLUE
field
signal · output
B+ SENSE
v-sense
signal · input
A dash means a current rating is not specified here.
Method & provenance
Manufacturer specifications describe the equipment. Crimp calculates cable results from the circuit and assumptions you enter.
From the maker
Manufacturer, model, ratings and which terminal does what come from the catalog. A newer revision, or the nameplate on the unit in your hand, can say something different — when it does, the nameplate wins.
ABYC E-11
Sized against ABYC E-11. Boats built to UK or EU rules answer to ISO 13297 — check these figures against it before you build. The run length and the current above are what drive the result. Crimp doesn't know how warm your space gets; draw the cable inside an engine-bay zone on the canvas and it sizes for the heat.
Next step
Open this example as a new project. Add your equipment and cable lengths, then review the sizing and checks for your setup.