Funny. You would think this would be more uniform. The interstate 4Ds I just took off my boat had 5/16" for both.
Weird.
Two Stupid Battery / Connector Questions
- Thread starter Ward H
- Start date
Weird.
I suspect some folks are just skimming that content and not actually reading it? I am not at all anti-nyloc for batteries camp unless you don't have the physical post length for them to work...
It seems like that might be the case with some batteries based on other discussions in this thread.
Which fuse block are you using? The ANL fuse blocks have 5/16" posts. So do the MRBF Terminal fuse blocks.
I made a quick wiring diagram so I could get your setup straight in my head. See attached.
Here are some questions/comments I have:
1) It seems that using 3/8" posts on positive side and 5/16" posts on the negative side might be a way to dummy proof the system a little bit. Did not know of this before this thread but it seems like a good plan. I would measure your positive battery post to make sure it is 3/8" because it appears that is not universal. You don't want to use a lug that is too big for the post. See this article: http://www.pbase.com/mainecruising/battery_cables
2)I didn't see where any house load was listed as attached. How do you run the nav. lights, cabin lights, etc.?
3)As I asked above, what fuse block are you using and what size fuse? Also, what size wire?
4)You can get a negative buss bar with 5/16" posts. I would suggest you do that instead of changing the negative terminal lug on the outboard lead.
5)What is the purpose of the connection to the outboard? Is it for battery charging or outboard starting?
6) I assume part of the reason for adding the buss bars is to make putting the outboard back on and taking it off easier as far as wiring. You could go right to the battery otherwise with the addition of the appropriate fuse.
I wouldn't drill out the lug. If they are the correct type they are tinned copper. You will take away the tinning and add to the potential for corrosion.
Hope this was helpful.
Jesse
"Here are some questions/comments I have:
1) It seems that using 3/8" posts on positive side and 5/16" posts on the negative side might be a way to dummy proof the system a little bit. Did not know of this before this thread but it seems like a good plan. I would measure your positive battery post to make sure it is 3/8" because it appears that is not universal. You don't want to use a lug that is too big for the post. See this article: http://www.pbase.com/mainecruising/battery_cables
2)I didn't see where any house load was listed as attached. How do you run the nav. lights, cabin lights, etc.?
3)As I asked above, what fuse block are you using and what size fuse? Also, what size wire?
4)You can get a negative buss bar with 5/16" posts. I would suggest you do that instead of changing the negative terminal lug on the outboard lead.
5)What is the purpose of the connection to the outboard? Is it for battery charging or outboard starting?
6) I assume part of the reason for adding the buss bars is to make putting the outboard back on and taking it off easier as far as wiring. You could go right to the battery otherwise with the addition of the appropriate fuse."
1. The OB cable was connected straight to the battery last year but there was no slack at all. The positioning of the new battery switch and busbars allows slack in the cable. If 3/8 on a 5/16 stud is an issue, I will have to see what others do for the MRBF fuses recommended by Maine Sail. I will check out that link.
2. I did not include the accessory connections in this thread as it was only related to the battery, busbar, outboard connections.
3. Attached diagram shows cable size, fuse size and part numbers. Genuinedealz.com has a wire size configurator that I used. Last year Maine gave me some advice also on what size fuses to use. My electrical load is pretty light but the panel will handle much more than I can fit on my boat.
4. All the negative or common busbars are made for multiple connections. I only needed two so went with the busbar that I did. The Blue Sea DC panel has negative busbar connections for all circuits so I did not need another common/negative one.
5. OB has power tilt, electric start and charging.
6. Assumption is correct. Positive busbar gives me location for the Dual Fuse Block Terminal nearer the bat switch and DC panel. Negative busbar brings DC Panel and OB negative connections to a better location.
Attached is my diagram as I planned it, before this wrong size ring came up. Also attached are the specs for the busbars and Fuse Block Terminals.
Appreciate all the comments.
PS: I used genuinedealz custom cable service to make my cables. Happy with the cost and the results. Only issue is if the post on the battery is not what I expected I may have to cut that nicely crimped terminal off and try to put the right size on myself using borrowed tools or have the yard do it.
1) It seems that using 3/8" posts on positive side and 5/16" posts on the negative side might be a way to dummy proof the system a little bit. Did not know of this before this thread but it seems like a good plan. I would measure your positive battery post to make sure it is 3/8" because it appears that is not universal. You don't want to use a lug that is too big for the post. See this article: http://www.pbase.com/mainecruising/battery_cables
2)I didn't see where any house load was listed as attached. How do you run the nav. lights, cabin lights, etc.?
3)As I asked above, what fuse block are you using and what size fuse? Also, what size wire?
4)You can get a negative buss bar with 5/16" posts. I would suggest you do that instead of changing the negative terminal lug on the outboard lead.
5)What is the purpose of the connection to the outboard? Is it for battery charging or outboard starting?
6) I assume part of the reason for adding the buss bars is to make putting the outboard back on and taking it off easier as far as wiring. You could go right to the battery otherwise with the addition of the appropriate fuse."
1. The OB cable was connected straight to the battery last year but there was no slack at all. The positioning of the new battery switch and busbars allows slack in the cable. If 3/8 on a 5/16 stud is an issue, I will have to see what others do for the MRBF fuses recommended by Maine Sail. I will check out that link.
2. I did not include the accessory connections in this thread as it was only related to the battery, busbar, outboard connections.
3. Attached diagram shows cable size, fuse size and part numbers. Genuinedealz.com has a wire size configurator that I used. Last year Maine gave me some advice also on what size fuses to use. My electrical load is pretty light but the panel will handle much more than I can fit on my boat.
4. All the negative or common busbars are made for multiple connections. I only needed two so went with the busbar that I did. The Blue Sea DC panel has negative busbar connections for all circuits so I did not need another common/negative one.
5. OB has power tilt, electric start and charging.
6. Assumption is correct. Positive busbar gives me location for the Dual Fuse Block Terminal nearer the bat switch and DC panel. Negative busbar brings DC Panel and OB negative connections to a better location.
Attached is my diagram as I planned it, before this wrong size ring came up. Also attached are the specs for the busbars and Fuse Block Terminals.
Appreciate all the comments.
PS: I used genuinedealz custom cable service to make my cables. Happy with the cost and the results. Only issue is if the post on the battery is not what I expected I may have to cut that nicely crimped terminal off and try to put the right size on myself using borrowed tools or have the yard do it.
Attachments
Now I feel more confused.
1) Why a 4 position switch for one battery with one motor?
2) Why do you have the negative from the outboard and your house load fused and connected to the 4 position switch?
3) The MRBF Terminal has 5/16 posts and your outboard has a 3/8 ring.
4) Why not use something like the SafetyHub instead of the combination of the positive buss bar and the MRBF Terminal?
5) Actually, the fusing is in the wrong location. It should be between the battery and the switch.
"1) Why a 4 position switch for one battery with one motor?
2) Why do you have the negative from the outboard and your house load fused and connected to the 4 position switch?
3) The MRBF Terminal has 5/16 posts and your outboard has a 3/8 ring.
4) Why not use something like the SafetyHub instead of the combination of the positive buss bar and the MRBF Terminal?
5) Actually, the fusing is in the wrong location. It should be between the battery and the switch. "
1. Expansion. Plan to install second battery at some point. Off, 1, 2, Both.
2. Your reading that wrong. Single Fuse Block Terminal is on the positive post of the battery (red dot). That goes to the switch, then to positive busbar. Black negative cable goes from negative post on battery to busbar.
3. Blue Sea modified their Fuse Block Terminals so either 3/8 or 5/16 rings can be used over the fuse. Defender.com still says 5/16 only but the Blue Seas site talks about the improvements.
4. Could have done that but thought this looked simpler considering I only needed the two fuses at the busbar.
5. There is a Single Fuse Terminal block on the positive post of the battery before the switch. Then after the switch the DC panel circuit and Outboard circuit are fused again so if one blows, it does not kill the other. They also protect the smaller size wire.
I have a Blue Sea 8 breaker panel waiting to be installed when I get a slow day.
2) Why do you have the negative from the outboard and your house load fused and connected to the 4 position switch?
3) The MRBF Terminal has 5/16 posts and your outboard has a 3/8 ring.
4) Why not use something like the SafetyHub instead of the combination of the positive buss bar and the MRBF Terminal?
5) Actually, the fusing is in the wrong location. It should be between the battery and the switch. "
1. Expansion. Plan to install second battery at some point. Off, 1, 2, Both.
2. Your reading that wrong. Single Fuse Block Terminal is on the positive post of the battery (red dot). That goes to the switch, then to positive busbar. Black negative cable goes from negative post on battery to busbar.
3. Blue Sea modified their Fuse Block Terminals so either 3/8 or 5/16 rings can be used over the fuse. Defender.com still says 5/16 only but the Blue Seas site talks about the improvements.
4. Could have done that but thought this looked simpler considering I only needed the two fuses at the busbar.
5. There is a Single Fuse Terminal block on the positive post of the battery before the switch. Then after the switch the DC panel circuit and Outboard circuit are fused again so if one blows, it does not kill the other. They also protect the smaller size wire.
I have a Blue Sea 8 breaker panel waiting to be installed when I get a slow day.
(1) Use a 'step drill' for thin stock, it is less apt to grab. They are inexpensive at Harbor Freight Tools. The drill is cone shaped with cutting faces of increasing diameter in about 1/16 inch increments.
(2) Makes no difference, just don't over-torque the hex nuts.
Typically larger batteries still have 3/8 Positive and 5/16 negative. The MRBF has a 3/8" at the post and 5/16" at the fuse (where the wire will be connected). When I did my rewire last year, I chose to go with a BS negative Buss bar because I could get the amperage rating I needed with 4 posts. It also helped me standardize all lugs to 5/16 except the one on my main battery Positive which is 3/8.
So, you change all your equipment to 5/16... then if your next battery has 3/8 like the stuff you have now...????
Drill it out. You'll put grease on the connections, right?
Ron,
Grease?
"So, you change all your equipment to 5/16... then if your next battery has 3/8 like the stuff you have now...????"
I was thinking the same thing. Simple for me, I have one battery. What do you guys do with large battery banks when you replace them if the terminals are not standard?
Anyway, drilling it out is simplest way to go. The OB cable goes with the OB for winter storage so it will be inspected every spring before putting it back on the busbar. It's not like I will bolt it on and never see it again. Sometimes the simplest solution is the best solution.
Grease?
"So, you change all your equipment to 5/16... then if your next battery has 3/8 like the stuff you have now...????"
I was thinking the same thing. Simple for me, I have one battery. What do you guys do with large battery banks when you replace them if the terminals are not standard?
Anyway, drilling it out is simplest way to go. The OB cable goes with the OB for winter storage so it will be inspected every spring before putting it back on the busbar. It's not like I will bolt it on and never see it again. Sometimes the simplest solution is the best solution.
OK, looking at it again. Now that I clearly understand what you are working with on your boat.
It feels like you are over fusing and making the system more complicated then needed.
Why the 125 amp fuse at the battery then the 100 amp for the connection to the outboard?
Since you already ordered the cables there might be some issues here. What gauge wire is the wire from the outboard? Based on the 100 amp fuse it might be around 6-8 AWG. If it is larger wire then you could probably cut that fuse right out since you are fused at the battery.
It looks like the remainder of the outboard run is 1/0 AWG (from the fuse through the switch to the battery), why so big? What is the load? It can't be that big if you are fusing at 100 amps.
Then you have a 125 amp fuse on the positive battery terminal. That's about half of what the 1/0 AWG wire should be fused at and could lead to voltage drop. (http://www.pbase.com/mainecruising/fuse_voltage_drop)
If you are going to fuse below what the wire can handle then just put one 100 amp fuse at the battery and eliminate the second fuse in that same line. You will have voltage drop and possibly nuisance blows but you would anyways with the way you laid out the system.
I think what you might really need to do is relook at the wire for the entire system. This might mean reordering wire for the connection from positive buss to the switch and switch to the battery. What is the load and length (round trip) of the wire to the outboard? You can then use a sizing chart to find the correct wire size to be used. http://assets.bluesea.com/files/resources/reference/20010.pdf
The fuse at the battery should then be chosen based on the wire size not the load. (http://www.pbase.com/mainecruising/battery_fusing) Keeping in mind that undersizing the fuse can lead to voltage drop.
On the wire from the switch to the house load panel, I have not seen fuses separately for this load. If you are going smaller than the wire for the rest of the system I could see doing that but why make things more difficult? Use the same size wire as the rest of the system (provided that is appropriate for the load and length which I think it would be based on what you have said so far). Then you don't need any separate fuses and you can connect the outboard and the house load to the common post on the battery switch. Just the one fuse at the battery.
If you want to make a separate location for connecting the battery so it's easier, just use one of these: http://www.bluesea.com/products/category/PowerPost_Connectors/PowerPost. You can get one in 3/8 for the positive side and one in 5/16 for the negative.
Sorry for all of the confusion earlier and going back and forth. Once I understood the system diagram it made much more sense.
Jesse
It feels like you are over fusing and making the system more complicated then needed.
Why the 125 amp fuse at the battery then the 100 amp for the connection to the outboard?
Since you already ordered the cables there might be some issues here. What gauge wire is the wire from the outboard? Based on the 100 amp fuse it might be around 6-8 AWG. If it is larger wire then you could probably cut that fuse right out since you are fused at the battery.
It looks like the remainder of the outboard run is 1/0 AWG (from the fuse through the switch to the battery), why so big? What is the load? It can't be that big if you are fusing at 100 amps.
Then you have a 125 amp fuse on the positive battery terminal. That's about half of what the 1/0 AWG wire should be fused at and could lead to voltage drop. (http://www.pbase.com/mainecruising/fuse_voltage_drop)
If you are going to fuse below what the wire can handle then just put one 100 amp fuse at the battery and eliminate the second fuse in that same line. You will have voltage drop and possibly nuisance blows but you would anyways with the way you laid out the system.
I think what you might really need to do is relook at the wire for the entire system. This might mean reordering wire for the connection from positive buss to the switch and switch to the battery. What is the load and length (round trip) of the wire to the outboard? You can then use a sizing chart to find the correct wire size to be used. http://assets.bluesea.com/files/resources/reference/20010.pdf
The fuse at the battery should then be chosen based on the wire size not the load. (http://www.pbase.com/mainecruising/battery_fusing) Keeping in mind that undersizing the fuse can lead to voltage drop.
On the wire from the switch to the house load panel, I have not seen fuses separately for this load. If you are going smaller than the wire for the rest of the system I could see doing that but why make things more difficult? Use the same size wire as the rest of the system (provided that is appropriate for the load and length which I think it would be based on what you have said so far). Then you don't need any separate fuses and you can connect the outboard and the house load to the common post on the battery switch. Just the one fuse at the battery.
If you want to make a separate location for connecting the battery so it's easier, just use one of these: http://www.bluesea.com/products/category/PowerPost_Connectors/PowerPost. You can get one in 3/8 for the positive side and one in 5/16 for the negative.
Sorry for all of the confusion earlier and going back and forth. Once I understood the system diagram it made much more sense.
Jesse
Interesting setup on the new boat. Looks like you have two 4Ds in parallel. Do you have a reserve/starter battery too?
JK
" (http://www.pbase.com/mainecruising/battery_fusing)"
"Keeping in mind that undersizing the fuse can lead to voltage drop."
I did not find support for the statement that followed the link you provided. It looks like you're saying voltage drops can be caused by under sizing the fuse, a clarification would be helpful.
Thanks Lloyd
" (http://www.pbase.com/mainecruising/battery_fusing)"
"Keeping in mind that undersizing the fuse can lead to voltage drop."
I did not find support for the statement that followed the link you provided. It looks like you're saying voltage drops can be caused by under sizing the fuse, a clarification would be helpful.
Thanks Lloyd
Ditto to Lloyd's comment...
OK, so I understand that wire size and similarly, fuse (essentially a meltable wire) size will have impact on the voltage delivered to the load(s). The larger the fuse/wire, the less of a voltage loss on the line, and vice versa.
But what is the percentage loss when comparing fuse sizes (up to the rating of the wire / cable), per the referenced example in (http://www.pbase.com/mainecruising/fuse_voltage_drop) ? Is it REALLY that large of a concern ? Are the load(s) that you plan to power up, sensitive to a tenth of a volt difference ?
OK, so I understand that wire size and similarly, fuse (essentially a meltable wire) size will have impact on the voltage delivered to the load(s). The larger the fuse/wire, the less of a voltage loss on the line, and vice versa.
But what is the percentage loss when comparing fuse sizes (up to the rating of the wire / cable), per the referenced example in (http://www.pbase.com/mainecruising/fuse_voltage_drop) ? Is it REALLY that large of a concern ? Are the load(s) that you plan to power up, sensitive to a tenth of a volt difference ?
Charging is very sensitive to voltage drops and low voltages lead to poor charging performance. Keep in mind even a .1 volt drop across the fuse is additive to every connection and any marginal wire. Lots of folks assume 3% is okay on a charging circuit but if your alt is set for say 14.4V and you have a 3% drop this takes us to 13.9V and now take another .1v off for a marginally sized fuse and you are at 13.8V and have horrible charging performance....
The fuse is there to protect the wire and should not impact charging performance. Voltage drop in charging circuits is one of the biggest killers of charging performance I deal with..
For devices that are not voltage sensitive then a smaller fuse can be used...
For the OP he has limited charging current anyway so the proposed fuse is of minimal concern at the amperage an outboard can supply...
Jesse,
Good links. I had read all but the one on fuse voltage drop. (or had and forgotten).
Let's start with why I chose the 1/0 wire size.
I used the genuinedealz.com voltage drop calculator. I had 7' run to the busbar. The 1/0 gave me something like 1% voltage drop at the busbar for 100 amp current draw.
My DC Panel is rated at 100 amp but since I will never get there, I used 80 amp and 3' from the busbar to the panel. #8 wire kept the voltage drop under 3%. A more realistic 20 amp current draw should have a voltage drop of less than 1% while the 80 ampacity of the wire is closer to the panel rating.
The #8 wire will allow a little more flexibility for pulling and working on the panel.
The battery switch is in a location not easy to get to without taking things apart. I mounted the busbars where I can easily get to them to change fuses and connect/disconnect the OB cable at the end and beginning of each season.
If I used just the one fuse at the battery, I would have had to run a much heavier wire to the DC Panel so I put a dual fuse holder on the positive busbar.
Considering your point about voltage drop due to being under fused, I should move up to a 250 or 300 fuse at the battery.
Then move up to a 80 fuse for the DC panel.
Then I need to determine the gage wire of the OB. I know the length is 7'. I will then be able to determine the size fuse for the OB.
Finally, all of this is bought and installed. The yard stores the battery and OB and just reinstalled on the boat last week. I told them I would make the connections, which led to the original questions in this thread.
So, it sounds like I need higher amp fuses to reduce their voltage drop and find the wire size for the OB cable so I can get the proper size fuse for that cable?
Does that work?
Good links. I had read all but the one on fuse voltage drop. (or had and forgotten).
Let's start with why I chose the 1/0 wire size.
I used the genuinedealz.com voltage drop calculator. I had 7' run to the busbar. The 1/0 gave me something like 1% voltage drop at the busbar for 100 amp current draw.
My DC Panel is rated at 100 amp but since I will never get there, I used 80 amp and 3' from the busbar to the panel. #8 wire kept the voltage drop under 3%. A more realistic 20 amp current draw should have a voltage drop of less than 1% while the 80 ampacity of the wire is closer to the panel rating.
The #8 wire will allow a little more flexibility for pulling and working on the panel.
The battery switch is in a location not easy to get to without taking things apart. I mounted the busbars where I can easily get to them to change fuses and connect/disconnect the OB cable at the end and beginning of each season.
If I used just the one fuse at the battery, I would have had to run a much heavier wire to the DC Panel so I put a dual fuse holder on the positive busbar.
Considering your point about voltage drop due to being under fused, I should move up to a 250 or 300 fuse at the battery.
Then move up to a 80 fuse for the DC panel.
Then I need to determine the gage wire of the OB. I know the length is 7'. I will then be able to determine the size fuse for the OB.
Finally, all of this is bought and installed. The yard stores the battery and OB and just reinstalled on the boat last week. I told them I would make the connections, which led to the original questions in this thread.
So, it sounds like I need higher amp fuses to reduce their voltage drop and find the wire size for the OB cable so I can get the proper size fuse for that cable?
Does that work?