ABYC and Batteries

[Sailing Drummer]

I know there are many that think some of the ABYC standards need not always apply. But I want to make sure there are no issues with insurance should a problem come up. So I'd like to hear feedback from people who know the ABYC.

I'm adding a second battery to my house bank. Because of the layout the second battery will be about 12 feet from the first one. The original battery is within proper distance from the fuse and the positive lead will come from this battery. The negative lead will come from the second battery.

So I'm questioning whether I am supposed to have another fuse in-line on the positive lead between the two batteries because of the distance. And if so, should it go close to the first battery, the second battery, or both?

Thanks,
Larry

[DeepFrz]

Both.

[Colin A]

First I agree with Deep FRZ in your case I would fuse both. I will mention I once witnessed a discussion between a boatbuilder and a ABYC Trainer on whether "the source of power" was the battery bank , the battery, the bus bar connected to the battery or some other distribution point. They seemed to come to the conclusion that for safety the battery was the source of power in DC systems but that may be up to some interpretation with some battery bank arrangements.

[knottybuoyz]

All I have is a copy of ABYC E-11 (7/03), which may have been superseded does not specify overcurrent protection for each battery. Starting batteries typically do not have fuses or breakers. House banks do and unless the ungrounded conductor is in a conduit or similar it has to have the overcurrent device within 7" of the battery terminal. Given your situation it's best to err on the side of caution and put one on each battery.

You should keep in mind that you've now substantially increased the length of each circuit in your system and could have issues with substantial current drop which will necessitate an increase in conductor size for those circuits.

[ontherocks83]

Originally Posted by knottybuoyz

You should keep in mind that you've now substantially increased the length of each circuit in your system and could have issues with substantial current drop which will necessitate an increase in conductor size for those circuits.

+1

The distance between batteries in one bank is not ideal but also not the end of the world. I would run as big of a cable as you can to minimize drop.

I also second what everyone else says, Fuse both to be safe. It may be overkill and it may not, but redundant safety systems is a plus in my book.

[Sailing Drummer]

Thanks for the help. I was leaning towards fusing both so now I will. As for the size of the cable, I know I have to go big. There are 2 lengths of 12' between the batteries and then the ground cable back to the ground buss (which is next to battery 1) so I'm looking at about 36' round trip? Or is it 24'?

Larry

[smac999]

Mrbfs are really handy here. Fuse both.


leave the pos and neg on battery one. Run two x 12' jumper to battery 2
Trying to go end to end on a bank 12' apart is silly.

2/0 is probably fine.

[Ex-Calif]

Why are there 2 lengths of 12 on the positive side?

[mitiempo]

Originally Posted by knottybuoyz

....does not specify overcurrent protection for each battery. Starting batteries typically do not have fuses or breakers. House banks do and unless the ungrounded conductor is in a conduit or similar it has to have the overcurrent device within 7" of the battery terminal. Given your situation it's best to err on the side of caution and put one on each battery.

You should keep in mind that you've now substantially increased the length of each circuit in your system and could have issues with substantial current drop.....

ABYC doesn't require a fuse for a DEDICATED start battery. If the batteries are selected by a 1/2/both switch neither bank is a dedicated start battery as it can be used for house loads and therefore requires fusing.

I usually fuse start batteries just the same.

I agree about the voltage drop due to length. I try to keep voltage drop as close to zero as possible in charging circuits. 14.4 volts @ 3% drop means the battery only sees 13.97 volts and either takes a lot longer to fully charge (hours more) or never is fully charged.

I would do everything possible to get the batteries closer together.

[Sailing Drummer]

smac99 - mrbf is what I was planning on using. They make a lot of sense and simplicity.

Ex-Calif - There is only one 12' positive run and two 12' negative (the extra neg is going back to the buss bar).

mitiempo - good point about charging. I hadn't thought about that. I was thinking about usage.

I'm going to look for space closer to battery one but I don't think I have it. I already have a 4D and it's basically new. So I'm adding another 4D and these are really big (and the box for them is even bigger!).

I'll have to evaluate cost/benefit of replacing and adding on using 6v batteries serial/parallel because it's not just the cost of one more battery. There's also the cost of all that heavy wire. I could fit 6v batteries in one space.

Thanks all for the input.

Larry

[Ex-Calif]

Originally Posted by Sailing Drummer

smac99 - mrbf is what I was planning on using. They make a lot of sense and simplicity.

Ex-Calif - There is only one 12' positive run and two 12' negative (the extra neg is going back to the buss bar).

Then I would fuse for the 24 foot run.

[mitiempo]

Originally Posted by Ex-Calif

Then I would fuse for the 24 foot run.

Why? You only fuse the positive - the negatives do not need fusing.

[Ex-Calif]

Because boats are grounded via the wire, not via, say a metal car frame.

It's pretty much standard practice.

[mitiempo]

Originally Posted by Ex-Calif

Because boats are grounded via the wire, not via, say a metal car frame.

It's pretty much standard practice.

I'm confused - are you saying to fuse the negative? Nothing standard about that.

You fuse the positive wire only, the fuse sized between expected max load and wire ampacity. The 24' of negative doesn't relate to it. Nor does the 12' feet of positive relate to it.

[Ex-Calif]

See attached.

You double the positive run when calculating fuse size.

Because OP was asking if he should calculate based on round trip (24 feet) or 36 feet because he has an extra wire run. My question was whether the extra run was a positive cable because it was not clear from his post.