I tend to be overly cautious of my vessel when not aboard. For instance I close all the seacocks and disconnect(via switch) all the batteries. I know some people who do not go to these measures. My fear with the battery is that a wire may chafe and cause a short. Well, I just bought a new AM/FM/CDR/MP# deck for the cabin. One of the leads needs constant power for it to retain clock and system settings. I thought it would not be a problem as I have no need for the clock feature. However, there are quite a few setup features that I have to reset everytime I reconnect the batteries. Am I being paranoid? Should I just connect this lead(via fuse) directly to the batteries? Should I install a smaller rechargeable just for this purpose that does not have the current to cause much of a problem? Any and all opinions are appreciated. Tim R.
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no your not
I would not install something that requires reprograming every time you shut down. Electrical fire is the largest cause of marine loss.
I would not install something that requires reprograming every time you shut down. Electrical fire is the largest cause of marine loss.
Electrical fires
Tim Being cautious is usually the best alternative but even that will not always help. Like you, we consistently shut the thru hulls and disconnect all power when not needed but that didn't prevent an electrical fire from totally destroying our boat 2 years ago. I won't bother to go through all the details but suffice it to say that the best practice is to carefully inspect and replace questionable components periodically as even disconnecting everything won't preclude a fire. Don
Tim Being cautious is usually the best alternative but even that will not always help. Like you, we consistently shut the thru hulls and disconnect all power when not needed but that didn't prevent an electrical fire from totally destroying our boat 2 years ago. I won't bother to go through all the details but suffice it to say that the best practice is to carefully inspect and replace questionable components periodically as even disconnecting everything won't preclude a fire. Don
Don
Do you mind telling me how it started? Obviously there are live wires going from the batteries to the switch but I check those reguarly and am planning on installing automotive type terminal switches. Tim R.
Do you mind telling me how it started? Obviously there are live wires going from the batteries to the switch but I check those reguarly and am planning on installing automotive type terminal switches. Tim R.
Cautious yes, Obsessive, no
I agree you should be wary of your electrical system, but I would not re-engineer it from an abundance of caution. Your radio draws very little current to maintain the memory. You ABSOLUTELY should have a direct feed to your bilge pump and water level switch, for the unforseen flooding.This connection should be off the hot lead of your battery switch to the float switch. I would connect your radio's memory lead (fused) there and be done with it. I have my boat in Portland as well. If you like I can come over and help you with it, if you like. I was a Marine Electrician for many years.
I agree you should be wary of your electrical system, but I would not re-engineer it from an abundance of caution. Your radio draws very little current to maintain the memory. You ABSOLUTELY should have a direct feed to your bilge pump and water level switch, for the unforseen flooding.This connection should be off the hot lead of your battery switch to the float switch. I would connect your radio's memory lead (fused) there and be done with it. I have my boat in Portland as well. If you like I can come over and help you with it, if you like. I was a Marine Electrician for many years.
No problem
Connecting the Audio device directly to a Fuse on the Positive Distribution post should not pose undue hazard; since the KAM feature only draws something on the order of 10 ma (0.01 Amps), and the Radio Power Lead Wire (& Fuse) will be rated much higher (perhaps 2 - 3 Amps). Remember bigger wire is better, so don’t be afraid to oversize the lead from the battery to the equipment. Do not up-size the fuse, but do use the recommended size. The Fuse provides Short Circuit protection. Electronics with “Keep Alive Memory” (K.A.M.) can be a real pain. They will inevitably screw up your troubleshooting efforts (ground fault or leak detection). Gord
Connecting the Audio device directly to a Fuse on the Positive Distribution post should not pose undue hazard; since the KAM feature only draws something on the order of 10 ma (0.01 Amps), and the Radio Power Lead Wire (& Fuse) will be rated much higher (perhaps 2 - 3 Amps). Remember bigger wire is better, so don’t be afraid to oversize the lead from the battery to the equipment. Do not up-size the fuse, but do use the recommended size. The Fuse provides Short Circuit protection. Electronics with “Keep Alive Memory” (K.A.M.) can be a real pain. They will inevitably screw up your troubleshooting efforts (ground fault or leak detection). Gord
Mine's OK
As Mark stated, you always have to have your bilge pump hot-wired. Mine is hot-wired, but also my control panel is, too. The digital clock and the battery level meters are always active (they are switch-activated). Use the fuse, as you suggested. If you have a cigarette lighter plug on board, that is probably hot-wired, also. Use that same connection. Good Luck.
As Mark stated, you always have to have your bilge pump hot-wired. Mine is hot-wired, but also my control panel is, too. The digital clock and the battery level meters are always active (they are switch-activated). Use the fuse, as you suggested. If you have a cigarette lighter plug on board, that is probably hot-wired, also. Use that same connection. Good Luck.
Geeze, don't you guys use circut breakers and
fuses? The plus side of your batteries should be led away from negative side cables and large, hard, metal, moving/shaking objects. (read: engine) Make sure your boat was wired with good practices, (ABYC is pretty good
) then rest easy. You don't turn off your house when you go out on the boat. Relax.
fuses? The plus side of your batteries should be led away from negative side cables and large, hard, metal, moving/shaking objects. (read: engine) Make sure your boat was wired with good practices, (ABYC is pretty good
) then rest easy. You don't turn off your house when you go out on the boat. Relax.J.C. Whitney...
..has a computer memory saver for cars that runs on a 9v battery. $9.95 SD818203U. You might be able to wire a 9v battery to the common ground and the backup wire yourself. While the stereo is running under 12v use a voltmeter to check for any current from the backup wire. If there is current don't hook up the 9v battery, buy the saver from JCW. You do not want 12v going to a 9v battery. It would heat up and cause a fire. I hope this helps. Monty
..has a computer memory saver for cars that runs on a 9v battery. $9.95 SD818203U. You might be able to wire a 9v battery to the common ground and the backup wire yourself. While the stereo is running under 12v use a voltmeter to check for any current from the backup wire. If there is current don't hook up the 9v battery, buy the saver from JCW. You do not want 12v going to a 9v battery. It would heat up and cause a fire. I hope this helps. Monty
Hot lead off battery switch still goes dead
Millham's bilge pump advice is absolutely true, but if you operate your battery switch like I do (turning it through the off instead of the both position) you still lose your programming whenever you switch batteries or turn power off to the house bus for any repairs. I've got the same deal. I installed it last year and I hooked a fused wire to one battery only for the preset memory connection. Seemed to work good, but at some point after the radio install my combiner stopped working (I don't know if was exactly when I made the change) and I've got one dead battery this year. I don't know if the failures are related yet but I'm going to forgo the presets and wire it like you did (no always on power) I think mine only loses the radio station presets.
Millham's bilge pump advice is absolutely true, but if you operate your battery switch like I do (turning it through the off instead of the both position) you still lose your programming whenever you switch batteries or turn power off to the house bus for any repairs. I've got the same deal. I installed it last year and I hooked a fused wire to one battery only for the preset memory connection. Seemed to work good, but at some point after the radio install my combiner stopped working (I don't know if was exactly when I made the change) and I've got one dead battery this year. I don't know if the failures are related yet but I'm going to forgo the presets and wire it like you did (no always on power) I think mine only loses the radio station presets.
Fuse protect and sleep tight
Hi Tim, It's a good idea to have power to some devices when you leave your boat like the bilge pump or a solar panel. These devices should be wired per mfg which will specify wire size and protection device. There's always a trade off. I feel a bit better with power to the bilge pump when I leave the boat. The main is off - pump connected through fuse direct to battery.
Hi Tim, It's a good idea to have power to some devices when you leave your boat like the bilge pump or a solar panel. These devices should be wired per mfg which will specify wire size and protection device. There's always a trade off. I feel a bit better with power to the bilge pump when I leave the boat. The main is off - pump connected through fuse direct to battery.
Cause of fire
Tim All the advice you are getting is on the right track but fail to mention that the neg side(s) should also be fused. From what the insurance company told me after their investigation, the PO had installed a radar without both sides fused and apparently chafe caused a branch circuit wired in reverse to short. Sufficient heat generated during the day caused the fire to start sometime around 2a.m. the next morning after having shut EVERYTHING down and disconnecting the mains and 110v AC side the previous night at 7 p.m. Not an uncommon situation but with uncommon results! It was a 1995 H40.5 so clearly the wiring being up to the current standards wasn't the issue. I think the lesson here is not to be as concerned with what is/isn't powered but rather that good insp and maintenance practices be followed. By the way, witnesses reported the flames as 20 ft high and were so hot that the self-tailer aluminum winch rings were melted. Needless to say the boat was toast. The only survivors were the davits and CQR anchor. Don
Tim All the advice you are getting is on the right track but fail to mention that the neg side(s) should also be fused. From what the insurance company told me after their investigation, the PO had installed a radar without both sides fused and apparently chafe caused a branch circuit wired in reverse to short. Sufficient heat generated during the day caused the fire to start sometime around 2a.m. the next morning after having shut EVERYTHING down and disconnecting the mains and 110v AC side the previous night at 7 p.m. Not an uncommon situation but with uncommon results! It was a 1995 H40.5 so clearly the wiring being up to the current standards wasn't the issue. I think the lesson here is not to be as concerned with what is/isn't powered but rather that good insp and maintenance practices be followed. By the way, witnesses reported the flames as 20 ft high and were so hot that the self-tailer aluminum winch rings were melted. Needless to say the boat was toast. The only survivors were the davits and CQR anchor. Don
Don, Fusing the ground?
Thats the first time I've heard that? Not saying that it wouldn't have helped prevent the problem. But thats like saying to put a fuse on the block of your engine. No where does anything I have ever read say to do that. I have yet to see any industry standard that specs fusing a 12V ground. Your post said "apparently chafe caused a branch circuit wired in reverse to short". Reading that closer (circuit wired in reverse to short) its obvious that the Radar installer wired the power to Radar in REVERSE !!!! *yks No wonder you had problems ! There was no fuse in the REAL hot lead. IF the installation was wired **CORRECTLY** There would be no need to fuse the negative lead, but as it was the negative lead was in reality the positive lead. No wonder that happened , it was an accident waiting to happen. If the HOT side (+12VDC) was fused ***PROPERLY** and in the **CORRECT LOCATION** then you don't need a fuse in the return circuit as the current source would be cut off when the current exceeded the threshold of the fuse in the +12VDC side. Obviously there was no fuse to blow at the **source** of the power supply thus the short happened **before** the fuse could protect it. If people put fuses on the Negative side the same problem could still happen if the fuse is before the source and in the wrong location. This is why some people decide to put big fuses **right at** the positive battery posts of their House bank, then they are ensured that they will protect the whole circuit. BTW ABYC does not mandate these fuses if the wiring from the battery's to the first mainbreaker is under a certain distance and also the cabling is a certain spec (Thickness, type, etc) Not saying adding fuses don't help protect things, but its their **exact** placement that is more critical. Here is primer on Boat wiring and some ABYC standards and some very good reading. http://www.bluesea.com/sections.asp?id=139&Title=ABYC+Excerpts http://www.bluesea.com/sections.asp?id=145&Title=Technical+Briefs http://www.bluesea.com/sections.asp?id=137&Title=Application+Briefs sorry for your loss --
Thats the first time I've heard that? Not saying that it wouldn't have helped prevent the problem. But thats like saying to put a fuse on the block of your engine. No where does anything I have ever read say to do that. I have yet to see any industry standard that specs fusing a 12V ground. Your post said "apparently chafe caused a branch circuit wired in reverse to short". Reading that closer (circuit wired in reverse to short) its obvious that the Radar installer wired the power to Radar in REVERSE !!!! *yks No wonder you had problems ! There was no fuse in the REAL hot lead. IF the installation was wired **CORRECTLY** There would be no need to fuse the negative lead, but as it was the negative lead was in reality the positive lead. No wonder that happened
, it was an accident waiting to happen. If the HOT side (+12VDC) was fused ***PROPERLY** and in the **CORRECT LOCATION** then you don't need a fuse in the return circuit as the current source would be cut off when the current exceeded the threshold of the fuse in the +12VDC side. Obviously there was no fuse to blow at the **source** of the power supply thus the short happened **before** the fuse could protect it. If people put fuses on the Negative side the same problem could still happen if the fuse is before the source and in the wrong location. This is why some people decide to put big fuses **right at** the positive battery posts of their House bank, then they are ensured that they will protect the whole circuit. BTW ABYC does not mandate these fuses if the wiring from the battery's to the first mainbreaker is under a certain distance and also the cabling is a certain spec (Thickness, type, etc) Not saying adding fuses don't help protect things, but its their **exact** placement that is more critical. Here is primer on Boat wiring and some ABYC standards and some very good reading. http://www.bluesea.com/sections.asp?id=139&Title=ABYC+Excerpts http://www.bluesea.com/sections.asp?id=145&Title=Technical+Briefs http://www.bluesea.com/sections.asp?id=137&Title=Application+Briefs sorry for your loss --Fusable Links
Tom brought a point that solves a lit of concern here. My 356 has fusable links on both pos and neg at the battery co nnections. Some call them shunts, but do the same function in this application. Not a bad idea, relatively inexpensive for the protection they offer. I wouldn't have thought to mention it by myself, It's just so natural for me to expect them in place.
Tom brought a point that solves a lit of concern here. My 356 has fusable links on both pos and neg at the battery co nnections. Some call them shunts, but do the same function in this application. Not a bad idea, relatively inexpensive for the protection they offer. I wouldn't have thought to mention it by myself, It's just so natural for me to expect them in place.
How About Your Automatic Bilge Pump?
If you're killing all power, are you turning off your pump? Do you have that wired directly to the battery?
If you're killing all power, are you turning off your pump? Do you have that wired directly to the battery?
BASIC Circuit Protection
Basic Circuit Protection: WARNING: The following should NOT be considered exhaustive. I would be pleased to provide additional specific information (as time allows). Good practice dictates limiting the number of cables & wires connected directly to the battery. I like to limit these direct connections to: 1. Positive Distribution Cable(s) through High Amperage (& Hi I.C.) Fuse to Positive Distribution Bus Bar(s), One for Each Battery ‘Bank” - thence to Battery Selector/Disconnect Switch - thence to Breaker (or Fuse) Distribution Panel - and ultimately (through individual circuit Breakers or Fuses) to end-use circuits. 2. Battery Monitor wires, including thermisters. 3. Negative Battery Cable to the Negative Ground Bus. Unswitched (essential) circuits, (such as Bilge Pumps, KAM memory circuits, etc), are wired (through Fuses) from Positive Distribution Bus to each device. The only Un-Protected (Fuse or Breaker) cables are the Battery Positive to Starter, and any interconnecting (between Batteries) cables. Disconnect & Selector Switches: I often eliminate the Battery Selector Switch, in favour of Battery Disconnect Switches, and an Emergency Parallel Switch. Battery Selector Switches should be “Make before Break” type, which allows safe switching selections (except ‘Off”) with alternator running. An Alternator Disconnect feature is desirable. Some references: Blue Sea Systems has a decent tutorial on Circuit Protection at: http://www.bluesea.com/Article_detail.asp?id=121&Section_Id=140 and ABYC (Standards) Excerpts at: http://206.129.99.60/Article_detail.asp?id=119&Section_Id=139 and from E-T-A (Multiple Tech’ Papers): http://www.etacbe.com/n_america/e-t-a/etacbeframeset_can.html and from CARLING (Breaker Info’): http://www.carlingtech.com/pdf/circuit_breaker_introduction.pdf and http://www.carlingtech.com/products/circuit-protection/learn_more.asp and from Australia (Boat Maintenance from ‘Boatpoint’) http://boatpoint.ninemsn.com.au/expert/ExpertQuestions.asp?type=Maint Specificall “Electrics”: http://boatpoint.ninemsn.com.au/expert/ExpertAnswer.asp?ID=116675&Type=Maint HTH Gord
Basic Circuit Protection: WARNING: The following should NOT be considered exhaustive. I would be pleased to provide additional specific information (as time allows). Good practice dictates limiting the number of cables & wires connected directly to the battery. I like to limit these direct connections to: 1. Positive Distribution Cable(s) through High Amperage (& Hi I.C.) Fuse to Positive Distribution Bus Bar(s), One for Each Battery ‘Bank” - thence to Battery Selector/Disconnect Switch - thence to Breaker (or Fuse) Distribution Panel - and ultimately (through individual circuit Breakers or Fuses) to end-use circuits. 2. Battery Monitor wires, including thermisters. 3. Negative Battery Cable to the Negative Ground Bus. Unswitched (essential) circuits, (such as Bilge Pumps, KAM memory circuits, etc), are wired (through Fuses) from Positive Distribution Bus to each device. The only Un-Protected (Fuse or Breaker) cables are the Battery Positive to Starter, and any interconnecting (between Batteries) cables. Disconnect & Selector Switches: I often eliminate the Battery Selector Switch, in favour of Battery Disconnect Switches, and an Emergency Parallel Switch. Battery Selector Switches should be “Make before Break” type, which allows safe switching selections (except ‘Off”) with alternator running. An Alternator Disconnect feature is desirable. Some references: Blue Sea Systems has a decent tutorial on Circuit Protection at: http://www.bluesea.com/Article_detail.asp?id=121&Section_Id=140 and ABYC (Standards) Excerpts at: http://206.129.99.60/Article_detail.asp?id=119&Section_Id=139 and from E-T-A (Multiple Tech’ Papers): http://www.etacbe.com/n_america/e-t-a/etacbeframeset_can.html and from CARLING (Breaker Info’): http://www.carlingtech.com/pdf/circuit_breaker_introduction.pdf and http://www.carlingtech.com/products/circuit-protection/learn_more.asp and from Australia (Boat Maintenance from ‘Boatpoint’) http://boatpoint.ninemsn.com.au/expert/ExpertQuestions.asp?type=Maint Specificall “Electrics”: http://boatpoint.ninemsn.com.au/expert/ExpertAnswer.asp?ID=116675&Type=Maint HTH Gord
Gord - Additional insight on a couple items?
Gord - thanks for your clear input on this topic. A couple questions that come to mind when I think of applying these guidelines to our boat. 1. Any thoughts on how/where to locate the high amp fuses for the positive batt cables? With battery boxes, cramped engine space, etc. it's not obvious how close to the batteries they could be located. Seems like the best solution would be to mount a board to mount the fuses, and as close to the batts as possible. Similar question for the positive distribution bus bar - should it ideally be near the distribution panel, or could that be on the same board as the high amp batt fuses? 2. I just purchased a Xantrex batt charger, and the instructions say to run the leads directly to the batts. Any thoughts on why they couldn't be run to the bus bar or the batt selector switch? Thanks for your response when you have time. Ed
Gord - thanks for your clear input on this topic. A couple questions that come to mind when I think of applying these guidelines to our boat. 1. Any thoughts on how/where to locate the high amp fuses for the positive batt cables? With battery boxes, cramped engine space, etc. it's not obvious how close to the batteries they could be located. Seems like the best solution would be to mount a board to mount the fuses, and as close to the batts as possible. Similar question for the positive distribution bus bar - should it ideally be near the distribution panel, or could that be on the same board as the high amp batt fuses? 2. I just purchased a Xantrex batt charger, and the instructions say to run the leads directly to the batts. Any thoughts on why they couldn't be run to the bus bar or the batt selector switch? Thanks for your response when you have time. Ed
Batt Fuse Location
Ed: You’re definitely on the right track, and I suspect you understand the conflicting trade-offs involved. 1. Mount the Positive (technically the Un-grounded conductor) Hi-Amp Fuse as near as possible to Battery (72" Max), with it’s Load Side connected directly to the Positive Bus Bar. BTW: All Positive equipment must be dead-front. 2. Although the Battery Charger is Fuse/Breaker protected on it’s AC Input side, I like to also Fuse the Positive DC Output(s) right at the charger. You can take the DC Output (+) leads to a Battery Switch. I’ll try to provide more detail over the weekend. BTW: Wouldn’t it be nice if someone manufactured a Hi-Amp Fusible Battery Terminal Connector? HTH for now Gord
Ed: You’re definitely on the right track, and I suspect you understand the conflicting trade-offs involved. 1. Mount the Positive (technically the Un-grounded conductor) Hi-Amp Fuse as near as possible to Battery (72" Max), with it’s Load Side connected directly to the Positive Bus Bar. BTW: All Positive equipment must be dead-front. 2. Although the Battery Charger is Fuse/Breaker protected on it’s AC Input side, I like to also Fuse the Positive DC Output(s) right at the charger. You can take the DC Output (+) leads to a Battery Switch. I’ll try to provide more detail over the weekend. BTW: Wouldn’t it be nice if someone manufactured a Hi-Amp Fusible Battery Terminal Connector? HTH for now Gord
Battery Connections
Ed's question was: "I just purchased a Xantrex batt charger, and the instructions say to run the leads directly to the batts. Any thoughts on why they couldn't be run to the bus bar or the batt selector switch?" They recommend that because of voltage drop based on the wire size they recommend. If you stay within the 3% drop tables, and up size the wire, it will make no difference and you could put it at the bow! There is no reason they couldn't be run to the positive distribution post. All the PDP does, albeit very importantly, is, if close to the battery, avoids having more than one connection to the battery positive post. It's essentially the same point, functionally and electrically. The batt selector switch is usually further away, so why go further with wiring if the purpose is to avoid voltage drop in the first place? Again, with proper size wire, no difference. The location of the high amp fuses is based on how much space you have on your boat. All it takes is a MEGA fuse base and fuse, about 3 inches high, six to eight inches long, not much. Need to route the wires to it, though, with reasonable bends. The hardest part is the planning... Stu
Ed's question was: "I just purchased a Xantrex batt charger, and the instructions say to run the leads directly to the batts. Any thoughts on why they couldn't be run to the bus bar or the batt selector switch?" They recommend that because of voltage drop based on the wire size they recommend. If you stay within the 3% drop tables, and up size the wire, it will make no difference and you could put it at the bow!
There is no reason they couldn't be run to the positive distribution post. All the PDP does, albeit very importantly, is, if close to the battery, avoids having more than one connection to the battery positive post. It's essentially the same point, functionally and electrically. The batt selector switch is usually further away, so why go further with wiring if the purpose is to avoid voltage drop in the first place? Again, with proper size wire, no difference. The location of the high amp fuses is based on how much space you have on your boat. All it takes is a MEGA fuse base and fuse, about 3 inches high, six to eight inches long, not much. Need to route the wires to it, though, with reasonable bends. The hardest part is the planning... StuStu is right (sort of)
Application of the 3% V.D. tables (or a calculation) will ensure safe & proper operation of the Charger output - no matter the cable length. Unfortunately, Xantrex (who provide the tables /w their instructions) don’t provide large enough terminals to accommodate longer DC output runs. As I recall (from 1999), the lugs will only accommodate a maximum #6 AWG cable size - which would limit the 40A Charger to a round-trip length (Pos. + Neg.) Of about 15 Feet total. I’ve had to compromise, and trim larger cables to fit into the lug. I complained to Xantrex, but don’t know if they have since corrected this deficiency (can anyone advise?). Regards, Gord
Application of the 3% V.D. tables (or a calculation) will ensure safe & proper operation of the Charger output - no matter the cable length. Unfortunately, Xantrex (who provide the tables /w their instructions) don’t provide large enough terminals to accommodate longer DC output runs. As I recall (from 1999), the lugs will only accommodate a maximum #6 AWG cable size - which would limit the 40A Charger to a round-trip length (Pos. + Neg.) Of about 15 Feet total. I’ve had to compromise, and trim larger cables to fit into the lug. I complained to Xantrex, but don’t know if they have since corrected this deficiency (can anyone advise?). Regards, Gord
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