Advice please regarding wiring Lifepo4 batteries in compliance with ABYC

Q&A and troubleshooting
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1

Hello community,

I am installing 6 x 48V 100Ah Victron NG batteries into a yacht, and wish to comply with ABYC specification.

“11.10.1.1.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection within a distance of seven inches (175mm) of the point at which the conductor is connected to the source of power measured along the conductor.”

I wish to use Lynx Class-T Power in modules, however Victron documentation and example schematics show a single cable from each battery terminal to the Lynx Class-T, making it all but impossible to comply with the 7-inch rule.

Can anybody provide more information on this?

Many thanks

Richard

2

That is true. If you want or need to stay within ABYC guidelines then you could look at putting a Class T fuse and fuseholder within 7 inches of the positive battery terminal. ABYC also required an OCPD with an AIC rating of 50kA I believe. The Class T fuse at the battery terminals satisfy both requirements. Then you can use a regular Lynx PIN to land the battery cables on the DC buss.

3

Thanks Ed for your response.

I see from a related thread that you use an MRBF on each terminal plus class-t fuses at the power in.

This was my original design but was deterred by the lower AIC rating of the MRBF.

I’m interested in your thoughts - it would be a very neat solution.

4

That’s what I’m comfortable doing and I can’t think of many reasons why it’s not a good idea. The only one I can come up with is if you have a short circuit between the battery terminal and the input to the Lynx PIN, the MRBF fuse will likely take the brunt of it, possibly explode, and send shards of plastic and molten metal around the compartment. But, MRBF fuses are small and I don’t personally view this as a problem. If it were an engine compartment with flammable or explosive fuel, maybe I’d feel differently.

If a certified ABYC electrical installer can answer this I would appreciate it. If not, then I would suggest you reach out and ask a distributor who is more marine focused. We don’t see a lot of marine installations here. If you want a referral I can send you a couple of good guys in Florida who are marine focused. Send me an email and I can provide those.

P.S. I have my guys cover MRBF and battery terminals (positive and negative) with two or three layers of kapton tape just to help reduce accidental short circuits across the terminals. I certainly haven’t tested it, but that might help mitigate the concerns of an MRBF fuse rupturing. We’ve accidentally shorted batteries with MRBF fuses and never had one explode, but as soon I give a full throated endorsement someone else might have a horror story.

5

Thanks Ed - those contacts would be very helpful, thank you.

6

Please send me an email and I will give you the names. I’m not allowed to post my email address here, but you can easily find it with 10 seconds of sleuthing :slight_smile: Thanks!