ABYC Overcurrent Protection for battery charger

[jimv]

I am doing some electrical upgrades to my 2011 R27 and would like to bring all the new wiring into compliance with the current ABYC standards that have changed or are new since the boat was built.

One point I would like some clarification on is the overcurrent protection for the conductors between my batteries and the new battery charger.

Reading ABYC 11.10.1.1.1:

Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent
protection device(s) within a distance of seven inches (178 mm) of the point at which the conductor is connected to
the source of power measured along the conductor

I was wondering which device one would consider the "source of power" - since when the charger is active, it is a source of power, but the battery is also considered a source of power for most (if not all) other circuits.

Then I read 11.10.1.1.2:

In addition to the provisions of E.11.10.1.1.1 the ungrounded conductors to a battery charger, alternator, or another charging source shall be provided with overcurrent protection within the charging source, or within seven inches (178 mm) of the charging source, based on the

(I added the bold for emphasis)

My charger is fused, so I believe that meets the "overcurrent protection within the charging source, but I'm also now thinking that if I have a 18 inch conductor between my battery and charger, the internal fuse on the charger doesn't count as meeting 11.10.1.1.1 an I'll need to add a fuse at the battery end of this conductor as well.

Am I interpreting this correctly?

 

[Submariner]

You need an OCP on the battery charger cable closest to the battery. The easiest way to accomplish this is either an inline fuse (which is how the factory does it) or an MRBF fuse on the battery terminal.

The fuses on the battery charger are too far away. The battery is the source of power on a battery charger circuit. Consider what would happen if you ran a cable from the battery to the battery charger, and that wire was to short out. What would protect that wire from the battery's nearly infinite power in a dead-short situation? The battery charger isn't really going to give you more than it's rated capacity (say, 60 amps).

Power Time with Jeff Cote - Battery Charger, Fusing and Chassis Ground Tips
https://youtu.be/xHEK9C_qgEw

In my electrical schematic, you'll see the two battery charges both have fuses near the battery. Also included is the green chassis ground wire that's also important.
https://www.letsgochannelsurfing.co...48310aa0d84d70a4f687475046e9d9.pdf?index=true

 

[jimv]

Thanks for the confirmation Martin,

I did see the two fuses on your schematic, which is what got me down this path 🙂

I do have the ground wires (properly sized) to both the charger and inverter per the updated standards.

I'm going to end up copying your use of the Blue Sea Systems 5196 Common source MRBF blocks, as they will help with space savings overall with all these new fuses!

~J

 

[Submariner]

For clarification... since I know you're going with LFP... MRBF fuse's need to be used after a T-class fuse.

The LFP battery should go directly to a T-Class fuse, which in turn connects to a bus bar. On that bus bar is where you would use an MRBF fuse to connect to your battery charger and other loads and charging sources.

MRBF's are insufficient for LFP. In a dead-short situation the T-class is necessary with it's much higher AIC rating.

 

[YukonRon]

I upgraded to a lithium house bank, so I installed a T-class fuse close to the battery, before the bus bar. The ANL fuse from the factory was removed, so I repurposed that on the DC output of the Victron 3000 inverter/charger. Having a fuse at both ends of a 4 ft run with 4/0 cable maybe overkill, but I had the extra fuse, so if in doubt, it can't hurt.