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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems > Fusing Batteries
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Thread: Fusing Batteries Reply to Thread
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Topic Review (Newest First)
04-11-2014 07:26 AM
tatracy
Re: Fusing Batteries

Thank you all for the help with this


Sent from my iPhone using Tapatalk
04-10-2014 08:35 PM
Maine Sail
Re: Fusing Batteries

Quote:
Originally Posted by tatracy View Post
Bumping back up on inquiry regarding fusing the starter cable at the 1/2/B switch.
No need for additional fuse..
04-10-2014 08:22 PM
tatracy
Re: Fusing Batteries

Quote:
Originally Posted by tatracy View Post
Ok, *hopefully* one last question on fusing. I will have 200a terminal fuses on each battery, currently I will have 1AWG wire from house battery to 1/B/2 switch, and 4AWG from backup battery (it's what I have at this point, but will eventually upgrade to 1AWG). Will add echo charger connected at switch 1 & 2 posts per suggestion.

Starter cable will run from Common post on switch, currently 4AWG, also to be upgraded to 1AWG. AM I good to connect the starter cable without an addition fuse, on the assumption that the terminal fuses will protect the circuit from battery to starter in case of a short? I'm struggling with determining which fuse type to use and how to mount if I DO fuse the starter cable.
Bumping back up on inquiry regarding fusing the starter cable at the 1/2/B switch.
04-07-2014 12:47 PM
MarkSF
Re: Fusing Batteries

If you are looking to upgrade the 4 gauge wiring, I recommend genuinedealz.com for custom battery cables. The quality and price are both excellent, and I used the savings to upgrade the cable gauge a bit (both batteries now connected to the switch with 2/0)

Note that although your starter is 75A continuous, there will be a surge of higher current to get the engine turning over. This is when voltage drops in the cable can be noticable if the wiring gauge (or connections) are marginal. BTDT.
04-07-2014 12:17 PM
tatracy
Re: Fusing Batteries

Ok, *hopefully* one last question on fusing. I will have 200a terminal fuses on each battery, currently I will have 1AWG wire from house battery to 1/B/2 switch, and 4AWG from backup battery (it's what I have at this point, but will eventually upgrade to 1AWG). Will add echo charger connected at switch 1 & 2 posts per suggestion.

Starter cable will run from Common post on switch, currently 4AWG, also to be upgraded to 1AWG. AM I good to connect the starter cable without an addition fuse, on the assumption that the terminal fuses will protect the circuit from battery to starter in case of a short? I'm struggling with determining which fuse type to use and how to mount if I DO fuse the starter cable.
04-04-2014 06:18 PM
Maine Sail
Re: Fusing Batteries

Quote:
Originally Posted by tatracy View Post
Thanks Maine Sail. On the ground side. In the USE Switch setup, do I run a common negative cable between the house and reserve batteries in addition to a negative run to the Engine ground?
Yes house>start>engine neg are all tied together. The only time this would get tricky is if you needed a shunt for the house ban for a battery monitor.
04-04-2014 06:09 PM
tatracy
Re: Fusing Batteries

Thanks Maine Sail. On the ground side. In the USE Switch setup, do I run a common negative cable between the house and reserve batteries in addition to a negative run to the Engine ground?
04-04-2014 05:16 PM
Maine Sail
Re: Fusing Batteries

Quote:
Originally Posted by tatracy View Post
Hi Folks,

Working on a rewire of my 1977 Santana. Came across this discussion, along with Maine Sail's musings on the 1/2/B switch. I have a follow on question that I can't seem to find much info on in regards to the MRBF terminal fuses.

Specifically, I am looking to setup as a use switch, with alternator leading back to the house bank, then using a battery relay handle keeping the reserve battery topped off.

My question is this: If I setup with terminal fuses, likely 125A at the battery to the 1 and 2 inputs on the switch, can I with a 2 position terminal fuse also have the Alternator directly wired to the House battery with a second Terminal fuse (I think in 75A range)? I see that blue sea carries 2 fuse terminal fuse blocks, but there's little documentation on them and I'm unclear if they are independent of each other, although that would seem to be the intent.

I expect highest amp draw is going to be the starter which according to spec will draw 75A (rated .9KW), and my alternator is 35A output. Engine is a Westerbeke 12b Two Diesel.

If this is possible, then I'm thinking I'd attach the Blue Sea mini ACR to the 1 and 2 terminals back of the 1/B/2 switch. Am I on the right track?
Two post will be fine for alt and starting loads. I would suggest 200A for each bank as a min and 75A on a 35A alt will be fine. Ignore starter motor "specs" as there is no standard to accurately rate them into "starting loads"...

An Echo charger may be easier on the back of the switch as the wires are only 10GA....
04-04-2014 04:58 PM
tatracy
Re: Fusing Batteries

Hi Folks,

Working on a rewire of my 1977 Santana. Came across this discussion, along with Maine Sail's musings on the 1/2/B switch. I have a follow on question that I can't seem to find much info on in regards to the MRBF terminal fuses.

Specifically, I am looking to setup as a use switch, with alternator leading back to the house bank, then using a battery relay handle keeping the reserve battery topped off.

My question is this: If I setup with terminal fuses, likely 125A at the battery to the 1 and 2 inputs on the switch, can I with a 2 position terminal fuse also have the Alternator directly wired to the House battery with a second Terminal fuse (I think in 75A range)? I see that blue sea carries 2 fuse terminal fuse blocks, but there's little documentation on them and I'm unclear if they are independent of each other, although that would seem to be the intent.

I expect highest amp draw is going to be the starter which according to spec will draw 75A (rated .9KW), and my alternator is 35A output. Engine is a Westerbeke 12b Two Diesel.

If this is possible, then I'm thinking I'd attach the Blue Sea mini ACR to the 1 and 2 terminals back of the 1/B/2 switch. Am I on the right track?
01-28-2014 07:05 PM
Maine Sail
Re: Fusing Batteries

Quote:
Originally Posted by boatpoker View Post
Unless I missed it in Mainesail's post, you do not need a fuse in the positive conductor from the starting battery.
If this "not needed" is defined by the ABYC's "exemption" for cranking batteries then it is pretty foolish to abide by that on small sailboat aux engines that are EASILY over current protected.

Sometimes I agree with the ABYC and in this case I strongly disagree with the E-11 on this. Why? Because it is foolishly & needlessly applied to all boats and is very often misinterpreted as you should not fuse a starting bank which could not be further from the truth or intent of that exception... There are many of us on the electrical committees who would love to see that wording changed.

So yes the ABYC has an "exception" to this rule for cranking motor batteries. This exception however is more broad based and written to include for large engines which have massive amounts of starting current being drawn. These engines are very expensive to fuse properly hence the "exception".. Think big sport fishing boats, and our engines are about as far away from that as can be... Small diesel or gas AUX engines on sailboats would be best served fused than unprotected.

I quote our good friend Nigel Calder here:

"The net result is that nowadays, electrical shorts are probably the number-one cause of fires on boats.

There is simply no excuse for not protecting all high-current circuits , including the cranking circuit."
Nigel Calder Cruising Handbook


The ABYC also refuses to address the vast majority of boats out there that are fed by a 1/2/BOTH switch where either bank can be house or start with the flip of a switch and NEITHER bank is really considered a "cranking battery". In these circumstances one would be very wise to protect both banks.

Relying on the ABYC exemption in this case is a cop-out and can be flat out unsafe....


Here is a good case study of where this foolishness fails us:

This was a junior sailing program chase boat used at our club. It was a 15' Whaler with a Honda OB motor.

STOOPID #1 - Because the battery on this boat was not more than 800CCA it was exempted from needing a battery switch. D'oh.. Okay if the ABYC says so.....

STOOPID #2 This battery was ABYC exempted from over current protection because it is a "cranking battery".. D'oh......

STOOPID #3 Because of the failings of the ABYC standards in this instance three 8 year olds and a sailing instructor were almost burned up.... Safe..?

A simple $30.00 fuse or battery kill switch could have prevented this yet this boat was ABYC compliant....

Yes a single battery less than 800CCA (exempted from a battery switch) and one that "cranked" a motor (exempted from over current protection at the battery) caused all this....


So yes I often exceed ABYC standards in my wiring because the standards are often quite insufficient or too broadly applied.
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