Fusing a Starter Battery?

Question:

I love the YouTube videos! Please could you advise what type of fuses I need on my batteries?  I have 2 X 100amp house 12v and 1 X 100 amp engine 12v to battery switch type 1 both 2 and off. Thank you for your advice.  - Mark

Answer:

Hi Mark, with an off-1-2-both switch that is used for both house and engine loads, fusing gets complicated as either battery (normally engine battery but maybe house battery in the event of an emergency) can be used for engine starting.  

Fusing a starter circuit is really tricky, because high cranking amps can trip a starter fuse, and hence that’s why ABYC does not require it.

So basically, when using an off-1-2-both battery switch to start and engine both batteries connected to switch do NOT need to be fused.

You should fuse the house loads connected from the common post.  - Jeff

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