When we bought Circe there was a very basic DC power system in place. General utility needs were supplied by a 'House' system comprising two Trojan T105 6volt lead-acid golf cart batteries, connected in series, delivering 12volt power with approximately 225 Amp hour capacity. One additional group 27 (DieHard) 12volt lead-acid battery rated at 550 CCA capacity provided starting power for the main diesel engine. All three batteries were re-charged either from a small, engine driven, 70 amp Balmar alternator or from 110 VAC shore power source controlled by an on-board Heart Freedom 10 combination charger/inverter. To monitor the system, analog voltmeter and ammeters were installed. To manage the system, the three batteries were linked through a user-operated selector/isolator switch that had to be manually switched to suit battery condition and charging mode.
View of DC distribution panels showing analog instruments in the right hand panel voltmeter (top) and ammeter (bottom). Below the instruments is the control panel for the Freedom 10 inverter/charger.
Shot of the original Perko selector switch that had to be operated as necessary to select the preferred power source and control the charging and discharging of the three batteries.
This simple system is very common on production boats and has proven to be reliable and stable, but it has some limitations. The biggest shortcoming is the lack of any active monitoring and control capability. This means the operator must physically monitor power useage on all three batteries and use the selector switch to control power sources and replenishing charges as necessary. While this process isn't particularly difficult, any oversight in the monitoring or switch operation can cause complete or partial loss of power. We wanted a more active, smart system that required minimal operator input so we started looking for some professional advice.
View of DC distribution panels showing analog instruments in the right hand panel voltmeter (top) and ammeter (bottom). Below the instruments is the control panel for the Freedom 10 inverter/charger.
Shot of the original Perko selector switch that had to be operated as necessary to select the preferred power source and control the charging and discharging of the three batteries.
This simple system is very common on production boats and has proven to be reliable and stable, but it has some limitations. The biggest shortcoming is the lack of any active monitoring and control capability. This means the operator must physically monitor power useage on all three batteries and use the selector switch to control power sources and replenishing charges as necessary. While this process isn't particularly difficult, any oversight in the monitoring or switch operation can cause complete or partial loss of power. We wanted a more active, smart system that required minimal operator input so we started looking for some professional advice.
Earl Mathiesen of Mathiesen Marine was our 'go-to' resource and he proposed some options that would fit our requirements. We were originally planning to combine this upgrade with a complete electrical panel clean-up and re-wire but based on Earl's advice we decided to just do the power management upgrade first and then build the new panel and re-wire as a second step. The new power management system comprised a Blue Sea automatic charging relay monitored through a shunt by a Xantrex LINKLite unit and controlled by a combiner switch.
Here is the new Blue Sea automatic relay and combiner switch.
This shot shows the old selector switch coming out.
Here is the new combiner switch installed. It has the same footprint as the old selector switch and so was an easy swap. In normal operation the switch stays in the 'on' position, the relay switches the battery connections automatically between House and Start batteries based on power input and output from either circuit.
Here is the new Blue Sea automatic relay and combiner switch.
This shot shows the old selector switch coming out.
The shunt for the battery monitor was located on the battery box to keep the cable runs short. The blue multi-conductor cable is the hook up to the Xantrex LinkLITE monitor.
This is the Blue Seas combining relay we used.
Not the best shot but it shows the automatic relay in place next to the combiner switch, again to keep cable runs short.
So far the new system is working perfectly and a quick glance at the monitor shows exactly how much power is being used and the overall condition of the batteries. An alarm will alert us to the batteries reaching 50% of capacity. When we have our wind and solar generation and LED lighting projects completed we will disconnect from shore power for a few days and see exactly how much power we are using and how much we are able to replace without running the engine. This will help us decide if we need a bigger alternator and/or house battery bank. Putting more batteries on the boat can extend periods between charges but also extends the time needed for re-charging. We are currently investigating Lithium-iron-phosphate batteries that can solve that problem without the weight and space penalty of lead-acid or AGM batteries. We will be updating this post periodically as and when we have more data and operating experience.
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