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Old 05-27-2014, 10:34 PM   #42
Brent Hodges
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City: Seabrook, Texas
Vessel Name: Friendship
Vessel Model: Albin 43 Sundeck
Join Date: Oct 2007
Posts: 156
[QUOTE=FF;236369]This way the starting loads don't go through the 150 amp rated bus bar but rather through the higher rated 500 amp shunt.

The starter loads should NEVER be run thru a shunt.
1. too small a load over time,

2. a shunt is basically a measured resistance,

A FUSE is a measured resistance .

Just do what 100% of the boats do and forget about measuring start amperage on the OC.


Timjet is correct. FF is pretty much wrong on on all counts.

It is just fine to run starter loads through a shunt provided the shunt is rated to carry the current. A shunt is a measured resistance, but so small of a resistance that an engine starter will never see it. A 500 amp, 50mv shunt like most all of these monitors use only cause a 50mv drop with 500 amps of current. If you are starting from this house bank, and don't run the start current through the shunt, you have lost accurate measurement of the battery bank. I've started my 135 Lehmans through a 500 amp shunt for almost 13 years with no ill effects. Mater of fact, I've installed many, many shunts in starter circuits (properly sized) and have NEVER seen a shunt failure.

A fuse IS NOT a measured resistance. It is a fusable link.

100% of boats DON'T forget about measuring start current. I've seen many that do, including mine. Generally, if they have a separate start battery it doesn't get measured, but if they are started from the house, and they have a properly wired battery monitor installed, they do.
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