Battery and High Amperage Wiring
An overview of all electrical work undertaken in the 2020 refit with links to greater detail is found in the New Wiring section of the Electrical Work Planned for 2020 web page. Many of the links provide detailed descriptions of the charging and other systems being installed.
The web page describes the battery and high amperage wiring. There is a lot of information on wiring separated into the following sections and pages.
Wire Sizing
| AWG wire gauge ampicity and resistance in milliohm per foot | ||||||||||
| AWG | current | resistance | AWG | current | resistance | AWG | current | resistance | ||
| 2/0 | 231-330 | 0.08 | 6 | 84-120 | 0.40 | 12 | 32-45 | 1.75 | ||
| 2 | 147-210 | 0.16 | 8 | 56-80 | 0.62 | 14 | 25-35 | 2.53 | ||
| 4 | 112-160 | 0.24 | 10 | 42-60 | 1.00 | 16 | 18-25 | 4.00 | ||
A number of resource provide wire sizing information. The Blue Sea ABYC Ampicity Rating Table is a reprint of the American Boat and Yacht Council (ABYC) recommendation for minimum wire size to safely carry a current load. The Ancor catalog provides ABYC recommended wire colors (which we will ignore) and the often cited or reprinted tables of conductor size for 10% or 3% voltage drop. More useful is the table of AWG Wire and Cable Specifications. Using this table, the exact voltage drop and power loss can be computed for a given wire length and current.
An excerpt table is provided, giving the ABYC Amp rating for wire with 105°C insulation (Ancor marine wire) that is not exposed to the heat of an engine room (we no longer have a diesel engine). A current range is given for bundled wires and unbundled. This range takes into account variations in air flow around the wire and inability of heat to escape the wire due to bundling.
The four parallel 48V battery modules will each have a separate AWG #2 gauge wire from the module positive side to the 48V load bus bar and a separate AWG #6 gauge wire from the 48V module positive side to the charge side bus bar. With one module each, no bus bar is needed for the 24V or 12V bank. The 24V and 12V modules will also have AWG #2 gauge wire from the module but connect directly to a load side breaker and WG #6 gauge wire from the module to the charge side ProStar charge controller.
The 48V bank will require AWG #2/0 load side wire from the 600A bus bar where the 48V battery modules are connected in parallel to the battery switch for the motor and in the future to the circuit breakers for the galley stove inverter. The 24V and 12V banks can use AWG #2 load side wiring. A common 600A ground bus bar will serve all three battery banks. AWG #2/0 wire will be used for all wires used to connect the 48V bus bar to the fuse, the battery switch, the shunt, and then to the motor power terminals.
Wires from the 48V load bus bar to the breakers will be AWG #2/0. Wires from the 24V or 12V battery to the breakers will be AWG #2. Wires on the load side of the breakers will be AWG #6 for all breakers of 50A or less or AWG #2 for breakers greater than 50A. All feed side wires (5) to the cabin mounted breaker panel assembly will be AWG #6. The cabin mounted breaker panel assembly load side wires to the terminal blocks behind the breaker panel will be AWG #10, except loads with 30A breakers (water heaters) or 50A breakers (small inverters) which will be AWG #6.
Wires to the large inverter used for the electric galley stove will be AWG #2 or AWG #2/0 (if we have enough #2/0 left over). The AC/heat inverter and water heaters will use AWG #6 wire. The smaller inverters for the galley and vanity AC sockets will use AWG #6 wire.
All other loads are connected to 15A or smaller breakers and will use AWG #10 wire to the terminal block nearest the load and then a fuse in some cases and the size wire used by the load if smaller to the load itself. For loads with short wires a butt connector and either AWG #10 or AWG #14 wire will be used, appropriately sized for the butt connector. LED lights or other low current loads using smaller than AWG #16 wire will use step down butt connectors to bring the wire size up to AWG #14.
Battery Charge and Load Wiring
There are three battery banks: 48V, 24V, and 12V. Each has a charging side and load side so that the charging and load can never be connected together without a battery. Details on the battery installation plan and battery wiring can be found on the Battery Installation Plan web page. Details on the charge controllers can be found on the Charge Controllers page.
The high current charging and loads will be handled with bus bars, battery switches, and battery protectors. The battery protectors shut off when a low battery voltage is detected and turn back on when battery voltage recovers, with some hysteresis in the voltage threshholds. The 24V and 12V load side bus bars and battery protected bus bars will be connected to the electrical panel for distribution to sets of lower current loads.
Bus bars and primary charge and load wiring
A total of eight load buses will be used, designated by voltage and priority. The priorities are LSOC for loads available at any state of charge, MSOC for loads that will become unavailable when battery protectors sense low battery voltage, and HSOC (high voltage) for loads that are only available when the battery has a relatively high state of charge. Only 12V has a MSOC. The bus bars are 48V LSOC, 48V HSOC, 24V LSOC, 24V HSOC, 12V LSOC, 12V MSOC, and 12V HSOC. In some cases where there is a single load for a given designation that load may be connected to a battery switch or battery protector directly rather than using a bus bar.
Each battery module will have separate charge and load ground cables. There are six modules, so 12 ground cables from the batteries. Two or three 600A x 4 bus bars will be used. Grounding is discussed in greater detail in the Grounding and Bonding section.
48V Charging Bus
Each battery module will also have a charging and load positive side. The four 48V modules charging positive cables will lead to a 150A x 4 48V charging bus bar. Also connected to this bus bar is a battery switch labeled "48V charging" and second 48V charging bus bar where the two solar panels, wind generator when installed, and AC charger will be connected.
Each charging source will be separately fused. Each source will have a separate charging shunt to allow monitoring of the individual charging sources. Each of the solar panels will be connected to a separate charge controller. The difference in solar panel outputs should provides insights into the effects of shading on the panels.
48V Load Bus
The 48V module load positive cables will be lead to a 600A x 4 bus bar. Also connected to this bus bar will be a a battery switches and a 40A circuit breaker. The battery switch will be labeled "48V load". The circuit breaker will be labeled "24V charging". The 48V load switch will only be connected to a fuse and then the auxilliary propulsion motor at this time. The 24V charging breaker will be connected to a battery protector and then Morningstar Prostar 25A MPPT charge controller, then the 24V charging single positive battery cable.
| Major 48V Loads and Charging Feed | |||
| V | A | type | desription |
| 48V | 300A | Hiitio breaker | 48V total loads including motor |
| 48V | 250A | Class-T Fuse | auxilliary propulsion electric motor |
| 48V | 200A | Hiitio breaker | 48V loads excluding motor |
| 48V | 150A | Series 285 breaker | solenoid and cooktop/oven inverter |
| 48V | 30A | Series 285 breaker | solenoid and 24V charging |
| Major 24V Loads, Panel Feeds and Charging Feed | |||
| V | A | type | desription |
| 24V | 200A | Hiitio breaker | 250A bus for 24V total loads |
| 24V | 100A | Series 285 breaker | windlass (future) |
| 24V | 150A | Series 285 breaker | 24V 1800W galley inverter |
| 24V | 150A | Series 285 breaker | 24V 1800W vanity inverter |
| 24V | 150A | Series 285 breaker | 24V 1800W heat pump inverter |
| 24V | 100A | Series 285 breaker | 24V water maker |
| 24V | 50A | Series 285 breaker | 24V LSoC panel feed |
| 24V | 50A | Series 285 breaker | solenoid and 24V HSoC feed |
| 24V | 30A | Series 285 breaker | solenoid and 12V charging |
| Major 12V Loads and Panel Feeds | |||
| V | A | type | desription |
| 12V | 200A | Hiitio breaker | 250A bus bar for 12V total loads |
| 12V | 50A | Series 285 breaker | 12V LSoC panel feed |
| 12V | 50A | Series 285 breaker | solenoid and 12V MSoC panel feed |
| 12V | 50A | Series 285 breaker | solenoid and 12V HSoC panel feed |
| 12V | 50A | Series 285 breaker | solenoid and galley water heater |
| 12V | 50A | Series 285 breaker | solenoid and forw water heater |
24V Load Bus
The 24V battery bank (single module) positive load side will be connected to a 150A circuit breaker labeled "24V load". The load side of the breaker will be connected to a shunt and then a fuse and bilge pump switch and a 150A bus bar and labeled "24V battery load". This bus bar will be connected to breakers for 24V high priority loads, 24V low priority loads, and 12V charging. The low priority breaker will have a solenoid to cut off loads when battery state-of-charge is low. Both priority load feeds will be connected to the cabin mounted breaker panel assembly. The 12V charging circuit breaker will be connected to a shunt, a solenoid, and a Morningstar Prostar 25A MPPT charger and then the single 12V battery module charging side cable.
12V Load Bus
The 12V battery bank (single module) positive load side will be connected to a 150A circuit breaker, a shunt, then a fuse and bilge pump switch and a 150A bus bar and labeled "12V load". Connected to the bus bar will be three circuit breakers for 12V high, medium and low priority loads. The medium and low priority loads will connected to solenoids. All three priority load feeds will be connected to the cabin mounted breaker panel assembly.
Major Load and Panel Feed Breakers
Major individual loads and the breaker panel feed lines will be supported by Blue Sea Systems 285-Series Circuit Breakers which are 25-150A thermal breakers rated for 48V use. These have studs for ¼" ring terminal connectors.
Shore Power AC Charging
Shore power will be connected only to a 48V charger. This provides isolation from badly grounded or improperly polarized shore power. This avoids an all too common source of galvanic corrosion problems and safety issues.
Connecting loads directly to shore power is not an option if some of the loads can exceed the shore power connector rating. For example, an electric stove can draw up to 4.9kW of power. Full power is over 20A at 230V or over 40A at 115V. A 120V 30A shore power connection could provide a little more than ⅓ of that power. A better solution is to provide multiple inverters, near the loads, for stove, galley appliances, vanity, and an heat/AC load. This avoids 115V wiring runs which if leaking due to contact with seawater could endanger crew.
The selection of a shore power charger is described in the Shore Power Charger section of the Battery Charging Plans web page.
Electrical Panels and Breakers and Fuses
The original breaker panel had a small number of DC circuits plus a small number of AC circuits connected directly to shore power. No AC charger and no inverter was installed. There were no high amperage loads which is a good thing since the battery bank was a single 12V 100Ah AGM battery.
It would have been possible to reuse the breaker panel enclosure with updated breaker panels but it would have been an extremely tight fit if it would fit at all. The 24V and 12V banks complicate the panel layout. A single positive bus can't be used. Due to the prioritization of 24V and 12V loads the new design requires five positive bus bars. Small loads such as the NAV switches, anchor light and overall circuits such as cabin lighting, domestic water pumps and instruments will be controlled by switches on the panel. Some larger loads such as water heaters, watermaker and the 24V inverters will have a breaker that only serves to operate a solenoid. Finer fusing on loads will be accomodated by individual fuses located closer to the load.
Original Breaker Panel Enclosure and Wiring
The low amperage breaker panel will be simplified. Mystery switches, such as "Loran" will be eliminated. Loads installed by previous owners that bypass the panel such as VHF will be put on the panel (for example, VHF would be connected to "instruments" on the panel but have its own fuse). The original enclosure will not be used.
The original electrical panel enclosure is a teak shallow box with a 17" high by 10" wide openning and is mounted on the port side above the ice box. It is hinged for access to the wiring with the hinge on the port side. Wiring behind the panel was very tight. It is set up for two batteries with an A, B, A+B switch and analog voltmeter. The battery switch and meter takes up a lot of room and the battery switch requires bringing battery cables into the box. There is very limited room behind the box for wiring. The cabinetry slopes back at the bottom so the panel is deeper at the bottom. This creates a head strike hazard when accessing the ice box.
The original wiring resembled spagetti. None of the wires were routed near the hinge, including the battery cables so the box coukd barely be openned and closed. Many of the wires were too small for the breaker size and some used automotive wire.
Currently there are only hole saw cutouts for the wires. Depth may be an issue on the shallower upper part but the existing enclosure. The cabinetry will be cut out behind the circuit panel box to improve depth and reduce wire bends.
New Low Amperage Breaker Panel Enclosure
A new teak enclosure will be made with a constant depth rather than sloping and deep toward the bottom. The new enclosure will be wider and taller to allow cables a greater bend radius at the hinge and making it easier to open the enclosure for access to the wiring.
Low Amperage Breaker Panel Wiring
Due to the use of 24V and 12V battery banks and circuit groups prioritized using battery protectors, multiple panels will be used. The battery switches will be located elsewhere and no analog meter will be used.
Blue Sea makes two small panels with two columns of breakers, with LED indicators on each breaker. Both are rated for 12v or 24V. Each column has a separate simple bus bar which need not be used. If the provided bus bar is removed then depth is reduced slightly and the breakers are can more easily be changed. The Blue Sea 8096 has two columns of three rows each for six total breakers. Dimensions are 10½" wide by 3¾" high. The panel overlaps by ¼" on each side and top and bottom so requires a 10" wide by 3¼" high cutout. The Blue Sea 8385 is similar with four rows for eight total breakers and is 4½" high. Both are 2½" deep.
The allocation of breakers is shown in the illustration to the right. Only 15A breakers are used. If a load requires higher current a solenoid will be used and a thermal breaker will provided for the load on the high amperage breaker panel. For these high amperage loads the 15A breaker serves only as a switch for the load.
Many panels in other boats are wired with both positive and DC ground with per circuit DC ground wires from the panel. In some installations this serves a purpose, avoiding having the positive and DC ground wires taking different paths and potentially creating a magnetic field which could affect the compass. Minimizing this magnetic field is accomplished by running load wires back through the same path that the bus wires were run to a point where both positive and negative wires can be run in parallel.
The existing panel is separated from the very large area behind it by a small gap between the bridgedeck seat and interior cabinetry. Not bringing high amperage ground wires through the same restricted space means positive feed current passes about 18 inches to the panel, then 18 inches back without corresponding ground current. Very small ground wires will be available but used solely to provide ground to the LEDs in the panels themselves. Since the panel bus and load wires are close together and in parallel no significant magnetic field should result.
The existing wire paths back through a very restricted space will not be used. The wires will be run through the back of the small cabinet under the bridgedeck and above the companionway stairs. There is much better space for wiring on the starboard side and the starboard side is also where the high amperage breaker enclosure will be mounted.
A set of terminal blocks will be placed in the area where the breaker panel load wires reach the starboard side. A total of 28 wires from the panel (number of breakers including spares) will have ring terminals to connect to these terminal blocks. From these terminal blocks the loads will be bundled into common runs to the various parts of the boat where the loads reside. A ground bus bar can be placed near these terminal blocks so the ground path will be the same. Rather than individual ground wires, a larger ground distribution wire can be run in parallel to feed runs to avoid creating magnetic fields. The Cabin Wiring section provides further details.
High Amperage Breaker Panel Enclosure
High amperage DC thermal breakers were used rather than using fuses. These need to be accessible and so they are placed on the left of the companionway (on the starboard side) opposite the low amperage breaker panel.
Some of the high amperage breakers also appear in the low amperage breaker panel with the low amperage breakers only operating solenoids. These include the 24V inverters and the 12V water heaters which are more often switched on and off and where the wire sizes needed would be excessively big for the low amperage breaker panel.
Some of the breakers are followed by solenoids that are automatically switched off if the battery SoC is low. These include the 24V high SoC (lower priority) loads and the 12V medium SoC (medium priority) and 12V high SoC (lower priority) loads. Charging of the 24V bank from the 48V bank and charging of the 12V bank from the 24V bank is also switched on or off depending on the relative SoC of the batteries.
Breaker Panel Enclosure Dimensions
On both the port and starboard side there is enough room to easily fit the low amperage and high amperage breaker panels. In both cases the enclosure dimensions were increased slightly to cover prior damage. On the port side it is damage due to the installation of the original breaker panel enclosure. On the starboard side it appears a previous owner added a fire extinguisher and small notepad shelf. The fire extinguisher is one of two B-2 extinguishers on the boat. It will remain in approximately the same place.
Both enclosures will have a hinge at the bottom to provide access to the back of the panel for maintenance. Both enclosures will have a door with a tempered glass or polystyrene window (plexiglass or lexan) that is hinged at the top. A hook and eye on the headliner will hold the door open for routine access.
Low Amperage Enclosure Dimensions
The new enclosure can be made larger than the original. It needs to be made taller and a little wider to hide damage.
The 6 breaker and 8 breaker panels are both 10½" wide. The new enclosure will be 13½" wide. The frame is ¼" wide so ½" is lost to the framing. This leaves 1½" on either side of the breaker panels. Inside the excess spaces on either side four bus bars will be located plus one at the top of the enclosure. Only AWG #10 wires from these bus bars will have to bend with the hinge, not the AWG #6 bus wires to the bus bars.
The 6 breaker and 8 breaker panels are 3¾" high and 4½" high respectively. There are two of each of these for a total of 16½" of height. There will be ½" space between panels and ½" below the bottom panel. There will be 2½" above the top panel. This additional height hides the holes for the prior latches above and below the original enclosure plus provides plenty of room for the fifth bus bar.
High Amperage Enclosure Dimensions
Quite a bit of space is provided above and below each high amperage breaker to accomodate the hard to bend small gauge wires which will be between AWG #6 and AWG #2. Additional space is provided at the bottom since this is where the wires will need to exit. To give a symetric look and to accomodate top hinges for a cover extra space is provided at the top. A set of panels hides the wiring and provides a place to put labels.
Each Series 285 breaker is 2" wide and 3¼" tall. There is 3¼" horizontal distance between breakers and between the outer breakers and the frame. The frame is also ¼" wide. This yields a width of 12". The vertical distance between breakers is 1¼" with 1¾" between the top and bottom breaker and the frame. Adding the ¼" frame width yields 20¾". The outer dimensions of the enclosure is therefore 12"Wx20¾"H.
Adjacent to the breaker panel enclosure is a short and wide enclosure holding four battery switches. These provide emergency shut off or storage shutoff for the motor, the other 48V loads, the 24V loads, and the 12V loads. This enclosure extends to where the wires can be passed in the deep cavity formed by the cockpit coaming.