Marine Battery Cables

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I frequently get asked about Marine battery cable requirements. Here is a summary as I understand the requirements for them.

Marine Battery Cable Requirements

The specifications for battery cables in wet environments are designed to keep you and your water-craft safe.

We promote safety first. Please read the following information before asking us to build your custom marine battery cables.

United States Coast Guard Regulations:

Ocean going vessels are covered by USCG regulations. I am not an attorney and this is not legal advice.

Battery Terminal Covers:

Battery Terminal Covers 50

“Each battery must be installed so that metallic objects cannot come in contact with the ungrounded battery terminals.” (see note 1).

An accidental short circuit from positive to the ground will cause a spark that could ignite explosive hydrogen gas which is given off as a battery discharges. To prevent this, battery cables must have non-conductive terminal protectors (covers) or the batteries must be in covered battery boxes.

We sell a large selection of battery terminal covers

Bolts or Nuts on Battery Terminals:

20 Battery Terminal with Bolt 50

“Each battery terminal connector must not depend on spring tension for its mechanical connection to the terminal.” (see note 2)

You must have a good mechanical connection in order to have a good electrical connection. A good mechanical connection is necessary to prevent sparking and overheating of the terminal which could result in a fire and explosion hazard.

At least one major car company (GM) tried spring-type terminals decades ago. I don’t know if any are still in use except by people who are doing faithfully restorations of vintage cars. Don’t use them on your boat. I wouldn’t even recommend them on your car unless it is a showroom restoration.

Use the automotive clamp-type terminal connector with a bolt that tightens the clamp or side post style or stud top with stainless steel nut.

We have a large selection of battery terminal connectors here.

Stranded Copper Wire:

Marine battery cable boat wire 50

“Each conductor must be insulated, stranded copper.” (see note 3)
Stranded wire is resistant to failure due to vibration and flexing. Copper has excellent conductivity and corrosion resistance. Don’t use aluminum or solid wire no matter how much old house wire you have laying around.

Buy our quality stranded copper battery wire here.

Temperature Specs and Self-Extinguishing:

“Conductors … must:
(1) Meet the requirements of 183.435; or
(2) Meet … requirements of SAE Standard J378; and SAE Standard J1127 or SAE Standard 1128.” (see note 4)

These specs can be confusing but as I understand it SAE (Society of Automotive Engineers) J1127 is the spec for “Battery Cable”. SAE J1128 is for “Low Tension Primary Cable”. Battery cables of SGT, SGX, and MTW meet these specs.

SAE J378 is for “Marine Engine Wiring” and says wire used for marine applications must be self-extinguishing. In other words, if exposed to a flame it won’t continue to burn by itself once the flame is removed.

Battery wire that meets UL Standard 1426 (also called BC-5W2) meets these specs and is what we recommend.

Stud Covers:

Battery Cable Stud Covers 50

“Each ungrounded terminal or stud that is continuously energized must
meet 183.455 or must have a boot, nipple, cap, cover, or shield that
prevents accidental short-circuiting at the terminals or studs.” (see note 5)
Use “stud” or “tab” covers on things like starter or alternator lugs.

See our selection of stud covers here.

Circuit Breakers or Fuses
(except on battery cables):

“Each ungrounded current-carrying conductor must be protected by a manually reset, trip-free circuit breaker or fuse. Note: Cables from Battery to the starter are exempt. (see note 6)

Protect all ungrounded wires with fuses or circuit breakers except cables from battery to starter.

Get a Price for your Custom Cable

We’ll be happy to provide you with a price for your specific needs. Get your Custom Marine Battery Cable Quote here:

Marine Battery Cable USCG Notes:

The United States Coast Guard boating website has all of the regulations regarding boat electrical systems outlined in this builders handbook document.

  1. Battery Terminal Covers: Page 30 Federal law 183.420(b)
  2. No Spring Clips: Page 36 Federal law 183.420(g)
  3. Stranded Wire: Page 37 Federal law 183.425(a)
  4. Temperature Specs: Page 46 Federal law 183.430
  5. Stud Covers: Page 61 Federal law 183.445
  6. Circuit Breakers/Fuses: Page 63 Federal law 183.455

For more information refer to the following standards:
IEEE 45 “Electric Installations on Shipboard”.
SAE J378 “Marine Engine Wiring”.
SAE J1127 “Battery Cable”.
SAE J1128 “Low Tension Primary Cable”.

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