One of the things I wanted to change on the boat right from the start was the way the batteries are connected, and the batteries used. The boat used a 1-2-both switch to connect two batteries to everything. The previous owner had two 8D starter batteries working a dual-purpose role, something I wanted to change. For me, I should be using a starter battery to start the engines and power the thrusters, and a deep-cycle battery for the house loads.
After buying the boat, I immediately set about researching the DC system to see what I would have to do to make the change, and after investigating the existing wiring in detail was confident that I could re-wire the system to use separate battery systems. Basically, I spent a few hours on the boat tracing all of the existing connections, starting from the batteries and feeding to the main power bus and loads in the engine room. Happily, these wires matched the DC schematic from mainship, so I would not have to trace down any “mystery” wires put in by a previous owner. I was also happy to see that everything was properly connected, suggesting that any work that was done on the boat was done by someone knowledgable.
The following shows a schematic of the wiring when we bought the boat, which was essentially the way it was created in the factory. Basically, the batteries power the entire boat through the battery switch, and the engine charges the batteries through this same switch. The unswitched loads (safety systems such as bilge pumps or gas detectors) and battery charger are wired to the battery posts on the battery switch. Pretty standard for production boats. The boat came with a 30 amp battery charger, which I considered small for the size of batteries used, and certainly too small for the upgrade I was planning.
The plan was to connect the engine starter and the bow thruster to a starter battery (which will be two group 27 batteries wired in parallel), with all other loads being connected to the house system (four golf cart batteries wired in series-parallel). This way the unswitched loads (bilge pumps) will be powered by the deep cycle batteries rather than starter batteries. Deep cycle batteries will power the pumps much better (and longer) than starter batteries will, and I won’t have to worry about the starter batteries being depleted by pumps or sensors.
This is what the battery switch looked like from the back. Lots of heavy wires leading to batteries and loads.
Each battery terminal on the battery switch was connected to a bus bar that powered unswitched loads on the breaker panel at the top left. Each of these terminals is also connected to the battery charger, so that the batteries can be charged without the battery switch. The bow thruster, engine and house system are all connected to the load side of the battery switch.
The first step was to remove all of the old batteries. This gave room to work, and also made it possible to clean the old battery area (the old lead acid batteries were stored in trays, not boxes). I cleaned the battery shelf and bilge area using dish soap and water, then rinsed it with a baking soda solution to get rid of any acid residue.
Next, the wire leading to the starter, and the wire leading to the thruster were disconnected from the load terminal of the battery switch. These two wires were removed from the junction box and were re-wired to a switch I added for the purpose.
Next, I removed the shorter batter lead from battery terminal 2, and I also removed the leads for the battery charger from both battery posts. This left a battery lead on post 1, and a lead for unswitched loads on each post. I then moved the unswitched lead from post 2, and connected it to post 1. This post (that had the longer wire attached) will connect to the house bank, which can now supply power to the all the unswitched loads. I decided to keep the 1,2-both switch, and will simply place it in the “1” position to power the boat (will add a safety label for repairmen). The final task was to connect the battery lead to an ANL fuse holder, which I attached to the bulkhead near the house bank.
The engine starter wire and thruster wire were then connected to the output of a new battery switch, and the other post of this switch was connected to an ANL fuse holder, which was mouted on the bulkhead near the starter bank. The thruster on the boat was wired through a 500 amp ANL fuse, I used the same size fuse for the starter bank. Thrusters normally pull more power than engine starter motors do (the cranking amps are high but for a very short duration) so this size of fuse will not cause nuisance trips.
The wiring on the boat (supply only) now looks like this.
The next step was the charging systems. First is the battery charger. I replaced the existing 30 amp charger with a Victron 60 amp unit. The old charger was removed, and the Victron mounted in its place. Since this was a bigger charger than the boat originally had, the existing DC wires were too small to carry the amp loads. I replaced the wires connecting the charger to the DC system with larger wires to match the wire size I plan to use from the alternator. This way I could save a little by using one fuse for both the charger and alternator wires (much cheaper to go with a slightly larger wire than to need separate fuses and holders). I also added ANL fuses to all the positive outputs of the charger, and removed the fuse from the ground. The ANL fuse holders were connected with high amp bar connectors.
Next was the alternator, which was the most complex part of the job. If the batteries were all connect to the alternator they would also be connected to each other. This means that when the alternator is not working, that the batteries could discharge each other. To prevent this from happening, some kind of device is needed to electrically combine the batteries during charging, but electrically separate the batteries once charging is complete. On previous boats I had used Bluesea automatic charge relays, which would be a simple install on this boat. However, I may want to add an externally regulated alternator to the boat in the future. For this reason, I decided to use a Victron Argofet battery isolator, since this will work better with the future alternator and regulator. To use this device, the alternator had to be re-wired slightly. Originally, the alternator was wired back to the batteries via the starter.
This wiring would work with the ACR but not with the argofet. To use the Argofet, I disconnected the alternator wires (negative and positive) and ran a new positive wire directly back to the argofet, and a new negative wire directly back to the main negative bus.
From the argofet, positive wires run via ANL fuses to each battery bus (the wires were sized to handle a larger future alternator). This required disconnecting the old alternator wire in the engine junction box, something that was simple to do because of the engine design. I left the old wires in place (disconnected with ends covered and labeled) as this was much easier than messing with the engine wiring harness.
The negative connection from the house bank to the main bus on the back wall of the engine room was the last wiring task. The house bank will consist of four 6V golf cat batteries wired in series-parallel. The negative wire from the battery bank first connects to the battery monitor shunt, which is connected to the boat’s negative bus. The battery monitor was another upgrade I wanted to have. These have been very useful on previous boats, and give you a big piece of mind when anchoring.
Securing the battery bank was the final problem. For this each battery was placed in a battery box. The boxes were secured to the base using wooden cleats. These I pre-sealed at my shop at home using west system epoxy. Each battery box was also held in place using U-bolts attached to the base, which are connected to the battery straps supplied with the boxes.
The system worked flawlessly over our first summer. we have been very happy with the upgrade. The house bank has enough capacity to power the boat (refrigerator included) for about 3 days before recharging. We recharge every day, but nice to know we have a good reserve. We are planning to increase our refrigeration capacity this summer, and may add an inverter in the future (have not decided yet) so we have lots of reserve capacity.
