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Wiring: Wire Gauge from Battery to Fuse Block
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ContinuousWave Whaler Moderated Discussion Areas
ContinuousWave: Small Boat Electrical
Wiring: Wire Gauge from Battery to Fuse Block
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| Author | Topic: Wiring: Wire Gauge from Battery to Fuse Block |
| hc803 |
posted 08-03-2010 04:12 PM ET (US)  
I'm wiring navigation lamps, pumps, radios, audio amplifiers, and a depth finder. [The positive circuit] from battery [goes] through the master switch in stern, into a BlueSea Systems 5025 6-circuit fuse block. [The negative circuit] is going straight to fuse block [from the battery]. What wire gauge should I have going to the master switch? From the switch to the fuse block. And for direct negative connection? Am I doing this all wrong? |
| AZdave |
posted 08-03-2010 11:51 PM ET (US)
There have been a number of threads on wiring. Here is a diagram that appears to be close to what you will be doing. Note that switches and fuses are all on the positive side. Negative wires are connected to a bus which is connected to the negative post on the battery. http://www.fishingandboats.com/boat-wiring.html |
| davej14 |
posted 08-04-2010 01:20 PM ET (US)
Which fuse block are you using? Some of the Blue Seas fuse blocks have a negative bus which serves as a common connection point and should NOT be fused. Only the positive circuits should be fused. Most of the fuse blocks are rated for 100A total. Based upon the Blue Seas table for allowable amperage you should be using a 6 ga conductor between the battery and the fuse block: |
| hc803 |
posted 08-04-2010 01:51 PM ET (US)
Dave, I'm using the 5025: http://bluesea.com/category/5/21/products/5025 It has the negative common bus, fuses are on pos end. |
| bluewaterpirate |
posted 08-04-2010 03:19 PM ET (US)
Here you go ........ Tom |
| hc803 |
posted 08-04-2010 03:42 PM ET (US)
Tom, that's a very nice (and intimidating) setup. I'm guessing you have multiple batteries? Another question that had a thread years ago: the vhf and fishfinder have in-line fuses and the stereo has 10-amp in the head unit. Do I need to remove these since I'm wiring into the fuse block? I don't want to cut any more wires than I need to. |
| bluewaterpirate |
posted 08-04-2010 09:58 PM ET (US)
I have a single 225 Optimax with two batteries. One is used as the starting battery and the other the house. Cut the inline fuses out then use the same size on the fuse block. It's really not that difficult to rig ... just be methodical. Tom |
| davej14 |
posted 08-04-2010 10:52 PM ET (US)
I removed the inline fuses to my electronics so that I would only have one place to look if I needed to replace a fuse. This most likely will void the warranty. There is no reason that you need to remove the inline fuse. Now that I think about it, I have never had to replace a blown fuse. |
| bluewaterpirate |
posted 08-05-2010 08:22 AM ET (US)
Most of the manufacturers tell you you can remove their inline fuse and replace it at the fuse block. Tom |
| davej14 |
posted 08-05-2010 09:02 AM ET (US)
If the warranty is not voided I would definitely take out the inline fuse when powering from a fuse block. Be sure to use a quality inline splice like the Anchor brand with adhesive heat shrink. http://www.marinco.com/product/ adhesive-lined-heat-shrink-butt-connectors |
| jimh |
posted 08-07-2010 07:33 PM ET (US)
The feed from a battery to a electrical distribution panel on a small boat is a secondary power distribution, the primary power distribution being to the outboard motor. The electrical conductors that carry the battery power to the secondary distribution panel should be sized according to two parameters: --the maximum current that is anticipated to be drawn by the secondary distribution panel loads; and, --the minimum voltage drop that can be tolerated as determined by the length of the conductors, the current to be drawn, and the size of the conductors. Because the battery voltage being distributed is only 12-volts, the consideration for minimum voltage drop to be tolerated will usually determine the size of the conductors. To help calculate the appropriate conductor size, the ANCOR WIRE company has provided an on-line wire size calculator. Its use is recommended for the purpose of calculating the size of conductor needed. See http://www.marinco.com/files/applets/wirecalculator.html A typical installation in a small boat will have a wire length between a 12-volt battery and secondary distribution panel of 15-feet, a maximum current of 30-amperes, and an allowable voltage drop of three percent. The calculator selects a conductor of size 8-AWG. In my Boston Whaler boat, where the secondary distribution panel conforms to the specifications I gave above, the OEM installation uses conductors of 8-AWG for supply battery power to the secondary distribution panel. |
| jimh |
posted 08-07-2010 07:54 PM ET (US)
The circuit from the battery to the master power switch to the outboard is the primary power distribution circuit. The primary power distribution circuit conductor size is determined by two considerations: --the maximum current that is anticipated to be drawn by the secondary distribution panel loads; and, --the minimum voltage drop that can be tolerated as determined by the length of the conductors, the current to be drawn, and the size of the conductors. Because the battery voltage being distributed is only 12-volts, the consideration for minimum voltage drop to be tolerated will usually determine the size of the conductors. To help calculate the appropriate conductor size, the ANCOR WIRE company has provided an on-line wire size calculator. Its use is recommended for the purpose of calculating the size of conductor needed. See http://www.marinco.com/files/applets/wirecalculator.html The manufacturer of the outboard motor usually supplies the motor with power conductors of a size that is appropriate to connect directly to a battery. If adding a master switch, use the same size conductor or one size larger to connect the switch to the battery. The length of the conductor from the battery positive to the master power switch should be kept as short as possible. There are probably American Boat and Yacht Council recommended practices which will give a specific length. I would suggest that the distance between the battery and its master ON-OFF switch should be no more than 36-inches. If you need to extend the primary power cables between the battery and the outboard motor, you will typically have to increase the size of the conductor and replace the existing cables with new cables so that there is a single, new, larger size conductor. Consult the literature from your outboard motor manufacturer regarding cable size. This information is usually found in the rigging manual that is supplied by the manufacturer to its authorized installers. |
| davej14 |
posted 08-07-2010 10:31 PM ET (US)
The fuse block being used is rated for 100A. According to the calculator for secondary circuits you could go up to 8 feet with a 6 ga wire and be within the 3% voltage drop. If the battery and fuse block are within the console then 8 feet of wire is more than enough. I would wire the fuse block for maximum capacity of 100A and not have to think about it in the future. My Scotty downrigger has a 30A requirement by itself so I think that planning for a 30A total load is way under what the future may dictate. |
| hc803 |
posted 08-09-2010 10:32 AM ET (US)
Ok, I'm re-working this and here's what I've got: Positive wire: (6 ga) from + battery terminal to master on/off switch, (6 ga) to Blue Sea DualBus Plus 150A distribution panel. Distance from back of 1987 Montauk to panel ~9 ft. I figure this way I don't have to splice out any in-line fuses, possibly voiding any warranty. |
| davej14 |
posted 08-10-2010 01:49 AM ET (US)
I think you are making a mistake by not using a fuse block. You can leave the in-line fuses in your electronic equipment if you want. Two fuses in series will not be an issue. The problem I see with your approach is that if you add electronics that do not have an inline fuse then you will need to add one. You will end up with fuses in decentralized locations and the wiring up to the fuse is not protected. Another nice thing about the fuse block is that you can label the circuits. Believe me, you will forget which wire powers which device in short order. What are you using for a master switch ? If the master switch powers the electronics and the motor starter then a 6 ga wire is inadequate. You may want to seek professional help in this project before you get yourself in trouble. |
| hc803 |
posted 08-10-2010 02:49 PM ET (US)
I'm using a Blue Seas battery switch seen here: http://bluesea.com/category/1/productline/2 . Positive cable in to switch, out to the distribution panel stud. Negative straight from battery terminal to distribution panel stud. Electronics hook up to panel. I don't see the difference between this and wiring everything straight into the battery, other than the convenience of a switch and localized power source. The motor starter is on a completely seperate line, independent of this switch. |
| jimh |
posted 08-10-2010 08:57 PM ET (US)
As a general rule all electrical power distribution should be protected by an over-current trip device (such as a fuse or a circuit breaker) that is placed as closely as possible to the source of power (which in a small boat is the boat battery). Advice to include a fuse or circuit breaker is very good advice and complies with the general practice. About the only time an over-current protection device is not employed is in the circuit feeding power to the outboard engine electric starter motor. The current drawn by the electric starter motor is almost as much current as a short circuit, and therefore an over-current device would be difficult to configure so as not to trip off during normal starting. Electrical power distribution to a secondary power panel is always protected by an over-current device--to ignore this recommendation is foolish. I describe the recommended installation in a concise manner in http://continuouswave.com/whaler/reference/boatWiring.html for small boat electrical distribution. |
| hc803 |
posted 08-11-2010 10:20 AM ET (US)
So Jim, would your recommendation be to put a circuit breaker in line from the + battery terminal before the on/off switch? |
| bboeri |
posted 08-19-2010 06:38 PM ET (US)
Tom, Very nice set up, wish I had that much room on my Montauk. What make/model is the secondary bus? I like that it is enclosed. Also, what type of switch system to you use for the equipment after the secondary bus? Finally, what guage wire goes directly to the motor/ Thanks. Bob |
| jimh |
posted 08-20-2010 06:50 AM ET (US)
quote: I am not clear what is meant by "the on/off switch." Please clarify. |
| hc803 |
posted 08-20-2010 12:43 PM ET (US)
Well, I went ahead and put a second battery in the console just for the electronics except for the bilge [pump] and navigation lamps. Setup goes: battery positive--> Blue Sea Maxi Fuse Block--> Blue Sea mini battery switch--> Blue Sea DualBus Plus 150 Distribution Panel |
| jimh |
posted 08-20-2010 09:42 PM ET (US)
Sounds good. |
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