Voltage
The nominal operating voltage of the battery bank.
Electric narrowboat guide
Narrowboat Battery Capacity Guide.
Battery capacity becomes useful only when it is translated into stored energy, usable energy and the demands of the actual boat.
Ah and kWh
Do not compare amp-hours without voltage.
Amp-hours describe charge. Kilowatt-hours describe stored energy and make systems at different voltages easier to compare.
Amp-hours
The amount of electrical charge available at that voltage.
Kilowatt-hours
Nominal energy is approximately volts × amp-hours ÷ 1,000. Usable energy is lower and depends on approved operating limits.
Example: a nominal 51.2V, 600Ah battery bank represents approximately 30.7kWh before allowing for reserve, system limits and losses. It is an explanation of the calculation, not a universal Oakums specification.
Size around use
More capacity is not automatically the best value.
A well-sized system balances autonomy, charging time, weight, space, cost and the ability of the charging sources to replenish it.
Propulsion demand
Cruising speed, hull, propeller, water conditions and hours underway affect motor energy use.
Domestic demand
Cooking, refrigeration, hot water controls, laundry, entertainment and working aboard add to the daily budget.
Season and route
Winter solar, shaded moorings and consecutive cruising days change the required charging strategy.
Reserve and longevity
The agreed operating window should protect the system while leaving a sensible reserve for real cruising.
Battery management
The battery is part of a controlled system.
BMS communication, isolation, fusing, cabling, temperature limits, monitoring and service access matter alongside the headline capacity.
- Compatible charging parameters
- Appropriate DC protection and isolation
- Temperature-aware operation
- Clear state-of-charge monitoring
- Accessible inspection and servicing
Questions buyers ask
Clear answers before specification.
How do I convert battery Ah into kWh?
Multiply nominal voltage by amp-hours and divide by 1,000. The result is nominal stored energy; usable energy depends on the permitted operating window and system losses.
Is a larger battery always better?
No. Additional capacity should be justified by genuine demand and supported by suitable charging, protection, space and weight allowances.
What protects a lithium battery bank?
The design combines the battery management system with correct charger settings, isolation, fusing, cabling, temperature limits, monitoring and service access.
Plan your Oakums
Turn the technical questions into the right specification.
Tell Oakums how you expect to cruise, live and recharge. We will relate the equipment choices to the boat and your intended use.