Battery Sizing for Gyro Systems — Exact Calculations by Model

Why Battery Sizing Matters

Install a gyro on an undersized battery bank and you'll experience:

Gyro shutdowns during normal use
Premature battery failure (12–18 months vs. 10+ years)
Generator dependency ($3,000–$8,000/year in fuel)
Frustration and troubleshooting instead of fishing

Install on an oversized bank and you'll spend 30–50% more than necessary. The key is right-sizing — calculated from your actual use profile, not generic tables.

Most common mistake: Using the gyro manufacturer's "minimum battery recommendation" without adding house loads, Peukert correction, or safety margin. The manufacturer's number is for the gyro ALONE. Your vessel has other demands.

The Battery Sizing Formula

Required Battery Capacity (Ah) =

(Gyro Load + House Load) × Runtime Hours × 1.5 Safety Factor

Where:

Gyro Load: Continuous current draw from published specs
House Load: All other electrical devices (measured, not estimated)
Runtime Hours: Longest typical trip without charging
Safety Factor: 1.5x for aging, temperature, and unexpected loads

            Critical: This formula uses continuous load, not peak. Peak loads (spin-up, transients) are handled by the battery's discharge rate capability and any load-smoothing modules. If you size for peak, you'll oversize by 200–300%.
        

Exact Sizing by Gyro Model

These calculations assume a typical sportfish/center console with house loads of 20A @ 24V (refrigeration, electronics, pumps, lighting). Adjust for your actual vessel.

Gyro Model	Gyro Load	House Load	Total	4-Hr Trip	8-Hr Trip	Min Battery
SK2 (12V)	18A @ 12V	15A @ 12V	33A	132Ah	264Ah	200Ah (12V)
SK6 (24V)	35A @ 24V	20A @ 24V	55A	220Ah	440Ah	400Ah (24V)
SK9 (24V)	40A @ 24V	20A @ 24V	60A	240Ah	480Ah	500Ah (24V)
SK16 (24V)	48A @ 24V	22A @ 24V	70A	280Ah	560Ah	600Ah (24V)
SK18 (24V)	50A @ 24V	22A @ 24V	72A	288Ah	576Ah	600Ah (24V)
SK26 (24V)	55A @ 24V	25A @ 24V	80A	320Ah	640Ah	700Ah (24V)
SK35 (24V)	65A @ 24V	25A @ 24V	90A	360Ah	720Ah	800Ah (24V)
SK40 (24V)	70A @ 24V	28A @ 24V	98A	392Ah	784Ah	900Ah (24V)

            Important: The "Min Battery" column includes the 1.5x safety factor. For example, SK6 with 55A total × 8 hours = 440Ah. 440Ah × 1.5 = 660Ah → round to nearest standard size = 400Ah is insufficient, 600Ah is correct. Never round down.
        

Chemistry Selection Guide

Chemistry	Best For	Avoid If	Typical Lifespan
AGM	Budget installs, short trips (<4 hrs), easy access for replacement	Continuous loads >40A, enclosed spaces, daily deep cycling	2–3 years (gyro use)
LiFePO4	Weight-critical installs, fast charge available, thermal management possible	Enclosed machinery rooms, cold-weather charging, insurance restrictions	8–12 years
Sodium-Ion	Continuous high loads, enclosed spaces, safety priority, cold weather	Weight is absolutely critical (20% heavier than LiFePO4)	10–15 years

Our recommendation: For gyro applications, sodium-ion is optimal. It handles continuous high loads with minimal voltage sag, operates safely in enclosed spaces, and delivers 10+ year lifespan. Cost is 40–50% less than LiFePO4 per usable kWh.

Quick Reference: Minimum Battery by Chemistry

Gyro Model	AGM Minimum	LiFePO4 Minimum	Sodium-Ion Minimum
SK2	200Ah (12V)	150Ah (12V)	150Ah (12V)
SK6	600Ah (24V)	400Ah (24V)	400Ah (24V)
SK9	800Ah (24V)	500Ah (24V)	500Ah (24V)
SK16	1,000Ah (24V)	600Ah (24V)	600Ah (24V)
SK26	1,200Ah (24V)	800Ah (24V)	800Ah (24V)
SK35	1,400Ah (24V)	1,000Ah (24V)	1,000Ah (24V)
SK40	1,600Ah (24V)	1,200Ah (24V)	1,200Ah (24V)

All values include 1.5x safety factor and assume 20–25A house loads. For vessels with higher house loads (air conditioning, large inverter loads), add proportional capacity.

Don't Guess Your Battery Size

A $500 load audit prevents $3,000 in premature battery replacements. We measure your actual loads and specify the exact battery capacity, chemistry, and architecture for your vessel.

Request Battery Sizing Analysis