Hallberg-Rassy 40 electric repower: motor, battery and cable sizing

The Hallberg-Rassy 40 is a 12.4 m monohull with a 10.6 m waterline and 10,000 kg displacement. From those figures, the configurator's sizing model puts an electric conversion at 15 kW and 48 kWh on a 96 V system.

Boat data: Hallberg-Rassy — Hallberg-Rassy 40 standard specification, checked 23 October 2026

Motor power

15 kW

10.2 kW needed at 6 kn

Battery pack

48 kWh

2 h at full rating, with reserve

DC design current

289 A @ 96 V

cabling burden: heavy

Range on that pack

12 nm

at 6 kn

Open the Hallberg-Rassy 40 in the configurator Compare motors for 15 kW

The boat

Length: 12.4 m
Waterline length: 10.6 m
Beam: 3.82 m
Displacement: 10,000 kg
Hull: Lead keel on deep bilge
Designer: Germán Frers
Builder: Hallberg-Rassy (Sweden)
Built: 2002–2018
Number built: 162
Original engine: Volvo Penta D2-55 — 41 kW / 55 hp, shaft drive

Power needed by speed

Speed	Shaft power
3 kn	1.9 kW
4 kn	3.6 kW
5 kn	6.2 kW
6 kncruise target	10.2 kW
7 kn	16.4 kW
7.9 knhull speed	24.7 kW

The configurator's power-per-tonne heuristic, not a tank test — real boats vary by about ±25% with hull form, fouling, sea state and propeller. Near hull speed the power climbs steeply.

48 V or 96 V

48 V system

521 A

design DC current · cabling burden very heavy · 300 mm² for a short run

96 V systemconfigurator's choice

289 A

design DC current · cabling burden heavy · 120 mm² for a short run

Motor lines that cover 15 kW at 96 V

ePropulsion

I-Series (I-10, I-20, I-40)

Inboard · 10–40 kW · 96 V class

From our motor comparison, matched by power and system voltage only — check drive type and fit with the maker.

What these numbers assume

The published displacement. Your boat loaded for cruising is heavier — use your own figure in the configurator.
Cruise target of 6 kn, which is 75% of the 7.9 kn hull speed.
A shaft drive, as the source states.
A pack sized for 2 hours at the motor's full rating, 15% reserve and 80% usable depth of discharge.
Hallberg-Rassy's model page gives an 11.04 m waterline, the figure on its Hallberg-Rassy 40 Mk II data sheet (built 2016–2018, 11 t, Volvo Penta D2-60). The standard specification for the original boat gives 10.60 m and 10 t, which we use. Length is the hull length.
The Hallberg-Rassy 40 was built from 2002 to 2018; versions changed over that time, so check your own boat's figures.

Hallberg-Rassy 40

Common questions

How many kW does a Hallberg-Rassy 40 need for electric propulsion?+

About 10.2 kW to hold 6 knots — 75% of its 7.9-knot hull speed — so the configurator suggests a 15 kW motor. Power rises steeply above that: about 24.7 kW at hull speed. These are estimates from the boat's published waterline length and displacement; real boats vary by roughly ±25%.

What size battery does a Hallberg-Rassy 40 need?+

The configurator sizes about 48 kWh of LiFePO4 for 2 hours at the motor's full 15 kW rating, with a 15% reserve and 80% usable depth of discharge — about 12 nautical miles at 6 knots. Cruising below full power stretches that.

Should a Hallberg-Rassy 40 use 48 V or 96 V?+

At 15 kW the design DC current is about 521 A at 48 V (cabling burden: very heavy) and about 289 A at 96 V (heavy). The configurator picks 96 V for this boat: it stays on 48 V unless the 48 V current reaches its "very heavy" level.