Jocalia’s battery monitoring
New batteries were fitted to Jocalia last August, and a fresh alternator is now installed. At the AGM, the club’s Technical Director called for careful battery monitoring (charge rate and charge level), especially during long periods of sailing or anchoring.
This follows a history of unscheduled replacements of batteries and service alternators during Jocalia’s time with the club.
Jocalia’s battery system includes a Magnatronix DCC4000 monitor at the navigation station. This displays all the information required, by pressing the MODE key to cycle through. Users can check charge status in Ampere Hours; battery percentage; current flow (in Amps); and, voltage at the terminals.
Key figures to remember:
- 100% | 12.7v or more – no action required, fully charged
- 75% | 12.4v – no action required
- 50% | 12.1v – recharge recommended
- 25% | 11.6v – battery needs a full recharge as soon as possible, and equalisation on shore power
- 0% | 10.5v – fully discharged battery. Recharge and equalise immediately and report in Tech Log
Remember: all voltage readings above should be taken with charging systems turned off (i.e. engine not running and shore power not connected). The battery voltage takes a short time to stabilise when charging is stopped.
Battery load and sailing time
The batteries fitted have a rated capacity of 429 Ampere Hours. Estimated average consumption during daylight sailing with manual helming – using instruments, displays, VHF, autopilot, radar, fridge, and lighting – is around 4.0 Amps.
This figure rises significantly if the radar is used on transmit (+1A) or the Autohelm is engaged (+4A to 5A, depending on sea state and response setting). The working party in Troon will assess the actual battery drain during Jocalia’s shakedown trial in Scotland.
This equates to around 55 hours of sailing before the battery drains to 50% capacity. However, this level of discharge must not be repeated unless the battery is fully recharged – a short engine run is unlikely to achieve this. Continued monitoring is essential until shore power is available.
Maintaining battery health
Battery capacity will naturally reduce over time and can degrade significantly if not managed correctly. The DCC4000 monitor is adjusted annually (by your friendly bosun) to take account of this reduction in capacity, so the percentage displayed still accurately reflects what the battery is expected to supply.
The 50% rule should always be followed. Dropping below this level can lead to sulphation – crystal growth on the lead plates – which increases the battery’s internal resistance. Jocalia’s shore power charger is capable of counteracting this through a special charging mode at 15.5V, which helps reverse sulphation. However, this can cause gassing, so it’s important to keep the battery compartment (aft cabin) well-ventilated if this occurs.
The best way to manage a battery is through a regular cycle of partial discharge followed by a full recharge. Avoid leaving the battery in a partially discharged state for extended periods.
Leave the maintenance to us – Tops’l ensures Jocalia’s systems stay shipshape year-round.