Question: What type of over current protection for my bank/banks?


Generally speaking larger banks should be protected with the following types;


ANL
CLASS T
MRBF


These fuses are available from Blue Sea and others. They should however be "Ignition Protected" fuses if installed on a gasoline boat and Blue Sea is the only one I know of offering ANL fuses with ignition or spark protection for ANL's. Class T fuses are not IP rated however they are fully encased in a metal body. Class T fuses have simply not been tested for IP rather than do not meet IP. In speaking with Blue Sea systems I was told they have no documented cases of an IP breach on any Class T fuses.


Question: "What is AIC?"


AIC stand for Amperage Interrupt Current and Class T, ANL and MRBF fuses all have AIC suitable for decent sized house banks. If you have a large bank of Odyssey or Lithium batteries then a Class T would be best bet as the AIC rating of Class T fuses is nearly 20,000 amps. ANL fuse AIC is 6000A and MRBF is 10,000A.


The concern with AIC is that some breakers can literally weld shut before tripping, if the bank has enough short circuit behind it. For decent sized battery banks you ideally want an AIC rated fuse or breaker of 5000A AIC or greater. AIC is a greater concern for breakers but fuses are also AIC rated and can fail dangerously when subjected to shorting amperage greater than their AIC rating. The actual ABYC requirement for batteries is that any bank over 1100 CCA needs 5000 AIC rated protection or greater. Even two parallel group 27 batteries can supply more than 1100 cold cranking amps...