Black Series BKS-240DMAX 240A alternator, three quarter view showing the black housing and the 7PV fixed pulley

Rear view of the Black Series BKS-240DMAX showing the B plus terminal stud, the LIN connector plug and the ventilated end housing

Dimensioned drawing of the BKS-240DMAX showing the M8 top mount, 10.5mm bottom mount hole, seven groove 60mm pulley and overall case dimensions

Output curve for the BKS-240DMAX plotting hot amps against alternator RPM, rising from around 1200 RPM and levelling near 216A

Manufacturer fitting notes for the BKS-240DMAX covering cable requirements, battery charging advice, the hot speed current table and lithium battery limitations

Jaylec

Black Series ALT 12V 240A, ISUZU D-MAX - 4JJ1, 4JJ3-TCX DSL [FIXED PULLEY]

Name: Black Series ALT 12V 240A, ISUZU D-MAX - 4JJ1, 4JJ3-TCX DSL [FIXED PULLEY]
Brand: Jaylec
SKU: BKS-240DMAX
Price: 939.00 AUD
Availability: InStock

BKS-240DMAX

$939.00

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or finance your build with Allied Finance

Important note

Jaylec alternators are designed and tested for use with standard lead-acid battery systems. These units are not suitable for direct use with lithium (LiFePO4) battery setups

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Suits the Isuzu D-MAX fitted with either the 4JJ1 or the 4JJ3-TCX diesel engine. Not compatible with L or M regulator alternators.

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CHARGES HARDER AT IDLE

Higher charge at lower RPM, holding a dual battery bank in a full state of charge.

FITS 4JJ1 AND 4JJ3-TCX

One alternator covers both D-MAX engines. Only the wiring harness is engine specific.

240A REPLACES 130A

Close to double the factory output, so a loaded touring system is no longer sitting at capacity.

DIRECT OE FITMENT

161mm mount spacing, M8 top mount and a 17mm shaft. Goes in where the original came out.

2 YEAR WARRANTY

2 years or 25,000km against defects in materials and workmanship, direct from the manufacturer.

The BKS-240DMAX is the Black Series 240A alternator for the Isuzu D-MAX, and it suits both the earlier 4JJ1 and the later 4JJ3-TCX. It replaces a standard 130A unit, so you are close to doubling the available current. It delivers 13.5V at 240A cold and 13.5V at 217A hot, and it makes that current available lower in the rev range, which is where a factory alternator struggles once a dual battery system, a fridge, driving lights and a compressor are all asking at once.

It is a direct OE fit in the factory location, with 161mm centre to centre mount spacing, a 55mm mount leg ID, an M8 top mount and a 17mm shaft. The pulley is a 7PV fixed type with 7 grooves. The regulator is internal with LIN communication, so the alternator talks to the vehicle the way the original did.

One compatibility check before you order: this unit is not compatible with L or M regulator alternators. If your vehicle runs one of those, this is not the right part.

Plan for the wiring. A battery positive wiring upgrade is required. Run 0 B&S cable from the alternator to the battery with a 250A mega fuse inline of the new B+ terminal. The factory cable was sized for a 130A alternator and will not carry this safely, and reusing it is the most common reason a high-output alternator never delivers what it is rated for. We build complete kits that pair this exact alternator with a harness cut for your engine bay:

Isuzu D-MAX RG 4JJ3 240A Upgraded Alternator Kit →
This alternator with the harness, fuse and holder for the RG 4JJ3-TCX.

Isuzu D-MAX RC 4JJ1 240A Upgraded Alternator Kit →
The same alternator with the harness cut for the earlier 4JJ1.

Worth knowing before you buy: this alternator must not be connected directly to a lithium battery, and doing so voids the warranty. A DC to DC charger goes between the alternator and any LiFePO4 bank. Wired that way it works exactly as intended and gives the charger far more current to draw on than the standard 130A unit ever could.

13.5V at 240A cold and 13.5V at 217A hot
Replaces the standard 130A alternator, close to doubling available current
Higher charge at lower RPM, so the gain shows up at idle rather than only at speed
Keeps a dual battery bank held in a full state of charge
Direct OE fitment, 161mm centre to centre with an M8 top mount
Internal regulator with LIN communication
Environmental protective coating, durable bearings and efficient cooling
Suits both the 4JJ1 and the 4JJ3-TCX

Part Number: BKS-240DMAX

Voltage: 12V

Output: 13.5V at 240A cold, 13.5V at 217A hot

Mount Leg ID: 55mm

Mount Spacing: 161mm centre to centre

Top Hole ID: M8

Bottom Hole ID: 10mm

Shaft Size: 17mm

Pulley: 7PV fixed, 7 grooves, 62mm diameter

Regulator Type: Internal LIN

Terminals: B plus and LIN

Excitation: External

Ground: Negative

Mount leg distance: 161mm center to center

Shaft diameter: 17mm

Pulley diameter: 62mm

Everything this install needs

0 of 0 in the box

Direct OE fitment using the factory mounting location.
Not compatible with L or M regulator alternators. Check which regulator type your vehicle runs before ordering.
Run 0 B and S cable for the main B plus wire from the alternator to the battery.
Fit a 250A mega fuse inline of the new B plus terminal.
Do not connect this alternator directly to a lithium battery. A DC to DC charger must be fitted between the two, and connecting direct voids the warranty.
Keep the vehicle battery on charge if it is not driven weekly. High amperage units can damage a battery sitting in a low state of charge.
The manufacturer recommends fitting by a trade qualified auto electrician, to avoid damage to the vehicle wiring harness.
Disconnect the battery terminals before starting work, and confirm charging voltage once everything is back together.

Suits the Isuzu D-MAX fitted with either the 4JJ1 or the 4JJ3-TCX diesel engine. Not compatible with L or M regulator alternators.

Q: Will this fit my D-MAX?
A: It suits the Isuzu D-MAX with either the 4JJ1 or the 4JJ3-TCX diesel engine. The one thing to check is the regulator - this unit is not compatible with L or M regulator alternators.

Q: Should I buy this or the complete kit?
A: The alternator on its own suits both engines, but you still need a wiring upgrade. Our kits pair this same alternator with a harness cut for your specific engine bay plus the fuse and holder, so unless you already have suitable cable the kit is usually the better buy. Both kits are linked in the description above.

Q: What cable and fuse do I need?
A: Run 0 B and S cable for the main B plus wire from the alternator to the battery, with a 250A mega fuse inline of the new B plus terminal.

Q: How much more is it than standard?
A: The factory unit is 130A, so this is close to double. The manufacturer hot test figures at 13.5V are 117A at 1801 alternator RPM, 155A at 2200, 190A at 3200 and 206A at 4001, levelling out around 216A.

Q: Can it charge a lithium battery?
A: Not directly, and connecting it straight to a lithium battery voids the warranty. A DC to DC charger must be fitted between the alternator and the lithium bank.

Q: What output will I actually see at idle?
A: That depends on your alternator pulley and harmonic balancer sizes, which set how fast the alternator spins for a given engine speed. Output starts from roughly 1200 alternator RPM.

Q: Do I need to do anything differently with my starting battery?
A: If the vehicle sits for more than a week at a time, put the battery on a charger. A high output alternator will push hard into a flat battery, and lead acid batteries do not like accepting that much current at once. Keeping it topped up means the alternator never has to, which is easier on both.

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